CALIFORNIA STATE UNIVERSITY 1 NORTHRIDGE
OPTIMAL FERMENTATION CONDITIONS AND
''NUTRITIONAL QUALITIES OF LAO-CHAO
A thesis submitted in partial satisfaction of the
requirements for the degree of Master of Science in
Home Economics
by
Susan Kathleen Cable
August, 1974
The thesis of
Committee Chairman
California State University, Northridge
AuguD~,
ii
1974
DEDICATION
This thesis is dedicated to Vaughn P. Cable
and Phyllis A. Gearhart.
My dear husband,
Vaughn, has been a source of strength and
belief all through this research.
I thank
my mother, Nrs. Gearhart, who helped me to
develop a value and love for learning and
doing.
____j
iii
ACKNOWLEDGHENTS
I would like to acknowledge the very kind and
expert guidance given to me throug·hout this
research by Dr. T. S. Chen.
remained
thro~ghout
Karen Mays has
this effort an indispen-
sable co-worker and friend.
I
wish to express
my gratitude for all they have done in my
behalf.
I
would also like to express my
appreciation for the assistance given to me
in this research by Dr. ·Robert Lamb and Mrs.
Christine Smith.
iv
TABLE OF CONTENTS
Page
DEDICATION .
.
.
.
iii
ACKNOV'JLEDGMENTS
iv
LIST OF TABLES .
.
vii
LIST OF FIGURES
ABSTR...~CT
.
.
.
ix
.
X
Chapter
I. INTRODUCTION .
1
STATE!vlENT OF THE PROBLEM .
II.
REVIEW OF LITERATURE
INTRODUCTION .
ALCOHOLIC
.
.
2
.
2
FER~..ENTATION
GLUTINOUS RICE .
.
.
.
.
IV.
5
7
METHODS OF EVALUATING LAO-CHAO QUALITY .
III.
1
MATERIALS AND METHODS
8
11
HATERIALS
11!
METHODS
11
Lao-Chao Fermentation
11
Preparation of the Sample for Analysis
131
Methods of Analysis
14
RESULTS AND DISCUSSION .
'
19
THE EFFECT OF TEMPERATURE ON THE COMPOSITION
AND QUALITY OF LAO-CHAO • • • . . • • • .
19
THE EFFECT OF DURATION OF FERMENTATION ON
LAO-CHAO COMPOSITION AND QUALITY . • • • .
28:
l
.. -----------·--·-·-····--····---·--·····-·"--··-··--·--···!
v
1"·~-------.--
!
...
.
---~·---·--~---------~--- ----·-----·-·------~---·-~--------·--·-----·-·-------· -----··--·---~
i
EFFEC'r OF VARYING DEGREES OF AEP-ATION ON
LAO-CHAO COMPOSITION AND QUALITY • • •
I
I!
361
!
NU'l'RITIVE VALUES .fu~D COMPOSITION STUDIES
ON LAO-CHAO
• • • • • • ~ • • • • • •
I
I
44
!
Simple Sugars Present in Lao-Chao
V.
Effect of Ferment.ation on the Thiamin
Content of Steamed Rice
. . . . . . . •
45
Protein Content of Lao-Chao
48
Changes in Total Solid Content of Waxy
Rice . . . . . . . . . . . . . . . .
48
49
SUI-1MARY AND CONCLUSIONS
REFERENCES CITED •
APPENDIX A.
iAPPENDIX B.
I
;APPENDIX C.
• .•
53
EFFECT OF 'VJATER ADDED BEFORE STEAMING
ON LAO-CHAO QUALITY
56.
EFFECT OF. STEAiviiNG TINE ON TEXTURAL
QUALITY OF LAO-CHAO
58
. . . . . . . .
. . . . . . . . . .
GAS CHROl\1.ATOGRAM OF STANDARD ALCOHOL
SOLUTIONS AT VARIOUS CONCENTRATIONS
(% V/V) . . . . . . . . .
. . .
.
.
60
jAPPENDIX D.
COMPARATIVE RATING SHEET
62
\APPENDIX E.
A TRADITIONAL !1ETHOD FOR PREPARING
LAO-CHAO IN THE Hm1E
• • • • • •
64
'
___
vi
___.
•
•
-----~
•
•~••- ~-
-
--~-·-••·-•-•- «~
•·'
~•- -.-~·~•~• -~---·~··
-
•
-·--~~---··.,
-•·
~--.~~~~-~~--•·- ~ •"-~·~~-•~---,_,,__,~
_
•• ._,......_._~·
w~-~-
..
~----~·•~ -·---~~--~"'"'""'-1
I
I
LIST OF TABLES
Page
1.
2.
3A.
3B.
4A.
4B.
SA.
SB.
6A.
6B.
The effect of fermentation temperatures
ranging from 26°C to 22°C on alcohol content, reducing sugar content, total acidity
and pH of lao~chao .
. . . . • . . . . . . .
21
'I'he effect of fermentation temperatures
ranging from 29°C to 38°C on alcohol content, reducing sugar content, total acidity
and pH of lao-chao .
. . . . . .
22
Mean scores, F-ratios and Duncan's Multiple
Range test for sensory data on lao-chao
samples fermented at 26°C, 3l°C, 34°C,
and 42°C .
. . . . . . .
24
I1ean scores, F-ratios and Duncan's Multiple
Range test for sensory data on lao-chao
samples fermented at 26°C, 3l°C, 34°C,
and 42°C .
. . . . . . .
. . .
25
Mean scores, F-ratios and Duncan's I·1tlltiple
Range test for sensory values on lao-chao
samples fermented at 29°C, 34°C, and 38°C
26
Mean scores, F-ratios and Duncan's Multiple
Range test for sensory values on lao-chao
samples fermented at 29°C, 34°C, and 38°C
27
Mean scores, F-ratios and Duncan's Multiple
Range test for sensory data on lao-chao
samples fermented for 48, 64, 80, and 96
hours
. . . . . . . . . . .
. . .
31
Mean scores, F-ratios and Duncan's Multiple
Range test for sensory data on lao-chao
samples fermented for 48, 64, 80, and 96
hours
. • . •
32!
Mean scores, F-ratios and Duncan's I.ful tiple
Range test for sensory data on lao-chao
samples fermented for 56, 72, and 88 hours
33!
Mean scores, F-ratios and Duncan's ~1ul tiple
Range test for sensory data on lao-chao
samples fermented for 56, 72, and 88 hours .
34;
vii
7.
8A.
8B.
9A.
9B.
10.
The effect or 1ncreasing amounts of aeration
on alcohol content, reducing sugar content,
total acidity, and pH of lao-chao
. • • .
37
Mean scores, F-ratios and Duncan's Multiple
Range test for sensory data on lao-chao
samples sealed air tight after 12, 36, and
60 hours of fermentation • . • .
. .
40
Mean scores, F-ratios, and Duncan's Multiple
Range test for sensory data on lao-chao
samples sealed air tight after 12, 36, and
60 hours of fermentation .
. . . .
Mean scores, F-raties and Duncan's Multiple
Range test for sensory data on lao-chao
samples sealed air tight after 0, 24, 48,
and 72 hours of fermentation .
. .
.
41
.
42
Mean scores, F-ratios and Duncan's Multiple
Range test for sensory data on lao-chao
samples sealed air tight after O, 24, 48,
and 72 hours of fermentation . . • • . .
43
Analysis of thiamin content, total protein
and percent solid of lao-chao
. . .
47
:
i
;----~~------------·--·---·--- -·--------------------------·----··---------------------------------------------------------_j
viii
LIST OF FIGURES
Page
1.
2.
3.
Effect of fermentation temperature on reducing
sugar content, total acidity, and alcohol
content of lao chao
. . . .
. . . .
23
Effect of duration of fermentation on reducing
sugar content, total acidity, pH, and alcohol
content of lao-chao
. . .
. • .
29
Paper chromatogram and Rf values of simple
sugars and lao-chao extract
. • .
46
ix
ABSTRACT
OPTIMAL FERMENTATION CONDITIONS AND
NUTRITIONAL QUALITIES OF LAO-CHAO
by
Susan Kathleen Cable
Master of Science in Home Economics
August, 1974
The purpose of this study was to establish optimum
conditions for fermenta·tion of lao-chao, also known as sweet
or glutinous rice wine.
It is a dessert-like food and, in
China, is traditionally served on special occasions.
Lao-
chao samples were fermented at various experimental conditions of temperature, duration, and aeration.
Changes in
alcohol content, pH, reducing sugar content, and total acidity were determined and sensory evaluations were made by an
expert laboratory panel.
The results show that lao-chao
samples fermented at 31°C to 34°C for 64 to BO hours and
with the fermentation jar sealed airtight between 24 and 36
hours of fermentation were preferred by the laboratory taste
panel.
Lao-chao fermented under these conditions contained
4.-..6% (v/v} alcohol, 30-34 g/100 ml reducing sugar, 0.4-0.5
. g/100 rnl titratable acidity and had pH values of 3.8-4.0.
X
rR"esuifs-~-c;f:·-nutrTtion-ai'-·anaTys-es---Tncffcate····Eflat'··-rao::cEa_o_
. ha·s··m
1a total protein content of 2.32 percent and a total solid
I
!content of 38.02 percent.
i
The thiamin content of glutinous
:rice is reduced during the fermentation process.
The
simple sugars detected in lao-chao samples are glucose and
·maltose.
xi
INTRODUC'riON
Lao-chao, which is also known as sweet or glutinous
rice wine, is a fermented glutinous rice product which has
been known to the Chinese for many centuries.
It differs
from the usual wine in that the liquid and the rice are consurned together.
It is a dessert-like food and, in China,
is traditionally served for special occasions.
The Chinese
also believe that lao-chao helps pregnant and lactating
:women maintain their strength (Wang and Hesseltine, 1970).
