Radiation Physics and Chemistry 81 (2012) 466–472
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Radiation Physics and Chemistry
journal homepage: www.elsevier.com/locate/radphyschem
Effects of low-level gamma irradiation on the characteristics of fermented
pork sausage during storage
I.S. Kim a, C. Jo b, K.H. Lee c, E.J. Lee d, D.U. Ahn d, S.N. Kang a,n
a
Department of Animal Resources Technology, Gyeongnam National University of Science and Technology, Gyeongnam 660-758, Republic of Korea
Department of Animal Science and Biotechnology, Chungnam National University, Daejeon 305-764, Republic of Korea
c
Department of Food Science and Nutrition, Chungju National University, 368-701 Chungj, Republic of Korea
d
Department of Animal Science, Iowa State University, Ames, IA 50011-3150, USA
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 March 2011
Accepted 23 December 2011
Available online 5 January 2012
The effect of gamma irradiation (0.5, 1, 2, and 4 kGy) on the quality of vacuum-packaged dry fermented
sausages during refrigerated storage was evaluated. At Day 0 of irradiation, the pH, redness (CIE an),
yellowness (CIE bn), 2-thiobarbituric acid-reactive substances (TBARS) and volatile basic nitrogen (VBN)
values of samples irradiated at 2 and 4 kGy were higher (p o 0.05), but the CIE Ln values (lightness) were
lower than those of the non-irradiated control (po 0.05). Ato 1 kGy irradiation, however, the pH, CIE
Ln, CIE an and CIE bn-value of samples were not significantly influenced by irradiation. The CIE an, and
CIE bn-values of samples irradiated at 2 and 4 kGy decreased with the increase of storage time. The VBN,
TBARS, and CIE Ln-values of samples irradiated at 4 kGy were not changed significantly during
refrigerated storage for 90 days (p4 0.05). The total plate counts (TPC) and lactic acid bacteria (LAB)
in the samples irradiated at 4 kGy were significantly lower (p o 0.01) than those with lower irradiation
doses. At the end of storage, the TPC, coliform, and LAB in the samples were not increased after
irradiation at 1, 0.5 and 1 kGy, respectively. TPC and LAB were not detected in samples irradiated at
4 kGy at Day 90. In addition, no coliform bacteria were found in samples irradiated at 1 kGy during
refrigerated storage. Sensory evaluation indicated that the rancid flavor of samples irradiated at 4 kGy
was significantly higher, but aroma and taste scores were lower than those of the control at Day 3 of
storage. Irradiation of dry fermented sausages at 2 kGy was the best conditions to prolong the shelf-life
and decrease the rancid flavor without significant quality deterioration.
& 2011 Elsevier Ltd. All rights reserved.
Keywords:
Fermented sausage
Gamma irradiation
Storage
Lactic acid bacteria
Lipid oxidation
1. Introduction
Several methods, which include cooking, freezing, fermenting,
salting, drying, and pickling (Choi et al., 2009; Jin et al., in press;
Kang et al., 2002; Kim et al., 2009) have been used to reduce the
number of microorganisms and increase the shelf-life and safety
of meat (Farkas, 1998). One of the most promising approaches to
improve microbial safety of meat, however, would be the use
of low or medium-dose irradiation (1–10 kGy) (WHO, 1999).
A number of investigators have shown that irradiation is very
effective in controlling the growth of pathogenic and spoilage
bacteria in meat (Grant and Patterson, 1991; Huhtanen et al.,
1989; Patterson et al., 1993; Sommers et al., 2003; Thayer and
Boyd, 1993; Thayer et al., 1990; Zhu et al., 2005). However, meat
is generally susceptible to oxidative deterioration due to the
oxidation of polyunsaturated fatty acids in phospholipids.
n
Corresponding author. Tel.: þ82 55 751 3288; fax: þ 82 55 751 3689.
E-mail address: white@gntech.ac.kr (S.N. Kang).
0969-806X/$ - see front matter & 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.radphyschem.2011.12.037
Irradiation accelerates free radical reactions resulting in the
possibility of color changes, lipid oxidation and odor generation,
which may generate negative consumer responses (Ahn et al.,
1997; Du et al., 2000; Jo and Ahn, 2000; Luchsinger et al., 1996;
Patterson and Stevenson, 1995; Thayer and Boyd, 1993).
Fermented sausages have a long tradition and have been
originated from Mediterranean countries with a dry climate
(Spain, Italy, France, Portugal and Turkey) (Lücke, 1985; PerezAlvarez et al., 1999). A mixture of comminuted lean meat (pork
and/or beef), pork back fat, salt, curing agent (nitrate and/or
nitrite), and spices with lactic acid starter culture is used
to produce fermented sausages (Caplice and Fitzgerald, 1999).
During fermentation, a slow but substantial heating takes place,
which is very important for encouraging the growth of lactic acid
bacteria (LAB) (Acton and Dick, 1977). These LAB, together with
the lipolytic and protelytic enzymes (Olesen and Stahnke, 2000),
determine the characteristics of the final product. At the end
of the ripening process, fermented sausages are characterized
with accentuated acidity, slight sourness, elastic, and semi-hard
consistency (Comi et al., 2005; Houben and van’t Hooft, 2005).
I.S. Kim et al. / Radiation Physics and Chemistry 81 (2012) 466–472
Dry fermented sausages being relatively high fat foodstuffs and
long period of manufacturing steps and post-fermentation
storage, lipid oxidation can damage their sensorial properties,
which are associated to rancid taste and odor (Ansorena and
Astiasarán, 2004).
Numerous studies have been conducted to determine the
impact of irradiation on meat quality (Badr, 1998; Brewer,
2009; Brewer, 2004; Hampson et al., 1996; Zhou et al., 2010),
but little information on the quality changes of irradiated
dry fermented meat products is available (Cava et al., 2009).
The quality characteristics of irradiated fermented sausages
would be very important for the acceptance of irradiation technology. Smith and Palumbo (1983) suggested that fermented
sausages treated with irradiation induced the dominance of lactic
acid bacteria (LAB) in the microflora to produce desirable flavor.
