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PubMed2001

Volatile and non-volatile compounds in irradiated semi-rigid crystalline poly(ethylene terephthalate) polymers.

In this study two different semi-rigid crystalline and oriented polyethylene terephthalate materials were used and were irradiated at 25-kGy dose at room temperature by using a caesium137 radiator. Volatile and non-volatile compounds present in the irradiated materials were identified and quantified. The qualitative results obtained from HS/GC/TCD/FID analysis at room temperature showed volatiles could not be identified. The HS/GC/MSD analysis performed at 106 degrees C showed that the irradiation generated 668-742 micrograms/kg formic acid, 868-922 micrograms/kg acetic acid, 17-32 micrograms/kg 1,3-dioxolane, and 47-71 micrograms/kg 2-methyl-1, 3-dioxolane based on PET weight. The results obtained from the thermal desorption and GC/MSD performed at 200 degrees C showed that 10-12 mg/kg acetaldehyde, 479-975 micrograms/kg 1,3-dioxolane, and 6.6-11.2 mg/kg methyl-1, 3-dioxolane were detected after irradiation. The concentrations of the two dioxolanes found from thermal desorption were much higher than those observed in the HS, although formic and acetic acids were not detected. It is possible that the formic and acetic acids produced by irradiation underwent further reactions with ethylene glycol during thermal desorption to form the dioxolanes. The soluble solid extracted from various PET specimens before and after irradiation were in a range of 0.67-0.78%. PET cyclic trimer is the major component and is present at 0.41-0.50%, accounting for more than 50% of the percent total solid in PET. Statistically, irradiation did not increase the soluble solid and cyclic trimer. The overall results suggest that 25-kGy irradiation had a significant effect on increasing the volatile but not the non-volatile compounds detected in the PET specimens.

Analysis of Variance↗
PubMed1990

Effects of high-energy electron irradiation of chicken meat on Salmonella and aerobic plate count.

Four experiments were used to determine the effects of high-energy irradiation on the number of aerobic microorganisms and Salmonella on broiler breasts and thighs. Irradiation ranging from 100 to 700 kilorads (krads) was provided by a commercial-scale, electron-beam accelerator. Irradiation of broiler breast and thigh pieces with electron beams at levels of 100, 200, 300, 400, 500, and 600 krads showed that levels as low as 100 krads would eliminate Salmonella. When 33 thighs were tested after irradiation at 200 krads, only one thigh tested presumptive positive. The total number of aerobic organisms was reduced by 2 to 3 log10 cycles at irradiation levels of 100, 200, 300, 400, 500, 600, and 700 krads. Increasing the dose above 100 krads gave little if any additional benefit.

Animals↗
PubMed2006

Effectiveness of radiation processing in elimination of Salmonella typhimurium and Listeria monocytogenes from sprouts.

The effectiveness of radiation treatment in eliminating Salmonella Typhimurium and Listeria monocytogenes on laboratory inoculated ready-to-eat sprouts was studied. Decimal reduction doses (D10-values) for Salmonella Typhimurium and L. monocytogenes in dry seeds of mung (green gram), matki (dew gram), chana (chick pea), and vatana (garden pea) ranged from 0.189 to 0.303 kGy and 0.294 to 0.344 kGy, respectively. In sprouts made from these seeds, the D10-values ranged from 0.192 to 0.208 kGy for Salmonella Typhimurium and from 0.526 to 0.588 kGy for L. monocytogenes. Radiation treatment with a 2-kGy dose resulted in complete elimination of 10(4) CFU/g of Salmonella Typhimurium and 10(3) CFU/g of L. monocytogenes from all the four varieties of sprouts. No recovery of Salmonella Typhimurium and L. monocytogenes was observed in the radiation treated samples stored at 4 and 8 degrees C up to 12 days. Radiation treatment with 1 kGy and 2 kGy resulted in a reduction of aerobic plate counts and coliform counts by 2 and 4 log CFU/g, respectively; the yeast and mold counts and staphylococci counts decreased by 1 and 2 log CFU/g, respectively. However, during postirradiation storage at 4 and 8 degrees C, aerobic plate counts, coliform counts, yeast and mold counts, and staphylococci counts remained constant throughout the incubation period. This study demonstrates that a 2-kGy dose of irradiation could be an effective method of processing to ensure microbial safety of sprouts.