STATEtlliNT OF THE PROBLEM
Lao-chao fermentation has always been a household
;art, and the conditions for producing a product of consis'
;tently high quality remain unpublished.
!'
The purpose of this study was to establish optimQm
l
!conditions for production of lao-chao.
Specifically, this
study was designed to examine certain physical, chemical,
lI~nd
organoleptic changes
~n
i
lao-chao brought about by rangeJ
.
lof temperature, amounts of· aeration, and duration of the
I
!fermentation process.
_______j
1
REVIEW OF LITERATURE
INTRODUCTION
The term "fermentation" originally referred to the
bubbling observed when sugar and starchy materials underwent
the transformation which yielded alcoholic beverages (Pradhan, 1969).
However~
over the years, fermentation has
gained broader meaning and applies to the metabolic activi.ties of microorganisms in which specific chemical changes
!are brought about in an organic substrate.
Fermentation,
,from an industrial standpoint, refers to almost any process
1
involving microorganisms which results in a product of
economic value.
i
Some of the major fermentations cited in
.
.the l1terature are production of alcoholic beverages, pro-
;duction of yeasts, hydrocarbon fermentation as a source of
i
!animal foodstuff, production of lactic, acetic, citric, and
!certain amino acids, production of flavor enhancers such as
I
i
lribonucleotides, production of enzymes, and production of
~edicines
such as antibiotics and oral contraceptives
I(Miall, 1970).
I
Fermentation is also used to modify raw
~aterials
~f
!
the
.
agricultura~
into both palatable and nutritious foods.
~st beneficial ~difications
are destruction of
lndes1rable flavors, odors and enzymes, production of
2
Some
I
_jI
.3
r-·--"-------------·----_,-----·------------···---------·---------.. --..
-------------·--·----~---·:
!desirable enzymes, flavor and odor, preservation,
synthesis~
!
!of vitamins, increased digestibility, textural changes,
!
i
land color synthesis (Hesseltine and Wang, 1967).
I
Fermentation by many fungi is known to produce
1
certain antibiotics.
It is well known that antibiotics
minimize infections in animals.
They have also been shown
to stimulate growth in animals whose diets are deficient in
some essential nutrients, such as vitamins and proteins.
Wang et al.
(1969) have isolated a compound from soybean
tempeh, a traditional Oriental fermented product, which
exhibits antibacterial activity.
!
The mold strain isolated
from lao-chao studies by Wang and Hesseltine (1971) produced the same antibacterial compound.
It is believed that
I
;this antibiotic activity provides a basis for the tradi:tional claims made about the beneficial properties of laochao in helping new mothers
r~gain
their strength.
In diets which are composed almost exclusively of
rice and vegetables, food flavor takes on added significance.
The majority of the world population lives on just
this kind of diet where a cereal grain or a starchy root is
made into the main dish and eaten with small amounts of
sid~
dishes, relishes, soups, sauces, or gravy (Platt, 1964).
The fermentation of kaffir corn into kaffir beer
is an example of an alcoholic fermentation which enhances
native African diets in two ways (Platt, 1964).
Consump-
tion of the beer stimulates the appetite and results in an
·
~--------------------------------_j
4
...
..
..
!increase in total calorie intake, and the germination of
•'"'~...,.,._.....-~~--
,=--~··----~~~~--~Q---~~~~~~~--~-~-~~~-·~···-·--~----~~--_.......-~~~·~--~-~~·.o<·~~-
------"'"~M-~-py----
~-7-0~~·-•4WT<
....
I
0,1
I
i
!the grain by a mold enhances ·the B-vitamin content of the
!
!original corn in all cases except for thiamin.
I
Further
;
\
!increases in riboflavin were observed from the growth of
,yeast during the alcoholic fermentation of the saccharified
cereal grain.
Some similarities between kaffir beer and
lao-chao are seen in that both products are traditionally
made in the home and the first step in both fermentations
is the saccharification of the grain starches by a fungus.
Also, in kaffir beer; some of the malted grain is consumed
with the beer; however, this does not occur to the same
·extent that the rice and liquor are consumed together in
i
.lao-chao.
The presence of larger amounts of malted grain
.in the beer increased its nutritional contribution to these·
i
;native diets (Platt, 1964).
Enzymes produced in fermentations by fungi result
:in another important advantage of fermentation.
These
jenzymes hydrolize starches and proteins present in the
!substrate and in this way increase the digestibility of
I
the raw food (Hesseltine and Wang, 1967).
There are some disadvantages of fermentation such
as the extra time and costs which may be involved, losses
of material during washing and preparation for fermenta-
~t~on,
and losses of energy resulting from growth of the
~1croorgan1sms
(Hesseltine, 1965).
L_______
------------------1
5
.
r--·~--~---~.,..~~-· ~---·-~
I
...
I
----~~~..,_.~~~----~--~N·~-·--~--~-~--~-~"-~-~~------...~·~--------~----·--_,__.----~...,
ALCOHOLIC FERMENTATION
Ij
,
The production of wine by the fermentation of grapeT
I
!Can be traced back to 3500 B.C., and wines were first
intra~
l
!duced in Europe by traders of the Mediterranean (Amerine,
'1960).
The principle products formed in wine fermentation
are alcohol and carbon dioxide.
Flavor and bouquet of wine
are influenced by other fermentation products of considerable importance, such as glycerol, succinic acid, acetaldehyde, acetic acid, lactic acid, and esters (Uchimoto and
Cruess, 1953).
The basic goal in fermentation is the controlled
growth of the microorganisms to yield the desired products.
I
Three important parameters controlling microbial growth are
I
iPH, aeration and temperature (Brock, 1970), and only a
·relatively narrow range of these conditions allows the
)desired microbial growth to occur.
The pH range falls pri-;
imarily between 5 and 8, with bacteria
growing best near
~neutrality and fungi better in more acidic mediums. Optimuml
'temperature range usually is between 25°C and 40°C.
Aera-
tion can vary from anaerobic to aerobic, which requires
constant agitation in the presence of oxygen.
synonymous with optimum product formation (Pradhan, 1969).
Fermentation temperature affects the quality of
Studies by Amerine et al.
e of wine is altered by changes in the fermentation
Ough et al.
I
l
!
I
(1965) showed that the acid
l
erature.
-----
l
Optimum con-:
ditions for microbial growth, however, are not always
!wine.
II
(1961) found that yeast grew
6
r-------------·--·---..----·---·
------------------------~------·--·-··---------------------------,
!better in wines fermented at 21°C than at 33°C or 1ooc.
.
I
This greater yeast growth caused higher enzyme activity
1
!
l
I
I
'
and increased uptake of buffering material from the sub-
istrate.
The combination of these effects, along with rapid
'production of organic acids, resulted in higher values for
titratable acidity and lower pH values for the wines fermented at 21°C than at the other two temperatures.
Fermen-
tation of fruit wines at a medium temperature of about 2QOC
resulted in wine with a higher ester content than those
produced at other temperatures (Yang, 1953).
These wines
were also reported to retain more of their original fruit
!
flavor.
Alcoholic beverages are produced from the fermenta-
i
[tion of cereal grains as well as from grapes and fruit.
An'
:important step in cereal fermentation is the germination
:or malting phase (Faparusi, 1970).
During this phase, the
igrain starches are hydrolyzed to simple sugars, which are
i
!subsequently fermented to alcohol and lactic acid.
Lao-
1
ichao is an example of mixed culture fermentation of glutilnous rice by a member of the Mucoraceous fungi and a yeast
'
lof
the Endomycopsis species (Wang and Hesseltine, 1970).
!This wine has a sweet-tart taste and a fruity aroma.
In
this fermentation, the rice starches are broken down to
fermentable sugars by the fungus and these sugars are then
used by the yeast.
7
r--~---···--~---------
I
GLuTiNous___R:.ici·-·-..--·-·-·-··-·--·-·-···-·-·---l
Glu·tinous, or -r.vaxy, rice becomes very cohesive when!
!cooked and it is this quality that is responsible for the
l
lformation of good anaerobic conditions for the fermentation
0f lao-chao (Wang and Hesseltine, 1970).
1
This rice differs
from other varieties of rice in its starch content which is
composed primarily of amylopectin and little amylose (Vidal
and Juliano, 1967).
The amylose content in the nonwaxy
varieties may be as high as 37 percent of the total starch,
while it represents only 5 percent or less of waxy rice
starch (Juliano, 1970).
Starch composition is the only
property which has been positively correlated with differ-
!
ences in texture of cooked rice.
Waxy rice, when cooked,
!becomes more cohesive, tender and glossy in appearance than'
\
1the high amylose varieties.
Wang and Hesseltine (1970)
;studied lao-chao fermentation using a nonwaxy rice and
I
!found the resulting product to be abundant in black spore
!
jformation and generally unsatisfactory.
I
Carbohydrates comprise 80 to 90 percent of rice
solids and this is predominantly starch (Juliano et al.,
1965).
Some simple sugars are found in rice but these
represent only about 0.3 to 0.5 percent of the rice solids.
These free sugars are primarily sucrose with smaller
amount~
of glucose and fructose.
Although rice varieties may vary in starch composition, the gene which is responsible for the waxy property
has no effect on either the protein or fat
composit_~on C:~.-1
--·~
a particular variety.
..
~ ~·
--·
·- -·--·
It has been shown that differences
in climate, season and soil composition during the grmvth
stage cause variations in the amino acid, protein and fatty
acid composition of isogenic rice (Houston and Kohler,
19 70) •
METHODS OF EVALUATING LAO-CHAO QUALITY
In experiments where several test preparations of
a product are being compared with a standard product, the
aim is to examine whether the variants differ appreciably
from the standard and to what extent they differ among
themselves (Carlin et al., 1956).
Also, it is helpful to
know how these variants are ordered in relation to the
standard.