However, consumer awareness of food irradiation, in general, is
very low, as majority of consumers are uncertain about the safety
of irradiated foods. Therefore, establishing optimum process
conditions to minimize the negative effects of irradiation on lipid
oxidation and LAB survival is critical to increase consumer
acceptance of irradiated dry fermented sausage.
The objective of this study was to investigate the effect of lowlevel gamma-irradiation (0.5, 1, 2 and 4 kGy) on the color, lipid
oxidation, microbial counts, and sensory characteristics of
vacuum-packaged dry fermented sausages during storage.
2. Materials and methods
2.1. Preparation of dry, fermented sausages
Fresh boneless pork loin and backfat were ground separately
in a mincer (Model 5K5SS, USA) equipped with an adjustable
plate set with a hole diameter of 5 mm, and used to make
sausages. Seasonings, additives, and a starter culture were added
according to the following formula: (a) raw material (%, w/w):
pork meat (86), pork backfat (9), NaCl (2.5), NaNO3 (0.012),
NaNO2 (0.008), sodium ascorbate (0.25), glucose (0.3), sucrose
(0.4), powdered black pepper (0.2), red pepper (0.2), garlic (0.5)
and commercial seasoning (0.58), and mixed in a silent cutter
(K15, Roman, Spain) for 3 min at 10 1C. Seasonings and additives
were obtained from MSC Co., Ltd. (Seongnam, Korea). A commercially available frozen meat starter (Abiasa, Canada) (0.05%)
consisting of Lactobacillus pentosus and Staphylococcus carnosus
(C-P-77S Bactoferm TM, Chr. Inc., Hansen, Denmark) was added at
a concentration of ca. 9 log CFU/g, according to the manufacturer’s
instructions. All the sausages were manufactured at the same day,
using the same technology, ingredients and formulation. The final
mixture was stuffed into synthetic casings (4.5 mm diameter).
The sausages were fermented in a ripening cabinet at 25 1C and
90% relative humidity (RH) for 24 h. Then, the temperature and
RH were slowly reduced to reach 10 1C and 70% RH, respectively
and ripened for 30 days. At the end of the ripening process, the
final products were vacuum-packaged (0.5 cm3/m2/atm/24 h,
Danisco Flexible Lyngby, Denmark) and stored at 4 1C for 3
days. The experiment was triplicated with 2 observations per
replications.
2.2. Irradiation and storage conditions
The vacuum-packaged sausages were irradiated at 0 (control),
0.5, 1, 2, and 4 kGy using a Co-60 gamma irradiator (point source,
AECL, IR-79, MDS Nordion International Co., Ltd., Ottawa, Ontario,
Canada) with the source strength of 100 kCi. The dosimetry was
performed using 5 mm-diameter alanine dosimeters (Bruker
Instruments, Rheinstetten, Germany), and the free radical signal
467
was measured using a Bruker EMS 104 EPR Analyzer. To confirm
the target dose, alanine dosimeters attached to the top and
bottom surfaces of the sample packs were read. The actual dose
was within 72% of the target dose. The non-irradiated control
was placed outside of the irradiation chamber to maintain the
temperatures conditions as the irradiating ones. The control and
irradiated samples were transferred to a 4 1C refrigerator and
stored at 4 1C for 90 days. The quality (pH, color, lipid oxidation,
volatile basic nitrogen, microbial) and sensory characteristics of
the dry fermented sausages were determined after 1, 3, 30, 60,
and 90 day of storage at 4 1C.
2.3. Quality evaluation
The pH values were determined by homogenizing (T25B, IKA
Sdn. Bhd., Malaysia) 10 g of a ground sample with 90 mL distilled
water, and then measured with a pH meter (Model 8603,
Metrohm, Swiss).
For color measurements, sausages were cut into slices of 3 cmthickness and the surface color of the slices was measured three
times for each sample using a spectrocolorimeter (CR 400,
Minolta Co., Japan) (l ¼400–700 nm, Dl ¼10 nm, D65, 101) calibrated with a white plate and light trap supplied by the manufacturer. Color was expressed using the CIE Ln, an, bn color system
(CIE, 1976).
TBARS method (Tarladgis et al., 1960) was used to determine
the degree of lipid oxidation in fermented sausages. A 5 g sample
was homogenized in a 50 mL centrifuge tube with 50 mL of BHA
(7.2% in ethanol) and 15 mL of distilled water using a homogenizer (IKA model T-25 Basic, Malaysia). 2 mL of the homogenate
was mixed with 4 mL of thiobarbituric acid (TBA)/trichloroacetic
acid (TCA) solution (20 mM TBA in 15% TCA), heated at 90 1C in
water bath, cooled in ice and centrifuged for 15 min at 2,000 rpm
(UNION 5KR; Hanil Science Industrial, Co. Ltd., Incheon, Korea).
The absorbance of the supernatant was measured at 532 nm
using a spectrophotometer (Spectronic model Genesys 5, USA).
The concentration (mg malonaldehyde/kg sample on the basis of
wet weight) was calculated using a standard curve prepared with
1,1,3,3 tetraethoxypropane (0–1.0 mM).