Colony Count, Microbial↗
PubMed2006

Effect of gamma-irradiation on pathogens inoculated into ready-to-use vegetables.

Three ready-to-use vegetables, cucumber, blanched and seasoned spinach, and seasoned burdock were selected and the effects of an irradiation treatment for eliminating pathogens were investigated. The pathogens tested were Salmonella Typhimurium, Escherichia coli, Staphylococcus aureus, and Listeria ivanovii. Inoculated viable cells of S. Typhimurium and L. ivanovii into cucumber and blanched and seasoned spinach were reduced about 4 decimal points by 2 kGy of irradiation and that of S. aureus inoculated into burdock showed about 4-decimal point reduction by 1 kGy. E. coli inoculated into burdock was not detected by 1 kGy. All the bacterial contents of test pathogens into the samples were reduced to below the limit of detection by 3 kGy irradiation. The range of the D10 value was 0.28-0.42 among the four pathogens. A Salmonella mutagenicity assay (Ames test) indicated that the 10 kGy-irradiated ready-to-use vegetables did not cause any increase. The studies indicated that a low-dose irradiation (3 kGy or less) can improve the microbial safety of ready-to-use vegetables.

Colony Count, Microbial↗
PubMed2001

Volatiles, color, and lipid oxidation of broiler breast fillets irradiated before and after cooking.

Chicken breast fillets were equally divided into three groups. One group was vacuum packaged, cooked in a water bath (cooked-in-bag) at 82 C for 25 min, and then irradiated at 0 or 3 kGy with a linear accelerator (V-C-I). The other two groups were irradiated at 0 or 3.0 kGy in vacuum packaging (V-I-C) or aerobic packaging (A-I-C). After 3 d of storage at 4 C, the irradiated meats were cooked in a water bath (cooked-in-bag) at 82 C for 25 min. After being cooked, meats were repackaged under vacuum and stored at 4 C. Breast fillets were analyzed at 0 and 21 d after cooking and analyzed for lipid oxidation, color, and volatiles. Irradiation accelerated lipid oxidation of breast fillets. Three days of storage of raw meat in aerobic conditions after irradiation had only minor influences on lipid oxidation after cooking. However, irradiation had a significant effect on the volatile production in meat. Dimethyl disulfide, related to irradiation odor, was significantly higher in irradiated fillets than in nonirradiated fillets for V-C-I and V-I-C, whereas it was only slightly higher for A-I-C. Other volatiles, such as 3-methyl butanal and 2-methyl butanal, were also produced in significant amounts after irradiation, especially in V-C-I and V-I-C. These results showed that irradiating cooked meat induced slightly more changes in volatiles than irradiating raw meat and then cooking. The amount of dimethyl disulfide between irradiated and nonirradiated samples for A-I-C was not different, because the dimethyl disulfide produced by irradiation disappeared during the 3 d in aerobic storage before cooking. Color a* value of irradiated fillets was higher than that of nonirradiated fillets. Irradiation also induced color L* and b* value changes. After 3 d of aerobic storage after irradiation of raw meat, the influence of irradiation on color after cooking was reduced. No significant lipid oxidation occurred during storage as shown by the low values for TBA-reactive substances.

Aldehydes↗
PubMed1965

Ecology of Micrococcus radiodurans.