Distance from the standard can be measured by
analysis of certain physical or chemical components.
This
provides a different measure of distance for each of the
components considered.
Sensory tests are frequently used
as a composite measure of all the particular attributes of
;a food and human acceptance is the final judge of the proi
iduct quality (Carlin et al., 1956).
Many opportunities for error arise during taste
1
panel tests, and it is important to control the testing
methods and test environment carefully (Larmond, 1970).
;Whatever methods for taste testing are selected, they
:should be strictly adhered to for all the experiments.
i
>Samples should be presented in random order and coded,
I
j
\.
_________ ..____________________________ ... ___________
l
~-------··-·----·------·-------------·---'
\
9
rather than assigned sequential letters or numbers.
The
test area should be free of extraneous odors and preferably
air conditioned.
The panelists should be isolated to avoid
influencing each other in any way.
It is best to avoid the
influence of interfering tastes by conduct.ing tests one or
two hours after meal time.
ducted
ilTh~ediately
Also, tests should not be con-
before a regular meal to avoid any inter-
ference evoked by hunger.
The evaluator's own capabilities are a limiting
factor in any sensory evaluation.
Fatigue, defined as the
diminishing ability of a taster to recognize small differences during prolonged testing, reduces the ability of a
taster to evaluate at his optimum efficiency (Laue et al.,
1953).
To avoid this, samples presented at a testing should
be limited in number and a basic rule to follow is the
stronger the taste and odor, the fewer the number of samples.
It is useful to use a rinse to remove adherent materials
from the mouth and spring water and crackers are sometimes
used for this purpose.
An expert panel of three to ten is
:usually adequate for laboratory testing (Dawson et al.,
!1963}.
Panelists should be selected for their interest,
'motivation, intelligence, and abilities to detect flavor
!I
:differences and sustain concentration.
!
i
Some chemical tests have been positively correlated ·'
.with sensory tests in the evaluation of wines.
The impor-
itant acid taste is recognized as a function of the pH and
,total acidity of wine (Amerine et al., 1965).
-- ~ ...
-~-------·· ·--~ --------~----- ··--·--·~·--·-
The presence ·
----------- .....
~-------·--
---.----
~----
-
---~->
10
r·-~
....... . . . . . . .
~
,~
-~~----·-··
. . . . .·· . . .
..
·--~.--..·-·~........,......~---~___..-~-~------·~~~--~~~-
----~
....
. . ----..-----,
----··......__-~----~-~-·-~~·~~~.....----~··~~~~
lof ethyl alcohol has been shown to increase the taste
threshold for acidity.
Alcohol content itself is consid-
ered a major result of yeast fermentation and its produc\
.
;tlon is of interest in studies on wine fermentation and
'composition.
The reducing sugar content is important, particularly in dessert wines, since it can be employed in determining the end point of fermentation (Amerine and Cruess,
1960) .
The reducing sugar content of lao-chao is related
to the important
swe~t
taste and the amount of substrate
available for yeast fermentation.
Other tests which were recommended by Valaer (1947)
as standard for wine analyses are total acids, ash, volaltile acids, phosphates, alkalinity of ash, specific gravity
and color.
Fermentation may also enhance the nutritive value
jof the waxy rice and thus increase lao-chao's significance
as a food.
Among the important components particularly
!related to nutritive value of fermented foods are certain
IB-vitamins·and proteins (Platt, 1964).
'
CHAPTER III
MATERIALS AND METHODS
MATERIALS
The lao-chao for this study was prepared from a
waxy rice, mochigomi, purchased from a local market (Hughes
Market, Granada Hills, California).
This rice was marketed
by the Bill and Ed Koda Company of Dos Palos, California.
The microorganisms for fermentation were introduced in the
form of a commercial starter which was obtained from Taiwan,
Republic of China.
METHODS
Lao-Chao Fermentation
1.
Preparation of the Rice.
All rice samples were
prepared according to the following procedure:
2000 grams
of rice were washed in tap water at 20°C to a clear rinse.
This was covered with tap water and allowed to soak at roont
:temperature, 21°C, for six hours.
The rice was drained in
]No. 8 sieves for 10 minutes and divided equally into two
'stainless steel trays, 20"xl2"x2", and water was added to
each tray before steaming.
Since the amount of water added before steaming and•
·the steaming time have a profound effect on the resulting
:~ao-chao,
preliminary experiments were conducted in order
ito establish a basis for selection of the best procedure.
11
12
~
______
~
,
···---
-~--·--·-
-~--.
-··
·---·----~---···
----.
~_,
.In one series of experiments, 50 ml, 100 ml and 150 ml of
water were added to 1000-gram p6rtions of rice before
steaming for 15 minutes.
The samples were inoculated and
fermented as described below, at 31°C, for 68 hours and
sealed airtight for the duration of the fermentation.
The
samples were evaluated on the basis of juiciness of the
lao-chao.
The best lao-chao was obtained when 100 ml of
water were added per kilogram of rice (see results, Appendix A) , and this procedure was followed in all subsequent
experiments.
In another set of experiments to determine the best
steaming time, three 1000-gram samples of rice were prepared and steamed for 10 minutes, 15 minutes, and 20 minutes.
The lao-chao from these tests was evaluated on the basis of
rice softness, whole rice integrity, and the occurrence of
uncooked rice grains.
The steaming time of 15 minutes pro-
duced lao-chao with the best texture and whole rice integrity (see Appendix B for results).
Since a steaming time of
15 minutes produced the best lao-chao, a 15-minute steaming
! .
:t1me was used in all further experiments.
The trays of soaked and drained rice were then
placed in a steamer (Steam-It, Model ST-AG, Mass Market
,Forge) and steamed at 15 psi.
2.
Inoculation and Fermentation.
The steamed rice
.was cooled with running tap water and allowed to drain for
:five minutes in No. 8 sieves.
Three grams of commercial
istarter were dispersed into 20 grams of bleached all-purpose
13
--
w·heat flour.
•-
u-•••"•--~·
•
"
•-•
•
•"•••
•
••"-•••--•-•••~·~-~-·-•••--•
.. ~•"•
This mixture was folded into the steamed rice
and mixed thoroughly with a wooden spoon.
The original
2000 grams of rice after soaking, steaming and inoculation
were weighed into eight 500-gram portions.
Each 500-gram
portion of the rice was lightly packed into a 32-ounce widemouth laboratory glass jar with a lid which could be sealed
airtight.
A "well" was made in the center of the packed
rice with a glass stirring rod, and as the fermentation progressed, the "well" allowed observation of the liquid
produced.
Preparat~on
l.
of the Sample for Analysis
Lao-Chao Samples.
mixed well prior to sampling.
The lao-chao was always
This insured that the sample
taken was representative of the contents of the entire fermentation container.
Samples for sensory evaluation, total
solid, protein and thiamin determinations were taken
directly from the well mixed lao-chao.
2.
Lao-Chao Extracts.
'in the following analyses:
Lao-chao extracts were used·
pH, total acidity, reducing
'sugar content, alcohol content, and simple sugars.
They
~ere prepared by blending lao-chao samples in a Waring
blender for five minutes.
Twenty-five ml of the blended
;suspension were measured by water displacement into a 100 ml
graduated cylinder and transferred volumetrically to a 500
'ml volumetric flask.
This flask was then brought to volume
'
with distilled water and blended again for five minutes.
i
L____________ ----··--- ·----~----------- ------- ------------------------------------------------------------------------__j
14
The resulting suspension was filtered through Whatman No. 1.
filter paper under refrigeration at 7.5°C.
Methods of
1.
Analy~is
pH Determination.
Amerine (1959) recommends
that the pH of wines be determined using a pH meter with
glass electrodes.
A Brinkman pH 102 pH meter wi t.h a single
glass electrode was used for these studies.
Brinkman refer-
ence solutions of pH 7 and pH 4 were used as standards.
2.
Total Acidity Determination.
Total acidity was
measured by titration against a standardized 0.1 N NaOH
solution using a l percent phenolphthalein indicator.
The
procedure for degassing of samples under vacuum and subsequent titration is that described by Guyman and Ough (1962).
Results are reported as grams tartaric acid per 100 ml of
lao-chao, using the formula:
ml NaOH
=
x
N NaOH
x
0.075
x
100/5
g tartaric acid/100 ml lao-chao •
Average value of three tests was reported.
3.
Reducing Sugar Content Determination.
The pro-.
'cedure followed is that described for total reducing sugar
)by Lane and Eynon (1942) .
The concentration of the copper
;sulfate solution was adjusted with the aid of an atomic
,absorption spectrophotometer (Perkin-Elmer Model 290B) .
The correction factor for 10 ml of Soxhlet reagent
·was obtained from the Official Methods of Analysis (AOAC,
:1970) and the corrected formula for total reducing sugar
i
~·
1 _J
is given by
51.5858 mg x 100/titer x 0.02
=
4.
g reducing sugar/100 ml lao-chao .
Alcohol Content Determination.
Gas chromatog-
raphy was used to determine the total alcohol content of
the lao-chao following the procedure described by Trachman
(1969).
A Varian Aerograph Hodel 1200 with a flame ioniza-
tion detector was employed for the alcohol determinations.
The chromatographic settings were:
Injector-temperature
Detector temperature
Column temperature
Rate
Recorder range
Chart speed
- 40" per hour
Gas flow rate
- H2 , 30 ml per minute
N , 60 ml per minute
2
Compressed air, 300-400
ml per minute
Column
- 5 feet stainless steel
1/8" inner diameter
Support packing
Porapak Q, 50-80 mesh
Sample size
0.8 microliter
Peak areas were computed with the formula
A
where H
=
= H
X
1/2
w,
height of the peak above the baseline and W
=
width measured at the point where an extension of the
i
....... -- -·-----·- --.. .... ···--·----- ·----------·--------· ---------------------------------------------------------------------_j
16
,straight sides of the peak intercept the baseline.
srunple peak areas were then compared to that of reference
alcohol solutions at concentrations of 0.1, 0.2, 0.3, 0.4,
and 0.5 percent V/V (see Appendix C for sample chromategram).
