PAK. J. FOOD SCI., 24(4), 2014: 211-217
ISSN: 2226-5899
Lactic acid bacteria in sourdough fermentation; a safe approach for food preservation
Muhammad Saeed, Iqra Yasmin*, Muhammad Issa Khan, Imran Pasha, Moazzam Rafiq Khan, Asim Shabbir and
Wahab Ali Khan
National Institute Of Food Science & Technology, University of Agriculture Faisalabad-Pakistan
*Corresponding Author: [email protected]
ABSTRACT
Bacterial starters have been developed for various fermented cereal products to improve their sensory and
technological qualities. The earliest production of fermented foods was based on spontaneous fermentation due to
the development of the microflora naturally present in the raw material. The quality of the end product was
dependent on the microbial load and spectrum of the raw material. The direct addition of selected starter cultures to
raw materials has been a breakthrough in the processing of fermented foods, resulting in a high degree of control
over the fermentation process and standardization of the end product. The latter can contribute to the microbial
safety or offer one or more organoleptic, technological, nutritional, or health advantages. Examples are lactic acid
bacteria that produce antimicrobial substances, sugar polymers, sweeteners, aromatic compounds, vitamins,
enzymes, or that have probiotic properties.
Key words: Fermentation, sourdough, bread, lactic acid bacteria
INTRODUCTION
Food fermentation has been used for centuries as a
method to preserve perishable food products.
Fermentation
was
invented
long
before
microorganisms were discovered, and therefore the
process seemed mysterious. The need for an
inoculum was understood and usually satisfied by
keeping a sample from the previous production. This
procedure is still in use for propagation of sourdough.
With the discovery of microorganisms, it became
possible to improve the products and the fermentation
processes by using isolated and well characterized
cultures. Lactic acid bacteria are widely used in the
production of fermented food, and they constitute the
majority of the volume and the value of the
commercial starter cultures. The primary activity of
the culture in food fermentation is to convert
carbohydrates to desired metabolites as alcohol,
acetic acid, lactic acid or CO2. Alcohol and organic
acids are good natural preservatives, but also
appreciated in their own right in the fermented
product. The CO2 produced by some cultures
contributes the gas needed to rise the dough. The
cultures used in food fermentations are, however,
also contributing by ‘‘secondary’’ reactions to the
formation of flavor and texture. This secondary
contribution can often be responsible for the
difference between products of different brands, and
thereby contribute significantly to the value of the
product. Spontaneous sourdough fermentation is one
of the oldest cereal fermentations known in mankind.
Its main function was to leaven the dough to produce
a more gaseous dough piece and as such a more
aerated bread. In a later stage, beer yeast was used for
dough leavening. Currently, researchers are still
further elucidating the wide strain variety and the
strain interactions using state-of-the-art analytical
methods (Kulp and Lorenz, 2003).
Microflora of sourdough
Lactic Acid Bacteria (LAB) are constituted of a
heterogeneous group of Gram-positive bacteria with
a strictly fermentative metabolism from which lactic
acid is the key metabolite. The natural habitat of
these organisms includes humans, animals and plants.
Their long history of safe use (Holzapfel et al.,
2001),commonly referred to as the GRAS (Generally
Recognized As Safe) status, combined with a variety
of interesting metabolic characteristics have led to a
wide range of industrial applications, i.e., Flavor,
texture and preservative qualities of many fermented
foods such as cheese, yoghurt, sausages, sourdough
breads and silage (Wood, 1998). Genera of LAB
Pakistan Journal of Food Sciences (2014), Volume 24, Issue 4, Page(s): 211-217
211
PAK. J. FOOD SCI., 24(4), 2014: 211-217
ISSN: 2226-5899
identified from sourdoughs are Lactobacillus,
Leuconostoc, Pediococcus and Streptococcus, but the
majority belongs to the genus Lactobacillus. The
content of lactic and acetic acid is considered to be an
important factor in the overall flavour perception
during bread consumption. Homofermentative LAB
are able to convert hexoses almost completely into
lactic acid (>85%), whereas heterofermentative LAB
degrade hexoses into lactic acid, acetic acid/ethanol,
and CO2. Besides the type of starter culture, also the
temperature influences the ratio of lactic acid to
acetic
acid
(Spicher
and
Rabe,
1980).
