86.
CHENlCAL A N D P H Y S I C A L FACTORS I N V O L V f D IN
FRANKFURTER P E E L A B I L I T Y
J.
A.
CARPENTER and R .
L.
SAFFLE
IMlRODUCT ION
Since the advent of the skinless frank, new problems have a r i s e n
i n t h e sausage f i e l d . One of t h e most serious t o t h e processor i s the removal of the cellulose casing o r "peeling" of the process frank. Tauber
(1958) and Wilson (1960) reported t h a t two of the main f a c t o r s r e l a t e d t o
peeling of franks a r e surface formation o r coagulation of the soluble prot e i n by heat t o form a "skin" and the moisture relationship between the
surface of the f r a n k f u r t e r and the casing. Although surface formation and
moisture relationships of t h e frankf'urter a r e undoubtedly important factors
in peeling, neither of' the above two autkors presented any research information t o substantiate t h e i r reports, nor was any research information found
i n the l i t e r a t u r e concerning t h i s problem.
To investigate t h i s problem, a study was conducted t o determine
the chemical composition of t h e surf-ace and the center of a skinless frank
as affected by the smokehouse temperature, t w o d i f f e r e n t types o f fat, the
addition of collagen and the relationship of smokehouse temperature and the
diameter of casing t o the formation of a surface skin.
Further study was made t o determine the e f f e c t s of humidity, t e m perature, and types and l e v e l s of corn-syrup s o l i d s on peeling characteri s t i c s of frankfurters. These studies were conducted both i n t h e laboratory
and i n a sausage plant under a c t u a l plant conditions.
The same basic formula was used f o r a l l of t h e various treatments
conducted and i s reported by Saffle e t al . (1963). All batches were handled
in t h e same manner except where t h e treatment was involved.
The e f f e c t of two extremes i n smokehouse temperatures on the
migration of chemical constituents was studied by placing one-half of each
batch i n t o a smokehouse a t 1300F and the other half of the batch i n t o a
smokehouse a t 170°F f o r 2 hours. After showering, samples 3 mm i n diameter
from the center and 1 m i n thickness from t h e surface of t h e f r a n k f u r t e r
were removed f o r analysis. Protein, s a l t , moisture, sugar and f a t analyses
were conducted on both surface and center s m p l e s .
The e f f e c t of type of f a t
WE;
studied
by s u b s t i t u t i n g beef kidney
knob f a t f o r pork f a t and processing a t 130°F i n i t i a l temperature and r a i s i n g
t h e temperature 10 degrees every 15 minutes u n t i l a smokehouse temperature
of 180°F was obtained. Casing s i z e was investigated by s t u f f i n g i n t o 21 mm
casings and 30 m casings and processing a t both 130°F and 180°F i n i t i a l
temperature.
The e f f e c t of collagen on peeling ease ms determined by the
87.
addition of 1055 of t h e meat block a s pork skin emulsion and processing i n
2 1 mm casings a t the two d i f f e r e n t i n i t i a l temperatures, 130°F and 180°F.
All frankfurters were processed t o 15S°F i n t e r n a l temperature i n the conventional manner.
The same basic formula and procedures were used t o study the
e f f e c t s of corn-syrup s o l i d s on peeling ease except t h a t corn-syrup s o l i d s
hzving dextrose equivalents (DOE,) of 30.2, 52 and 7 1 were added a t t h e rate
of 0, 1, 2, and 3 percent of t h e meat block. A second s e r i e s of s t u d i e s
were made concerning corn-syrup s o l i d s except only t h e 5 2 and 7 1 D,E.'s
were used. Dextrose equivalent is defined a s a measure of the reducing
sugar content of a sweetener calculated a s dextrose and expressed a s a
percentage of t h e t o t a l dry substance.
The same basic formula and procedures were used t o study the e f f e c t
of four d i f f e r e n t l e v e l s of r e l a t i v e humidity (27, 52, 74, 88$) and 40, 50,
and 60°F temperature l e v e l s on p e e l a b i l i t y of f r a W r t e r s .
A l l of the frawere peeled by a t r a i n e d panel and scored on a
hedonic scale of 11 points ranging from one (extremely d i f f i c u l t ) t o 11
(extremely easy). The frankfurters were held f o r a t l e a s t 6 hours but not
more than 1 8 hours in a constant controlled humidity-temperature cabinet
before each peeling panel conducted. Unless otherwise specified the tempera t u r e was 50°F and the r e l a t i v e humidity was 88$. The minimum degrees of
freedom f o r any one s e r i e s of panels were 287.
