Potential Chemical Markers for the Identification
of Irradiated Sausages
Joong Ho Kwon, Kashif Akram, Ki Chang Nam, Byungrok Min, Eun Joo Lee, and Dong U. Ahn
C: Food Chemistry
Abstract: Hydrocarbons, gas compounds, and off-odor volatiles were determined for irradiated (0 or 5 kGy) commercial
sausages with different fat contents (16% and 29%) during a 60-d storage period at 4 ◦ C. Total of 4 hydrocarbons (C14:1,
C15:0, C16:2, and C17:1) were detected only in irradiated sausages: the amount of C16:2 was the highest, followed
by C17:1, C14:1, and C15:0. The concentrations of hydrocarbons decreased significantly (P < 0.05) with storage,
but were still detectable at the end of 60-d storage. Irradiated sausages produced significantly higher amounts of CO
than the nonirradiated ones. CH4 was detected only in irradiated sausages. Dimethyl disulfide was detected only in
irradiated sausages and its concentration decreased significantly (P < 0.05) with storage. Fat content of sausages showed
a significant effect on the production and retention of hydrocarbons, gas compounds, and sulfur volatiles in irradiated
sausages during storage. Some hydrocarbons (C16:2, C17:1, C14:1, and C15:0), CH4 , and dimethyl disulfide were only
found in irradiated sausages indicating that these compounds can be used as potential markers for irradiated sausages.
Keywords: hydrocarbons, identification, irradiation, sausages, volatiles
Introduction
in fat-containing irradiated foods. The determination of evolved
gases such as carbon monoxide, hydrogen, hydrogen sulfide, and
ammonia from irradiated foods has also been explored (Stewart
2011). Furuta and others (1992) determined the concentrations
of carbon monoxide in irradiated frozen chicken meat, beef, and
pork using microwave heating to release trapped gas and detecting
carbon monoxide in the headspace by gas chromatography.
Huber and others (1953) reported that irradiated meat developed a distinguishing “metallic,” “sulfide,” “wet dog,” “wet
grain,” or “burnt” odor. Radiolytic breakdown of amino acids,
especially sulfur amino acids, is the major source of off-odor in irradiated meat. The off-flavor in irradiated raw meat is considered
as the combined effect of radiolytic S-volatiles and lipid oxidation products (Jo and Ahn 2000; Ahn and Lee 2002). Irradiation
may induce off-flavors by enhancing lipid oxidation in different
meat products (Trindade and others 2010; Ahn and others 2001;
Patterson and Stevenson 1995). However, irradiation off-odor was
mainly produced by the sulfur-volatiles such as dimethyl sulfide,
dimethyl disulfide, and dimethyl trisulfide rather than aldehydes
from lipid oxidation (Ahn and others 2000b). Sulfur-volatiles are
highly volatile and detected less in aerobically packaged than vacuum packaged meats as they escape from packaging bags with time
(Ahn and others 2000b).
Many different types of sausages are now approved for irradiation
to control microbial growth as well as to extend their shelf life in
many countries (IAEA Staff Report 2009). This study was aimed
at monitoring the radiation-induced chemical changes, such as
production of fat-derived hydrocarbons, gas compounds, and offMS 20120467 Submitted 3/26/2012, Accepted 6/11/2012. Authors Kwon and odor volatiles in commercial sausages with different fat contents
Akram are with the Dept. of Food Science & Technology, Kyungpook Natl. Univ., during storage at 4 ◦ C, and at evaluating the potential of using
Daegu 702–701, Korea. Author Nam is with the Dept. of Animal Science & Tech- these chemical compounds as radiation markers for the sausages.
As foods travel around the globe, control of pathogens in foods
becomes even more important than before (IAEA Staff Report
2009). Extensive research for many decades indicated that food
irradiation is a safe and effective technology to control food borne
pathogens as well as to increase the shelf life of many food products.