Average values from two readings were taken.
5.
Total Solid Content Determination.
Lao-chao
and rice samples were dried to a constant weight to determine the total solid content.
The drying conditions were
those described by Wang and Hesseltine (1966).
Whole rice samples were ground in a Wiley Mill to
pass a No. 20 sieve before drying.
Percent solid is
reported as an average value for two samples.
6.
Simple Sugar !dentification.
Paper chromatog-
raphy was used to identify simple sugars present in the
lao-chao extract.
The lao-chao extract was spotted along
with lactose, raffinose, sucrose, maltose, fructose, galactose, glucose, mannose, mannitol, and xylose.
The procedure followed for the separation and
identification of the sugars is that described by McCready
and McComb (1954).
Samples were developed in a solvent
system of 10 volumes of ethyl acetate, 6 volumes of water,
'and 5 vol.umes of pyridine.
The indicator dip for color
'development of the separated sugars was 2 percent aniline
and 2 percent trichloracetic acid in ethyl acetate, mixed
.immediately before use.
The dipped chromatogram was dried
:in air in a vertical position for 30 minutes and heated at
i'
!
t-~-'··----·~~-~------·--·-····---·------~---~-..-,_----~---~---~y-~--~-~---·---------~·---------·--·--_j
\
\
17
----
~-
'
:85°C for five minutes to develop the color (see Figure 3,
page 46, for chromatogram).
7.
Protein Determination.
The micro-Kjeldahl
method described by Ogg {1960) was used to determine the
total nitrogen content of the lao-chao.
The distillation
apparatus employed was a Van Waters and Rogers (51100-002)
micro-Kjeldahl.
The digestion time of 90 minutes recom-
mended by Ogg resulted in a hard digest.
The results of
preliminary determinations indicated that a 30-minute digestion time and 50 to 60 minutes after boil were satisfactory
for the lao-chao sample.
8.
Thiamin Determination.
The thiamin extraction
procedure described by Deutsch et al.
this analysis.
(1960) was used in
The subsequent analysis of thiamin was made
with the aid of a fluorescence spectrophotometer (PerkinElmer Model 203).
The procedure followed is that described
by Strohecker and Henning (1966).
9.
Sensory Evaluation.
A trained panel of four
persons was used to evaluate several quality factors of
ilao-chao.
l
The tests were conducted in the laboratory and
!each panelist made his decisions separately in order to
!minimize any possible distraction or interference.
The
!testing sessions were held at least two hours after the
i
mid-day meal and one to two hours before the evening meal.
!
'Lao-chao samples were presented at room temperature.
All
:panelists swallowed the samples and water was provided as
:.~. -~()~~?-_ __ =-:_~:r1se •________
!
-------------------------------------------------------------J
18
No more than four samples, including the reference,
were presented at a single tasting session (Amerine et al.,
1962} .
The sensory test method is the comparative rating
technique described by Baker et al.
for sample rating sheet) .
(1965)
(see Appendix D
The panelists were instructed to
first score the reference sample using a scale of 5-6 as
standard or acceptable on a scale of 10 points.
Reference
samples were those which most nearly represented lao-chao
fermented according to traditional methods and may or may
not be the most acceptable wine presented at a tasting (see
Appendix E for traditional method of lao-chao preparation).
After scoring the reference sample, all other samples were
scored on a 1-10 scale, using the reference sample for comparison.
The 10-point scale offered enough points to show
significant differences between samples while putting some
practical limitations on the panelists (Baker et al., 1965).
All samples were first tested for overall acceptability and
, then re-evaluated for each of the following:
, alcohol, tartness, flavor, and texture.
sweetness,
Analysis of vari-
ance was conducted with the aid of a digital computer (CDC
Model 3170) using an IBM canned program (program name,
·ONEWAY).
The significance of differences between samples
/was determined by the standard Duncan's Multiple Range Test'
'
(Larmond, 1970) .
I
l
!
·-·---'
..
. -·--"'---·-·-------·----·---rl
r~--~-~ ~----~--·-----~----~----~-·--···-···-·-------------
I
.I
I
:\
I
!
I
I.
!!'I
CHAPTER IV
11
I
'l
RESULTS AND DISCUSSION
THE EFFECT OF TEMPERATURE ON THE COMPOSITION
AND QUALITY OF Ll'~O-CHAO
Temperature is the major factor controlling the
rate of fermentation (Ough and Amerine, 1961) and has been
shown to affect the pH and total acidity of wine (Ough et
al., 1969).
T".vO experiments were conducted to study the effe:cl:
of temperature on alcohol content, total acidity, reducing
1
i
:sugar content, pH and taste quality of lao-chao.
The first
!experiment covered a temperature range of 26°C to 42°C and
,the second experiment covered a narrower range of 290C to
i38°C.
The fermentation temperatures examined in the first
jexperiment were 26°C, 31°C, 36°C, and 42°C, with duplicate
!samples fermented for each temperature.
The fermentation
ljars were sealed airtight at the beginning of the fermentation period and all samples were removed from the
lat
incubator~
60 hours and stored at 7.5°C in a refrigerator until
they were analyzed.
The temperatures studies in the second
experiment were 29°C, 34°C, and 38°C, and all other condi-
!tions
were the same as those described above.
Taste tests were used to determine the overall
quality of the lao-chao samples fermented at the different
19
20
results obtained from chemical analyses to determine whether
·results of these analyses could be correlated.
The results of analyses for alcohol content, reducing sugar content, total acidity, and pH of lao-chao samples
are given in Tables 1 and 2.
Lao-chao fermented at 34°C
had the highest alcohol content and lowest pH, while the
reducing sugar content and total acidity were greatest for
the lao-chao fermented at 36°C.
Figure 1 shows alcohol con-
tent, total acidity and reducing sugar content plotted
versus fermentation temperature.
From these curves, it can
be seen that the rate of fermentation gradually increases
to a point somewhere near 36°C.
Above 36°C, the fermenta-
tion rate declines very sharply and, by 42°C, the maximum
temperature for the metabolism of these microorganisms has
been exceeded.
Results of the sensory evaluations of lao-chao fermented at the various experimental temperatures are pre.sented in Tables 3A, 3B, 4A, and 4B.
The tasters indicated
overall preference for samples fermented from 29°C to 36°C.
'
;The highest mean scores obtained for overall preference
were for samples fermented at 3l°C and 34°C; however, the
mean scores of the 29°C sample and the 36°C sample did not
.;differ significantly from the 31 °C and 34 °C samples.
1
The
taste panel scored highest for sweetness, alcohol, tartness,
flavor and texture for samples fermented at 3l°C and 34°C.
;Taste preference for tartness correlated with lowest pH in
:..1:~~
]4 °C sample; however, there ~Ci~ __n<?:t:. a signifi_?_c:l~~ ____________,
..----------------------·····--···--··········'"--
........ ···-·-··-···
····-· -······· ··-···----------1
·-·-
il
1
!
iI
Table 1. The effect of fermentation temperatures
ranging from
26°C to 42°C on alcohol content, reducing sugar content, total acidity
and pH of lao-chao
..
l
I
===============================================================================!
l
(OC)
Alcohol content
(ml ETOH/100 ml
lao-chao)
.
Reduc1ng sugar
(g/100 ml lao-chao)
Total a~idi t~ ., .
(g tartarlc ac1oj
100 ml lao-chao)
pH
26
2.66
25.86
0.306
4.03
31
3.54
30.49
o.4o2
4.oo
36
4.58
35.22
0.472
3. 94
lI
42
0.46
13.99
0.270
4. 01
1
IFermentation
temperature
1
1
!
I
1
-I
!
I
II
L __ _ _,_ _ _ _ ___,_~--------.,·-~········-··
I
.... l
. -~-. ·-·---------~"- ...3
r-.>
1-'
r··-···--·-.
I
I
'i
Table 2. The effect of fermentation temperatures ranging from
29°C to 38°C on alcohol content, ,reducing sugar content, total acidity
and pH of lao-chao
I
I
Fermentation
temperature
( oc}
--
Alcohol content
(ml ETOH/100 ml
lao-chao)
Reducing sugar
(g/100 ml lao-chao}
Total acidity
(g tartaric acid/
100 ml lao-chao)
pH
29
3.0
128.76
0.328
3.95
34
5.08
!
31.72
0.458
3.84
38
4.12
27.02
0.377
3~89
I
I
I
I
II
I
!
I
l____···--------·--------------··
IV
i'.J
23
--------------------------~6.0
- - - - HJ.::DUC!NG SUGAR CONTENT
- - - - TOT.b.L
ACIDITY
CONTENT
- - - - - - ALCOHOL CONTEt·JT
- 0.5
E
I
I
~
0.4t-
u
~
I
~
<t
-'
4
10
t-
t1
0.3-...--..
/
>~
0
0
~
I
~ / ;' /
_//
Il ..----_....
.
.
.
-~~~~
<t
~
/fl //
I
1
<t
I
\>.
~!--~\
;,
~\
0
0
.........
0
f
~5.0
•• ,
..
·.
II -~~
\\ \
--
~
\
' \
~
-
.::::_ '52
E )(
I
-\ " '"-·-13.0
J
i3
\..
~---
!--
\
2
l--
~g
\
\
\
zu
()
u~
<
r--·
'\
I
O.lr
'
o.!!
4.0 E
o0
--iI ., ()
I' ·-·
c5 {!)~
I
~~
<u
1.0
I
01.
25
TEMPERATURE (DEGREES
CENTtGRADE.)
Figure 1~ Effect of· fermentation temperature
on reducing sugar content, total acidity, and
alcohol content of lao-chao
;
I
I
.