An ecological study of Micrococcus radiodurans indicated that microorganisms possessing the same morphological and radiation-resistance characteristics as that organism could be isolated from ground beef and from pork sausage. Further studies showed that such organisms also could be isolated from beef hides and from water from a creek adjacent to the packing plant from which the meat samples were obtained. Similar microorganisms were not isolated, however, from a limited number of samples of soil, hay, and fecal material. The use of high levels of gamma-radiation in the initial isolation procedures proved to be advantageous in inactivating most of the other microflora and facilitating the isolation of M. radiodurans. Control experiments indicated that M. radiodurans did not compete well with the microflora present in ground meat, soil, and beef hides. Preincubation before irradiation of meat and soil samples or enrichment culture techniques did not enhance the isolation of M. radiodurans. The presence of M. radiodurans in creek water suggested one possible source of this organism.

Ecology↗
PubMed1965

RADIATION STERILIZATION OF BACON FOR MILITARY FEEDING.

Sliced, cured bacon, packed in cans and seeded with 6 x 10(5) spores per can of Clostridium botulinum strains 33A or 41B, or with 3 x 10(6) spores per can of strains 36A, 12885A, 9B, or 53B, was irradiated to various dose levels with gamma radiation. Evidence provided by swelling, toxicity, and recoverable C. botulinum with 2,200 inoculated, irradiated cans demonstrated that: (i) 4.5 Mrad were more than adequate as a sterilization dose; (ii) the experimental minimal sterilizing dose was 2.0 Mrad, and the theoretical 12-log reduction dose was 2.65 or 2.87 Mrad depending on the method of calculation; (iii) some spoilage occurred at dose levels below 2.0 Mrad; (iv) all visible spoilage of irradiated bacon was due to strains 33A and 12885A only, whose D values were, respectively, 0.141 and 0.177 Mrad based on spoilage data, and 0.221 and 0.188 Mrad, respectively, when based on recovery data; (v) toxic cans did not always result in swelling, nor did swollen cans always produce toxic spoilage; and (vi) viable C. botulinum can exist for at least 8 months in storage at 30 C without producing visible or toxic spoilage at doses below 2.0 Mrad.

Botulinum Toxins↗
PubMed1978

Immune response in rats given irradiated wheat.

1. Rats given diets containing freshly-irradiated wheat showed significantly lower mean antibody titres to four different antigens, decreased numbers of antibody-forming cells in the spleen and rosette-forming lymphocytes as compared to rats given either unirradiated wheat or irradiated wheat stored for a period of 12 weeks. 2. The immune response in rats given 90 g protein/kg diet was essentially similar to that seen in animals given 180 g protein/kg diet.

Animal Feed↗
PubMed2006

Combination of hot-water surface pasteurization of whole fruit and low-dose gamma irradiation of fresh-cut cantaloupe.

Improvements in methods for disinfecting fresh-cut cantaloupe could reduce spoilage losses and reduce the risk of foodborne illness from human pathogen contamination. The objective of this study was to investigate the feasibility of using hot-water treatment in combination with low-dose irradiation to reduce native microbial populations while maintaining the quality of fresh-cut cantaloupe. Whole cantaloupes were washed in tap water at 20 or 76 degrees C for 3 min. Fresh-cut cantaloupe cubes, prepared from the washed fruit, were then packaged in clamshell containers, and half the samples were exposed to 0.5 kGy of gamma radiation. Native microflora populations and sensory qualities were evaluated during the subsequent 7 days of storage at 4 degrees C. The hot-water surface pasteurization reduced the microflora population by 3.3 log on the surface of whole fruits, resulting in a lower microbial load on the fresh-cut cubes compared with cubes cut from fruit treated with cold water. Irradiation of cubes prepared from untreated fruit to an absorbed dose of 0.5 kGy achieved a low microbial load similar to that of cubes prepared from hot-water-treated fruit. The combination of the two treatments was able to further reduce the microflora population. During storage, the headspace atmosphere of the packages was not significantly influenced by any of the treatments. Color, titratable acidity, pH, ascorbic acid, firmness, and drip loss were not consistently affected by treatment with irradiation, hot water, or the combination of the two. Cubes prepared from hot-water-treated whole fruit had slightly lower soluble solids content. The combination of hot-water pasteurization of whole cantaloupe and low-dose irradiation of packaged fresh-cut melon can reduce the population of native microflora while maintaining the quality of this product.

