Full text of DOI:10.1111/j.1365-2621.2000.tb10275.x

JFS: Sensory and Nutritive Qualities of Food
Irradiation in Contrast to Thermal Processing
of Pepperoni for Control of Pathogens:
Effects on Quality Indicators
S.C. JOHNSON, J.G. SEBRANEK, D.G. OLSON, AND B.R. WIEGAND
ABSTRACT: Differences in product quality resulting from use of irradiation or thermal processing for control of
pathogens in pepperoni were investigated. Treatments consisted of irradiation doses of 1.25 kGy or 3.0 kGy, a heat
treatment, and a control without heat or irradiation. Results showed that irradiating meat prior to production of dry,
fermented sausage such as pepperoni, can yield products with quality indicators closely resembling those of tradi-
tional dry sausage, while still providing the required 5-log reduction of E. coli O157:H7.
Key words: irradiation, thermal processing, dry sausage, color, texture
Introduction
HEN THE USDA ESTABLISHED THE REQUIREMENT OF A 5-log
the outer surface, causing cupping.
A third hypothesis for the study was that irradiation will permit
W
reduction in Escherichia coli O157:H7 for dry sausage faster fermentation. Previous work conducted by Dickson and
Reed 1995), the traditional means of producing dry sausage Maxcy (1985) showed that when meat was irradiated prior to the
(
such as pepperoni, along with the traditional characteristics of addition of starter culture, the rate of pH decline was greater than
these products, were significantly changed. Traditional produc- those treatments not irradiated. Irradiation of meat prior to the
tion techniques relied on a low pH and low water activity addition of the starter culture may serve to eliminate competitive
achieved by fermentation and drying to control spoilage and bacteria, thus allowing the starter culture to reach its growth po-
pathogenic microorganisms. However, this traditional process tential more rapidly. This would potentially save processors time
only served to provide a 2-log reduction in E. coli O157:H7 (Faith and money by decreasing the total fermentation time.
and others 1997; Riordan and others 1998), requiring the addi-
Preblending meat with salt and nitrite prior to formulation is a
tion of a thermal processing step to ensure product safety. This practice utilized for some sausage products to increase color de-
additional thermal processing step may alter the traditional tex- velopment and microbial control. Fu and others (1995) reported
ture of dry sausage, along with other quality aspects of the prod- a greater effect of irradiation on total plate counts and patho-
uct such as color.
gens when used with salt and nitrite than when used without salt
Various studies have shown that heat processing at tempera- and nitrite. Consequently, preblending prior to irradiation might
tures sufficient for microbial control in meat leads to increased be a feasible treatment combination for sausage ingredients.
shear and compression values due to the denaturation of pro-
teins (Ledward and Lawrie 1975; Fernandez-Martin and others production of free radicals and potential for oxidative reactions
997). Although textural changes have been observed for meat resulting in off-odors and off-flavors (Murano 1995). Irradiation
One concern for irradiation treatments of meat products is the
1
irradiated at high doses, lower doses such as those that would be has been reported to result in increased thiobarbituric acid
used within the meat industry cause minimal differences in tex- (TBA) values and carbonyl content in ground meat (Kanatt and
ture (Kirn and others 1956; Luchsinger and others 1996; Abu-Tar- others 1998; Jo and Ahn 2000). It is obvious that while irradiation
boush and others 1997). A hypothesis for the current study was and heating both serve as excellent microbial barriers, the result-
that the texture of pepperoni manufactured with irradiated raw ant products may vary significantly between processes. The fol-
materials will resemble that of traditional pepperoni produced lowing research was based on the hypotheses that irradiation of
before governmental regulations requiring a 5-log reduction in E. pork trimmings prior to the production of pepperoni will result in
coli O157:H7. The implementation of such an irradiation process a more desirable texture, less cupping and a faster rate of pH de-
will eliminate the need for thermal processing, currently used to cline than if the product is heat-treated for control of pathogens.
accomplish USDA mandates.