I
I
--·<~·~·--~--·----~~--~~-~---·--·-~--~-»-·-~~k·.. ·~----··-~.~--------~~---------·~··-·-~·---~----~~-·-··-~-------------A_j
--·~
-· ....
""·"
.. -
·-
Table 3A. Mean scores, F-ratios and Duncan's Multiple Range test for
o
o
a
o
o
sensory data on lao-chao samples fermented at 26 C, 31 C,
34 C, and 42 C
i
1-
Fermentation
temperature (°C)
Sample mean
F
26
31
36
42
Overall Accep_'t_~bili ty
3.2
6.0
43.8
5.2
1.0
Sweetness
26
31
36
42
3.5
6.5
5.7
1.2
Duncan's Multiple Range
31° 36°
26° 42°b
31° 36°
26° 42°b
31° 36°
36° 26°b
20.0
Alcohol
26
31
36
42
3.2
7.0
5.2
1.0
12.6
26° 42°
aReference sample
bsamples differ significantly at 1 percent level
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other.
'j
F - Variance ratio for samples: Mean Square for Samples divided by
Mean Square for Error
l- - - ~- - - - - · "· - - - ' ..... " ' - - - -'
~~
...... _.
1\.)
~
r ..........
Table 3B. Mean scores, F-ratios and Duncan's Multiple Range test for
sensory data on lao-chao samples fermented at 26°C, 31°C,a 34°C, and 42°C
Fermentation
temperature ( °C)
F
Sample mean
Duncan's Multiple Range
Tartness
26
31
36
42
2.5
6.5
5.2
1.0
31° 36°
26° 42°b
31° 36°
26° 42°b
16.1
Flavor
26
31
36
42
3.0
7.0
5.2
1.2
19.7
Texture
26
31
36
42
4.5
6.5
5.7
1.2
31° 36°
36° 26°
42°b
19.1
--
a Reference sample
bsamples differ significantly at 1 percent level
i
!
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other.
F - Variance ratio for samples:
Mean Square for Error
Mean Square for Samples divided by
I
L ______ .............. .
N
t)l
r-..·------..
-
Table 4A.
Mean scores, F-raties and Duncan's Hultiple Range test for
o a
o
o
sensory values on lao-chao samples fermented at 29 C,
34 C, and 38 C
Fermentation
temperature (°C)
Sample mean
F
.......,
'
Duncan's Multiple Range
Overall Acceptability
I
I
29
34
38
I
29
34
38
6.2
29o 38ob
34° 29°
7.0
49.0
5.0
Sweetness
I
NS
5.7
7.2
0.49
6.5
Alcohol
\
29
34
38
I
I
l
I
34° 38°
5.0
6.2
6.0
29ob
5.7
aReference sample
bsamples differ significantly at 5 percent level
NS - Not statistically significant
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
i
F - Variance ratio for samples:
Mean Square for Error
Mean Square for Samples divided by
I
I
I ___ ___ ___
\..._.
....
,
~--~---·---·-···
--
-~- -----~---------_j
I'V
cr-,
Table 4B. Mean scores, F-ratios and Duncan's Multiple Range test for
sensory values on lao-chao samples fermented at 29°C,a 34°C, and 38°C
Fermentation
temperature ( oc)
F
Sample mean
Duncan's Multiple Range
Tartness
29
34
38
34° 38°
4.7
7.2
6.5
29°b
23.7
Flavor
,_,...~
I
29
34
38
I
4.7
6.2
5.7
NS
3.4
Texture
29
34
38
5.2
6.2
6.0
NS
1.8
aReference sample
bsamples differ significantly at 5 percent level
NS - Not statistically significant
I
!
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
F - Variance ratio for samples:
Mean Square for Error
IL _______________________ -
Mean Square for Samples divided by
!
~-- -------~-..~----.~
t..>
--·..J
28
icii'£t;~-~~;;~--i~---;;;~~;;-~ c;~~~- -·£·;~--ta~t~~~-~ be t;;en-~h~--34°c ---~~~-]
,l
I'
138°C samples.
land
Highest mean scores for alcohol, sweetness
tartness did not correlate with chemical data for
I
alco-~
lhol content, reducing sugar content and total acidity.
i
'
:Panelists indicated a significant preference for the flavor.
:and texture of the samples fermented from 31°C to 36°C.
Based on these data, the best temperature for laochao fermen·tation probably falls between 31 °c and 34 °C.
Acceptable results, however, were obtained at a broader
range of fermentation temperatures from 29°C to 36°C.
THE EFFECT OF DURATION OF FE~illNTATION
ON LAO-CHAO COMPOSITION AND QUALITY
The effects of duration of fermentation on taste
i
!preference, reducing sugar content, alcohol content, total
I
acidity and pH of lao-chao were studied.
Rice was prepared,
inoculated with starter, incubated at 33°C with the sample
1
I
!jars sealed airtight from zero hours of fermentation. After
I
48 hours of incubation, duplicate samples were removed at
1
l
,12-hour intervals from the incubator and stored at 7.5°C
bntil they were analyzed.
The last jars removed .had incu-
ated for 96 hours.
Figure 2 shows the effect of duration of fermentaion on the reducing sugar content, alcohol content, pH,
nd total acidity of lao-chao.
An uninterrupted increase
'n reducing sugar content is seen from 48 hours to 96 hours
f fermentation.
These results indicate that the fermenta-
bon environment was still able to support the metaboli_c::______J
29
•~••••·
-~-'"''~"~""'-'~
•·~-•
yo ·-·•-•••
o·-·-~
>
.-..
---'--~·«-
~k-·~~~--··~..,._~-
·~••"•••<~·~~~<'•>•-~~-~---·-·-..•--·~'- ~~ ~-·-·---~~ --·~·~••
,,_,__ _._
~->..,.o.,O•-·-~~~~-----i
I
·--"-·~- REDUCING SUGt~R CONTENT
0.7
~~
· - - TOTAL
ACID!TY
CONTENT
f\LCOHOL CONiENT
-
E
-co
'-0
0-
I
Q,
........ 0
0.6 t:--·
~u
I
-4
~
<J
'o -
x ":e
.....
•
E
1
0
0
'......E
·~~--..---- _ _ _,.5 . 0 ~ ~
~...,-
~ ~ o:4 I--/-~
(.)~
7.0
I
~ ~ 0.5,
a~· I
u !
i~
/
/
__
I
I
~
/
/
...,
--.
/
~
z
_ __,...
0
u
r / ----:.-~ ------~------- 1
///
/
~~
~.....
oc
••
48
/
~-
4.0
~--,
--~"'
t:=_.
0.3
/
/
-
3.0
I
56
64
72
80
FERMENTA!ION TIME (HOURS)
68
96
Figure 2. Effect of duration of fermentation
on reducing sugar content, total acidity, pH, and
alcohol content of lao-chao
~
~
30
activities of the saccharifying fungi after 96 hours of
•fermentation.
By 48 hours of fermentation, the alcohol content
had already reached nearly 3 percent.
A further small in-
crease in alcohol content is seen between 48 and 56 hours,
followed by a very rapid increase to a peak after 88 hours
of fermentation.
The total acidity reached its peak con-
centration by 80 hours, although the alcohol content continued to increase to 88 hours.
A possible explanation for
this is that the available oxygen in the headspace of the
fermentation jar was exhausted by 80 hours of fermentation
and the further metabolism of alcohol to acid could not
pr~
ceed in the absence of available oxygen (Brock, 1970). After
88 hours of fermentation, it is possible that the alcohol
and acid content of the lao-chao reached concentrations
which were not conducive to continued yeast metabolism.
The pH of the lao-chao was 4.03 at 48 hours of fermentation but dropped to 3.83 by 80 hours.
Lower pH values
followed closely the increases. in total acidity.
The pH
remained in the range of 3.83 to 3.85 from 80 hours to 96
i hours of fermentation.
Results of sensory evaluation of lao-chao fermented'
from 48 to 96 hours are presented in Tables SA, SB, 6A, and
6B.
These data indicate an overall preference for samples
fermented from 64 to 80 hours.
Highest scores for sweet-
ness, tartness, flavor, and texture were observed in the
fermented from 56 to 80 hours.
\
Although the alcohol
... _
~"
··~-··
Table SA. Mean scores, F-ratios and Duncan's Multiple Range test for
sensory data on lao-chao samples fermented for 48, 64,a 80, and 96 hours
Fermentation time
(hours)
Sample mean
F
48
64
80
96
Overall Accept.ability
5.0
7.25
5.4
6.0
4.75
Sweetness
48
64
80
96
6.25
7.25
5.25
5.25
Duncan's Multiple Range
64 80
80 48 96b
NS
1.8
Alcohol
48
64
80
96
NS
4.75
7.25
6.5
6.25
2.3
aReference sample
bsamples differ significantly at 5 percent level
NS - Not statistically significant
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
I
L ____,_________
F - Variance ratio for samples:
Mean Square for Error
Mean Square for Samples divided by
t..•
1---'
Table 5B. Mean scores, F-raties and Duncan's Multiple Range test for
sensory data on lao-chao samples fermented for 48, 64,a 80, and 96 hours
Fermentation time
(hours)
Sample mean
F
Duncan's Multiple Range
Tartness
48
64
80
96
I
64 80
4.5
7.0
6.25
5.0
80 96 48b
3.9
Flavor
48
64
80
96
NS
5.5
7.0
5.75
5.25
2.0
Texture
I
I
I
48
64
80
96
64
5.25
7.75
6.0
6.25
96 80 48b
6.4
aReference sample
bsamples differ significantly at 5 percent level
NS - Not statistically significant
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
I
I
I
F - Variance ratio for samples:
Mean Square for Error
'------·-~----·-·--·
Mean Square for Samples divided by
..