Heterofermentative LAB also produce both, lactic
and acetic acid, from pentoses (Hammes and Vogel,
1995). Several species of yeasts are also found in
sourdoughs; Saccharomyces cerevisiae is frequently
present or added. In particular, S. exiguous,
Torulopsis holmii, Candida krusei, Pichia
norvegensis and Hansenula anomala are generally
found in yeast genera from the sourdoughs (Gobbetti
et al., 1994).
Proteolysis
Lactic acid bacteria contribute to overall proteolysis
during sourdough fermentation by creating optimum
conditions for activity of cereal proteinases.
Furthermore, lactic acid bacteria with high
proteolytic activity contribute to the hydrolysis of
wheat proteins in a strain-specific manner (Di Gagno
et al., 2003). Generally, sourdough fermentation with
lactic acid bacteria results in an increase of amino
acid concentrations during fermentation, whereas
dough fermentation with yeast reduces the
concentration of free amino acids. The level of
individual amino acids in wheat doughs depend on
the pH level of the dough, fermentation time and the
consumption of amino acids by the fermentative
microflora (Thiele et al., 2002). In wheat sourdoughs,
Lb. brevis linderi, Lb. sanfranciscencis, Lb. brevis
and Lb. plantarum have been reported to increase the
levels of aliphatic, dicarboxylic, and hydroxyl amino
acids (Collar et al., 1991, Gobbetti et al. 1994). The
yeasts S. cerevisiae and S. exiguus decrease the total
level of amino acid in a similar way, the latter being
more effective in amino acid removal from the dough
(Spicher and Nierle 1984). The combination of yeast
and lactic acid bacteria shows intermediate values for
total amino acid levels. The estimated content of free
peptides of sourdough with Lb. brevis or Lb.
plantarum is lower than the estimated amount of
amino acids. Reactivity of peptides is higher during
fermentation in comparison to amino acids, and both
of the above-mentioned strains reduce the content of
peptides during fermentation, especially if S.
cerevisiae is associated with these LAB (Mascaros et
al., 1994). The proteolytic activity of wheat
sourdough depends on the microbial starter and the
processing conditions. For wheat sours, the extraction
rate of flour and the fermentation temperature have
been reported to be the main factors with positive
influence on the level of free amino acids and on the
accumulation of hydrophobic and basic amino acids.
Dough yield has also been reported to influence the
level of amino acids; soft doughs contain a lower
amount of amino acids (Martinez-Anaya 2003).
Starch digestibility
Food-related diseases, such as obesity and type 2
diabetes, are becoming a tremendous threat to the
health. White wheat bread, most rice products, potato
and many breakfast cereals are examples of common
starchy foods producing high glycaemic responses.
The GI of food is a ranking of foods based on their
immediate effect on blood glucose levels (FosterPowell et al., 2002). Sourdough has great potential to
modify the macromolecules in the dough, the most
well known examples being the ability of sourdoughs
to reduce digestibility of starch (Liljeberg et al.,
1995; Ostman, Nilsson et al., 2002). Organic acids
also play a role in the postprandial glyceamic
responses. They may be present in the raw foods,
produced upon fermentation processing (such as
sourdough fermentation) or added, as in the case of
pickled food. Certain acids, such as acetic, propionic,
and lactic acid have the ability to lower the
postprandial blood glucose and insulin responses,
when included in bread meals. In the case of acetic
acid added to bread meals, both Brighenti et al.
(1995) and Liljeberg and Bjorck (1998) have shown
blood glucose lowering effects. The presence of
lactic acid in bread, either added or formed during
sourdough fermentation, has also been reported to
reduce acute glyceamic and/or insulinaemic
responses (Liljeberg et al., 1995). However, the
lowering of glyceamic and insulinaemic responses of
breads with added lactic acid could not be attributed
to a reduced gastric emptying rate (Liljeberg and
Bjorck, 1996). The role of a reduced rate of starch
digestion in lowering glyceamia in bread containing
lactic acid was confirmed by Ostman et al. (2002).
Furthermore, their work suggested that the presence
of lactic acid during heat treatment promotes
Pakistan Journal of Food Sciences (2014), Volume 24, Issue 4, Page(s): 211-217
212
PAK. J. FOOD SCI., 24(4), 2014: 211-217
ISSN: 2226-5899
interactions between starch and gluten, hence
reducing starch bioavailability.
