MEAT
SCIENCE
Meat Science 67 (2004) 395–401
www.elsevier.com/locate/meatsci
The effects of irradiation on quality of injected fresh pork loins
Kathy J. Davis a, Joseph G. Sebranek b,c,*, Elisabeth Huff-Lonergan b,
Dong U. Ahn b, Steven M. Lonergan b
a
Burke Marketing Corp., 1516 South D Ave., Nevada, IA 50201, USA
Department of Animal Science, 215 Meat Laboratory, Iowa State University, Kildee Hall, Ames, IA 50011 USA
Department of Food Science and Human Nutrition, 215 Meat Laboratory, Iowa State University, Kildee Hall, Ames, IA 50011, USA
b
c
Received 16 June 2003; received in revised form 10 November 2003; accepted 10 November 2003
Abstract
A comparison of irradiation effects on injected and uninjected fresh pork loin quality was conducted. Sixty pork loins from pigs
of similar genetics were obtained from a pork harvesting facility immediately prior to processing. Thirty loins were injected with a
brine composed of 2.17% salt/3.04% phosphate/20.8% lactate brine while thirty were not injected. Injected loins were pumped to
13% added weight. Ten loins of each group of thirty were not irradiated while an additional 10 loins were irradiated at 2.2 kGy and
the final ten loins were irradiated at 4.4 kGy. Lipid oxidation, color, purge, volatiles, and tenderness were measured on sections of
the treated loins after 0, 7, 21, and 35 days of refrigerated storage. Lipid oxidation was minimal for the 0 and the 2.2 kGy-treated
loins, but was significantly greater (P < 0:05) at day 35 for the loins treated with 4.4 kGy. Warner–Bratzler shear (WBS) force
measurements were significantly lower (P < 0:05) for the injected loins, but irradiation did not have an effect on shear force. Purge
was significantly lower for the uninjected loins irradiated at 2.2 kGy than for those irradiated at 0 and 4.4 kGy. The injection
treatment did not alter the effects of irradiation on the quality characteristics measured.
Ó 2003 Elsevier Ltd. All rights reserved.
Keywords: Irradiation; Injected pork; Tenderness; Lipid oxidation
1. Introduction
Safety and quality are of utmost importance to the
meat industry. Treatments that have potential to ensure
safe, consistent, high-quality products have been a major priority for recent research. Use of ingredients and
processing technology such as irradiation appear to
have excellent potential, particularly in combination, to
achieve both safety and quality improvements. Among
the popular products in the meat case today are injected
or Ômoisture-enhancedÕ pork. Several ingredients are
injected in a brine formulation to improve the consistency and quality of pork and other meat products. The
ingredients most commonly included are salt, polyphosphates and lactate.
*
Corresponding author. Tel.: +1-515-294-1091; fax: +1-515-2945066.
E-mail address: sebranek@iastate.edu (J.G. Sebranek).
0309-1740/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.meatsci.2003.11.011
Salt added to the whole muscle meat products is
known to increase water retention by increasing myofibrillar spacing. The chloride ion increases electrostatic
repulsion between filaments which allows for more
water to be absorbed and retained in the filament lattice
(Offer & Trinick, 1983). Phosphates work synergistically
with salt and allow meat processors to achieve equivalent water-holding capacity with reduced amounts of
salt (Offer & Trinick, 1983). Sheard, Nute, Richardson,
Perry, and Taylor (1998) found that polyphosphates
improved water-holding, tenderness, and juiciness in
pork loins. Furthermore, phosphates allow cooking
pork to a higher temperature to ensure food safety while
still maintaining desirable texture and flavor.