V..l
N
Table GA. Mean scores, F-raties and Duncan's Multiple Range test for
sensory data on lao-chao samples fermented for 56,a 72, and 88 hours
Fermentation time
(hours)
I
I
I
Sample mean
I
I
II
Duncan's Multiple Range
Overall AcceEtability
56
72
88
72
5.25
6.75
3.75
l
-<I
F
56
88b
19.1
Sweetness
56
72
88
72 56
6.0
6.75
4.5
88b
12.6
Alcohol
56
72
88
NS
6.0
7.25
5.75
2.4
aReference sample
bSamples differ significantly at 5 percent level
I
NS - Not statistically significant
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
I
l ___
F - Variance ratio for samples:
Mean Square for Error
Mean Square for Samples divided by
i
i
___________j
(,J
w
·-··-·-·>
i
Table 6B. Mean scores, F-ratios and Duncan's Multiple Range ·test for
sensory data on lao-chao samples fermented for 56,a 72, and 88 hours
i
lI
I
Fermentation time
(hours)
Sample mean
I
I
I
F
Duncan's Multiple Range
Tartness
56
72
88
6.25
6.0
4.0
56 72
88b
72 56
88b
6.3
Flavor
56
72
88
6.25
6.5
4.0
5.8
Texture
l
I
I
56
72
88
6.0
6.75
5.75
NS
0.9
aReference sample
bSamples differ significantly at 5 percent level
NS - Not statistically significant
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
I
II
F - Variance ratio for samples:
Mean Square for Error
•--------~-·""'·~----·
Mean Square for Samples divided by
..
w
~
35
r;~;;t~~t-~f~l~~=~h~~-- we~t···f;-om -i~-;;~---tha·~-3-p;-;~~t-·t-;---;;·;;-----~
I
.6 percent between 48 and 88 hours of fermentation, the
i
!tasters were unable to make a significant selection on the
basis of alcohol.
It is possible that other volatile sub-
!stances formed during fermentation interfered with the
panelists' abilities to detect the alcohol taste in the
lao-chao.
Based on the results of taste panel choices for
overall preference, sweetness, tartness, flavor and texture,
64 to 72 hours of fermentation probably best describes the
optimum duration for·lao-chao fermentation.
A very accept-
able product is obtained, however, by fermenting lao-chao
'from 64 to 80 hours.
I
When microorganisms are introduced into a fresh
!medium, after a short lag time they experience rapid population growth (Brock, 1970).
During this growth phase,
!waste products of microbial metabolism are formed.
In
ialcoholic fermentation, the chief end products are con-
I
sidered to be alcohol and co , although many other compound\
2
1
!are produced that have a significant effect on product qualJ
I
,
ity (Uchimoto and Cruess, 1952).
After the rapid growth
phase, a stationary phase is reached.
This is the result
of the microorganisms either exhausting their nutrient supply or the waste products of metabolism having reached
I
I
1
I
toxi9
levels.
It appears that the first step in lao-chao fermenta,
tion is probably the breakdown of the rice starch to simple
sugars by amylases released by the fungus
(Wang and
!
l
I
36
jiie ss-eTt:Ii1e-~ --y§-;ToY:---·--'T-f-~e-se___ 5Til1r;T~---8·:u9:a·r-8---.;:re--t:ile~l--c-~n:~;;J;t;d:--l
!
Ito alcohol and
co 2
i
by the yeast.
In the presence of oxygen;
lthe alcohol will undergo further oxidation to acid and water.!
1
EFFECT OF VARYING DEGREES OF AERATION ON
LAO-CHAO COMPOSITION AND QUALITY
The effects of aeration on the alcohol content,
reducing sugar content, total acidity, pH and taste preference of lao-chao were examined.
The rice was rinsed,soaked,
steamed and inoculated according to the previously descrfred
experimental procedures.
Prior to incubation at 33°c, two
of the 14 samples were sealed airtight by securely handtightening the lids of the glass laboratory jars.
The other
i
12 samples were loosely covered to allow ventilation during
fermenta·tion.
Duplicate samples were then sealed every 12
hours during fermentation.
At 72 hours of fermentation,
all samples were removed to refrigeration at 7.5°C until
analysis.
It was assumed that, even after sealing, a limited
amount of oxygen was still available in the headspace of
the laboratory jar.
Data presented in Table 7 show alcohol content,
total acidity, pH and reducing sugar content of lao-chao
fermented with increasing amounts of aeration.
These
results demonstrate that delayed sealing time does affect
the degree of aeration and subsequently the quality of
lao-chao.
I
The reducing sugar content of lao-chao gradually
~d
with increased aeration to the sealing time of
'"---··-
,___ -
-·~
Table 7. The effect of increasing amounts of aeration on
alcohol content, reducing sugar content, total acidity, and pH
of lao-chao
Aeration
(as sealing time
in hours)
Alcohol content
(ml ETOH/100 ml
lao-chao)
Reducing sugar
content
(g/100 ml lao-chao)
Total acidi·ty
(g tartaric acid/
100 ml lao-chao)
pH
0
4.5
31.32
0.432
3.78
12
4.6
32.94
0.442
4.08
24
4.8
33.26
0.448
4.06
I
36
4.4
33.82
0.472
4.03
I
48
4.4
36.48
0.512
4.05
60
4.2
39.62
0.518
4.02
72
4.2
35.84
0.526
4.08
II
I
I
I
I
I
I
II
l
I
L___________________.___ - - - -·
w
-...1
38
tation involving breakdown of the rice starches to fermentable sugars by a saccharifying fungus (Wang and Hesseltine,:
i
I
;1970).
Frazier (1967) describes the process of breaking
:down starches to fermentable sugars, or
11
amylo process,"
as requiring good aeration and, in the case of Koji (Hesseltine and Wang, 1970), shallow fermentation trays are used
for this reason.
The alcohol content increased in lao-chao to a
sealing time of 24 hours and then declined with further
aeration.
Total acidity, however, continued to increase
with increased aeration and showed no tendency to peak.
In
.the presence of oxygen, alcoholic fermentation by yeast is
jsuppressed in favor of oxygen requiring respiration (Brock,
1970).
I
In incomplete respiration, yeast metabolism results
,in an accumulation of acids.
I
This incomplete respiration
by the yeast provides a probable explanation for the increased total acidity and lower alcohol content observed in
lao-chao samples which were sealed after 24 hours of fermentation.
The observed pH was lowest in lao-chao sealed at
zero hours of fermentation and reached its highest value in
lao-chao sealed at 12 hours.
The pH did not vary signifi-
cantly for all subsequent samples from that observed in the
lao-chao sealed at 12 hours.
Ough et al.
(1969) reported
that potassium, phosphate, amino acids, and organic acids
all exhibit significant buffering capacity in wines.
The
39
..
....
r~ -~---·--·----
..
·---------------~------- -------------~----~---~---~-·---------------------~--------1
jresistance to change in pH may be due to formation or spar-!
I
I
[ing of buffers resulting from yeast respiration.
I
I
.
1
Tables 8A, 8B, 9A, and 9B show the results of sen- ·r
'
'
!sory
evaluation of lao-chao samples fermented with increas-
:ing amounts of aera·tion.
The tasters indicated an overall
preference for samples sealed at 24 and 36 hours of fermentation.
For sweetness, the panelists preferred the samples
aerated for 12 and 36 hours and, for flavor, the 36-hour
sample was preferred.
The tasters were not able to make
significant judgments on the basis of alcohol, tartness,
and texture of lao-chao samples fermented with increasing
'amounts of aeration.
A possible explanation for this is
I
that aeration did not result in as great a variation in comjpositional characteristics of lao-chao as did temperature
;or duration of fermentation.
1
The panelists apparently were
unable to distinguish these individual flavor characteristics when they varied to a much lesser degree than in the
previous experiments.
The panelists' inability to make
selections on the basis of tartness may be related to the
relatively constant pH, in spite of increases in total
acidity.
Amerine et al.
(1965} describe the acid taste of
wines as a result of the combined effects of pH and total
acidity.
Wang and Hesseltine (1970} describe the conditions
lfor lao-chao fermentation as semi-anaerobic with the waxy
~ce
itself creating the desired semi-anaerobic environment
rom these experiments, it is seen that allowing some
-------
---
Table SA. Mean scores, F-ratios and Duncan's Hultiple Range test for
sensory data on lao-chao samples sealed air tight after 12,a 36, and 60 hours
of fermentation
Sealing Time (hours)
Sample mean
F
Duncan's Multiple Range
12
36
60
Overall AcceEtabilit~
6.0
14.86b
7.8
4.8
Sweetness
36
12
36
60 '
6.5
7.8
5.5
36 12
5.84c
12 60c
12 60c
Alcohol
12
36
60
6.5
7.2
6.0
1.46
NS
aReference sample
bsamples differ significantly at the 1 percent level
csamples differ significantly at the 5 percent level
I
NS - Not statistically significant
I
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
!i
1
F - Variance ratio for samples:
Mean Square for error
Mean Square for samples divided by
l________________ . .
ti:>o
0
Table 8B. Mean scores, F-ratios and Duncan's Multiple Range test for
sensory data on lao-chao samples sealed air tight after 12,a 36, and 60 hours
of fermentation
Sealing time (hours)
Sample mean
F
Duncan's Multiple Range
Tartness
12
36
60
6.0
7.2
5.5
NS
5.09
Flavor
12
36
60
6.0
7.8
I
7.9b
36
12 60b
5~2
Texture
12
36
60
6.2
6.5
5.5
2.05
NS
aReference sample
bsamples differ significantly at the 5 percent level
NS - Not statistically significant
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
F - Variance ratio for samples:
Mean Square for error
I
L...--·------·-·-·-···~-
..