Many of these quality aspects are significant concerns for the
A large amount of pepperoni is used as a pizza topping, which production of many other dry and semi-dry meat products in ad-
requires increased attention to processing parameters that yield dition to pepperoni. Thus, the objective of this study was to de-
high-quality pepperoni slices for pizza manufacturing. One con- termine if dry sausage, in this case pepperoni, could be pro-
cern for pepperoni used for pizza toppings is its potential for duced with minimal quality change while still meeting the USDA
“
cupping” (a condition when slices, after heating on a pizza, curl requirement for a 5-log reduction in E. coli O157:H7.
into a bowl shape, holding pools of liquid fat, resulting in an un-
desirable appearance). A second hypothesis for this study was
that irradiation will aid in the prevention of cupping. It is be-
Materials and Methods
lieved that cupping is more likely when pepperoni is heat-treat- Pepperoni production and irradiation procedures
ed, which causes a greater degree of denatured/dehydrated pro-
Eight treatments of pepperoni were each evaluated five
teins on the surface of the sausage. During subsequent heating times, resulting in a total of 40 observations. Three separate
of slices, the center will rehydrate and expand faster than that of batches were manufactured; the first production batch consisted
1260 JOURNAL OF FOOD SCIENCE—Vol. 65, No. 7, 2000
© 2000 Institute of Food Technologists

Quality of Irradiated and Cooked Sausage . . .
of eight treatments, whereas the second and third batches were treatments were removed, and fermentation time recorded, as
each divided into two 8-treatment blocks with treatments ran- they reached the target pH. Sticks were weighed, and samples
domly placed on the smokehouse truck to minimize variations in were taken for moisture:protein content and texture analysis.
the thermal processing unit. The experiment used a 2 × 4 factori- The sticks were then transferred to a computer-controlled one-
al treatment design, with the treatments as follows: 1.25-kGy ir- truck environmental chamber (Alkar, Lodi, Wis., U.S.A.) operating
radiation dose; 3.0-kGy irradiation dose; nonirradiated with a at 10 °C and 75% RH until the M:P ratio reached 1.6:1. Periodic
heat treatment; control-nonirradiated without a heat treatment; samples were taken during drying for moisture:protein ratios
preblend with 1.25-kGy irradiation dose; preblend with 3.0-kGy and texture analysis (Instron Series 4500; Instron Corp. Canton,
irradiation dose; preblend (nonirradiated) with a heat treatment; Mass., U.S.A.).
preblend (nonirradiated) without a heat treatment.
Pepperoni sticks to be subjected to a heat treatment were
Fresh 80% lean pork picnic trim was purchased from local sup- placed in a computer-controlled one-truck smokehouse (Alkar,
pliers. The meat was ground through a 1.27-cm plate (Biro model Lodi, Wis.) after drying, to be heated (70 °C, 85% RH) to an inter-
7
552; The Biro Mfg Co., Marblehead, Ohio, U.S.A.), after which nal temperature of 60 °C. It should be noted that irradiation
the meat was divided into two lots for preblended and non-preb- treatments in this study did not involve the finished processed
lended treatments. The batches to be preblended were then products but rather the raw meat materials which were subse-
mixed (Leland model L-100 DA; Leland Detroit Mfg Co., Detroit, quently used to manufacture the pepperoni.
Mich., U.S.A.) with all the salt (2.1%) and one-half the cure for
approximately 5 min, after which all batches were stored in a 4 °C Proximate analysis/yield measurements
cooler. Batches (both preblended and not preblended) requiring
Proximate analysis consisted of moisture (oven drying), fat
irradiation were then boxed in fiberboard boxes with liners ap- (ether extraction), and protein (combustion method) and was
propriate for irradiation processing and received a double-sided performed according to AOAC (1993) procedures. Samples were
irradiation treatment of 1.25 or 3.0 kGy using the linear accelera- measured for proximate composition throughout the drying
tor facility (Linear Accelerator-circle III R; Saint-Aubin, France) at treatment to confirm moisture:protein ratios. All measurements
Iowa State University. Actual measured minimum doses were were performed in duplicate.