While salt and phosphate have been shown to improve tenderness and water-holding capacity in meat,
lactate has been included in many formulations as a
bacteriostatic agent. Sodium lactate added at 3% lowered aerobic plate counts in comparison to controls at
42 and 84 days in beef top rounds (Papadopoulos,
396
K.J. Davis et al. / Meat Science 67 (2004) 395–401
Miller, Ringer, & Cross, 1991). Increasing sodium lactate in beef top rounds also increased cooking yields
(Papadopoulos et al., 1991). Despite the advantages of
added ingredients in injected fresh products, the injection process has potential to contaminate the interior of
the product with bacteria and this could pose a threat to
food safety.
Irradiation has been studied extensively for improving the safety of meat products. The USDA approved
irradiation of fresh red meats with up to 4.5 kGy and the
irradiation of frozen red meats with up to 7.0 kGy
(USDA, 1999). Irradiation is not approved currently for
processed pork, but it could provide a solution for the
potential problem of contamination from injection. Irradiation of meat is a viable way to eliminate foodborne
illnesses caused by organisms such as Escherichia coli
O157:H7, Salmonellae, Listeria monocytogenes, and
Staphylococcus aureus (Dempster, 1985). Most spoilage
and pathogenic bacteria, yeasts, and molds can be significantly reduced in number by irradiation at doses
between 0.5 and 3 kGy (Dempster, 1985; Murano,
1995).
Despite the advantages of irradiation for microbial
control, questions have been raised about potential
changes in meat quality attributes following irradiation
processing. Irradiation of pork has, for example, been
reported to result in the production of undesirable volatiles that have been suggested to be the result of oxidation reactions. Ahn, Jo, and Olson (1999) found that
these volatiles were not related to lipid oxidation but
were caused independently by radiation of protein and
lipid molecules. Ahn, Jo, Du, Olson, and Nam (2000)
reported that refrigerated storage of irradiated pork
patties allowed for dissipation of irradiation-induced
volatiles, which were not detected after one week. They
also found that pork patties that were irradiated and
stored in a vacuum package did not result in increased
lipid oxidation.
The color of pork can also be affected by irradiation.
Nanke, Sebranek, and Olson (1998) found that irradiation induced a bright oxymyoglobin-like pigment in
pork chops. The redness increased with increased dose
levels. Lightness values were not affected but the yellowness was also increased with doses from 0 to 4.5 kGy
and remained constant at higher dosages.
If irradiation could be used to reduce the risk of
contamination in injected pork products, there are still
questions about quality problems that could result from
the irradiation treatment. Because phosphates function
as antioxidants and chelators in processed meat
(Mielche & Bertelsen, 1994), addition of phosphates
may reduce quality changes induced in pork by irradiation. Thus, the hypothesis for this study was that injection of fresh pork with phosphate and added water
would reduce quality changes observed for irradiation
processing of fresh pork cuts.
2. Materials and methods
Sixty pork loins were acquired from a commercial
facility and were processed 7 days after harvest. Thirty
loins were injected (I) with a Townsend Model 1450
injector (Townsend Eng., Des Moines, IA) to 13% final
added weight with a brine composed of 3.04% sodium
tripolyphosphate, 2.17% sodium chloride, and 20.8%
potassium lactate. Following injection, loins were tumbled for 1 h. The remaining 30 loins were not injected
(N) or tumbled. Ten loins from each group were cut into
four sections and vacuum packaged to serve as unirradiated (0) controls (N, 0 and I, 0). The remaining 40
loins were each cut into four sections and individually
vacuum packaged. The loin sections were vacuum
packaged with a Multivac Model A6800 vacuum packaging machine (Multivac Inc. Kansas City, MO) in
pouches with a O2 transmission rate of 3–6 cc/m2 /24 h at
1 atm, 4.4 °C, and 0% RH, and a water vapor transmission rate of 0.5–0.6 g/645 cm2 /24 h at 100% RH.
Packages were stored at 0–2 °C.