Measurement of VBN in the sample was done according to the
Conway micropipette diffusion method (Pearson, 1968). Each
meat sample (3 g) was homogenized (T25B, IKA Sdn. Bhd.,
Malaysia) for 1 min with 25 mL distilled water, and then centrifuged (Hanil) at 13,000 rpm for 15 min. The supernatant was
filtered using a filter paper (no. 1, Whatman), and the filtrate was
placed in a test tube and made up to a final volume of 30 mL with
distilled water. A volume of 0.01 N boric acid as a VBN absorber
was placed in the inner section of a Conway micro-diffusion cell
(Sibata Ltd. Tokyo, Japan). 1 mL sample solution and 1 mL saturated K2CO3 were also placed in the outer section of the same cell
and the lid was immediately closed. Distilled water was used as
blank. The cell was incubated at 37 1C for 120 min, and then
titrated against 0.02 N sulfuric acid. The concentration of VBN
was calculated as ammonia equivalent using the following equation:
VBN value ðmg=100 g meatÞ ¼ ½0:28ðtitration volume of
sample solution2titration volume of blankÞ10=100:
For microbial analyses, duplicated samples (25 g for each)
were taken aseptically from each treatment, transferred to sterile
plastic pouches and homogenized for 2 min at room temperature
with 225 mL sterile 0.88% (w/v) NaCl solution using a stomacher
Lab-Blender 78860 (ST-Nom, Interscience, France). Appropriate
dilutions of samples were prepared in sterile 0.88% (w/v) NaCl
solution, plated in duplicate onto plate count agar (PCA; Difco
Laboratory, Detroit, MI, USA) for total bacteria and incubated at
468
I.S. Kim et al. / Radiation Physics and Chemistry 81 (2012) 466–472
32 1C for 48 h under anaerobic conditions. Lactic acid bacteria
were incubated anaerobically on Lactobacilli MRS Agar (Difco) at
32 1C for 2 days. Coliforms were incubated on E. coli/coliform
count plate petrifilm (3M Health care, Minnesota, USA) at 30 1C
for 2 days under the same aerobic conditions.
The sensory characteristics of the dry fermented sausages
were assessed by 12 trained panelists. To acquaint panelists with
product attributes and intensities, six 1 h training sessions were
carried out over a week period prior to sample testing. During this
phase, dry, fermented sausages from a variety of manufacturers
corresponding to maximum and minimum intensities that might
be found for each attribute (1, very low, to 6, very high) were
presented to panelists. To test the panel reproducibility, one
additional dry-fermented sausage was presented at each session.
It was the replicate of the second sample of the set and was
served as the last of the session. The panel sessions were held at
mid-morning, about 3 h after breakfast. Slices (1.5 mm-thick) of
the samples were prepared with a slicing machine (manufacturer,
spec) and served to panelists on plates with random codes. The
color, aroma, taste (1¼extremely undesirable, 6¼extremely
desirable) and rancid flavor (1¼extremely low intensity,
6¼extremely high intensity) of the samples were evaluated using
6-point descriptive scale. Panelists were required to clean their
palate between samples with water. Five samples were successively evaluated in each session at day 3, 60 and 90 of storage and
the sample order was randomized within sessions.
2.4. Statistical analysis
Whole experiment was conducted 3 times with 2 observations
per each replication and the results were presented as a
mean 7standard deviation. An analysis of variance were performed on all variables measured using the general linear model
procedure of the SAS software (SAS, 2002). Duncan’s multiple
range test was used to determine differences among treatment
means (p o0.05).
sugars (dextrose and lactose) added in the meat to lactic acid
(Flores and Alvarruo~ Âz, 1985). Irradiation had no effects on the
pH of the fermented sausages.
3.2. Color evaluation
The color changes of the irradiated dry fermented sausages
during storage are presented in Table 2. Color changes of dry
fermented sausages were dose-dependent after irradiation (day 1).
Lightness (Ln-value) decreased while redness (an-value) and
yellowness (bn-values) increased with irradiation. These results
are in agreement with previous findings in dry-cured ham (Cava
et al., 2005, 2009) as well as uncured raw and cooked meat
(Luchsinger et al., 1996; Millar et al., 2000; Nam and Ahn, 2002).
Nam and Ahn (2002) attributed the red color increase in irradiated turkey meat to the formation of carbon monoxide–
myoglobin (CO–Mb) complexes. Compared with oxymyoglobin,
CO–Mb complex is not easily oxidized to brown metmyoglobin,
because of the strong binding of CO to the iron-porphyrin in
myoglobin molecule (Sorheim et al., 1999).
After 90 day of refrigerated storage, irradiated dry fermented
sausages had significantly lower (po0.01) CIE an- and CIE bnvalues than those of the non-irradiated ones, while this trend was
not found in Ln-values. Storage tended to decrease the lightness of
non-irradiated dry fermented sausages while redness and yellowness tended to increase. The effects of irradiation on the color
changes in fermented sausages are not well established, but the
fading of redness in the irradiated dry fermented sausages during
storage could be related to the destruction of nitrosoheme
pigment by irradiation process.
The results suggested that the increase in redness and yellowness immediately after irradiation are a reversible phenomenon,
and the cured meat pigment can also be oxidized during storage.
Previous studies have reported that nitrite inhibited the changes
in color by irradiation (Fan et al., 2004), but Cava et al. (2009)
observed that the CIE an-values declined markedly upon extended
storage of dry-cured ham.
3. Results and discussion
3.3. TBARS values
3.1. pH value
Irradiation increased the TBARS of dry fermented sausages in a
dose-dependent manner at Days 1 and 30. The samples irradiated
at 4 kGy had higher TBARS values than those irradiated at 0, 0.5, 1,
or 2 kGy at Days 1 and 30 (0.52 and 0.45 mg MA/kg, respectively)
(Table 3). These results are in agreement with previous findings in
meat and meat products (Ahn et al., 1998, 1999; Hampson et al.,
1996; Luchsinger et al., 1996). However, irradiation had no
significant effects on the TBARS values of dry fermented sausages
at Days 60 and 90 of storage. The initial TBARS values (day 1) of
samples irradiated at 0, 0.5, and 1 kGy did not changed until
Day 30, but increased at day 60 (p o0.01), indicating a slow
development of lipid oxidation under refrigerated storage conditions. No significant changes in the TBARS values of dry fermented
sausages irradiated at 2 and 4 kGy during refrigerated storage
were observed after rapid increase of TBARS values at Day 1.
In general, irradiation induces lipid oxidation and accelerates
oxidative process during storage (Kanatt et al., 1998). However,
Choi et al. (2009) observed the decrease of TBARS values in dry
cured loin meat treated with electron beam irradiation (5 and
10 kGy) during refrigerated storage.
The pH changes of the irradiated dry, fermented sausages
during refrigerated storage are presented in Table 1. Fermented
sausages are characterized by low acidity and the final pH is in
the range of 4.8–6.2 (Aymerich et al., 2003; Dirinck et al., 1997;
Johansson et al., 1994; Sanchez-Molinero and Arnau, 2008).