Bacteria↗
PubMed2003

Irradiation and modified atmosphere packaging effects on residual nitrite, ascorbic acid, nitrosomyoglobin, and color in sausage.

The present study was undertaken to evaluate the irradiation and modified atmosphere packaging effects on emulsion-type cooked pork sausage during storage for 4 weeks. CO(2) (100%), N(2) (100%), or 25% CO(2)/75% N(2) packaged sausage were irradiated at 0, 5, and 10 kGy, and residual nitrite, residual ascorbic acid, nitrosomyoglobin (NO-Mb), color values, and their correlation were observed. Irradiation significantly reduced the residual nitrite content and caused partial reduction of NO-Mb during storage. No difference was observed in ascorbic acid content by irradiation. Irradiation decreased the Hunter color a value of sausage. CO(2) or CO(2)/N(2) packaging were more effective for reducing residual nitrite and inhibiting the loss of the red color of sausage compared to N(2) packaging. Results indicated that the proper combination of irradiation and modified atmosphere packaging could reduce the residual nitrite in sausage with minimization of color change.

Animals↗
PubMed1992

Use of electron beam irradiation for mold decontamination on cheddar cheese.

Cheddar cheese slices, surface-inoculated with either Penicillium cyclopium or Aspergillus ochraceus spores, were vacuum packaged and irradiated using an electron beam accelerator. Following treatment at .21 and .52 kGy, the shelf-life of cheese containing P. cyclopium was extended by 3 and 5.5 d, respectively, in comparison with inoculated, untreated samples. Under similar treatment and storage conditions, cheese containing A. ochraceus exhibited average shelf-life extensions of 42.5 and 52.2 d, respectively. Increasing the postirradiation storage temperature to 15 degrees C reduced the shelf-life of cheese, especially with samples containing A. ochraceus. The lowest dose required to inactivate ca. 50 to 60 spores/cm2 of either A. ochraceus or P. cyclopium on the surface of cheese was ca. .42 and .95 kGy, respectively. Irradiation survival curves of A. ochraceus and P. cyclopium spores in cheese yielded average values (the dose required to reduce initial population by 90%) of .21 and .42 kGy, respectively.

Animals↗
PubMed2000

Preservation of fish cutlet (Pangasius pangasius) at ambient temperature by irradiation.

Development of gamma irradiation preservation of ready-to-eat, commercially prepared fish cutlet and improvement of microbiological quality were studied. Studies on the shelf life extension by a combination of irradiation and ascorbic acid treatments of fish cutlets prepared at the laboratory and commercial scale have also been conducted. Cutlets prepared at the laboratory scale according to selected formulation and irradiated at a dose of 5 kGy could extend the shelf life up to 5 weeks at room temperature. In commercially prepared fish cutlets, maximum shelf life extension observed was 14 days for samples treated with 5 kGy of irradiation and stored at ambient temperature on the basis of combined microbiological, chemical, and organoleptic evaluation. The microbiological quality of the commercially prepared fish cutlets revealed the unhygienic conditions of the place where the fish was prepared and the unhygienic storage conditions and temperatures. As a result, the chemical and irradiation treatments were not effective in extending the shelf life of the cutlets under the storage condition used in this study compared with that of the laboratory scale-prepared cutlets.

Animals↗
PubMed2006

Effect of low-dose radiation on microbiological, chemical, and sensory characteristics of chicken meat stored aerobically at 4 degrees C.