However, informative labeling is needed to enhance consumer
understandings on the beneficial effects of irradiated foods and to
facilitate its quarantine requirements (Gunes and Tekin 2006). All
available methods to detect irradiated foods have certain advantages with some inherent limitations (Delincée 2002). Therefore,
none of a particular existing detection method can be used to
authenticate all irradiated food products (Marchioni 2006).
Ionizing radiation is known to generate hydroxyl radicals
in aqueous (Thakur and Singh 1994) or oil emulsion systems
(O’Connell and Garner 1983). These radicals can break acyloxygen bond in food components and form aldehydes, Cn-1
alkanes, short-chain hydrocarbons, CO, free fatty acids, and alcohols (Josephson and Peterson 2000). Merritt and others found the
presence of hydrocarbons in irradiated meat (Merritt and others
1965). Champaign and Nawar (1969) also found that hydrocarbons are the major radiolytic products in fat and the hydrocarbons produced are related to the fatty acid composition of fat.
Many scientists (Schreiber and others 1994; Delincée 2002; Lee
and others 2008) tested the possibility of using hydrocarbons and
2-alkylcyclobutanones as markers for radiation-induced changes
nology, Sunchon Natl. Univ., Suncheon, 540–742, Suncheon, Korea. Author Min is
with the Dept. of Agriculture, Food, and Resource Sciences, Univ. of Maryland Eastern
Shore, Princess Anne, MD 21853, U.S.A. Author Lee is with the Dept. of Food
and Nutrition, Univ. of Wisconsin-Stout, Menomonie, WI 54751, U.S.A. Author
Ahn is with the Dept. of Animal Science, Iowa State Univ., Ames, IA 50011–3150,
U.S.A. Direct inquiries to author Ahn (E-mail : duahn@iastate.edu).
C1000
Journal of Food Science r Vol. 77, Nr. 9, 2012
Materials and Methods
Samples and chemicals
Total of 6 packs of frankfurter sausages (each pack containing 10 sausages) with 2 different fat contents (16% and 29%,
R
C 2012 Institute of Food Technologists
doi: 10.1111/j.1750-3841.2012.02864.x
Further reproduction without permission is prohibited
Chemical markers for irradiated sausages . . .
Fat content and fatty acid composition
Total fat content was determined using the Folch’s extraction method (Folch and others 1957). Fatty acid composition
was analyzed after methylating fatty acids using BF3 -methanol.
The fatty acid methyl esters were separated (Metcalf and others 1966) on a gas chromatograph (GC, Model 6890, HewlettPackard Co., Wilmington, Del., U.S.A.) equipped with a flame
ionization detector. A splitless inlet was used to inject samples
into a Supelcowax-10 capillary column (0.25 mm × 30 m ×
0.25 μm), and a ramped oven temperature (from 180 ◦ C, increased to 200 ◦ C, 5 ◦ C/min, held for 6 min, increased to 220 ◦ C,
10 ◦ C/min, increased to 230 ◦ C, 5 ◦ C/min, held for 6 min) was
used. Inlet and detector temperature were set at 230 and 300 ◦ C,
respectively. Helium was the carrier gas at ramp flow of 1 mL/min
Table 1 –Fatty acid composition (%) of nonirradiated and irradiated sausages with different fat contents.
Fat 16%
Fatty acid
(carbon nr)
Myristic acid (14:0)
Palmitic acid (C16:0)
Palmitoleic acid (C16:1)
Heptadecanoic acid (C17:0)
Heptadecenoic acid (C17:1)
Stearic acid (C18:0)
Oleic acid (C18:1)
Linoleic acid (C18:2)
Linolenic acid (C18:3)
Arachidonic acid (C20:4)
Others
Total
Fat 29%
0 kGy
5 kGy
0 kGy
5 kGy
1.24Ab
18.47b
2.85b
0.29b
0.24b
7.37b
33.70b
28.38a
1.42a
1.60b
4.44a
100.00
1.16c
18.31b
2.83b
0.29b
0.23b
7.11c
33.49b
28.21a
1.38a
2.25a
4.74a
100.00
1.60a
21.40a
3.07a
0.32a
0.33a
8.68a
38.29a
19.38b
1.11b
1.08c
4.74a
100.00
1.65a
21.59a
3.07a
0.31a
0.31a
8.64a
37.71a
19.83b
1.15b
1.09c
4.65a
100.00
± standard deviation triplicate determinations. N = 3.