1
.24, 1.26 and 1.30 kGy in the three replications. Maximum esti-
Yields were recorded by labeling sticks of pepperoni for each
mated doses were 1.45, 1.76 and 1.88 kGy, respectively. The high- treatment and taking an initial weight immediately after stuff-
er dose treatments were measured at a minimum 2.85, 2.98 and ing. Weights were then taken periodically throughout drying and
3
.17 kGy in the three replications with estimated maximum dos- at the completion of drying and/or heat treatment.
es of 3.31, 4.17 and 4.44 kGy, respectively. Irradiation was con-
ducted at room temperature and required 8 to 10 min per treat- Texture/color analysis
ment. Product temperature did not increase by more than 1 °C
Texture measurements were recorded using both compres-
during the irradiation treatment. Doses were determined in ac- sion of sticks and puncture of slices periodically during drying
cordance with the USDA-FSIS, which reported that the D-value and at the completion of drying for each treatment. The stick
for Escherichia coli O157:H7 was 0.25 kGy for refrigerated product compression consisted of three repeated measurements taken
(
Federal Register, 1999). This requires a minimum dose of 1.25 with an Instron Universal Testing Machine (Instron Series 4500;
kGy to provide a 5-log reduction in E. coli O157:H7, as mandated Instron Corp., Canton, Mass., U.S.A.). The measurement was
by the USDA (Reed, 1995). The doses were measured by placing done by compressing a stick of pepperoni by 30% of the diameter
alanine pellet dosimeters (Bruker Instruments, Inc., Billerica, of the sausage with a 3.5-cm dia compression anvil (Model 2830-
Mass., U.S.A.) on the top and bottom of boxes for each treatment 011) attachment. The 30% compression was chosen from prelimi-
(
ASTM 1996). The dosimeters were read by electroparamagnetic nary work on commercial pepperoni which suggested that 30%
resonance (EMS 104; Bruker Analytiscne Messtechnik, Karlsruhe, was effective for detecting product differences. The Instron was
Germany). All of the treatments were then held in a 4 °C cooler equipped with a 1-KN load cell with conditions for a one-cycle
overnight, after which the 8.6-kg batches were mixed with spices, compression at 200 mm per min crosshead speed and by using a
salt, dextrose, and 78 or 156 parts per million (ppm) sodium ni- preload of 0.5 kg. The hardness of pepperoni slices was mea-
trite in a grinder-mixer (Hollymatic model 175; Hollymatic Corp., sured by the force needed to puncture a 0.2-cm slice with a 1.27-
Park Forest, Ill. U.S.A.). It is important to note that half of the cm dia probe on the Instron equipped with a 1-KN load cell. Con-
cure for the preblend treatments was added initially, with the re- ditions used for a one-cycle break of the slices were 400 mm per
maining half being added with the spices at the final mixing. Pa- min crosshead speed and a preload of 0.05 kg. Five measure-
prika oleoresin flavoring (Pepperoni Oleoresin Flavor; Chr. Hans- ments per treatment were taken for slice hardness.
en Inc., Milwaukee, Wis., U.S.A.) was added which contained an-
Color measurements of 0.2-cm slices were conducted by using
tioxidants BHA (1.12%), BHT (1.12%), and citric acid (1.12%). The a HunterLab LabScan Spectro Colorimeter (Hunter Associates
starter culture (LL2; Diversitech Inc., Gainesville, Fl., U.S.A.) was Lab, Inc., Reston, Virg., U.S.A.) with an illuminant A and 10° ob-
added last in accordance with manufacturers directions (2.95 g server light source (representing an incandescent lamp) and a
with 41 g water). The batches were then ground through a 0.318- 2.54-cm port insert. Color was first measured when the product
cm plate and vacuum-stuffed (Risco model RS 4003-165, Stough- processing was completed (drying or heating) and again after 4
ton, Mass., U.S.A.) into 1S × 30 fibrous cellulose casings. Samples wks of storage at 4 °C.
were taken during stuffing for measurement of initial pH and
proximate analysis. Initial weight of stuffed products was mea- Lipid oxidation analysis
sured after stuffing.