Mean Square for samples divided by
'
l
I
I
-··-·~~~--·-··----~-~--.1
~
I--'
Table 9A. Mean scores, F-raties and Duncan's Multiple Range test for
sensory data on lao-chao samples sealed air tight after 0, 24,a 48, and 72
hours of fermentation
Sealing time (hours)
Sample mean
F
Duncan's Multiple Range
Overall AcceEtability
0
24
48
72
5.0
7.0
4.2
5.2
11. 82b
24
68 0 48b
Sweetness
0
24;
48
72
5.5
7.0
5.7
5.2
2.32
NS
0.10
NS
Alcohol
0
24
48
72
5.2
5.5
5.2
5.8
aReference sample
I
I
l
j
I
bsamples differ significantly at the 5 percent level
NS - Not statistically significant
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
F - Variance ratio for samples:
Mean Square for error
Mean Square for samples divided by
L---------·. -...
.,1:;:.
tv
Table 9B. Mean scores, F-ratios and Duncan's Multiple Range test for
sensory data on lao-chao samples sealed air tight after 0, 24,a 48, and 72
hours of fermentation
Sealing time (hours)
Sample mean
F
Duncan's Multiple H.ange
Tartness
5.0
6.5
4.75
5.75
0
24
48
72
1.62
NS
1. 62
NS
1.65
NS
Flavor
0
24
48
72
I
4.75
6.5
5.0
5.75
Texture
0
24
48
72
5.25
6.5
5.0
6.0
aReference sample
NS - Not statistically significant
Duncan's Multiple Range - Samples which appear underscored together
do not differ significantly from each other
i
F - Variance ratio for samples:
!_____~.:____ Mean Square for error
Mean Square for samples divided by
_"_"___________ j
lI
or::.
w
44
ventilation during the first 24 to 36 hours of fermentation
results in a lao-chao with superior overall taste quality.
NUTRITIVE VALUES AND CO.r.-1POSITION
STUDIES ON LAO-CHAO
Lao-chao may contribute to the diet in several ways
and not the least of these is flavor and interest.
Rice
and rice products, however, generally belong in the category of the starchy foods which comprise the dietary basis
for most of the world's population.
Among the nutrients
most frequently lacking in these diets is protein and more
specifically good quality protein.
The fermentation of
idli from black gram and rice results in a 20 percent increase in methionine, an amino acid frequently lacking in
these foods
(Platt, 1964).
Besides the enhancement of pro-
tein, many types of fermentations have been reported to
increase the B-vitamin content of the substrate in all
cases except thiamin (Hesseltine, 1965).
Experiments were conducted to determine total protein, thiamin content, total solids and simple sugars in
lao-chao.
Lao-chao was prepared by fermenting 500-gram
iportions of prepared, steamed rice at 33°C for 72 hours.
'
!All fermentation jars were sealed airtight at 24 hours of
;fermentation.
The conditions for preparation and fermenta-
,tion were selected on the basis of results of previous
;experiments to determine optimum fermentation conditions
'for lao-chao.
;'
:
~--.-.---~··-··~-~---··---.,.._.,.~--·--·-~·A--~-·~·~·----------~---~---·---~---··~~--·-
\
J
45
------~------~---··-···-'"'''''--·-------------------------~-----------------------------~"-,
i
!simple Sugars Present in Lao-Chao
I
1
I
Mays (1973) reports that the microorganisms respon-i
isible for lao-chao fermentation ferment glucose, maltose,
I
:and sucrose.
Juliano (1970) reported that hydrolysis of
;rice starch primarily results in glucose and maltose.
The
presence of small amounts of other sugars such as galactose
and sucrose would be the result of their presence as part
of the total carbohydrate content of the rice (Houston and
Kohler, 1970).
The results of paper chromatographic analy-
sis of lao-chao extract have shown only the presence of
glucose and maltose (see Figure 3 for chromatogram).
!Effect of Fermentation on the Thiamin
Content of Steamed Rice
Results of analyses for thiamin content of steamed
,rice and lao-chao are presented in Table 10.
Exposure to
:heat during steaming would be expected to result in some
!
,loss of thiamin content of the waxy rice (Labuza, 1973).
'A loss of nearly one fourth of the thiamin content of the
!steamed rice was observed after fermentation.
Losses in
!thiamin are probably caused by utilization of the vitamin
lfor
the metabolism of the microorganisms responsible for
lao-chao fermentation.
l
Roelofsen and Talens (1964) reported
i
a one third loss of thiamin during soybean tempeh fermenta- '
tion.
However, they also reported that niacin and ribofla-
l
in content increased slightly during the same fermentation •'
Figure 3. Paper chromatogram and Rf values of simple sugars and La?-chao
extract. A=xylose, B=mannose, C=glucose, D=galactose, E=fructose, F=maLtose,
G=sucrose, H=lactose, I=Lao-chao extract.
a Rf=distance traveled by sample per unit distance traveled by solvent
~
0\
47
-~---···---·~--------------~--~-···-----···--·--·-·---·--·--------~-------l
l
Table 10. Analysis of thiamin content, total
protein and percent solid of lao-chao
Waxy Rice
.
.
a
Th1am1n content
(mg/100 g)
Steamed Rice
0.018
Protein contenta
(percent)
Total solid
(percent)
Lao-Chao
0.014
2.3
87.85
46.81
38.02
a Wet b as1s
.
bValues taken from USDA Handbook No. 8 (Watt and
Herrill, 1963)
48
I
. --..
r--~--
~------------~-·--------~------
~rotein
Content of
Lao~Chao
Results of protein determination on lao-chao are
~resented
in Table 10.
The total protein content was
I
I
1
I
i
i
)determined to be 2.32 percent.
When changes in total solid
'con·tent of the rice due to steaming and fermenting are
taken into account, this value correlates very closely with·
that reported in USDA Handbook No. 8 (Watt and Merrill,
1963).
Changes in Total Solid Content of Waxy Rice
Table 10 shows changes in total solid content of
waxy rice during steaming and fermenting.
The total solid
lcontent of the waxy rice changed from 87.85 percent to
46.81 percent after soaking and steaming.
1
Fermentation of
the rice resulted in a total solid content of 38.02 percent.
These changes are caused by the uptake of water during soak-
i
ing and steaming and the production of
co 2 ,
alcohol, water,
'volatile acids, and esters during fermentation.
I
i
----~·-,
CHAPTER V
SUMMARY AND CONCLUSIONS
Experiments were conducted to determine the optimum
conditions for the fermentation of lao-chao.
The effects of
temperature, duration and aeration of fermentation on the
total acidity, alcohol content, reducing sugar content, pH,
&nd sensory
properti~s
of lao-chao were examined.
The temp-
eratures studied in these experiments ranged from 26°C to
42°C.
Studies on the duration of lao-chao fermentation in-
I
'valved fermentation times ranging from 48 to 96 hours.
The·
aeration was controlled by sealing the fermentation jars
1
:airtight sequentially from 0 to 72 hours of fermentation.
The sensory quality of lao-chao was evaluated by a
;
I
In many cases in these studies, the
:trained taste panel.
l
itwo highest ranked samples in one experiment had to be con-
I
!sidered together since they did not differ significantly
from each other in mean score values.
For this reason, the
conditions selected as optimum from these experiments are
I
!
I
i
expressed as ranges of temverature, duration and aeration
lof fermentation.
The results show that lao-chao samples fermented at
31°C to 34°C for 64 to 80 hours and sealed between 24 and
I36
.
hours of fermentat1on were preferred.by the taste panel.
~--~--------------------------------------~--------------------__j
49
50
____,
r··----·-·--·--1\ic~'hoi-;;~t:e~t~-~~duc.ing--~u~~r--c~~tent, -~~d--t~t;_i
Ilac1.d1.
. . ·ty
!
reached maximum values at a fermentation temperature
I
!between 34°C and 36°C.
i
However, taste panelists generally
;
'preferred samples fermented at lower temperatures of 31°C
t.o 34°C.
A.t 42°C, the temperature range of the microorgan- ·
isms was exceeded, resulting in a totally unacceptable product with very low values for alcohol content, reducing
sugar content, total acidity, pH, and sensory value.
The taste panel preferred lao-chao fermented for 64
to 80 hours, although longer fermentation ~imes resulted in
higher values for alcohol content and reducing sugar content.
A peak was observed in the total acidity of lao-chao after
I
80 hours of fermentation. A probable explanation for this
;is that the available oxygen in the headspace of the fermentation jar was exhausted and the oxidation of alcohol to.
jacid could not proceed.
Results of taste tests conducted on lao-chao samples
fermented at different degrees of aeration indicate that
I
aeration has a significant effect on the sensory quality of;
j
lao-chao.
i
Samples sealed at 24 and 36 hours were preferred,
to those sealed at 0 and 12 hours or after 36 hours.
These
l1
I
ldata also indicate that higher values for total acidity
appear to be related to increases in taste acceptability.
!
!The alcohol content reached its peak value for lao-chao
1
l1
I
sealed at 24 hours, which coincides with highest mean scores
for taste preference of lao-chao.
However, at the sealing
time of 36 hours, the alcohol content declined and the
l'
I
tast~
51
£;-~·£ e~~~-~-~;-dj~d--~·;;t-~---~h·i-~h:-~i ndl~-~-t~;··th~-;-al·~-~h~l-· ·-~;~d-~as-~~-j
I
i
i
~reference were not related.
I
Based on ·the results of sensory evaluation of lao-
1chao fermented at the various experimental temperatures,
'durations and aerations examined here, certain conclusions
regarding the chemical composition of lao-chao are apparent.
Lao-chao samples scored as very acceptable in these studies
had an alcohol content of 3.54 to 6.08 percent and a reducing sugar content of 30.49 to 33.82 percent.
The total
acidity ranged from 0.402 to 0.503 gram per 100 ml with a
pH of 3.84 to 4.06.