Regardless of irradiation treatments, the pH values of the dry,
fermented sausages were in the range of 4.88 to 4.93 during the
refrigerated storage. The observed low pH values of sausages
were due to the activity of starter culture which metabolized
Table 1
pH values of vacuum-packaged dry fermented sausages stored for 90 days at 4 1C
after irradiation.
Dose (kGy)
0
0.5
1.0
2.0
4.0
n¼ 3.
Storage (day)
1
30
60
90
4.917 0.04
4.927 0.02
4.937 0.05
4.937 0.05
4.947 0.04
4.91 70.04
4.90 70.06
4.89 70.08
4.91 70.06
4.88 70.04
4.89 7 0.06
4.91 7 0.05
4.90 7 0.06
4.92 7 0.07
4.91 7 0.05
4.89 7 0.06
4.90 7 0.04
4.92 7 0.03
4.91 7 0.04
4.91 7 0.08
3.4. VBN values
The VBN values of dry fermented sausages irradiated at
41 kGy were significantly higher than those of the 0.5 kGy and
non-irradiated samples at Day 1 (p o0.01). The VBN values of
I.S. Kim et al. / Radiation Physics and Chemistry 81 (2012) 466–472
469
Table 2
Effect of gamma irradiation on the CIE Ln, an, and bn-values of dry-fermented sausages during storage.
Dose (kGy)
CIE Ln
0
0.5
1.0
2.0
4.0
Storage (day)
Sig.
1
30
60
90
44.607 0.36Aa
43.807 0.79ABa
43.707 0.56ABa
42.707 0.17BCab
41.67 70.85C
43.607 1.68ab
42.83 70.51ab
43.13 70.64a
43.23 70.64a
42.33 70.29
43.13 70.31ab
42.27 70.40bc
41.14 70.32b
41.907 0.95b
41.57 71.46
42.63 70.67b
41.607 0.35c
41.83 70.72b
41.63 70.35b
41.407 1.15
12.17 70.59ab
12.707 0.36
12.107 0.61
11.93 70.57b
11.037 0.50b
12.607 0.66Aa
12.107 0.79AB
12.107 0.66AB
10.937 0.51BCc
9.977 0.47Cc
13.077 0.67Aa
12.67 70.57A
12.57 70.38A
11.077 0.57Bc
9.607 1.06Cc
nn
nnn
6.207 0.44a
5.907 0.70
5.607 0.20
5.907 0.20a
5.807 0.36a
6.43 70.32Aa
6.007 0.32AB
5.67 70.26BC
5.077 0.32CDb
4.96 70.40Db
n
nnn
n
nn
Sig.
n
CIE a
11.207 0.66Cb
12.41 70.22B
12.307 0.26B
13.37 70.21Aa
12.83 70.15Aa
0
0.5
1.0
2.0
4.0
nnn
Sig.
CIE bn
5.407 0.10Cb
5.507 0.10C
5.777 0.35BC
5.937 0.15Ba
6.437 0.25Aa
0
0.5
1.0
2.0
4.0
5.637 0.21b
6.107 0.26
5.907 0.20
6.177 0.25a
6.107 0.26a
nnn
Sig.
n
nnn
nnn
nn
nn
nnn
nnn
n¼ 3.
Sig. means Significance.
a–d means with different letters within a row of the same irradiation dose are different (npo 0.05, nnp o0.01, nnnp o0.001).
A–D means with different letters within a column of the same day of storage are different (nnp o 0.01, nnnp o 0.001).
Table 3
2-thiobarbituric acid-reactive substances (TBARS) of vacuum-packaged dry-fermented sausages stored for 90 days at 4 1C after gamma-irradiation (mg malondialdehyde/kg meat).
Dose (kGy)
0
0.5
1.0
2.0
4.0
Sig.
Storage (day)
Sig.
1
30
60
90
0.337 0.05Db
0.417 0.03CBb
0.367 0.03Cc
0.457 0.01B
0.527 0.03A
0.367 0.01Bb
0.397 0.01Bb
0.367 0.03Bc
0.387 0.05B
0.457 0.04A
0.427 0.02a
0.477 0.03a
0.457 0.01b
0.437 0.04
0.467 0.03b
0.447 0.03a
0.497 0.01a
0.527 0.02a
0.457 0.01
0.497 0.04
nn
n
nn
nn
nn
n¼ 3.
Sig. means Significance.
a–c means with different letters within a rows of the same irradiation dose are
different (nnp o 0.01).
A–D means with different letters within a column of the same day of storage are
different (np o 0.05, nnpo 0.01).
Table 4
Volatile basic nitrogen (VBN) of vacuum-packaged dry-fermented sausages stored
for 90 days at 4 1C after gamma-irradiation (mg VBN/100 g meat).
Dose
(kGy)
0
0.5
1.0
2.0
4.0
Sig.
Storage (day)
Sig.
1
30
60
90
14.93 7 0.43Bd
14.93 7 0.43Bc
16.24 7 0.56Ac
17.08 7 0.28Ab
17.08 7 0.56A
16.05 70.43Bc
16.05 70.70Bbc
16.99 70.65ABc
16.80 70.56ABb
17.45 70.43A
19.60 7 0.28Ab
17.17 7 0.86Bb
16.15 7 0.70Bb
17.27 7 0.58Bb
16.80 7 0.48B
20.35 70.43Aa
19.41 7 0.43Aa
19.69 7 0.58Aa
19.79 7 0.43Aa
18.20 71.01B
nn
n
nn
n
nn
nn
nn
n
n¼3.
Sig. means Significance.
a–c means with different letters within a row of the same irradiation dose are
different (np o0.05, nnp o 0.01).
A–D means with different letters within a column of the same day of storage are
different (np o0.05, nnp o 0.01).