Immediately after vacuum packaging, 40 loins were
transferred to the Iowa State University Meat Laboratory Linear Accelerator Facility (LAF) for irradiation
treatments. The facility has a CIRCE IIIR electron
beam irradiator (Thomsen CSF Linac., Saint Aubin,
France) with an energy level of 10 MeV and a power
level of 10 kW. The loins were irradiated with two
passes, one on each side. Average dose rate was 92.7
kGy/min and the conveyor speed was 26 m/min for the
first side and 12.9 m/min on the second side. The group
of 20 loins [10 injected (I, 2.2) and 10 uninjected (N, 2.2)]
irradiated at a target dose of 1.5 kGy received an average delivered dose of 2.21 kGy with a maximum dose
of 2.91 kGy. The second group of 20 loins [10 injected (I,
4.4) and 10 uninjected (N, 4.4)] loins were irradiated at a
target dose of 3.0 kGy and received an average delivered
dose of 4.42 kGy with a maximum dose of 5.84 kGy.
The doses were confirmed using 99% pure alanine
dosimeters (Bruker Inst. Inc., Billerica, MA) placed on
cut ends between loin sections. The dosimeters were
verified by a EMS 104 Electron Paramagnetic Resonance instrument (Bruker Analytisctie Messtechnik,
Karlsruhe, Germany). Samples were collected for analysis immediately following irradiation. Loins were
stored at 0–2 °C for 1, 7, 21 or 35 days following the
treatment.
2.1. Purge
Purge in the packages was measured on day 7, 21,
and 35 after processing. To get the initial weight, the
vacuum-packaged loin sections were weighed. The loin
sample was then removed from the bag, the bag was
drained, and an absorbent towel was used to remove
excess moisture. The bag and sample were then
K.J. Davis et al. / Meat Science 67 (2004) 395–401
reweighed. The purge loss was calculated as the percentage of the loin weight that was lost by removal of
moisture.
2.2. Shear force
After injection and irradiation, 2.5 cm chops for
Warner–Bratzler shear (WBS) force measurement were
cut from loins of each treatment, packaged and frozen
immediately at )20 °C, or aged for 21 days before
freezing at )20 °C. Twenty-two days after freezing, the
chops were thawed at 0–2 °C, broiled to an internal
temperature of 71 °C and chilled 5–8 h in at 0–2 °C. For
the WBS measurement, three cores, each 1 cm in diameter, were cut parallel to the muscle fibers from each
chop. The WBS force was measured on each core using
a TA.XT2 Texture Analyzer (Texture Technologies
Corp., Scarsdale, NY), and the mean shear force calculated for each chop. The tests were performed using
Warner–Bratzler Probe and Guillotine Set number TA7B USDA. The probe was programmed to be lowered
30 mm after detection of resistance. The penetration
speed was 3.3 mm/s with a post-test speed of 10 mm/s
and a pre-test speed of 2.0 mm/s. The WBS measurements for the second set of chops (frozen after aging)
were then performed 25 days after freezing in the same
manner described above.
2.3. Color measurements
Chops (2.5 cm) were cut from the loin sections, allowed to bloom for 10 min at room temperature and
measured on the Hunterlab Labscan colorimeter
(Hunter Associated Laboratories Inc., Reston, VA). Illuminate A, 10° standard observer, and a 1.3 cm viewing
port area were used to measure the Hunter CIE L*
(lightness), a* (redness), and b* (yellowness). Three
measurements were made on the face of each chop.
Color was measured on all 60 samples immediately after
injection and irradiation, and repeated on day 7, 21, and
35 of storage.
2.4. Lipid oxidation
The day after injection and irradiation were completed, 2-thiobarbituric acid (TBA) measurements
(Tarladgis, Watts, Younathan, & Dugan, 1960) were
performed on the 60 loin samples to measure lipid oxidation. The TBA measurement was repeated at 7, 21,
and 35 days of storage on samples of all 60 loins.