Further studies to more closely determine optimum
'conditions for fermentation of lao-chao would be difficult
ito conduct due to the inability of the taste panel to make
significant judgments between samples which are fermented
!under very similar conditions and which vary only slightly
lin composition.
'
Itoward
It is suggested that further studies be directed
isolation and identification of the specific esters
I
and volatile acids responsible for the characteristic aroma!
,and flavor of lao-chao.
The results of other chemical analyses on fermented
1
glutinous rice indicate that the rice starches are broken
Ii
!down to glucose and maltose which are utilized by the yeast
I
for alcoholic fermentation.
The total solid content was
i
!
I
found to change from 87.85 percent in the waxy rice to 38. OZ
!,percent
in the lao-chao.
c.,__ _____________
Part of these results are due to
i1
52
r--·-----·--------.------·--------:-----------·---------·-------,
fosses of volat1les and do not ent1rely reflect loss of
·
r•oisture during drying.
l
Data obtained from thiamin assay of the steamed
'
waxy rice and the lao-chao indicate that the fermentation
;of waxy rice results in a reduction in thiamin content.
It:
is suggested that studies be conducted to determine the
sffect of fermentation on the niacin and riboflavin content •
of the waxy rice.
It is also suggested that any examination
of the changes in nutritive value of waxy rice caused by
fermentation include ·a study of amino acid composition and
quantity before and after fermentation.
r---.. -------------1
i
REFERENCES CITED
I
!l',merine, t-1. A.
"Report on determination of pH of winesr"
·
J. Assoc. Offic. Agr. Chemists, 42:337, 1959.
----------~'
and W. V. Cruess. The Technology of Wine Making. Westport, Conn.: Avi Publishing Co., 1960,
pp ... 5-9.
, E. B. Roessler,
-----acid taste.
1. The
and C. S. Ough.
"Acids and the
effect of pH and titratable
acidity," Amer. J. Enol. Vitic., 16:29, 1965.
AOAC.
Official Methods of Analysis. 11th ed. Washington,
D.C.: Assoc.·Offic. Agr. Chemists, 1970.
Baker, G. A., C. S. Ough, and M.A. Amerine.
"Scoring vs.
comparative rating of sensory quality of wine," J.
Food Sci., 30:1055, 1965.
Brock, D. Biology of Microorganisms. Englewood Cliffs,
New Jersey: Prentice-Hall, Inc., 1970, pp. 183-185,.
212-219.
:Carlin, A. F., 0. Kempthorne, and J. Gordon.
"Some aspects
of numerical scoring in subjective evaluation of
food," Food Res., 21:273, 1956.
(Dawson, E. H., J. L. Brogdon, and S. McManus.
"Sensory
testing of differences in taste," Food Technol.,
17:1251, 1963.
.
.
II
I
I
•
·Deutsch, M. J., S. S. Sch1aff1no, and H. W. Loy.
Experlence with an extraction method for thiamin," J.
Assoc. Offic. Agr. Chemists, 43:55, 1960.
!
Faparusi, S. I.
"Sugar changes during the preparation of
burukutu beer," J. Sci. Food Agr., 21:79, 1970.
Frazier, W. C. Food Microbiology. New York:
Book Co., Inc., 1967, pp. 218-219.
McGraw-Hill
Guymon, J. F., and C. s. Ough.
"A uniform method for total
acid determination in wines," Amer. J. Enol. Vitic.
13:40, 1962.
Hesseltine, C. W.
"A millennium of fungi,. food and fermentation," Mycologia, 57:149, 1965.
53
54
..
r~T~~---·~~.-----~
,~~·~·-~-·--:-~
...
~..----~--------------"----·--:-:-----··-~~------~~~·1
iHesselt1ne, C. W., ana H. L. Wang.
Trad1t1onal fermented
foods," Biotechnol. Bioeng., 9:~7~, 1967.
.
I
1
!Houston, D. F., and G. 0. Kohler. Nutr1t1onal Propert1es
of Rice. Washington, D.C.: National Academy of
'
Scie]U;8s, 1970, pp. 8-9.
I
,Juliano, B. 0.
"Studies on some physiochemical properties
and the biosynthesis of rice starch," J. Jap. Soc.
Starch Sci., 18:35, 1970.
, L. U. Onate, and A. M. del Mundo.
"Relation of
composition, protein content and gelatinization temperature to cooking and eating qualities of
milled rice," Food Technol., 19:1006, 1965.
------s-·~tarch
Labuza, T. B.
"Effects of dehydration and storage," Food
Tech., 27:21, 1973.
Lane, J. H., and L. Eynon.
"Determination of reducing
sugars by means of Fehling solution with methylene
blue as internal indicator," J. Assoc. Offic. Agr.
Chemists, 25:99, 1942.
Larmond, E. Methods for Sensory Evaluation of Food. Canadian Dept. Agr. Bulletin 1284, 1970, pp. 8-9, 2021, 40-41.
;Laue, E. A., N.H. Ishler, and G. A. Ballman.
"Reliability
of taste testing and consumer testing methods.
I.
Fatigue in taste testing," Food Technol., 7:387,
1953.
I
:Mays, K. L. Personal Correspondence. 1973.
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!McCready, R. M., and E. A. McComb.
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Miall, L. M.
"Fermentation--the last ten years and the
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VI. Effects of temperature and
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\
1
·
55
r·-:·······-..-·---·;--·---·---·
10ugh,
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'j
I:Platt,
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..
--:·--·-------------~-----:~----·--:--:-~-----l
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"Effect of temperature on
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!
.___________
-----·- - ------- . --- _ ___j
Yang, H.
.
--· ---·· -------
--~
---------
~--
----
·------·---- ----------------·-- --·----··----------------------"---
-------·-- ----------------------------------------- ----------------------···
----------~--,
I
I
APPENDIX A
EFFECT OF WATER ADDED BEFORE STEAMING
. ON LAO·-CHAO QUALITY
56
57
EFFECT OF v1ATER ADDED BEFORE STEMHNG
ON LAO-CHAO QUALITY
Water Added per
Kilogram of Rice
(ml)
50
Quality of Lao-Chao
Dry, lacking characteristic
juiciness
100
Good liquid solid rice ratio
150
Very liquid, diluted watery
flavor
APPENDIX B
EFFECT OF STEAMING TIME ON TEXTURAL
·QUALITY OF LAO-CHAO
I
I!
.
L. . . ---·-··-------~--·---------------------·--------------------------------------------_j
58
59
·~
~
..
···-~·-·
··-"-··-···
~
- .•.. - .
~-
~----~~
--
---~--<
-
-~..-~
-~~-~ ~--·--·--··--··--------~-
---..
--~- -••"'» --~-~--~ ~'-~·~ - · - - - ...... ~~,----- ~- --~~-----'"'-<>'- -~-
"··--·1
I'
EFFECT OF STEAMING •rn1E ON TEXTURAL
QUALITY OF LAO-CHAO
Steaming Time
(minutes)
Textural Quality of Lao-Chao
10
Hard, uncooked rice grains
15
Fully cooked rice grains, rice
maintained the grain integrity
20
Rice became mushy and lost
whole grain integrity
r-~-------·-------~--------·------·-
1
APPENDIX C
GAS CHROMATOGRM1 OF STANDARD ALCOHOL SOLUTIONS
AT VARIOUS CONCENTRATIONS (% V/V)
A~ • •
60
61
• •·-~· --- ,_..., ___ ~·~-·-·~·~·- •·e~<·•-•"--·--·
-··--~~--~~-.·~--·~·....,~-u·•-·~·-~~- ~--.~.,·~·-·-·--~~~··-- ~-·~--·- -~~---~~--·--~--..-.--
·---.--..., ....,
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:
!
~·
0.2 ''lo
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I'
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0.1 °/o
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_
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., l
.
1 1
__.__~'"""",;'-I((L
180
254
217
180
.
254
217
,
i
254'
217
180
217
T J ME (SECONDS)
GAS CHROI'·iATOGRAH OF STANDARD ALCOHOL SOLUTIONS
AT VARIOUS CONCENTRATIONS (% V/V)
l
I
COMPARATIVE RATING SHEET*
Name:
Test #:
Date:
Instructions:
You will receive a reference wine which is approximately standard quality.
Assign this wine a score, remembering:
9-10 outstanding, 7-8 very acceptable, 5-6
standard (acceptable), 3-4 below acceptable, and 1-2 unacceptable. After you have
given the reference wine its score and recorded it, you will keep that wine and be
given several more wines. These will be compared to the ~eference wine using the
quality scoring system scale for the comparative rating. Record these values in the
appropriate spaces below for each column.
over-all
sweetness
alcohol
tartness
flavor
texture
Reference sample
l
l
I
I
\ *Adopted from Baker et al.
(1965).
i
L____ ...
0\
w
APPENDIX E
A
TR~DITIONAL
METHOD FOR PREPARING
LAO-CHAO IN THE HOME
I
I
_j
64
65
A TRADITIONAL METHOD FOR PREPARING
LAO-CHAO IN THE HOME
Wash and clean 2 pounds of rice and soak in cold
water {3 inches above the rice) overnight.
Roll 1/5 cake of starter with a rolling pin to
grind up.
Put steamer on boiling water; put wet white cloth
in steamer as liner.
Pour rice in steamer and steam at high flame for
one hour.
Add three spoonfuls of boiling water and let steam
for 20 minutes more.
Pour rice in bamboo racks, run cold water through
until grains are separated, and let the rice drain dry.
Add starter {wine medicine) and stir.
Save some
starter.
Have a large bowl ready; transfer rice hand by hand'
:to bowl and sprinkle with remaining wine medicine.
i
;
Cover bowl with saran wrap and wrap with thread.
Cover bowl with a sweater.
Leave in a warm place
three to four days.
When the hole fills with liquid and it smells good,·
'it is ready.
Store in the refrigerator.