Volatile compounds
The generation of volatiles in sourdoughs is clearly
influenced by the activity of the LAB and the
sourdough yeasts. Generally, LAB are mostly
responsible
for
the
acidification.
Both
microorganisms are able to liberate aroma precursors,
such as free amino acids, and it has been previously
shown that the concentrations of free amino acids are
increased
significantly
during
sourdough
fermentation (Hansen et al., 1989; Kratochvil and
Holas, 1983). The key degradation reaction of amino
acids during dough fermentation is the Ehrlich
pathway leading to aldehydes or the corresponding
alcohols, respectively (Schieberle, 1996). The content
of lactic and acetic acid is considered to be an
important factor in the overall flavour perception
during bread consumption. Homofermentative LAB
are able to convert hexoses almost completely into
lactic acid (≥ 85%), whereas heterofermentative LAB
degrade hexoses into lactic acid, acetic acid/ethanol,
and CO2. Besides the type of starter culture, also the
temperature influences the ratio of lactic acid to
acetic
acid
(Spicher
and
Rabe,
1980).
Heterofermentative LAB also produce both, lactic
and acetic acid, from pentoses (Hammes and Vogel,
1995). In addition, the flour type used influences the
amounts of both acids formed during fermentation,
with fermented whole meal flour being higher
compared to wheat flour (Gobbetti et al., 1995;
Hansen and Hansen, 1994; Lund et al., 1989). The
production of acids in sourdoughs also increased with
increasing temperature due to a higher production of
lactic acid, whereas the production of acetic acid was
not influenced (Gobbetti et al., 1995; Hansen et al.,
1989). The production of acetic acid in sourdoughs
can be increased using heterofermentative cultures
and added fructose as hydrogen acceptor (Gobbetti et
al., 1995; Martinez-Anaya et al., 1994).
The LAB can also influence the production of certain
volatile metabolites, e.g. the content of ethyl acetate
was higher in firm wheat sourdoughs (Damiani et al.,
1996) fermented with heterofermentative LAB
compared
to
sourdoughs
fermented
with
homofermentative LAB. On the other hand, the
production of ethyl acetate was higher in fluid
sourdoughs fermented with homofermentative LAB
compared to firm sourdoughs. The flour type also
influenced the content of ethyl acetate, which was
higher in wheat sourdough made with high extraction
flour and heterofermentative cultures compared to
sourdough made with low extraction flour (Hansen
and Hansen 1994). Also, the formation of the
carbonyl compounds might be influenced by the
sourdough microflora (Lund et al., 1989). As an
example, the content of hexanal was very high in
sourdoughs fermented with a noncommercial
homofermentative culture. The content of diacetyl
was higher in sourdoughs manufactured with
homofermentative compared to heterofermentative
cultures (Damiani et al., 1996; Hansen et al., 1989;
Lund et al., 1989), and was also higher in the
corresponding bread (Hansen & Hansen, 1996).
Saccharomyces cerevisiae is the most frequent yeast
species isolated from sourdough; however, other
subspecies of Saccharomyces, Candida, Pichia and
Hansenula have occasionally been isolated
(Mantynen et al., 1999). Addition of yeasts
(Saccharomyces and Hansenula genus) resulted in
increased production of alcohols, esters and some
carbonyl compounds as compared to sourdoughs
without added yeast (Damiani et al., 1996; Hansen
and Hansen, 1994). Especially, the amounts of
ethanol, methylpropanol, 2- and 3-methylbutanol as
well as ethyl acetate and diacetyl were considerably
increased in sourdoughs with added yeast.
Mineral bioavailability
Wholemeal cereals are an important source of
minerals such as K, P, Mg, or Zn, but unfortunately
mineral utilization is limited by the presence of
phytic acid (Lopez and Demigne, 1998). Wheat
contains about 2–58 mg/g phytic acid, which is
localised in the aleurone layer of the kernel as the
magnesium–potassium salt (Garcia et al., 1999).