2.5. Volatiles
Gas chromatography for detection of volatiles was
performed on five of the samples from each treatment
group on day 1, 7, 21, and 35, as described by Ahn
397
et al. (1999). Four compounds (methanethiol, methylthio ethane, dimethyl disulfide and hexanal) were selected for monitoring differences between treatments
because these four have been reported to be increased
by irradiation and/or lipid oxidation (Ahn, Nam, Du, &
Jo, 2001). A purge-and-trap apparatus connected to a
gas chromatography/mass spectrometry was used to
analyze the volatiles that might be responsible for offodors. Precept II and Purge-and-Trap Concentrator
3000 (Tekmar–Dohrmann, Cincinnati, OH) were used
to purge and trap volatiles from the loin samples. A gas
chromatography (GC) unit (Model 6890, Hewlett–
Packard Co., Wilmington, DE) equipped with a mass
selective detector (MSD, HP 5973, Hewlett–Packard
Co.) was used to characterize and quantify the volatiles
observed.
For volatiles measurement, a minced meat sample
(3 g) was transferred to a 40-ml sample vial, and the
headspace was flushed with helium gas (99.999% purity)
for 5 s to minimize oxidative changes during holding. A
multiple ramped oven temperature program was used.
The oven was held at 0 °C for 2.5 min followed by three
different ramp temperatures: 2.5 °C/min to reach 10 °C,
5 °C/min until 45 °C was reached, and 10 °C/min to
reach a final temperature of 210 °C. Liquid nitrogen was
used to cool the oven below ambient temperature. Helium was the carrier gas at a constant pressure of 20.5
psi. Identification of volatiles was achieved by comparing mass spectral data of peak areas of samples with
those of the Wiley library (Hewlett–Packard Co.). Selected standards were used to verify the identities of
some volatiles. Each peak area was integrated using the
Chemstation software (Hewlett–Packard Co.) and reported as the amount of volatiles released (total ion
counts 104 ).
2.6. Statistical analysis
The statistical analysis was performed with the Statistical Analysis System (SAS, 2000) mixed model procedure. The main effects were irradiation dosage and
injection treatment with each compared within each
sampling day. Least squares means were used to determine significance at a P < 0:05 level.
3. Results and discussion
The overall least squares means for purge loss are
reported in Table 1. Injected loins showed significantly
less purge than uninjected loins for all irradiation
treatment groups. Purge from injected loins was unaffected by irradiation treatment. There was less purge
loss in uninjected loins at 7 and 21 days in those samples
irradiated at 2.2 kGy (N, 2.2) than either unirradiated
samples or those irradiated at 4.4 kGy. Purge was also
398
K.J. Davis et al. / Meat Science 67 (2004) 395–401
Table 1
Purge loss from injected (I) and uninjected (N) fresh pork loins after
irradiation
Irradiation/Injection
treatment
N, 0 kGy
I, 0 kGy
N, 2.2 kGy
I, 2.2 kGy
N, 4.4 kGy
I, 4.4 kGy
SEM
Storage time (days)
7
21
a
35
b
2.99
0.33c
1.42b
0.56c
3.05a
0.34c
0.51
4.17a
0.85b
3.26a
0.96b
4.54a
0.96b
0.62
2.63
0.64c
1.89b
0.69c
3.64a
0.48c
0.41
Means within the same column with different superscripts (a–d) are
significantly different (P < 0:05). N, uninjected; I, injected. 0, 2.2, and
4.4 kGy denote the dosage of irradiation the product received in kGy.
less at 35 days for the uninjected, 2.2 kGy treatment but
relatively large variation resulted in no statistical significance at 35 days. Lambert, Smith, and Dodds (1992)
reported that irradiation of vacuum-packaged fresh
pork resulted in decreased purge after 3 days of storage
compared to unirradiated product, but increased purge
at 14 and 28 days of storage. On the other hand,
Luchsinger et al. (1997) reported that irradiation dosage
did not affect purge loss. Because there was not a linear
relationship between irradiation dose and purge in our
study, the practical effects, if any, of irradiation on
purge are not clear.