Means with different superscripts in a row of the same compound are significantly
different (P < 0.05).
A
Mean
a−c
for 6 min, 1.7 mL/min for 4 min, and 2.5 mL/min for 10 min.
Detector air, H2 , and make-up gas (He) flows were 350, 35, and
39 mL/min, respectively. Fatty acids were identified by comparing
the retention times to known standards. Relative quantities were
expressed as weight percent of total fatty acids.
Hydrocarbons analysis
Total of 5 to 8 g of sausage samples depending on fat contents were homogenized with 10 volumes hexane (w/v) and
15 g of anhydrous sodium sulfate in a centrifuge tube, and centrifuged at 1500 × g for 20 min at 4 ◦ C. The supernatant was
collected and fat was concentrated by removing hexane using a
rotary vacuum evaporator at 45 ◦ C (Büchi, Switzerland). The
extracted fat was placed in a N2 -filled vial and used for hydrocarbon analysis. Hydrocarbons were separated using a deactivated
Florisil (EN 1784) column: 1 g of extracted fat was mixed with
an internal standard (1 mL of n-eicosane, 4 μg/mL in hexane),
loaded on the column, and eluted with 40 mL of hexane. The
hexane eluent was collected and concentrated to approximately
2 mL in a rotary vacuum evaporator, and further concentrated to
0.5 mL using nitrogen. A gas chromatograph/mass spectrometer
(GC/MS; Hewlett-Packard Co.) was used to analyze hydrocarbons. To identify the hydrocarbons produced by irradiation, hydrocarbon standards such as, 1-tetradecene (C14:1), pentadecane
(C15:0), 1-hexadecene (C16: 1), 1,7-hexadecadiene (C16:2), heptadecane (C17:0), 8-heptadecene (C17:1), and eicosane (C20:5)
were purchased from TeLA (Berlin, Germany). The standard solutions (5 μL, 10 ppm) and samples (5 μL) were injected to a
GC, analyzed using an HP-5 column (30 m × 0.25 mm i.d.,
0.25 μm nominal), and identified using a mass selective detector
(Model 5973; Hewlett-Packard Co.). Ramped oven temperature
was used: the initial oven temperature of 120 ◦ C was increased to
175 ◦ C at 10 ◦ C/min, and then increased to 275 ◦ C at 25 ◦ C/min.
The inlet temperature was set at 250 ◦ C and column flow was 1.5
mL/min. The ionization potential of mass selective detector was
70 eV, and the scan range was 20.1 to 350 m/z. Identification of
hydrocarbons was achieved by comparing the retention time and
mass spectral data of samples with those of an authentic hydrocarbons standard based on the Wiley library (Hewlett-Packard Co.).
The concentration of each hydrocarbon was determined using
n-eicosane (4 μg/mL) as an internal standard.
Gas compounds analysis
Minced sausage (10 g) was placed in a 24-mL screw-cap glass
vial with a Teflon∗ fluorocarbon resin/silicone septum (I-Chem.
Co., New Castle, Del., U.S.A.). The vial was microwave-heated
Table 2–Hydrocarbons (µg/g fat) of nonirradiated and irradiated sausages with different fat contents during 60-d storage at 4 ◦ C.