3.5. Microbiological properties
samples irradiated at 4 kGy were significantly higher than those
of non-irradiated samples at Day 30, while those of samples
irradiated at o4 kGy were significantly lower than that of the
non-irradiated control at Days 60 and 90. Storage significantly
increased the VBN of dry fermented sausages irradiated at 0, 0.5, 1,
and 2 kGy while no significant changes in VBN values were
observed for the sample irradiated at 4 kGy (Table 4). The
decrease of VBN formation in dry fermented sausages irradiated
at 4 kGy during storage was caused by the reduction of the initial
levels of common spoilage bacteria. The VBN is related to
bacterial activities (Banwart, 1981) and protein breakdown
(Eagan et al., 1981). The S-containing volatiles were highly
dependent upon irradiation dose in pork (Ahn et al., 2000) and
in ground beef (Ahn and Nam, 2004). In this study higher VBN
values were associated with a increase in protein breakdown
caused by the increase in applied radiation (Table 4). These
results agree with previous observations (Badr, 1998; Javanmard
et al., 2006).
The most common microorganisms in dry fermented sausages
are lactic acid bacteria and members of Micrococcaceae family
at levels higher than 6–7 log CFU/g (Ordóñez et al., 1999).
The changes of total plate counts (TPC) (log CFU/g) in the irradiated
dry fermented sausages during refrigerated storage are presented
in Table 5. Significant differences were observed between nonirradiated and irradiated samples at Days 1, 30, 60, and 90
(po0.01). The initial TPC (Day 1) of non-irradiated samples were
6.34 log CFU/g, while those irradiated at 1, 2, and 4 kGy were 5.23,
5.36, and 2.46 log CFU/g, respectively. Significant changes in TPC
were not found in samples irradiated at 0 and 1.0 kGy during
refrigerated storage. However, TPC of 2 and 4 kGy-irradiated
samples decreased significantly during refrigerated storage. In
addition, samples irradiated at 4 kGy initially had detectable TPC
numbers but undetectable after 90 days of storage. There was no
recovery of radiation-damaged cells and no growth in samples
irradiated at 2 kGy. Chung et al. (2000) also reported that TPC
decreased with storage time for 4 kGy-irradiated meat products.
Grant and Patterson (1992) reported that sublethal damage to cells
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I.S. Kim et al. / Radiation Physics and Chemistry 81 (2012) 466–472
Table 5
Changes of total plate count, coliform and lactic acid bacteria of vacuum-packaged
dry-fermented sausages stored for 90 days at 4 1C after gamma-irradiation.
Dose (kGy) Storage (day)
Sig.
1
30
60
90
TPC
0
0.5
1.0
2.0
4.0
6.34 7 0.13A
5.49 7 0.10Bb
5.23 7 0.82B
5.36 7 0.05Ba
2.46 7 0.17Ca
5.77 7 0.05A
5.13 7 0.23Bb
5.19 7 0.48B
3.68 7 0.10Cb
1.28 7 0.17Db
5.777 0.49A
5.607 0.53Ab
5.437 0.10A
3.817 0.28Bb
0.867 0.41Cb
6.367 0.33A
6.097 0.37Aa
5.117 0.12B
3.127 0.10Cc
NDDc
Coliform
0
0.5
1.0
2.0
4.0
2.87 7 0.23A
1.70 7 0.16B
NDC
NDC
NDC
2.22 7 0.42A
1.45 7 0.08B
NDC
NDC
NDC
2.237 0.62A
1.427 0.21B
NDC
NDC
NDC
2.137 0.52A
1.317 0.12B
NDC
NDC
NDC
LAB
0
0.5
1.0
2.0
4.0
Ab
4.93 7 0.31
4.25 7 0.42Ab
4.93 7 0.20Aab
4.85 7 0.38Aab
2.38 7 0.51Ba
Ab
5.17 7 0.12
4.19 7 0.08Bb
4.20 7 0.09Bbc
4.27 7 0.25Bb
2.44 7 0.38Ca
Ab
4.777 0.13
3.957 0.31ABb
3.687 0.85Bc
3.447 0.43Bc
1.487 0.01Cb
Aa
6.817 0.54
5.817 0.23Ba
5.567 0.23Ba
4.927 0.14Ca
NDDc
n
nn
nn
Table 6
Effect of gamma irradiation on the sensory characteristics of dry fermented
sausages during storage at 4 1C.
Dose
(kGy)
Color
0
0.5
1.0
2.0
4.0
Aroma
0
0.5
1.0
2.0
4.0
Sig.
nn
nn
nn
nn
nn
n¼ 3.
Sig. means Significance.
a–c means with different letters within a row of the same irradiation dose are
different (*p o 0.05, **p o0.01).
A–D means with different letters within a column of the same day of storage are
different (p o 0.05).
by irradiation is likely to increase their sensitivity to environmental
stress factor. Kim et al. (2000) reported that the decrease of
microbial population in irradiated meat during storage was due
to post-irradiation effect where survived cells that had been
damaged by gamma irradiation could not adapt to the surrounding
environment during storage and gradually died.
The initial coliform count (Day 1) of non-irradiated samples
was 1.87 log CFU/g, while that of the sample irradiated at 0.5 kGy
was 1.70 log CFU/g. No coliforms were detected in the samples
irradiated at 1.0 kGy or above. Significant differences in the
number of LAB were observed between non-irradiated and
irradiated samples at day 1, 30, 60 and 90 (p o0.01). The initial
LAB count (Day 1) of non-irradiated sample was 4.93 log CFU/g,
while those of irradiated samples at 0.5, 1, 2, and 4 kGy were 4.25,
4.93, 4.85, and 2.38 log CFU/g, respectively. There were no significant differences in LAB counts between non-irradiated and
irradiated samples up to 2 kGy at Day 1. However, the LAB counts
of samples irradiated at 4 kGy was reduced to 2.55 log CFU/g at
Day 1 (p o0.01). No growth in LAB was observed in samples
irradiated at 4 kGy during refrigerated storage. The increased
population of LAB during the fermentation process caused pH
drop, which resulted in reduced TPC and coliforms (Gonzalez and
Diez, 2002; Lizaso et al., 1999). The TPC and coliforms could be
significantly reduced by 2 kGy-irradiation, but the number of LAB
can be increased slowly during storage (Dickson and Maxcy,
1985).