The overall least squares means for the WBS force
values are shown in Table 2. Injected samples were
significantly (P < 0:05) lower in WBS values than uninjected samples. This agrees with previous research on
injection and would be expected for the injection
treatment (Offer & Trinick, 1983; Sheard et al., 1998).
There did not appear to be significant differences
(P > 0:05) between irradiation treatments, indicating
that irradiation did not have any effect on tenderness.
This coincides with the finding of Heath, Owens, and
Table 2
Shear (WBS) values (kg/cm2 ) for injected (I) and uninjected (N) fresh
pork loins after irradiation
Irradiation/Injection
treatment
N, 0 kGy
I, 0 kGy
N, 2.2 kGy
I, 2.2 kGy
N, 4.4 kGy
I, 4.4 kGy
SEM
Storage time (days)
1
21
a
3.11
2.21b
2.96a
1.79b
2.83ab
1.96b
0.24
2.71a
1.63b
3.10a
1.75b
2.64a
1.71b
0.19
Means within the same column with different superscripts (a–b) are
significantly different (P < 0:05). N, uninjected; I, injected. 0, 2.2 and
4.4 kGy denote the dosage of irradiation the product received in kGy.
Tesch (1990) and Niemand, van der Linde, and Holzapeel (1981) who reported that irradiation did not affect tenderness. Our results also demonstrated that the
injection process did not alter the effects of irradiation
on these products.
The main effects of irradiation on color are shown in
Table 3. The L* (lightness) values were not significantly
different (P > 0:05) between treatments on day 0 or day
7. However, at day 21, uninjected samples were lighter
than all the injected treatments. At day 35, uninjected
samples all resulted in greater L* values than injected
samples, but the differences were not significant. Table 3
also compares the a* values between treatments. Generally, the 4.4 kGy dosage resulted in a higher a* value
for both the injected and uninjected chops. This is in
agreement with Nanke et al. (1998) who reported that
irradiation increased redness in pork. The b* values
found in Table 3 were not consistently different
(P < 0:05) over time.
Lipid oxidation, as determined by TBA measurements, is shown in Table 4. Within injection treatments,
the TBA values increased with irradiation dosage at all
sampling times (1, 7, 21, 35 days). This can be interpreted as increased lipid oxidation resulting from irradiation treatment. However, no TBA values observed
were greater than 0.24 which means that relatively little
lipid oxidation occurred. Luchsinger et al. (1997), also
reported an increase in TBA values as irradiation dose
was increased for aerobically packaged ground beef
patties, but observed a decrease for samples in vacuum
packages.
Results from the volatiles analysis using gas chromatography measurements are shown as selected compounds in Tables 5–7. Methanethiol, methylthio
ethane, dimethyl disulfide, and hexanal were chosen to
compare the treatments because the first three have
been reported to be increased by irradiation, causing an
unappetizing odor (Ahn et al., 2000; Ahn et al., 2001;
Schweigert & Doty, 1954). Hexanal was included because it is a volatile produced from lipid oxidation
(Ahn et al., 2001) and one that may also increase with
irradiation.