The effect of gamma-radiation (0.5, 1, and 2 kGy) on the shelf life of fresh skinless chicken breast fillets stored aerobically at 4 degrees C was evaluated. Microbiological, chemical, and sensorial changes occurring in chicken samples were monitored for 21 days. Irradiation reduced populations of bacteria, i.e., total viable bacteria, Brochothrix thermosphacta, lactic acid bacteria (LAB), and the effect was more pronounced at the highest dose (2 kGy). Pseudomonads, yeasts and molds, and Enterobacteriaceae were highly sensitive to gamma-radiation and were completely eliminated at all doses. Of the chemical indicators of spoilage, thiobarbituric values for nonirradiated and irradiated aerobically packaged chicken samples were in general low (<1 mg of malonaldehyde per kg of muscle) during refrigerated storage for 21 days. With regard to volatile amines, both trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) values for nonirradiated aerobically packaged chicken increased steeply, with final values of ca. 20.3 and 58.5 mg N/100 g of muscle, respectively. Irradiated aerobically packaged chicken samples had significantly lower TMA-N and TVB-N values (P < 0.05) of ca. 2.2 to 3.6 and 30.5 to 37.1 mg N/100 g of muscle, respectively, during refrigerated storage for 21 days. Of the biogenic amines monitored, only putrescine and cadaverine were detected in significant concentrations in both nonirradiated and irradiated chicken samples, whereas histamine formation was noted only in nonirradiated samples throughout storage. On the basis of sensorial evaluation, low-dose irradiation (0.5 and 1.0 kGy) in combination with aerobic packaging extended the shelf life of fresh chicken fillets by ca. 4 to 5 days, whereas irradiation at 2.0 kGy extended the shelf life by more than 15 days compared with that of nonirradiated chicken.

Animals↗
PubMed1999

Irradiation and modified atmosphere packaging for the control of Listeria monocytogenes on turkey meat.

When radiation-sterilized ground turkey meat was inoculated with Listeria monocytogenes, packaged under mixtures of nitrogen and carbon dioxide, and irradiated with gamma-radiation doses of 0 to 3.0 kGy, there was a statistically significant (P < 0.05), but probably not a biologically significant, lower (0.39 log) predicted bacterial survival in the presence of 100% carbon dioxide than in the presence of 100% nitrogen. Possibly because all atmospheres contained oxygen and because a response surface design was used, gamma-radiation resistance was not significantly (P < 0.05) different in air than in modified atmosphere packaging (MAP) mixtures containing 5% O2 or containing 20, 40, 60, and 80% CO2 and balance N2. The antilisterial effects of MAP mixtures containing 17.2, 40.5, and 64% CO2 and balance N2 were compared to those associated with air and vacuum packaging on turkey inoculated with approximately 5 x 10(3) CFU/g. Samples were irradiated to doses of 0, 0.5, 1.0, 1.5, 2.0, and 2.5 kGy and were stored at 7 degrees C for up to 28 days. Irradiation treatments were significantly more lethal in the presence of air packaging than in either vacuum packaging or MAP, and in those samples that received >1.0 kGy, there was a concentration-dependent CO2 inhibition of L. monocytogenes multiplication and/or recovery.

Animals↗
PubMed2002

Sensorial and chemical quality of gamma-irradiated fresh-cut iceberg lettuce in modified atmosphere packages.

A study was conducted to investigate the effects of various doses of irradiation on the quality of fresh-cut iceberg lettuce and to determine a suitable maximum dose. Fresh-cut iceberg lettuce packaged in film bags was exposed to 0, 1, 2, 3, and 4 kGy of gamma radiation and stored at 3 degrees C for 14 days. CO2 levels were higher and O2 levels were lower in packages containing irradiated lettuce than in those containing nonirradiated lettuce for most of the storage period. Comparison with nonirradiated lettuce indicated that total ascorbic acid (ascorbic acid plus dehydroascorbic acid) content and firmness were not significantly influenced by irradiation at 1 or 2 kGy. The overall visual appearance was best for lettuce irradiated at 1 or 2 kGy. This improved quality may be related to the high CO2 and low O2 levels observed for the irradiated samples. Electrolyte leakage for lettuce increased with higher radiation doses and was correlated (R2 = 0.99) with a soggy appearance. The leakage for lettuce irradiated at > or = 2 kGy was significantly more extensive than that for nonirradiated lettuce. The irradiation of fresh-cut lettuce in modified atmosphere packages at doses of 1 kGy and perhaps 2 kGy for safety enhancement and quality improvement is feasible.