3.6. Sensory analysis
The rancid flavor and taste scores of 4 kGy-irradiated
samples were significantly lower than those of the control at
Day 3 of storage. However, no differences in color and aroma
among the tested samples at Day 3 of storage were observed
(Table 6). Previous studies showed that irradiation initiated the
auto-oxidation of fats and increased lipid oxidation and rancid
Storage (days)
3
30
60
90
5.23 7 0.78a
5.11 7 0.57a
4.85 7 0.53
4.72 7 0.81
4.63 7 0.49
5.177 0.76a
4.567 0.50a
4.487 0.58
4.817 0.17
4.857 0.50
4.33 7 0.58b
4.17 7 0.76ab
4.50 70.87
5.02 71.04
4.92 7 1.04
3.627 0.76c
3.787 1.32b
4.237 1.44
4.927 1.32
4.837 0.76
n
3.70 7 0.70a
3.50 7 0.26a
3.30 7 0.26a
2.37 7 0.98
3.30 7 1.04
3.877 0.32Aa
3.337 0.58ABa
3.007 0.20ABab
2.677 0.58B
2.707 0.52B
3.50 70.50Aa
3.37 7 0.55ABa
2.60 70.17ABCbc
2.30 70.26BC
1.83 7 1.04C
2.307 0.75b
1.937 0.55b
2.137 0.40c
1.907 0.55
1.637 0.32
n
n
n
3.527 0.55
3.557 0.37
3.587 0.35
3.777 0.45
3.987 0.42
3.65 7 0.58
3.50 70.50
3.67 7 0.39
3.78 7 0.52
4.05 70.36
3.657 0.50
3.707 0.55
3.777 0.42
3.757 0.89
4.027 0.48
3.47 7 0.06A
3.03 7 0.45AB
3.30 7 0.36A
2.37 7 0.32B
2.33 7 0.49B
3.177 0.35A
2.977 0.35AB
2.937 0.21AB
2.337 0.58BC
2.107 0.36C
3.07 70.12A
3.07 70.12A
2.80 70.61AB
2.10 70.66BC
1.73 7 0.47C
3.137 0.55A
3.007 0.26A
2.807 0.50A
1.977 0.26B
1.837 0.32B
nn
n
nn
n
Rancid flavor
0
3.37 7 0.32B
0.5
3.32 7 0.45B
1.0
3.36 7 0.24B
2.0
3.88 7 0.45A
4.0
3.98 7 0.38A
Taste
0
0.5
1.0
2.0
4.0
Sig.
Sig.
n
nn
nn
n¼3.
Sig. means Significance.
a–c means with different letters within a row of the same irradiation dose are
different (*p o0.05, **po 0.01).
A–D means with different letters within a column of the same day of storage are
different (*p o0.05, **po 0.01).
Color, aroma, taste (1 ¼extremely undesirable, 6¼ extremely desirable), rancid
flavor (1 ¼extremely low intensity, 6¼ extremely high intensity).
off-flavors in vacuum-packaged meat products (Dempsters et al.,
1985; Formanek et al., 2003).
The color, aroma and taste scores of all dry fermented sausages
gradually decreased with storage. In samples irradiated at 0 and
0.5 kGy, color and aroma scores at Day 90 of storage were
significantly lower than those at Day 3 (p o0.05); however, no
significant changes in the color, aroma, rancid flavor and taste
score for samples irradiated at 2 and 4 kGy were observed.
4. Conclusion
The application of irradiation to vacuum-packaged dry fermented sausages induced significant changes in color, VBN, lipid
oxidation and microbial counts (TPC, coliform and LAB) in a dose
dependent manner. These modifications could have an important
impact on meat quality. In the case that irradiation doses
necessary to control the pathogens in dry fermented sausages
are lower than those used in this study, less changes in color and
lipid oxidation after irradiation than those described in the
present results can be expected. When refrigerated storage is
applied, irradiation of dry fermented sausages at 2 kGy was the
most effective on the survival of LAB with significant reduction in
total plate counts and coliforms at the initial stage of fermentation. At this dose, sensory quality was maintained with minimal
rancid flavor and off-taste.
I.S. Kim et al. / Radiation Physics and Chemistry 81 (2012) 466–472
Acknowledgments
This work was supported by Priority Research Centers Program
through the National Research Foundation of Korea (NRF) funded
by the Ministry of Education, Science and Technology (20090093813) and the grant of Gyeongnam National University of
Science and Technology.
References
Acton, J.C., Dick, R.L., 1977. Cured colour development during fermented sausage
processing. J. Food Sci. 42, 895–897.
Ahn, D.U., Jo, C., Du, M., Olson, D.G., Nam, K.C., 2000. Quality characteristics of pork
patties irradiated and stored in different packaging and storage conditions.
Meat Sci. 56, 203–209.
Ahn, D.U., Nam, K.C., 2004. Effects of ascorbic acid and antioxidants on color, lipid
oxidation and volatiles of irradiated ground beef. Radiat. Phys. Chem. 71,
149–154.
Ahn, D.U., Olson, D.G., Jo, C., Chen, X., Wu, C., Lee, J.I., 1998. Effect of muscle type,
packaging, and irradiation on lipid oxidation, volatile production, and color in
raw pork patties. Meat Sci. 49, 27–39.
Ahn, D.U., Olson, D.G., Jo, C., Love, J., Jin, S.K., 1999. Volatiles production and lipid
oxidation in irradiated cooked sausage as related to packaging and storage. J.
Food Sci. 64, 226–229.
Ahn, D.U., Sell, J.L., Jeffery, M., Jo, C., Chen, X., Wu, C., Lee, J.I., 1997. Dietary vitamin
E affects lipid oxidation and total volatiles of irradiated raw turkey meat. J.
Food Sci. 62, 954–958.
Ansorena, D., Astiasarán, I., 2004. Effect of storage and packaging on fatty acid
composition and oxidation in dry fermented sausages made with added olive
oil and antioxidants. Meat Sci. 67, 237–244.