Samples were measured for oxidative rancidity by using the
modified 2-thiobarbituric acid (TBA) procedure of Tarladgis and
others (1960). The initial TBA measurements were done for all
treatments immediately following irradiation of appropriate
batches. Measurements were also conducted after the comple-
tion of drying and/or heating, and every 3 wk thereafter during
Pepperoni was placed in a computer-controlled one-truck
smokehouse (Alkar, Lodi, Wis., U.S.A.), which was programmed
for fermentation at 27 °C dry bulb, 26 °C wet bulb, (96% RH) until
the required pH was reached. The fermentation was considered
complete when the pH of the pepperoni declined below 5.0 as
periodically measured by a hand-held pH-Star probe (pH-Star S;
SFK Technology Inc., Cedar Rapids, Ia., U.S.A.). The pepperoni
5
-mo of storage at 4 °C. Additional samples of each treatment
were also stored at room temperature and in direct sunlight to be
Vol. 65, No. 7, 2000—JOURNAL OF FOOD SCIENCE 1261

Quality of Irradiated and Cooked Sausage . . .
evaluated at the end of the 5 mo period.
Table 1—Percentage moisture, protein, fat and yield for finished
pepperoni from experimental treatments
Cupping measurements
Treatment
Final moisture Final protein
Final fat
Yield
Because cupping of pepperoni slices results from a rigid outer
edge on slices for which the center of the slice expands during 3.0 kGy
heating, cupping of the pepperoni slices was measured for each
treatment after cooking, using 0.2-cm slices. Slices were arranged
on frozen double-cheese pizzas (Jacks® Great Combinations®
2" Double Cheese pizza; Jacks Frozen Pizza, Inc., Dist. Little bIrradiated at 3.0 kGy
Chute, Wis., U.S.A.) to evaluate cupping after cooking. The pizza
a
1
.25 kGy
40.5
39.9
40.1
40.9
29.3
27.6
27.6
27.0
26.2
26.8
27.0
26.1
0.56
61.4
61.9
60.8
61.8
0.57
b
With heat
Without heat
SEM
0.40
0.90
aIrradiated at 1.25 kGy
1
was divided into eight equal portions, with two pepperoni slices Table 2—The effect of irradiation dose, heat treatment and preblending
on pH values during fermentation
per treatment on each pie-shaped portion of pizza, one peppero-
ni slice near the crust and the other near the center. The pizzas, Treatment
with added pepperoni slices, were cooked according to the man-
ufacturer’s recommendations (preheat oven to 425 °F, cook 10-12 3.0 kGy
0 h
8 h
20½ h
29 h
30 h
30½ h
31½ h
a
c
c
c
c
c
5.52c
c
5.02c
4.99c
c
c
c
c
c
1
.25 kGy
6.06
6.01
6.10
6.11
6.07
6.06
6.00
5.98
5.99
5.99
6.00
5.09
5.11
5.02
5.00
5.05
4.98
5.01
4.97
4.92
4.99
b
d
c
d
d
d
d
d
5.57
5.08
5.06
c
c
c
With heat
Without heat
Preblend
5.48
5.44
5.51
4.98
4.96
4.99
4.97
4.96
5.01
min or until the cheese is golden brown) in a conventional oven
GE model CN60; General Electric, Chicago Heights, Ill., U.S.A.)
c
c
c
(
c
c
c
with a total cooking time of 11 minutes. Objective measurements Non-preblend
5.97c
5.49c
5.06d
5.02c
5.01c
4.98c
for cupping were taken by removing the slices from the cooked
pizzas, removing excess cheese, placing the slices upside down
on a countertop, and measuring the height from the countertop
to the apex of the slice.
a
Irradiated at 1.25 kGy.
b Irradiated at 3.0 kGy.
c,d Means within a column with different letters are significantly different at P < 0.05.