Fat
content
(%)
16
Irradiation
dose
(kGy)
0
5
29
0
5
C14:1
Storage day
C15:0
Storage day
C16:2
Storage day
0
0
0
0
60
0
0
60
0
0
60
0
ax
1.08
± 0.08
0
bx
0.43
± 0.03
0
ax
1.03
± 0.04
0
bx
0.20
± 0.01
0
ax
2.77
± 0.16
0
bx
1.22
± 0.58
0
ax
0.99
± 0.03
bx
0.24
± 0.01
ax
0.87
± 0.05
bx
0.16
± 0.01
ax
2.20
± 0.07
bx
0.67
± 0.04
ax
C16:1
Storage day
C17:1
Storage day
0
0
2.16
± 0.34A
ax
1.92
± 0.12
ax
0.87
± 0.34
ax
1.25
± 0.07
60
ax
0.90
± 0.11
bx
1.03
± 0.1
ay
0.76
± 0.12
bx
0.98
± 0.06
0
C17:0
Storage day
60
0
0
ax
ax
2.30
± 0.12
0
bx
0.87
± 0.1
0
1.08
± 0.05
ax
1.17
± 0.12
0
ax
2.40
± 0.11
bx
0.84
± 0.03
ax
1.17
± 0.09
60
bx
0.95
± 0.05
bx
0.95
± 0.03
0
bx
0.82
± 0.03
A
Mean ± standard deviation triplicate determinations. N = 3.
xy
Means with different superscripts within a column of same fat
ab
content are significantly different (P < 0.05).
Means with different superscripts in a row of the same compound are significantly different (P < 0.05).
Vol. 77, Nr. 9, 2012 r Journal of Food Science C1001
C: Food Chemistry
made with the mixed meats from turkey and pork, Oscar Mayer,
Wieners) were purchased from a local grocery. The original packages of sausages were opened, the sausage sticks were individually
vacuum-packaged in oxygen-impermeable nylon/polyethylene
bags (9.3 mL O2 /m2 /24 h at 0 ◦ C, Koch, Kansas City, Mo.,
U.S.A.), and stored overnight at 4 ◦ C to minimize changes before
irradiation. The samples were irradiated at 0 or 5 kGy using a Linear accelerator (Circe IIIR, Thomson CSF Linac, France) with an
average dose rate of 107 kGy/min). To confirm the target dose, 2
alanine dosimeters per cart were attached to the top and bottom
surfaces of the sample. The control and irradiated samples were
analyzed in triplicates at day 0 (within 18 h after irradiation) and
after 60 d of storage at 4 ◦ C.
Chemical markers for irradiated sausages . . .
C: Food Chemistry
for 10 s at full power (1200 W) to release gas compounds from
the sample. After 5 min of cooling at ambient temperature, the
headspace (200 μL) was withdrawn using an airtight syringe and
injected into a gas chromatograph (HP 6890, Hewlett Packard
Co.). A Carboxen-1006 Plot column (30 m × 0.32 mm i.d.,
Supelco, Bellefonte, Pa., U.S.A.) was used to analyze the gas compounds. The oven temperature was set at 120 ◦ C and helium was
the carrier gas at a constant flow of 2.4 mL/min. Flame ionization detector equipped with a Nickel catalyst (Hewlett Packard
Co.) was used, and the temperatures of inlet, detector and Nickel
catalyst (Hewlett Packard Co.) were set at 250, 280, and 375 ◦ C,
respectively. Detector air, hydrogen, and make-up gas (He) flows
were 400, 40, and 50 mL/min, respectively. The identification of
gas compounds was achieved using standard gases (CO, Aldrich,
Milwaukee, Wis., U.S.A.; CH4 and CO2 , Praxair, Danbury,
Conn., U.S.A.) and a GC/MS (Model 5873, Hewlett Packard
Co.). The area of each peak was integrated using the Chemstation
software (Hewlett Packard Co.). To quantify the amounts of gases
released, each peak area (pA∗ s) was converted to a gas concentration (ppm or %) contained in the headspace (14 mL) of 10 g meat
samples using the concentration of CO2 in air (330 ppm).