Irradiation treatments resulted in production of
methanethiol (Table 5) while none of this volatile
compound was observed for unirradiated treatments. In
general, the higher irradiation doses (N, 2.2; N, 4.4; I,
4.4) also resulted in significantly greater amounts of
(P < 0:05) of methanethiol than low-dose treatments
(N, 0; I, 0) and (I, 2.2), suggesting greater production of
this volatile compound as irradiation dosage was increased. Table 5 also shows that the methanethiol levels
declined over time in treatments N, 2.2, N, 4.4, and I,
4.4, suggesting that this volatile dissipated. The methanethiol appears to be reduced by the injection treatment
but this is significant for only three of the eight irradiation treatment/time combinations. However, the times
K.J. Davis et al. / Meat Science 67 (2004) 395–401
399
Table 3
Color (L*, a*, b*) values for injected (I) and uninjected (N) fresh pork loins after irradiation
Injection/Irradiation treatment
Color value
Storage time (days)
0
7
a
21
a
35
a
N, 0 kGy
L*
a*
b*
54.64
5.72d
16.98w
56.19
4.18ef
16.73w
57.64
3.38e
16.10w
59.59a
4.23de
18.30w
I, 0 kGy
L*
a*
b*
57.23a
4.26de
16.58w
53.53a
3.08f
15.81w
54.71b
2.74de
15.67xy
55.62a
2.84f
16.56wx
N, 2.2 kGy
L*
a*
b*
56.12a
3.97e
15.11y
56.25a
5.28de
16.80w
58.20a
4.23de
15.78w
59.88a
4.50de
18.06w
I, 2.2 kGy
L*
a*
b*
54.94a
4.12de
15.41xy
54.59a
4.28ef
15.48w
54.40b
3.98de
15.28wx
57.39a
3.41ef
16.04x
N, 4.4 kGy
L*
a*
b*
55.93a
5.77d
15.46xy
56.78a
6.28d
16.63w
59.39a
5.43d
16.29w
60.37a
5.48d
17.78wx
I, 4.4 kGy
L*
a*
b*
56.20a
5.50d
15.98wx
53.55a
6.13d
15.84w
54.82b
5.57d
14.75xy
55.10a
5.34d
16.67wx
SEM
SEM
SEM
L*
a*
b*
1.58
0.59
0.50
1.54
0.42
0.51
1.39
0.59
0.44
1.88
0.69
0.56
Means within the same column for L* (a–c), a* (d–f), and b* (w–z) with different superscripts are significantly different (P < 0:05). N, uninjected;
I, injected. 0, 2.2, and 4.4 kGy denote the dosage of irradiation the product received in kGy.
Table 4
TBA values (mg malonaldehyde/kg meat) for injected (I) and uninjected (N) fresh pork loins after irradiation
Injection/
Irradiation
treatment
N, 0 kGy
I, 0 kGy
N, 2.2 kGy
I, 2.2 kGy
N, 4.4 kGy
I, 4.4 kGy
SEM
Storage time (days)
1
0.08bcd
0.07d
0.11abc
0.08bcd
0.13a
0.10abc
0.01
7
0.10bc
0.08d
0.13ab
0.10bc
0.14a
0.12ab
0.01
21
0.10c
0.07d
0.12b
0.11bc
0.12b
0.15a
0.02
35
0.09cd
0.08d
0.10c
0.10c
0.19b
0.24a
0.02
Table 5
Methanethiol (ion count 1000) production from injected (I) and
uninjected (N) fresh pork loins after irradiation
Injection/Irradiation
treatment
Storage time (days)
0
7
21
35
N, 0 kGy
I, 0 kGy
N, 2.2 kGy
I, 2.2 kGy
N, 4.4 kGy
I, 4.4 kGy
SEM
0d
0d
2908.8b
151.4c
7575.0a
5206.8ab
910.9
0d
0d
358.0c
0d
7302.2a
4131.6b
440.1
0c
0c
1139.8b
123.6b
4738.0a
3759.6a
746.2
0c
0c
1195.4ab
558.6ab
2777.8a
1897.0a
1053.1
Means within the same column with different superscripts (a–d) are
significantly different (P < 0:05). N, uninjected; I, injected. 0, 2.2, and
4.4 kGy denote the dosage of irradiation the product received in kGy.
Means within the same column with different superscripts (a–d) are
significantly different (P < 0:05). N, uninjected; I, injected. 0, 2.2, and
4.4 kGy denote the dosage of irradiation the product received in kGy.
when differences are significant are all either at day 0 or
day 7 which may indicate that differences were reduced
over time by dissipation. Also, the I, 2.2 kGy treatment
resulted in values within one standard deviation of zero,
suggesting that volatiles the values were not different
than zero and were suppressed by the injection treatment. Similar results were observed for dimethyl disulfide (Table 6) except that a low level of this volatile was
observed in samples that were not irradiated. Methylthio ethane (Table 7) was present only in the irradiated
samples but did not dissipate during storage. Hexanal
(data not shown) increased slowly during storage but no
significant effects of irradiation or injection treatments
were observed. Hexanal is a volatile often used to indicate lipid oxidation (Ang & Lyon, 1990), but does not
always correlate directly the TBA analysis. In this study,
the TBA values (Table 4) indicated significant effects of
irradiation treatments. However, all the TBA values
were relatively low (<0.24) meaning that very little
oxidation occurred.