Sensory analysis
Sensory analysis was conducted by using a panel consisting dent for the final protein measurement, with no difference ob-
of 9-12 experienced members, all being students, staff, or faculty served for the finished product between treatments. Preblend-
in the Meat Science program at Iowa State University. All panel- ing had no effect on protein content for either the initial or final
ists were volunteers and were informed of the experimental pro- measurements. It is important to note that the moisture, protein,
tocols according to Iowa State University requirements for utili- and fat contents were not significantly different in the finished
zation of human subjects. Training of the panelists consisted of product, from which all of the objective and subjective measure-
preliminary evaluation of pepperoni slices from each treatment ments are taken. Consequently, observed differences in product
combined with discussion of the properties to be measured and properties were not due to differences in composition. Further,
the scales to be used. Each panelist was then given slices in ran- no differences (P < 0.05) were observed between preblended
dom order to evaluate texture, flavor, and color. Color evalua- and non-preblended or between irradiated and heated treat-
tions were conducted separately from that of texture and flavor, ments for final yields (Table 1).
which were evaluated with red lighting to prevent any color dif-
ferences influencing panelists. Line scales were used for three pH measurements during fermentation
textural attributes (initial chewiness, chewiness, and hardness)
The rate of pH decline in pepperoni during fermentation was
with values reported on a graduated scale of 0 to 150. The scales measured to compare rate of pH change. The data in Table 2
ranged from none to intense; flavor attributes included peppero- show the pH decline for treatments over 31 1/2 h of fermenta-
ni flavor and off-flavor ranging from none to intense; and color tion. Preblending had no effect (P < 0.05) on rate of pH decline,
evaluation ranged from light to dark. All sensory evaluations while the highest irradiation dose of 3.0 kGy extended (P < 0.05)
were conducted within two weeks of completion of processing the time to reach the final pH of < 5.0 as compared with the re-
and were repeated three times. Treatments that were not irradi- maining treatments. This contradicts the initial hypothesis that
ated or cooked to eliminate risk of pathogens were not included irradiation will eliminate competitive bacteria allowing the start-
in the sensory evaluations.
er culture to rapidly multiply, forming lactic acid and lowering
the pH. However, because very high quality (fresh) raw materials
were used for this study, it is likely that the number of competi-
Statistical analysis
Statistical analysis was performed using the general linear tive bacteria was relatively low in all treatments. If such was the
model (GLM) procedure PROC GLM (SAS Institute, Inc., 1990). case, irradiation to reduce competitive bacteria would not result
The pH data were analyzed by plotting the values measured in much change compared to that in raw materials with high ini-
during fermentation and using the linear portion of the graph to tial microbial numbers.
best represent the rate of pH decline to a final pH below 5.0. Sta-
tistical analyses of all other measurements were done with a 2 × 4 Texture measurements
factorial design with fixed effects of preblend and thermal pro-
cesses.
Texture of pepperoni sticks was measured immediately after
stuffing, periodically (days 1, 4, 6, 10, 12, 13, and 16) during dry-
ing, and for finished products using an Instron compression test.
A hardness value was achieved by measuring the force needed
to compress the stick 30% of its diameter, and calculating the av-
erage of three measurements per treatment. Results showed
Results and Discussion
Proximate analysis and yield measurements
There were no differences (P < 0.05) between the irradiated that preblending did not affect either stick or slice hardness
and heated samples for final moisture, protein, or fat content in (data not shown). This is similar to the report from Hand and oth-
the finished product (Table 1). Preblending also had no effect on ers (1987), who found that preblending had no effect on the tex-
moisture in the final measurements. The protein contents were tural properties of frankfurters. An increase (P < 0.05) in hard-
different (P < 0.05) for the initial product samples taken during ness was observed for heated pepperoni relative to irradiated
stuffing (data not shown); however, this difference was not evi- treatments and to controls without heat (Table 3). Results ob-
1262 JOURNAL OF FOOD SCIENCE—Vol. 65, No. 7, 2000

Quality of Irradiated and Cooked Sausage . . .