Off-odor volatiles analysis
Dimethyl disulfide, hexanal, and carbon disulfide were determined as off-odor volatiles of irradiated sausages (Nam and
Ahn 2002). A vial autosampler (Solatek 72 Multimatrix, TekmarDohrmann, Cincinnati, Ohio, U.S.A.) and a Purge-and-Trap concentrator (3100, Tekmar-Dohrmann) were used to purge and trap
volatile compounds as described by Jo and Ahn (2000) with some
modifications. A gas chromatograph (GC, Model 6890, Hewlett
Packard Co.) equipped with a mass selective detector (MSD,
Model 5973, Hewlett Packard Co.) was used to qualify and quantify volatile compounds. Sample (2 g) was transferred to a 40-mL
sample vial, and headspace was flushed with helium gas (99.999%
purity) for 5 s to minimize oxidative changes in sausages during
the waiting period before analysis. Sample was purged with helium
(40 mL/min) for 15 min at 40 ◦ C. Volatile compounds
were trapped using a Tenax/silica/charcoal column (Tekmar-
Dohrmann), focused in a cryofocusing module (–80 ◦ C), and then
thermally desorbed into a GC column for 60 s at 220 ◦ C. A modified column was used to improve separation of volatile compounds.
An HP-Wax (7.5 m, 250 μm i.d., 0.25 μm nominal) column was
combined with an HP-5 column (30 m, 250 μm i.d., 0.25 μm
nominal) using 0 dead volume connectors (Hewlett Packard Co.).
A ramped oven temperature (7 ◦ C for 2.5 min, increased to 25 ◦ C
at 3 ◦ C/min, to 120 ◦ C at 10 ◦ C/min, and to 200 ◦ C at 20 ◦ C/min)
was used. Liquid nitrogen was used to cool the GC oven below
the ambient temperature. Helium was the carrier gas at constant
column pressure of 23.5 psi. The temperature of transfer lines was
maintained at 155 ◦ C. The ionization potential of MS was 70 eV;
the scanned mass range was 46.1 to 350 to eliminate carbon dioxide peak, and the scan velocity was 2.94 scan/s. The identification
of volatile compounds was achieved by comparing mass spectral
data with those of the Wiley library (Hewlett Packard Co.).
Statistical analysis
The experiment was designed primarily to determine the effect
of electron beam irradiation and subsequent storage of sausages
with different fat content on the production of radiation-induced
markers such as fat-derived hydrocarbons, gas compounds, and
off-odor volatiles. A sausage randomly selected from a sausage
pack was used as a replication. Analysis of variance (ANOVA) was
used by the generalized linear model procedure of SAS software
(SAS Institute 2001); Student–Newman–Keul’s multiple range test
was used to compare the mean values at P < 0.05.
Results and Discussion
Fat content and fatty acid compositions
A total of 10 different fatty acids were detected as illustrated in
Table 1. Oleic acid was the major fatty acid followed by linoleic
acid, palmitic acid, and stearic acid in sausages with 16% fat. In
sausages with 29% fat, oleic acid was predominant followed by
palmitic acid, linoleic acid, and stearic acid. This could be attributed to different ratio of pork and turkey meats used for the
sausage. Turkey meat has higher levels of unsaturated fatty acid
Table 3–Gas production (ppm) of nonirradiated and irradiated sausages with different fat contents during 60-d storage at 4 ◦ C.
Fat (%)
16
29
CH4
Storage time (d)
CO
Irradiation
dose (kGy)
0
60
0
60
0
5
0
5
3.6 ± 0.6A
bx
4.8 ± 0.4
by
3.6 ± 0.7
bx
14.9 ± 1.9
52.3 ± 14.3
ax
83.0 ± 8.5
ay
75.3 ± 8.6
ax
232.3 ± 13.3
0
bx
1.4 ± 0.2
0
bx
2.8 ± 0.6
0
ax
20.3 ± 2.5
0
ax
39.7 ± 8.8
by
ay
CO2
0
60
320 ± 36
bx
289 ± 5
by
242 ± 25
bx
613 ± 189
5154 ± 178
ax
8133 ± 416
ax
35770 ± 47, 15
ay
26682 ± 2375
bx
ay
A
Mean ± standard deviation triplicate determinations. N = 3.
xy
Means with different superscripts within a column of same fat
ab
content are significantly different (P < 0.05).
Means with different superscripts in a row of the same compound are significantly different (P < 0.05).
Table 4–Off-odor volatiles (total ion counts × 104 ) of nonirradiated and irradiated sausages with different fat contents during 60-d
storage at 4 ◦ C.