Plant t e s t s were conducted under a c t u a l plant condition.; with
d i f f e r e n t l e v e l s and amounts of corn-spxp solids. Results were expressed
a s t h e percent of those which were peeled by a Wdel 5GC Ty peeler.
-
R E W S AMD DISCUSSION
Results showed that more protein and f a t were found a t t h e surface
of t h e franks than f r o m t h e center sample in both 13OoF and 170°F treatments
(Ta31e 1). These differences were highly s i g n i f i c a n t . Soluble protein did
migrate t o t h e furface and was deposited a s moisture evaporated, forming a
smooth s k i n needed f o r good peeling. There was more difference i n surface
and center samples f r o m t h e 130'F treatment than from the 170°F treatment,
This may have been due t o a higher i n t e r n a l temperature i n -the 170° which
coagulated t h e soluble protein before it could migrate t o the surface t o foxm
a smooth skin. It i s postulated t h a t a smoother surface and b e t t e r peeling
i s aided by s t a r t i n g t h e processing a t lower temperatures.
Increasing the amount of f a t , even t o the point of "greasing out"
o r forming "whitecaps" will improve the peeling of franks but r e s u l t s i n a
greasy, uneconomical product. The s u b s t i t u t i o n of a higher melting point,
l e s s unsaturated f a t , beef kidney knob, f o r pork f a t i n t h e f o m l a resulted
i n l e s s f a t migration t o t h e surface of the frank during processing. However, franks w i t h pork f a t had higher peeling scores than franks with beef
f a t probably due, i n part, t o t h e g r e a t e r amount of f a t on the surface. This
e f f e c t is shown by a comparison of treatments 3 and 5 (Table 2 ) .
Treatments 3 and 6 (Table 2) show t h e e f f e c t of i n i t i a l processing
temperatures on t h e peeling ease of the frank. The lower s t a r t i n g texnperature
88
.
of treatment 3 allowed time for a g r e a t e r migration of soluble protein t o
t h e surface, thus c r e a t i q a smoother surface and aiding p e e l a b i l i t y of the
f rankf'urter.
The e f f e c t s of casing s i z e on peeling i s shown by comparison of
treatments 1 and 4 (Table Z), The difference of the mean peeling scores
w86 s i g n i f i c a n t and cannot be explained by only surface formation due t o
soluble protein migration a s the low temperature frankf'urter (treatment 4)
should have a t h i c k e r skin. There is no evidence t h a t a surface skin can
be too thick as f a r as peeling ease i s concerned. A possible explanation
might be that a t a higher temperature more f a t migrates t o the surface due
t o melting point c h a r a c t e r i s t i c s , thus a i a n g peeling.
A comparison of treatments 2 and 7 (Table 2) shows that franks
with pork skins added a t a r a t e of 105 of the meat block and processed a t
an i n i t i a l temperature of 180°F have g r e a t e r peelizq ease than those processed
a t 130°F i n i t i a l temperature. This may be p a r t i a l l y explained by the format i o n of a glue-like material from collagen, heat, and moisture i n t h e franks
processed a t a lower temperature which would not form as completely i n t h e
franks processed a t higher temperatures due t o i n s u f f i c i e n t time, Also,
franks processed a t higher temperaturns may have prevented the migration of
collagen t o the suzface where i t s concentration could have affected t h e
peeling of the franks. The reasons f o r these differences a r e not known and
warrant f u r t h e r study.
An analysis of the s a l t content o f surface and center samples of
frankf'urters before and a f t e r showering revealed that showering leaches t h e
s a l t f r o m the surface, thus r e s u l t i n g i n loner salt concentration (dry w t .
b a s i s ) on the surface than i n the center of the frank (Table 1).
The r e s u l t s a s shown in Table 3 revealed t h a t peeling ease increased as the percent r e l a t i v e humidity increased for each temperature, It
is postulated that one of t h e f a c t o r s necessary f o r good peeling is a l a y e r
of moisture between t h e frankfUrter and t h e casing. This lack of moisture
Table 1. Chemical analysis (dry weight b a s i s ) of frankfurthers
heat processed a t 13OoF and 17OoF.
Protein
Salt
Fat
Sugar
13OoFc
130OFS
17OoFc
1709s
45 86
46.79
38.60
39.23
6.16
3.83
5.58
3.03
46.28
47.38
54.46
56.54
1.70
2.00
1.36
.
C
center sample
S
surface simple
1.20
89
Table 2.