Table 3—The effect of irradiation dose and heat treatment on stick Table 4—The effects of irradiation dose and heat treatment on light-
compression (30%) and slice puncture hardness of pepperoni
ness (L*), redness (a*), and yellowness (b*) color values for pepperoni
slices
Treatmentc
Stick hardness (Kg)
Slice hardness (Kg)
Treatment
Initial L* Final L* Initial a* Final a* Initial b* Final b*
1
3
.25 kGya
.0 kGyb
17.0c
16.7c
0.99 c
0.91 c
a
c
c
d
e
c
c
d
c
c
c
d
e
c
c
d
c
1.25 kGy
3.0 kGy
44.5
44.8
49.1
45.5
45.1
49.5
46.0
30.9
29.9
30.9
30.7
0.37
33.03
33.00
31.63
33.93
30.8
30.8
30.0
29.5
0.71
31.6
32.6
29.6
32.4
d
d
b
With heat
Without heat
SEM
40.5
1.29
16.0 c
0.98
0.92 c
0.07
With heat
Without heat 46.6
SEM
0.56
0.54
0.25
0.57
a Irradiated at 1.25 kGy
b Irradiated at 3.0 kGy.
a
b
Irradiated at 1.25 kGy.
Irradiated at 3.0 kGy
c,d Means within a column with different letters are significantly different at P< 0.05.
c,d,e Means within a column with different letters are significantly different at P< 0.05.
served for the hardness of pepperoni slices, as measured by the
force required to puncture slices on the Instron, were also similar ing and subsequent heat processing for the final product, with a
to stick compression values. The lower hardness values observed second color measurement performed 4 wk after the first color
for irradiated samples as compared with heated samples support measurement. The Hunter Lab objectively measured the color
the initial hypothesis for this study. Ledward and Lawrie (1975) giving L* (0-100, with 100 being perfect white), a* (positive num-
discussed the dependence of texture on heating temperature. bers increasing with intensity of redness,), and b* (positive num-
They reported that a temperature of 50 °C caused an approxi- bers increasing with intensity of yellowness) values. Preblending
mate fourfold increase in meat toughening due to coagulation of (data not shown) had no significant effect on color characteristics
the actomyosin complex, while subsequent heating to a temper- of pepperoni slices. This conflicts with results of Hand and others
ature of 65 °C continued to increase toughness due to collagen (1987), who reported that preblended franks had significantly
shrinkage. Bailey and Rhodes (1964) researched the effects of ir- lower L* values (representing a darker colored product) com-
radiation doses of 2 and 4 Mrad (corresponding with 20- and 40- pared with non-preblended franks. The addition of paprika in
kGy doses) on the texture of beef and pork. Taste panelists had pepperoni production is likely to mask small color differences.