Phytic acid is highly charged with six phosphate
groups, and it forms insoluble complexes with dietary
cations, thus hindering mineral bioavailability (Lopez
et al., 1998). Reduction of phytic acid content during
bread making depends on phytase action. As with
other enzymatic reactions, various factors contribute
to phytate degradation in doughs, including phytase
activity, particle size of the meals, pH, temperature,
water content, and fermentation time (Fretzdorff and
Brummer, 1992). Phytate-degrading enzymes exist in
cereals, yeast and lactic acid bacteria isolated from
sourdoughs (Lopez et al., 2000; Shirai et al., 1994;
Turk et al., 2000). Reduction of phytic acid content
in different bread types may vary between 13 and
Pakistan Journal of Food Sciences (2014), Volume 24, Issue 4, Page(s): 211-217
213
PAK. J. FOOD SCI., 24(4), 2014: 211-217
ISSN: 2226-5899
100%, the highest levels of phytic acid obtained with
unleavened breads (Lopez et al., 2001). In general,
low pH favours degradation of phytic acid, optimal
pH value for hydrolysis being 4.5 in wheat doughs
according to Fretzdorff and Brummer (1992). Thus,
use of sourdoughs or acidified sponges can be
adjusted to improve mineral bioavailability by
increasing phytic acid hydrolysis. In the recent work
of Lopez et al. (2001), the influence of yeast
fermentation, and sourdough fermentation without
and with yeast, were compared on degradation of
phytic acid. Their results show that both types of
sourdough fermentation reduces phytic acid content
up to 62%, whereas conventional yeast fermentation
reduced it only by 38%. Furthermore, acidification
formed during sourdough fermentation also increased
magnesium and phosphorus solubility with 20–30%.
This effect was even more pronounced if the bran
fraction of wheat (rich in phytic acid) was fermented
with lactic acid bacteria; the percentage of phytic
acid breakdown was near 90% (Lopez et al., 2001)
Inhibitory role
The antimicrobial activity of LAB is due to the
production of organic acids (in particular, lactic acid
and acetic acid), carbon dioxide, ethanol, hydrogen
peroxide, and diacetyl. The inhibition, however, can
also be caused by bacteriocins that are low
molecular-mass peptides, or proteins, with a
bactericidal or bacteriostatic mode of action (De
Vuyst and Vandamme, 1994). The inhibitory
spectrum of some bacteriocins also includes food
spoilage
and/or
food
borne
pathogenic
microorganisms. Those bacteriocins may thus
contribute to the competitiveness of the producing
strain in the fermented food ecosystem (Caplice and
Fitzgerald, 1999). The use of bacteriocin producing
LAB starter cultures or co-cultures in the
fermentation of cereals is currently under
investigation. Even under stringent conditions of
production, bread can become contaminated with
moulds or bacteria such as Bacillus subtilis and
clostridia that subsequently grow and spoil the
product. To avoid outgrowth of these contaminating
microorganisms, addition of organic acids or
approximately 15% sourdough to the common dough
recipe is performed (Voysey and Hammond, 1993).
Sourdough addition is the most promising procedure
to preserve bread from spoilage, since it is in
agreement with the consumer demand for natural and
additive-free food products (Rosenquist and Hansen,
1998).
In general, LAB bacteriocins tend to be active against
a wide range of mostly closely related Gram-positive
bacteria (Jack et al., 1995). Gram negative bacteria
are generally insensitive to bacteriocins from LAB
strains because of their outer membrane providing
them with a permeability barrier. The sensitivity of
Gram-negative bacteria can be increased by sublethal
injury of the cells, using for instance high hydrostatic
pressure and pulsed electric field as nonthermal
methods of preservation (Caplice and Fitzgerald,
1999). In addition, food grade chelating agents such
as ethylene-diamine-tetra-acetic acid (EDTA) and
citrate can be used to bind magnesium ions in the
lipopolysaccharide outer layer of Gram-negative
bacteria to render them susceptible to bacteriocins
(Holzapfel et al., 1995). Yeasts and fungi are not
inhibited by LAB bacteriocins (De Vuyst and
Vandamme, 1994b). The use of LAB bacteriocins or
bacteriocin-producing sourdough LAB strains that
are active against Bacillus species can be
advantageous, since these species can cause spoilage
of bread by rope formation, and may constitute a
health risk. Rope formation occurs principally in
wheat breads that have not been acidified, or in
breads with high concentrations of sugar, fat, or fruits
(Beuchat, 1997). The acidification and production of
acetic acid by heterofermentative lactobacilli in
sourdough delay growth of B. subtilis in bread,
provided that the raw material and technological prefermentation conditions are optimal (Ganzle, 1998).