Fat (%)
16
29
Irradiation
dose (kGy)
0
5
0
5
Hexanal
Storage time (d)
0
60
Dimethyl disulfide
0
60
0
2487 ± 62
0
ax
1144 ± 94
ax
0
117 ± 5
0
bx
170 ± 18
bx
A
Mean ± standard deviation triplicate determinations. N = 3.
xy
Means with different superscripts within a column of same fat
ab
1692 ± 92A
3001 ± 121
ay
1974 ± 46
ax
2988 ± 48
by
ax
content are significantly different (P < 0.05).
Means with different superscripts in a row of the same compound are significantly different (P < 0.05).
C1002 Journal of Food Science r Vol. 77, Nr. 9, 2012
2483 ± 89
2227 ± 222
by
1336 ± 71
ax
2978 ± 196
ax
bx
0
0
0
0
0
Carbon disulfide
60
0
0
ay
10748 ± 1173
ax
18368 ± 1437
such as linoleic acid than pork. Hands (1996) reported oleic acid
as the most abundant fatty acid in pork followed by palmitic acid,
stearic acid, and linoleic acid, but its composition can vary depending on the fatty acid composition of diet. In sausages with
29% fat, no significant change was observed in fatty acid composition after irradiation at 5 kGy. In sausages with 16% fat content,
however, the concentrations of 3 out of 10 fatty acids (myristic
acid, stearic acid, and arachidonic acid) significantly (P ≤ 0.05)
decreased after 5 kGy irradiation, although the differences were
marginal. Hau and others (1992) also observed small changes in
fatty acid composition of raw or cooked meats by radiation.
the major sources of CH4 production. They also proposed that CO
and CO2 were produced by radiolytic degradation of phosphoglycerides: hydroxyl radicals generated by high-energy radiation
broke the ester bonds between fatty acids and glycerol first, and
then the -CO- group or carboxylic group of fatty acids was further
degraded to produce either CO or CO2 gas. Concentrations of
all 3 gases in all samples increased significantly (P ≤ 0.05) during
the 60-d storage at 4 ◦ C in vacuum packaged sausages. Ahn and
others (2000b) also reported higher concentration of volatiles in
irradiated vacuum-packaged meats as compared with aerobically
packaged ones.
Hydrocarbons
Total of 2 types of hydrocarbons were predominantly produced
from fatty acids by irradiation: one is the hydrocarbons with 1
carbon less than the parent fatty acids (Cn-1) and the other is
the one with 1 carbons less and an additional double bond at
position 1 (Cn-2, 1-ene) (Spiegelberg and others 1994). Therefore, 8-heptadecene (C17:1) and 1,7-hexadecadiene (C16:2) from
oleic acid, n-pentadecane (C15:0) and 1-tetradecene (C14:1) from
palmitic acid, n-heptadecane (C17:0), and 1-hexadecene (C16:1)
from stearic acid were detected in irradiated sausages. Table 2
shows hydrocarbons (μg/g fat) in irradiated sausages with different fat contents during storage at 4 ◦ C. Total of 4 hydrocarbons
(C14:1, C15:0, C16:2, and C17:1) were found in both types of
irradiated sausages, but not in nonirradiated ones. Detection levels of these 4 hydrocarbons were in the order of C16:2, C17:1,
C14:1, and C15:0 from the highest to the lowest. Hwang (1999)
suggested that the pattern of the 4 hydrocarbons detected could
be used for correct identification of irradiated pork. As expected,
the detected amounts of C17:1 and C16:2 generated from oleic
acid were higher than any other pair of hydrocarbons from a fatty
acid in all samples. C17:0 was found in both nonirradiated and
irradiated sausages with 16% fat, but was found only in irradiated sausages with 29% fat. Hydrocarbon C16:1 was found in all
samples, but irradiation significantly increased its concentration in
both sausages (16% and 29% fat), mainly due to the radiationinduced cleavage of stearic acid (Stewart 2011; Hwang 1999).