400
K.J. Davis et al. / Meat Science 67 (2004) 395–401
Table 6
Dimethyl disulfide (ion count 1000) production from injected (I) and
uninjected (N) fresh pork loins after irradiation
Injection/
Irradiation
treatment
Storage time (days)
0
7
N, 0 kGy
I, 0 kGy
N, 2.2 kGy
I, 2.2 kGy
N, 4.4 kGy
I, 4.4 kGy
SEM
73.2d
32.4d
3158b
1415.2c
6583.6a
5270.6a
783.1
50.6c
56.8c
460.8b
284.6b
5197a
5597a
614.7
21
132.2cd
53.8cd
2194.2b
460.2c
4810.2a
4499.4a
755.7
35
0c
59.7c
2861a
655.0bc
2010.4a
1257.4ab
932.7
Means within the same column with different superscripts (a–d) are
significantly different (P < 0:05). N, uninjected; I, injected. 0, 2.2, and
4.4 kGy denote the dosage of irradiation the product received in kGy.
Table 7
Methythioethane (ion count 1000) production from injected (I) and
uninjected (N) fresh pork loins after irradiation
Injection/
Irradiation
treatment
Storage time (days)
0
7
21
35
N, 0 kGy
I, 0 kGy
N, 2.2 kGy
I, 2.2 kGy
N, 4.4 kGy
I, 4.4 kGy
SEM
0c
0c
98.2ab
65.0b
128.0a
122.0a
29.8
0c
0c
86.6ab
58.4b
155.2a
138.8a
24.2
0c
0c
128.4ab
62.6b
155.2a
157.8a
21.2
0c
0c
164.0ab
101.2b
222.0a
205.8a
28.9
Means within the same column with different superscripts (a–c) are
significantly different (P < 0:05). N, uninjected product; I, injected. 0,
2.2, and 4.4 kGy denote the dosage of irradiation the product received
in kGy.
4. Conclusions
The results of this experiment indicated that injection
of pork loins with a salt/phosphate/lactate brine had
relatively little effect on quality changes often observed
for irradiation. Some of the volatiles increased by irradiation appeared to be reduced by the injection treatment especially during the first 7 days following
irradiation, but this effect was not consistent for all
treatment/storage time combinations studied. Lipid oxidation, as measured by TBA values, increased with irradiation dosage, but the change in TBA value with
irradiation did not seem to be affected by injection
treatment. Likewise, color changes were observed with
irradiation treatment but injection did not appear to
have an influence on irradiation-induced color changes.
In uninjected loins, purge seemed to be decreased at
2.2 kGy, but not at 4.4 kGy and further investigation of
irradiation effects on purge is required. Injection treatment resulted in decreased WBS force values indicating
a consistent tenderness improvement regardless of the
irradiation treatment. Thus, injection of fresh pork with
a salt/phosphate/lactate brine did not change tenderness
or color characteristics of irradiated pork loins. At the
same time, injection processing may have potential to
decrease production of some volatiles produced by irradiation. The role of specific ingredients for control of
volatiles produced during irradiation of pork cuts requires further investigation.
Acknowledgements
This journal paper of the Iowa Agriculture and Home
Economics Experiment Station, Ames, Iowa, Project
Nos. 3700 and 3705, was supported by Hatch Act and
State of Iowa funds. A portion of this project was funded by the National Pork Board on behalf of the Iowa
Pork Producers Association. The authors express gratitude to Mike Holtzbauer, Marcia King-Brink and
Randy Petersohn for technical assistance.