Conclusions
Sourdough has proven useful in improving dough
properties, bread texture and flavor, delays the staling
process and prevents bread from spoilage. Texture
improvement is especially important in production of
gluten-free bread, where the demand for good texture
is especially challenging. Specific modifications in
baked product texture can be achieved by
development of new sourdough cultures, and by
optimizing acidity and interactions with grain
components.
The
production
of
prebiotic
oligosaccharides by sourdough lactic acid bacteria
also is an interesting possibility. Sourdough has also
shown useful in production of breads with slow
starch digestibility and hence low glyceamic
responses. With the knowledge about the genetics
Pakistan Journal of Food Sciences (2014), Volume 24, Issue 4, Page(s): 211-217
214
PAK. J. FOOD SCI., 24(4), 2014: 211-217
ISSN: 2226-5899
and the physiology of lactic acid bacteria, it is
possible to engineer starters for a variety of purposes
where a suitable starter culture cannot easily be found
in nature. More applications are expected to fully
utilize the potential of sourdough in this respect.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
Beuchat, L.R. and J.H. Ryu. 1997. Produce
handling and processing practices. Emerging
Infectious Diseases. 3: 459-465.
Brighenti, F., G. Castellani, L. Benini, M.
Casiraghi, E. Leopardi, R. Crovetti and G.
Testolin. 1995. Effect of neutralized and
native vinegar on blood glucose and acetate
responses to a mixed meal in healthy
subjects. Eur. J. Clin. Nutr. 64: 242-247.
Caplice, E. and G.F Fitzgerald. 1999. Food
fermentations: role of microorganisms in
food production and preservation. Int. J.
Food Microbiol. 50: 131-149.
Collar, C., J. Mascaros, J.A. Prieto and B. de
Barber. 1991. Changes in free amino acids
during fermentation of wheat doughs started
with pure culture of lactic acid bacteria.
Cereal Chem. 68(1): 66-72.
Damiani, P., M. Gobbetti, L. Cossignani, A.
Corsetti, M.S. Simonetti and J. Rossi. 1996.
The sourdough microflora. Characterization
of hetero- and homofermentative lactic acid
bacteria, yeasts and their interactions on the
basis of the volatile compounds produced.
Lebensm. Wiss. U. Technol. 29: 63-70.
De Vuyst, L. and E.J. Vandamme. 1994.
Bacteriocins of Lactic Acid Bacteria:
Microbiology, Genetics and Applications.
Blackie Academic and Professional,
London, 536 pp.
Di Cagno, R., M. De Angelis, A. Corsetti, P.
Lavermicocca, P. Arnault, P. Tossut, G.
Gallo, and M. Gobbetti. 2003. Interactions
between sourdough lactic acid bacteria and
exogenous enzymes: effects on the
microbial kinetics of acidification and dough
textural properties. Food Microbiol. 20: 6775.
Foster-Powell, K., S. Holt and J. BrandMiller. 2002. International table of glycemic
index and glycemic load values. Am. J.
Clinical Nutri. 76: 5-56.
Fretzdorff. B., and J.M. Brümmer. 1992.
Reduction
of
phytic
acid
during
breadmaking of whole-meal breads. Cereal
Chem. 69: 266-270.
10. Ganzle, M.G. 1998. Useful Properties of
Lactobacilli for Application as Protective
Cultures in Food. PhD thesis, University of
Hohenheim, Germany. 160 pp.
11. Garcia, E.R.M., E. Guerra-Hernandez and B.
Garcia-Villanova. 1999. Phytci acid content
in milled cereal products and breads. Food
Res. Int. 32: 217-221.
12. Gobbetti, M., A. Corsetti and J. Rossi. 1994.
The sourdough microflora. Interactions
between lactic acid bacteria and yeasts:
metabolism of amino acids. J. Microbiol.
Biotechnol. 10: 275-279.
13. Gobbetti, M., M.S. Simonetti, A. Corsetti, F.
Santinelli, J. Rossi and P. Damiani. 1995.