Ascorbic Acid↗
PubMed1992

Studies on the use of cobalt-60 gamma irradiation to control infectivity of Clonorchis sinensis metacercariae.

The purpose of the present study was to observe the survival and development of Clonorchis sinensis metacercariae in their final hosts after Cobalt-60 gamma irradiation of isolated metacercariae or the parasite in fish. Guinea pigs or albino rats were orally infected with irradiated metacercariae by gavage. Bioassay, fecal examination for ova, and necropsy of infected animals, were the methods used for the estimation of minimum effective dose of gamma irradiation to control infectivity of the metacercariae. Results showed that the minimum effective irradiation dose for isolated metacercariae was 0.05 kGy. The LD50 of the irradiation dose for metacercariae in fish was 0.05 kGy, and the minimum effective dose was 0.15 kGy. No significant difference in radiation susceptibility to Co-60 gamma irradiation was found among C. sinensis metacercariae in fishes collected at different localities in northern, middle or southern parts of China. The present finding suggests that irradiation of fish by 0.15 kGy could control infectivity of C. Sinensis metacercariae and thus be adopted as a control measure in preventing infections.

Animals↗
PubMed2002

Shelf-stable and safe intermediate-moisture meat products using hurdle technology.

A number of ready-to-use shelf-stable intermediate-moisture (IM) spiced mutton and spiced chicken products were developed with a combination of hurdles (reduced moisture, vacuum packing, and irradiation). The water activity of the products was reduced to about 0.80 either by grilling or by hot-air drying. These IM products were vacuum packed and subjected to gamma radiation processing at 0 to 10 kGy. Microbiological analyses revealed a radiation dose-dependent reduction in total viable counts and in numbers of Staphylococcus species. IM meat products that did not undergo radiation treatment showed visible mold growth within 2 months. The products subjected to irradiation at 10 kGy showed an absence of viable microorganisms and also retained high sensory acceptability for up to 9 months at ambient temperatures.

Animals↗
PubMed2006

Combined effects of antimicrobial coating, modified atmosphere packaging, and gamma irradiation on Listeria innocua present in ready-to-use carrots (Daucus carota).

The objective of this study was to evaluate the effect of an edible antimicrobial coating combined with modified atmosphere (MA) packaging (60% O2, 30% CO2, and 10% N2) and gamma irradiation on peeled minicarrots inoculated with Listeria innocua. Carrots were inoculated with L. innocua (10(3) CFU/g) and then coated with an antimicrobial coating based on calcium caseinate containing trans-cinnamaldehyde. The same formulation without trans-cinnamaldehyde was used as an inactive coating. Coated and uncoated carrots were packed under the MA or under air, irradiated at 0.25 or 0.5 kGy, and stored at 4 +/- 1 degrees C for 21 days. Samples were evaluated periodically for enumeration of L. innocua. Unirradiated carrots stored under air had the highest concentrations of L. innocua after 21 days of storage: 2.23 CFU/g in the uncoated samples and 2.26 CFU/ g in samples coated with the inactive coating. These results suggest that the inactive coating did not have any antimicrobial effect against L. innocua. However, the addition of the antimicrobial coating resulted in a 1.29-log reduction in the concentration of L. innocua in carrots packed under air after 21 days of storage and a 1.08-log reduction in carrots packed under MA after 7 days of storage. After 7 days of storage, no L. innocua was detected in samples treated at 0.5 kGy under air or in samples treated at 0.25 kGy under MA. A complete inhibition of L. innocua was also observed during all storage periods in uncoated and coated samples treated at 0.5 kGy under MA. These results indicate that the combination of irradiation and MA conditions play an important role in the radiosensitization of L. innocua.

Anti-Bacterial Agents↗