Aymerich, T., Martin, B., Garriga, M., Hugas, M., 2003. Microbial quality and direct
PCR identification of lactic acid bacteria and nonpathogeic staphylococci from
artisanal low-acid sausages. Appl. Environ. Microiol. 69, 4583–4594.
Badr, H.M., 1998. Studies on some irradiated food products, Ph. D. Thesis, Faculty
of agriculture, Zagazing University, Egypt.
Banwart, G.J., 1981. Basic food microbiology. Avi Publishing Company, Inc,
Westport, CT.
Brewer, M.S., 2009. Irradiation effects on meat flavor: a review. Meat Sci. 81,
1–14.
Brewer, S., 2004. Irradiation effects on meat color—a review. Meat Scie. 68,
1–17.
Caplice, E., Fitzgerald, G.F., 1999. Food fermentations: role of microorganisms in
food production and preservation. Int. J. Food Microbiol. 50, 131–149.
Cava, R., Tárrega, R., Ramirez, M.R., Mingoarranz, F.J., Carrasco, A., 2005. Effect of
irradiation on colour and lipid oxidation of dry-cured hams from free-range
reared and intensively reared pigs. Innovative Food Sci. Emerging Technol. 6,
135–141.
Cava, R., Ta’rrega, R., Ramirez, R., Cacciavillani, J.A., 2009. Decolouration and lipid
oxidation changes of vacuum-packed Iberian dry-cured loin treated with
E-beam irradiation (5 kGy and 10 kGy) during refrigerated storage. Innovative Food Sci. Emerging Technol. 10, 495–499.
Choi, J.H., Kim, I., Jueong, J.Y., Lee, E.S., Choi, Y.S., Kim, C.J., 2009. Effects of carcass
processing method and curing condition on quality characteristics of ground
chicken breasts. Korean J. Food Sci. Ani. Resour. 29, 356–363.
Chung, M., Ko, Y., Kim, W., 2000. Survival of Pseudomonas fluorescens and
Salmonella typhimurium after electron beam and gamma irradiation of refrigerated beef. J. Food Protect. 63, 162–166.
CIE, 1976. Commission International de l’Éclairage. Official recommendations on
uniform color spaces, color difference equations and metric color terms, Suppl.
no. 2, CIE Publication no. 15 Colorimetry, Paris.
Comi, G., Urso, R., Iacumin, L., Rantsiou, K., Cattaneo, P., Cantoni, C., Cocolin, L.,
2005. Characterisation of naturally fermented sausages produced in the north
east of italy. Meat Sci. 69, 381–392.
Dempsters, J.F., Hawrysh, Z.J., Shand, P., Lahola-Chomiak, L., Corletto, L., 1985.
Effect of low-dose irradiation on the shelf life of beef burgers stored at 3 1C. J.
Food Technol. 20, 145–154.
Dickson, J.S., Maxcy, R.B., 1985. Irradiation of meat for the production of fermented
sausage. J. Food Sci. 50, 1007–1009.
Dirinck, P., Van Opstaele, F., Vandendriessche, F., 1997. Flavour differences
between northern and southern European cured hams. Food Chem. 59,
511–521.
Du, M., Ahn, D.U., Nam, K.C., Sell, J.L., 2000. Influence of dietary conjugated
linolenic acid on volatile profiles, colour and lipid oxidation of irradiated raw
chicken meat. Meat Sci. 56, 387–395.
Eagan, H., Kirk, R.S., Sawyer, R., 1981. Pearson’s Chemical Analysis of Foods, 8th ed.
Churchill Livingstone, Edinburgh.
Fan, X., Sommers, C.H., Kimberly, J.B., Sokorai, B.J., 2004. Ionizing radiation and
antioxidants affect volatile sulfur compounds, lipid oxidation, and color of
ready-to-eat turkey bologna. J. Agric. Food Chem. 52, 3509–3515.
Farkas, J., 1998. Irradiation as a method for decontaminating food: a review. Int. J.
Food Microbiol. 44, 189–204.
471
Flores, J., Alvarruo~ Âz, A., 1985. Efecto de la temperatura de estu-fado sobre el
descenso del pH y sobre las caractero~ Âsticas analo~ Âticas de embutidos
curados. Rev. Agroquim. Tecnol. Alim. 25, 233–239.
Formanek, Z., Lynch, A., Galvin, K., Farkas, J., Kerry, J.P., 2003. Combined effects of
irradiation and the use of natural antioxidants on the shelf-life stability of
overwrapped minced beef. Meat Sci. 63, 433–440.
Gonzalez, B., Diez, V., 2002. The effect of nitrite and starter culture on microbiological quality of choizo- a Spenish dry cured sausage. Meat Sci. 60,
295–298.
Grant, I., Patterson, M., 1992. Sensitivity of foodborne pathogens to irradiation in
the components of a chilled ready meal. Food Microbiol. 9, 95–103.
Grant, I.R., Patterson, M.F., 1991. Effects of irradiation and modified atmosphere
packaging on the microbiological safety of minced pork stored under temperature abuse conditions. Int. J. Food Sci. Technol. 26, 521–533.
Hampson, J.W., Fox, J.B., Lakritz, L., Thayer, D.W., 1996. Effect of low dose gamma
radiation on lipids in five different meats. Meat Sci. 42, 271–276.
Houben, J.H., van’t Hooft, B.J., 2005. Variations in product-related parameters
during the standardised manufacture of a semi-dry fermented sausage. Meat
Sci. 69, 283–287.
Huhtanen, C.N., Jenkins, R.K., Thayer, D.W., 1989. Gammer radiation sensitivity of
Listeria monocytogenes. J. Food Prot. 52, 610–613.
Javanmard, M., Rokni, N., Bokaie, S., Shahhosseini, G., 2006. Effects of gamma
irradiation and frozen storage on microbial, chemical and sesory quality of
chicken meat in Iran. Food Control 17, 469–473.
Jin, S.K., Mandal, P.K., Kim, I.S., Kang, S.N.. Quality of Dry-cured Pork Neck as
affected by Packaging Methods during Refrigerated Storage at 40 1C. Asian
Journal of Animal and Veterinary Advances, in press.