Noleau and Toulemonde (1987) found long-chain hydrocarbons
in roasted chickens. Despite the fact that the concentrations of
hydrocarbons decreased during storage, radiation-induced hydrocarbons remained detectable after 60-d storage at 4 ◦ C. C17:1 was
detected only in irradiated sausages after 60 d of storage regardless
the fat content of sausages. The occurrence and long-term stability
of radiolytic hydrocarbons are well documented for various meat
samples (Schreiber and others 1994; Merritt and others 1978).
Off-odor volatiles
Production of off-odor volatiles (total ion counts × 104 ) in irradiated sausages with different fat contents during the 60-d storage
at 4 ◦ C is presented in Table 4. Dimethyl disulfide was produced
only in irradiated sausages. A significant decrease in dimethyl disulfide concentration was observed after 60 d of storage at 4 ◦ C. It
was reported that irradiation produced many new volatiles which
include 1-hexene, 1-heptene, and dimethyl disulfide, and dimethyl
trisulfide, which were not found in nonirradiated meat (Ahn and
others 2000b). Ahn and others (2000a) suggested that sulfurcontaining compounds could be the major volatiles responsible
for irradiation off-odor in meat. They also found that most of the
new volatiles created after irradiation were sulfur compounds, and
the amount of 2,3-dimethyl disulfide was the highest. Patterson
and others (1995) reported dimethyl trisulfide as the most potent off-odor compound in irradiated chicken meat. Hexanal was
found in all samples but at higher concentration in irradiated samples than nonirradiated ones. Ahn and others (2000b) also reported
increased hexanal concentration after irradiation in pork patties,
which revealed that irradiation accelerated lipid oxidation in meat.
Carbon disulfide, another sulfur-containing volatile compound,
was found in irradiated and nonirradiated sausages with 29% fat
after 60-d storage at 4 ◦ C, where its concentration was significantly
higher in irradiated than nonirradiated samples. Ahn and others (2001) found increase of sulfur-containing volatiles (dimethyl
disulfide and carbon disulfide) in pork after radiation treatments.
The presence of volatile sulfur compounds at high concentrations
could be used as a screening tool for the detection of irradiated
fat-containing foods (Kwon and others 2012); however, there is
a difference in mechanisms involved for the irradiation-induced
lipid oxidation and production of volatile sulfur compounds (Fan
and others 2004).
Gas compounds
Table 3 illustrates the amounts (ppm) of CO, CH4 , and CO2
production in irradiated sausages with different fat contents during
storage at 4 ◦ C. Carbon monoxide was present in both nonirradiated and irradiated sausages but its concentration increased significantly after irradiation. Furuta and others (1992) also reported the
presence of radiolytic CO gas in irradiated beef, pork, and poultry
meat. CH4 was absent in nonirradiated but was found in irradiated
sausages. Nam and Ahn (2002) suggested that CH4 could be used
as an indicator for irradiation because the increase of CH4 concentration was radiation dose-dependent. CO2 was also detected in
both irradiated and nonirradiated sausages, but greater amount was
found in sausages with 29% fat than 16% fat after irradiation. Lee
and Ahn (2004) explored the sources and mechanisms of gas production by irradiation and found that methionine and acetone as
Conclusions
Presence and pattern of 4 hydrocarbons (C16:2, C17:1, C14:1,
and C15:0), and production of CH4 and dimethyl disulfide could
be used as potential markers to detect irradiated sausages with different fat contents. The concentrations of radiation-induced detection markers significantly (P ≤ 0.05) decreased during storage,
but were still detectable after 60 d of storage at 4 ◦ C.
Acknowledgment
This study was supported jointly by Kyungpook Natl. Univ.,
Iowa State Univ., and WCU (World Class Univ.) program
(R31–10056) through the Natl. Research Foundation of Korea
funded by the Ministry of Education, Science and Technology.
References
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homopolymers by irradiation. J Food Sci 67:2659–65.
Vol. 77, Nr. 9, 2012 r Journal of Food Science C1003
C: Food Chemistry
Chemical markers for irradiated sausages . . .
Chemical markers for irradiated sausages . . .
C: Food Chemistry
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