reported a softening of meat after an irradiation treatment, al- Heat treatments yielded the lightest pepperoni slices (P < 0.05)
though meat considered initially tender was not over-tenderized compared with the other treatments used in this study (control
by irradiation. Although Bailey and Rhodes (1964) found that without heat and 1.25-kGy and 3.0-kGy irradiation treatments)
high doses increased softening, there was no detectable soften- (Table 4). The unheated control treatment, while darker than
ing in pepperoni due to irradiation in the current study. The re- heat-treated pepperoni, was significantly lighter than either irra-
sults reveal that the texture of irradiated pepperoni (1.25 kGy diated treatment for the initial lightness measurement. Thus,
and 3.0 kGy) was not as hard as that of heated pepperoni, with both irradiated treatments produced the darkest-colored pep-
no difference (P < 0.05) between irradiation treatments. The irra- peroni slices observed during the first color measurements (im-
diated product in this study was similar to pepperoni dried with- mediately after drying). The final lightness measurement (4 wk
out heat, which is considered to be a traditional pepperoni pro- later) also revealed a lighter coloration (P < 0.05) for pepperoni
cess. Thus, irradiation allows production of pepperoni similar to slices from heated treatments relative to irradiated samples or
that produced prior to the regulation requiring a 5-log reduction controls without heat. The redness values (a*) of pepperoni slic-
in E. coli O157:H7, which led to the implementation of the heat- es were not different initially, but at 4 wk, the treatment with
ing treatment. Figure 1 shows the change in texture of pepperoni heat was less red (P < 0.05) relative to that of either irradiated
sticks throughout the drying process. Drying was complete after treatments or the unheated control (Table 4). The unheated con-
1
6 days with no differences in hardness. The heating treatment trol, however, was redder than the other treatments. These re-
was then applied for the appropriate treatment group; the hard- sults indicate that the heating process decreased the redness of
ness was measured after chilling and recorded as 18 d samples.
the pepperoni. The degree of yellowness (b*) was not different
initially; however, the final color measurement showed that heat-
ed pepperoni was less yellow (P < 0.05) than the other treat-
Color measurements
The color of pepperoni slices was measured initially after dry- ments (Table 4). These color results show that by using irradia-
tion rather than heating to provide a reduction in pathogens,
lightness, redness, and yellowness color attributes will also be
modified with a darker, redder color resulting.
Sensory analysis
The sensory panel evaluated pepperoni slices for initial
chewiness, chewiness, sustained hardness, pepperoni flavor, off-
flavor, and color by using a line scale in graduations of 0 to 150.
The treatment which served as a control, without heat or irradia-
tion, was not included in the sensory analyses because of the
possible presence of pathogens. Slices from the unheated con-
trol were evaluated by the panel for visual color attributes, how-
ever. The treatment with heat had a higher (P < 0.05) initial
chewiness score, higher sustained chewiness score, and higher
hardness score than irradiated treatments (Table 5). These re-
sults are similar to the objective measurement of hardness by
stick compression and slice puncture as previously described.
The hardness values for the irradiated samples in the sensory
panel revealed a large difference (56 to 59 as compared with
Figure 1—Hardness of pepperoni sticks from control, irradiated, or
heated treatments during and after drying
Vol. 65, No. 7, 2000—JOURNAL OF FOOD SCIENCE 1263

Quality of Irradiated and Cooked Sausage . . .
Table 5—The effects of irradiation dose and heat treatment on pep- Table 6—The effect of irradiation dose and heat treatment on sen-
peroni texture determined by sensory panel evaluation
sory panel flavor and color of pepperoni
Treatment
Initial chewiness
Sustained chewiness
Hardness
Treatment
Flavor Intensity
Off-Flavor
Color
.25 kGya
.0 kGyb
69.6
70.2
93.3
N/A
c
69.6 c
59
56
c
1.25 kGy
3.0 kGy
a
79.7
82.7
85.1
N/A
2.33
35.3
34.3
33.6
N/A
97.5
97.0
61.3
87.9
c
1
3
c
c
c
b
c
68.8
d
99.8 d
N/A
d
d
With heat
Without heat
SEM
100
With heat
Without heat
SEM
e
c
c
N/A
3.14
2.25
2.10
2.86
2.91
aIrradiated at 1.25 kGy
bIrradiated at 3.0 kGy
aIrradiated at 1.25 kGy
bIrradiated at 3.0 kGy
c,dMeans within a column with different letters are significantly different at P< 0.05
c,dMeans within a column with different letters are significantly different at P< 0.05
e
e
not available
not available.
Table 7—The effect of irradiation dose and heat treatment on thio-
barbituric acid (TBA) numbers (mg malonaldehyde/kg sample) for
pepperoni
1
00), much like the large difference observed with the Instron
TBA number of
products stored at
room temperature
FinalTBA number of
refrigerated products
machine (16 to 17 as compared with 40). Although the control
without heat was not evaluated by the taste panelists, differenc-
es between irradiated and unheated treatments were minimal,
based on the objective texture measurements with the Instron.