References
Ahn, D., Jo, C., Du, M., Olson, D., & Nam, K. (2000). Quality
characteristics of pork patties irradiated and stored in different
packaging and storage conditions. Meat Science, 56, 203–209.
Ahn, D., Jo, C., & Olson, D. (1999). Analysis of volatile components
and the sensory characteristics of irradiated raw pork. Meat
Science, 54, 209–215.
Ahn, D., Nam, K., Du, M., & Jo, C. (2001). Volatile production in
irradiated normal, pale soft exudative (PSE) and dark firm dry
(DFD) pork under different packaging and storage conditions.
Meat Science, 57, 419–426.
Ang, C. Y. W., & Lyon, B. G. (1990). Evaluation of warmed-over
flavor during chill storage of cooked broiler breast, thigh and skin
by chemical, instrumental, and sensory methods. Journal of Food
Science, 55, 644–648.
Dempster, J. (1985). Radiation preservation of meat and meat
products: A review. Meat Science, 12, 61–89.
Heath, J., Owens, S., & Tesch, S. (1990). Effect of high-energy electron
irradiation of chicken meat on thiobarbituric acid values, shear
values, odor, and cooked yield. Poultry Science, 69, 313–319.
Lambert, A., Smith, J., & Dodds, K. (1992). Physical, chemical and
sensory changes in irradiated fresh pork packaged in modified
atmosphere. Journal of Food Science, 57, 1294–1299.
Luchsinger, S. E., Kropf, D., Garcia Zepeda, C., Hunt, M., Stroda, S.,
Marsden, J., & Kastner, C. (1997). Color and oxidative properties
of irradiated ground beef patties. Journal of Muscle Foods, 8, 445–
464.
Mielche, M. M., & Bertelsen, G. (1994). Approaches to prevention of
warmed-over flavour. Trends in Food Science and Technology,
5(10), 322–327.
Murano, E. A. (1995). Quality of irradiated foods. In E. A. Murano
(Ed.), Food Irradiation: A Sourcebook. Ames, Iowa: Iowa State
University Press.
Nanke, K., Sebranek, J., & Olson, D. (1998). Color characteristics of
irradiated vacuum packaged pork, beef and turkey. Journal of Food
Science, 63, 1001–1006.
Niemand, J., van der Linde, H., & Holzapeel, W. (1981). Radurization
of prime beef cuts. Journal of Food Protection, 44, 677–681.
K.J. Davis et al. / Meat Science 67 (2004) 395–401
Offer,G., & Trinick,J. (1983). On the mechanismofwater holdingin meat:
The swelling and shrinking of myofibrils. Meat Science, 8, 245–281.
Papadopoulos, L. S., Miller, R. K., Ringer, L. J., & Cross, H. R. (1991).
Sodium lactate effect on sensory characteristics, cooked meat color
and chemical composition. Journal of Food Science, 56, 621–626.
SAS, Statistical Analysis System Institute (2000). SAS userÕs guide.
Cary, NC: SAS Institute.
Schweigert, B., Doty, D., & Niven Jr., C. (1954). A summary of studies
on the irradiation of meats. In Radiation sterilization: Review of
the literature in selected fields. Chicago, IL: Chicago Quartermaster
Depot, US Army.
401
Sheard, P. R., Nute, G. R., Richardson, R. I., Perry, A., & Taylor, A.
A. (1998). Injection of water and polyphosphate into pork to
improve juiciness and tenderness after cooking. Meat Science, 51,
371–376.
Tarladgis, B., Watts, B., Younathan, M., & Dugan, L. (1960). A
distillation method for the quantitative determination of malonaldehyde in rancid foods. Journal of American Oil Chemists Society,
37, 44–48.
USDA, US Department of Agriculture (1999). Irradiation of meat
food products. Final Rule, 9CFR81 & 424 Docket No. 97076C.