Volatile compound and organic acid
productions by mixed wheat sour dough
starters:
influence
of
fermentation
parameters and dynamics during baking.
Food Microbiol. 12: 497-507.
14. Hammes, W.P. and R.F. Vogel. 1995. The
genus of Lactobacillus. In Wood, B. and W.
Holzapfel. (Eds.). The genera of lactic acid
bacteria. London: Blackie. 9-54.
15. Hansen, A. and B. Hansen. 1996. Flavour of
sourdough wheat bread crumb. Zeitschrift
fuer Lebensmitteluntersuchung und –
Forschung. 202: 244-249.
16. Hansen, A., B. Lund and M.J. Lewis. 1989.
Flavor of sourdough rye bread crumb.
Lebensmittelwissenschaft and Technologie.
22: 141-144.
17. Hansen, B. and A. Hansen. 1994. Volatile
compounds in wheat sourdoughs produced
by lactic acid bacteria and sourdough yeasts.
Zeitchcrift für Lebensmittel Unterschung
und Forschung. 198: 202-209.
18. Holzapfel, W.H., P. Haberer, R. Geisen, J.
Bjorkroth, and U. Schillinger. 2001.
Taxonomy and important features of
probiotic microorganisms in food and
nutrition. Am. J. Clinical Nutri. 73: 365-373.
19. Holzapfel, W.H., R. Geisen, U. Schillinger.
1995. Biological preservation of foods with
reference to protective cultures, bacteriocins
and food-grade enzymes. Int. J. Food
Microbiol. 24: 343-362. Beuchat, L.R. 1997.
Traditional fermented foods. In: Doyle, M.P.
20. Jack, R.W., J.R. Tagg and B. Ray. 1995.
Pakistan Journal of Food Sciences (2014), Volume 24, Issue 4, Page(s): 211-217
215
PAK. J. FOOD SCI., 24(4), 2014: 211-217
ISSN: 2226-5899
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
Bacteriocins of Gram-positive bacteria.
Microbiol. Rev. 59(2): 171-200.
Kratochvil, J., & Holas, J. (1983). Study of
proteolytic processes, Rye sour. Develop. in
food sci. 5: 791-798.
Kulp, K. 2003. Baker’s yeast and sourdough
technologies in the production of U.S Bread
Products. In: Kulp, K. and K. Lorenz. (eds.).
Handbook of dough fermentations. Marcel
Dekker Inc., New York, pp. 97-143.
Liljeberg, H. and I. Bjorck. 1996. Delayed
gastric emptying rate as a potential
mechanism for lowered glycemia after
eating sourdough bread: Studies in humans
and rats using test products with added
organic acids or an organic salt. Am. J.
Clinical Nutri. 64: 883-893.
Liljeberg, H. and I. Bjorck. 1998. Delayed
gastric emptying rate may explain improved
glycaemia in healthy subjects to a starchy
meal with added vinegar. Europ. J. Clinical
Nutri. 52: 368-371.
Liljeberg, H., C. Lonner and I. Bjorck. 1995.
Sourdough fermentation or addition of
organic acids or corresponding salts to bread
improves nutritional properties of starch in
healthy humans. J. Nutri. 125: 1503-1511.
Lopez, H., A. Ouvry, E. Bervas, C. Guy, A.
Messanger, G. Demigne and C. Remesy.
2000. Strains of lactic acid bacteria isolated
from sourdoughs degrade phytic acid and
improve calcium and magnesium solubility
from whole wheat flours. J. Agric. Food
Chem. 48: 2281-2285.
Lopez, H., C. Remesy, and C. Demigne.
1998. Phytic acid: a useful compound? Med.
Nutri. 34:135-143.
Lopez, H., V. Krspine, C. Guy, A.
Messager, C. Demigne and C. Remesy.
2001. Prolonged fermentation of whole
wheat sourdough reduces phytate level and
increases soluble magnesium. J. Agri. Food
chem. 49: 2657-2662.
Lund, B., A. Hansen and M.J. Lewis. 1989.
The influence of dough yield on
acidification and production of volatiles in
sourdoughs. Lebensmittel-Wissenschaft &
Technologie. 22: 150-153.