There was no difference (P < 0.05) for pepperoni flavor or off-fla- Without heat
vor between the treatments (Table 6). The color attributes of the
Treatment
a
0.350c
c,d
1
3
.25 kGy
.0 kGy
0.187
b
d
d
0.446
0.157
0.164
0.221
e
c,d
With heat
0.163
e
c
0.141
SEM
0.023
0.024
a
b
pepperoni slices, measured on a line scale from light (0) to dark
(
Irradiated at 1.25 kGy
Irradiated at 3.0 kGy
150), showed a lighter color (P < 0.05) resulting from the heat c,d,e Means within a column with different letters are significantly different at P< 0.05.
treatment relative to that of irradiated or unheated treatments
Table 6). This was similar to the measurements from the Hunter
(
Lab for objective L* values. This also showed that the panelists
perceived that irradiation treatments more closely resembled ping between cooking, irradiation levels, or preblending (data
the color of unheated controls. Preblending had no significant not shown). This contradicts research by Newkirk and others
effect on any sensory measurements (data not shown).
(1995), who reported that pepperoni cooked to an endpoint in-
ternal temperature of 60 °C resulted in slices with higher cupping
scores than unheated controls. In that study, slices were ar-
Lipid oxidation measurements
TBA measurements on pepperoni sticks, vacuum packaged ranged on a frozen pizza and cooked in a conveyer-fed impinge-
and stored at refrigerated temperatures, were taken initially af- ment oven for 3.5 minutes at 260 °C. The differing results by
ter production and at 3-wk intervals thereafter until the end of Newkirk and others (1995) relative to the current research may
the 5-mo storage period. The TBA measurements at the end of be due to the different cooking procedures.
the 5-mo period consisted of samples from vacuum-packaged
pepperoni stored at refrigerated temperatures in addition to
samples that were subjected to direct sunlight at room tempera-
ture (representing abused pepperoni). For the refrigerated sam-
Conclusions
RRADIATION OF MEAT RAW MATERIALS PRIOR TO THE PRODUC-
I
tion of dry, fermented sausage, such as pepperoni will provide
ples, the 3.0-kGy treatment resulted in higher TBA values the required 5-log reduction of E. coli O157:H7 and result in
P < 0.05) than the other treatments (Table 7). The 1.25-kGy products with quality characteristics closely resembling those of
(
treated samples had lower TBA values than the 3.0-kGy treat- traditional dry sausage. A heat treatment performed with proper
ments, but were higher than treatments with or without heat, time/temperature relationships is known to be very effective for
which did not differ (Table 7). Interestingly, it was noted that the destruction of pathogens, but the quality characteristics of pep-
TBA values of irradiated samples tended to decrease slightly peroni observed in this study show that texture and color are sig-
over time, while the heated and control treatments changed very nificantly altered. Implementing irradiation for raw meat materi-
little. This decline in TBA values over time may imply that TBA als as a microbial control measure rather than heating the dried
measurement for irradiated samples is not an accurate indica- product will permit production of pepperoni with characteristics
tion of lipid oxidation, perhaps due to other compounds formed which more closely resemble traditional pepperoni products.
during the irradiation process that result in an increase in TBA-
positive absorbance. The samples stored at room temperature
showed similar differences between treatments, with the 3.0-
kGy dose treatments exhibiting higher TBA values (P < 0.05)
than treatments without heat, which had the lowest TBA values.
These data support conclusions by Reineccius (1979) in that fur-
ther processing steps (irradiation and heating) increase cell dis-
ruption, leading to increased lipid deterioration observed by in-
creased TBA values. However, all TBA values for the pepperoni in
this study were low, indicating limited oxidation. Even samples
stored at room temperature showed relatively little change,
probably due to superior vacuum packaging.
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