Treatment
Number
-
Duncan's W t i p l e Range Test f o r mean peeling panel
scores as affected by types of f a t , pork skins,
size and processing temperature.
cas-
m e of
Fat
_ _
$ of Pork
Skins
Initial
Casing
Temp. of
Mean Peeling
Size (mm) 3nokehouse Panel Scores
~
1
Pork
0
30
180
6.3
2
Pork
10
21
180
6.23
3
Pork
0
21
130
4
Pork
0
30
130
5.53
5
Beef
0
21
130
5.24
6
Pork
0
21
180
5.04
7
Pork
10
21
130
]
=
.
I
4.4
1
J
any two o r more mans enclosed by the same bracket a r e not
s i g n i f i c a n t l y d i f f e r e n t f r o m each other a t the 0.05 l e v e l
of probability ( t o t a l degrees of freedom 503)
i s probably the reason that frankfurters w i l l not peel inmediately a f t e r heat
processing. It is believed that the l a y e r of moisture between the frankf i r t e r and t h e casing canes from the humlaity i n t h e air and/or the moisture
migrated from the center of the frankfurter and the higher humidity retarded
t h e evaporation of this l a y e r of moisture.
For any one day the panel only peeled frankfurters a t only one
temperature. To have a b e t t e r comparison of the e f f e c t of temperature on
p e e l a b i l i t y a second study was made holding r e l a t i v e humidity constant a t
88$ and varying the temperature. The man values f o r each temperature were
8.12, 7.74, and 8.72 f o r 40, 50, and 60°F., respectively. These differences
were highly s i g n i f i c a n t according t o Duncan's U t i p l e Range Test, indicating
that higher temperatures increased peeling ease.
The addition of various D. E. l e v e l s and amounts of corn-syrup
s o l i d s showed t h a t the 52 D. E. corn-syrup solids were s i g n i f i c a n t l y superior
t o the 31.2 and 7 1 D.E. corn-syrup s o l i d s a t both 455 and 88$ r e l a t i v e
humidity with the g r e a t e r peeling ease again bea t t h e higher r e l a t i v e
humidity. A t the 88$ r e l a t i v e humidity the 1 and 25 l e v e l of 52 D. E. cornsyrup s o l i d s were not s i g n i f i c a n t l y d i f f e r e n t from each other but were
s i g n i f i c a n t l y superior t o a l l other treatments. To substantiate these findings, another s e r i e s of panel detelmiaations were made a t 885: r e l a t i v e
humidity. Duncan's U t i p l e Range Test showed that t h e 52 D. El corn-SyrUp
solids were s i g n i f i c a n t l y superior t o the 71 D, E. corn-syrup s o l i d s (Table 4).
It was postulated t h a t the a i d t o peeling by corn-syrup s o l i d s could be due
90.
t o t h e i r hygroscopic nature a t t h e surface of the frank. The degree of
hygroscopicity increases a s t h e D, E. increases; thus, the higher D. E , ' s
should be most effective. However, there is a tendency f o r t h e adhesiveness t o increase as the D, E. increases which might explain t h e reduction
in peeling ease a t higher D, E . l s .
Results of plant
a l s o v e d f i e d t h a t increased peeling ease
of 52 D. E, corn-syrup s o l i d s over 2 and 35
l e v e l s of 30.2 and 7 1 D, E. corn-symp solids. I n the former group 97$ of
t h e batch was peeled while the highest of the l a t t e r groups only 83.3$
peeled.
rufuj
was obtained by t h e use of 25
Table 3.
Effects of temperature and r e l a t i v e humidity on
peeling ease a s expressed by panel mean scores.
Relative
€kuaidity
40°F
27
6.33
52
6.27
74
6.81
3
-~
60°F
3.03
5.917
3.663
4.4j
7.6g
8.537
8.0d
88
-
Constant Temperatures
5G°F
8.13
~~
= any two means enclosed by the same bracket a r e not s i g n i f i -
.
cantly d i f f e r e n t from t h e other a t the 0.05 l e v e l of
probability
Table 4.
8 of
Duncan's N t i p l e Range Test for the e f f e c t s of
2 types of corn-symp s o l i d s a t 3 l e v e l s a t 88$
r e l a t i v e humidity on peeling ease as indicated
by mean panel scores.
71
c.s.s,
0
&ans
5.04
.
1
5.22
3
5.49
52
2
6.30
-
2
9.10
-
1
3
9.56
10.02
-
Any two means underscored by the s8me line a r e not s i g n i f i c a n t l y
different
D, E.
Dextrose equivalent.
C.S*S.- c 0 r n - s ~
Solids.
~~~
-
91.
1.