Mantynen, V.H., M. Korhola, H.
Gudmundsson, H. Turakainen, G.A.
Alfredsson, H. Salovaara and K. Lindstrom.
1999. A polyphasic study on the taxonomic
31.
32.
33.
34.
35.
36.
37.
38.
position of industrial sour dough yeasts.
Systematic and Applied Microbiol. 22: 8796.
Martinez-Anaya, M. A., M.L. Llin, M.P.
Macias and C. Collar. 1994. Regulation of
acetic acid production by homo- and
heterofermentative lactobacilli inwholewheat
sour-doughs.
Zeitschrift
fuer
Lebensmitteluntersuchung und –forschung.
199: 186-190.
Martnez-Anaya, M.A. 2003. Associations
and interactions of micro-organisms in
dough fermentations: effects on dough and
bread characteristics. In: Kulp, K. and K.
Lorenz. (eds.). Handbook of dough
fermentations. Marcel Dekker Inc, New
York, pp. 63-195.
Mascaros, A.F., C.S. Martinez, and C.
Collar. 1994. Metabolism of yeasts and
lactic acid bacteria during dough
fermentation
relating
functional
characteristics of fermented doughs. Revista
Espanola de Ciencia y Tecnologia de
Alimentos. 34(6): 623-642.
Ostman E., M. Nilsson, H. LiljebergElmstahl, G. Molin and I. Bjorck. 2002. On
the effect of lactic acid on blood glucose and
insulin responses to cereal products:
mechanistic studies in healthy subjects and
in vitro. J. Cereal Sci. 36: 339-346.
Rosenquist, H. and D. Hansen. 1998. The
antimicro- bial efect of organic acids,
sourdough and nisin against Bacillus subtilis
and Bacillus licheniformis isolated from
wheat bread. J. Appl. Microbiol. 85: 621631.
Schieberle, P. 1996. Intense aroma
compounds—useful tools to monitor the
influence of processing and storage on bread
aroma. Advances in Food Science (CMTL).
18: 237-244.
Shirai, K., S. Revah-Molsey, M. GarciaGaribay and V. Marshall. 1994. Ability of
some strains of lactic acid bacteria to
degrade phytic acid. Letters in Applied
Microbiology. 19: 366-369.
Spicher, G. and W. Nierle. 1984. Microflora
of sourdough. XVIII. Proteolytic ability of
sourdough lactic acid bacteria. Zeitchcrift
für
Lebensmittel
Unterschung
und
Forschung. 178: 389-392.
Pakistan Journal of Food Sciences (2014), Volume 24, Issue 4, Page(s): 211-217
216
PAK. J. FOOD SCI., 24(4), 2014: 211-217
ISSN: 2226-5899
39. Spicher, G., and E. Rabe. 1980. Die
mikroflora des sauerteiges. XI. Mitteilung.
Der Einfluss der Temperatur auf die
Lactat/Acetatbildung
in
mit
heterofermentativen
Milchsaurebakterien
angestellten Sauerteigen. Zeitschrift fuer
Lebensmitteluntersuchung und –forschung.
171: 437-442.
40. Spicher, G., and H. Stephan. 1999.
Handbuch sauerteig, biologie, biochemie,
technologie. (5th ed.). Hamburg: Behr’s
Verlag.
41. Thiele, C., G. Ganzle and R.F. Vogel. 2002.
Contribution of sourdough lactobacilli,
yeast, and cereal enzymes to the generation
of amino acids in dough relevant for bread
flavour. Cereal Chem. 79: 45-51.
42. Turk, M., A.S. Sandberg, N. Carlsson and T.
Andlid. 2000. Inositol hexaphosphate
hydrolysis by baker’s yeast. Capacity,
kinetics and degradation products. J. Agric.
Food Chem. 48: 953-954.
43. Voysey, P.A. and J.C. Hammond. 1993.
Reduced-additive breadmaking technology.
In: Smith, J. (Ed.). Technology of ReducedAdditive Foods. Blackie Academic and
Professional, London, pp. 80-94.
44. Wood, B.J.B., 1998. Microbiology of
fermented foods. Blackie Academic &
Professional, London.
Pakistan Journal of Food Sciences (2014), Volume 24, Issue 4, Page(s): 211-217
217