Jo, C., Ahn, D.U., 2000. Volatiles and oxidative changes in irradiated pork sausage with
different fatty acid composition and tocopherol content. J. Food Sci. 65, 270–275.
Johansson, G., Berdague, J.L., Larsson, M., Tran, N., Borch, E., 1994. Lipolysis,
proteolysis and formation of volatile components during ripening of a
fermented sausage with Pediococcus pentosaceus and Staphylococcus xylosus
as starter cultures. Meat Sci. 38, 203–218.
Kanatt, S.R., Paul, P., D’Souza, S.F., Thomas, P., 1998. Lipid peroxidation in chicken
mat during chilled storage as affected by antioxidants combined with lowdose gamma irradiation. J. Food Sci. 63, 386–389.
Kang, S.N., Jang, A., Lee, S.O., Min, J.S., Lee, M., 2002. Effect of organic acid on value
of VBN, TBARS, color and sensory property of pork meat. J. Anim. Sci. Technol.
(Kor.) 44, 443–452.
Kim, D.H., Lee, K.H., Yoo, H.S., Kim, J.H., Shin, M.G., Byun, M.W., 2000. Quality
characteristics of gamma irradiation on the quality of bulgogi souce. Korean
Soc. J. Food Sci. Technol. 32, 640–645.
Kim, I.S., Jin, S.K., Kang, S.N., Hur, I.C., Choi, S.Y., 2009. Effect of olive-oil prepared
tomato powder(OPTP) and refining lycopene on the physicochemical and
sensory characteristics of seasoned raw pork during storage. Korean J. Food
Sci. Ani. Resour. 29, 329–334.
Lücke, F.K., 1985. Fermented sausages. In: Wood, B.J.B. (Ed.), Microbiology of
Fermented Foods. , Elsevier Applied Science, New York, USA.
Lizaso, G., Chaso, J., Beriain, M.J., 1999. Microbiological and biochemical changes
during ripening of salchichin, a spenish dry cured sausage. Food Microbiol. 16,
219–228.
Luchsinger, S.E., Kropf, D., Garcı!a Zepeda, C., Hunt, M., Marsden, J., Rubio Canas, E.,
1996. Colour and oxidative rancidity of g and electron bean-irradiated boneless pork chops. J. Food Sci., 61..
Millar, S.J., Moss, B.W., Stevenson, M.H., 2000. The effect of ionising radiation on
the colour of leg and breast of poultry meat. Meat Sci. 55, 361–370.
Nam, K.C., Ahn, D.U., 2002. Carbon monoxide-heme pigment is responsible for the
pink color in irradiated raw turkey breast meat. Meat Sci. 60, 25–33.
Olesen, P.T., Stahnke, L.H., 2000. The influence of Debaryomyces hansenii and
Candida utilis on the aroma formation in garlic spiced fermented sausages and
model minces. Meat Sci. 56, 357–368.
Ordóñez, J.A., Hierro, E.M., J.M, B., Hoz, L., 1999. Changes in the components of dry
fermented sausages during ripening. Crit. Rev. Food Sci. Nutr. 39, 329–369.
Patterson, M.F., Damoglou, A.P., Buick, R.K., 1993. Effects of irradiation dose and
storage temperature on the growth of Listeria monocytogenes on poultry
meat. Food Microbiol. 10, 197–203.
Patterson, R.L.S., Stevenson, M.H., 1995. Irradiation-induced off-odor in chicken
and its possible control. Br. Poult. Sci. 36, 425–441.
Pearson, D., 1968. Application of chemical methods for the assessments of beef
quality. J. Sci Food Agri. 19, 366–369.
Perez-Alvarez, J.A., Sayas-Barbera, M.E., Fernandez-Lopez, J., Aranda-Catala, V.,
1999. Physicochemical characteristics of Spanish-type dry-cured sausage.
Food Res. Int. 32, 599–607.
Sanchez-Molinero, F., Arnau, J., 2008. Effect of the inoculation of a starter culture
and vacuum packaging during the resting stage on sensory traits of dry-cured
ham. Meat Sci. 80, 1074–1080.
SAS, 2002. SAS/STAT Software for PC Release 6.11. SAS institute, Cary, NC, USA.
Smith, J.L., Palumbo, S.A., 1983. Use of starter cultures in meats. J. Food Prot. 46,
997.
Sommers, C., Fan, X., Niemira, B.A., Sokorai, K., 2003. Radiation (gamma) resistance
and postirradiation growth of Listeria monocytogenes suspended in beef
bologna containing sodium diacetate and potassium lactate. J. Food Protect.
66, 2051–2056.
Sorheim, O., Nissen, H., Nesbakken, T., 1999. The storage life of beef and pork
packaged in an atmosphere with low carbon monoxide and high carbon
dioxide. Meat Sci. 52, 157–164.
472
I.S. Kim et al. / Radiation Physics and Chemistry 81 (2012) 466–472
Tarladgis, B.G., Watts, B., Younathan, M.T., Dugan, L., 1960. A distillation method
for the quantitative determination of malonaldehyde in racid foods. J. Am. Oil
Chem. Soc. 37, 44–52.
Thayer, D.W., Boyd, G., 1993. Elimination of Escherichia coli O157:H7 in meats by
gamma irradiation. Appl. Environ. Microiol. 59, 1030–1034.
Thayer, D.W., Boyd, G., Muller, W.S., Lipson, C.A., Hayne, W.C., Baer, S.H., 1990.
Radiation resistance of Salmonella. J. Ind. Microbiol. 5, 385–390.
WHO, 1999. High-dose irradiation: Wholesomess of food irradiated with doses above
10 kGy. WHO technical report series 890. World Heath Organization, Geneva.
Zhou, G.H., Xu, X.L., Liu, Y., 2010. Preservation technologies for fresh meat–a
review. Meat Sci. 86, 119–128.
Zhu, M., Du, M., Cordray, J., Ahn, D.U., 2005. Control of Listeria monocytogenes
contamination in ready-to-eat meat products. Compr. Rev. Food Sci. Food Saf. 4,
34–42.