Protein and f a t migrated t o t h e surface of franks during processing and
a r e important f a c t o r s i n peeling ease.
2.
Franks i n 21 m casings peeled e a s i e r when p o c e s s e d a t lower (130OF)
i n i t i a l smokehouse temperature.
3.
Franks i n 30 mm casings peeled e a s i e r when processed a t higher (180'F)
smokehouse temperature.
4, The addition of collagen i n the form of 10% pork s k i n s resulted i n e a s i e r
peeling of franks processed a t higher smokehouse temperatures a s cornpared with those processed a t lower smokehouse temperatures
.
5.
Less f a t migrated t o t h e surface when beef f a t was substituted f o r pork
f a t which resulted i n poorer peeling characteristics.
6.
Showering lowered the s a l t content of t h e surface of the frank.
7.
The 52 dextrose equivalent corn-syrup s o l i d s resulted i n superior peeling
c h a r a c t e r i s t i c s as coqpared with other dextrose equivalents t e s t e d i n
both t h e laboratory and commercial plant studies.
A , 0. A , C,
1960. O f f i c i a l Ikthods 02 AnalysiS of O f f i c i a l Agriculture
Chemists. Eighth edition, Washington, D. C,
I
_
_
American Meat I n s t i t u t e Comittee on Textbooks. 1953. Sausage and Readyto-Serve Meats. Second revised edition. I n s t i t u t e of Meat Packing,
University of Chicago, Chicago, Ill.
Dische, C. E, and A , H, Zacharias. 1955. Anthrone reaction. Methods of
Biochemical Analysis. Interscience Publishers, Inc , New E r k and
London
.
.
Saffle, R, L., J. A. Carpenter and D. G. Moore. 1963. Peeling ease of
frankfurters. 1, Ef'fect of chemical composition, heat, collagen and
type of f a t .
Tauber, Id, F.
Food Technol. 17; (In p r e s s ) ,
1958.
Visking Service Mmual,
Visking Company, Chicago, Ill.
Wilson, G, D. 1960. Chapter ll. Sausage products. The science of meat
and meat products. 11, H. Free= and Company, San Francisco and London.
NR. W: I think we a r e picking up some time here,
and we do have time f o r some discussion. If anybody has questions
92.
t o anyone of the previous three speakers, we would be happj Lo have
them a t t h i s time.
MI, GEXXGE BRISSEY: I think J i m Price mentioned the
t e n s i l e strength measurement of the bologna, and I wonder if you
could t e l l us, Jim, how you made that measurement?
MR. PRICi?,: I'm not sure I can c i t e the reference t h a t
Harold used t o design t h e instruments, I d i d n ' t see it, and I
don't know i f anyone e l s e here can t e l l us o r not.
MR. SWIFT: I could answer that, t h i s was a design t h a t
a man in Be1tsviU.e made i n a s t u w of bologna about f i f t e e n years
ago and we got h i s permission t o describe it i n a peper and Dr.
Bratzler had it duplicated with 8ome minor modifications rounding
off some corners, and w h a t it simply is that across a couple of
blocks he s t r e t c h e s a s t r i p of product and adds weight i n t h e
middle u n t i l it snaps, and i n t h i s way he measured t h e strength
of t h i s s t r i p of product.
ElR. SAFFE3: Any other questions?
Lf not, Jim, I'll turn it back to you.
CmIRTaN KEW:
We will now have a recess of about twelve minutes.
MR. SPFLE: I don't believe everybody i s back i n yet, b u t we are
t r y i n g t o make up our time and we are about on schedule again and we will
go i n t o the second part of our Neat Processing Committee's program which is
Meat Pigments, which i n v i r t u a l l y ail. cases o r most cases, whether it i s
f r e s h o r processed, we f i n d t h a t the shelf l i f e i s b a s i c a l l y dependent upon
t h e color. IT the color fades we have l o s t t h e shelf l i f e , and it i s
b a s i c a l l y a matter of color rather than spoilage per se.
I n the area of color, of course, a number of schools have worked
i n t h i s area, and I believe t h a t i n the way of fundamental information that
became available concerning some of t h e pigments, etc., we would have t o take
our hats off t o t h e A.M.I.F., and s p e c i f i c a l l y t o J, B o Fox, who w i l l present
t h e area under t h e Fundamentcl Properties of k a t Pigments and Chemistry of
Curing.
To cover t h e first part, I should have
DR. J, B. FOX (A.M.I.F.):
had some s l i d e s , but I will cover fiome of t h e basic c h a r a c t e r i s t i c s on the
blackboard
.