Migration of dioctyladipate plasticizer from food-grade PVC film into chicken meat products: effect of γ-radiation

Food-grade PVC film containing 28.3% dioctyladipate (DOA) plasticizer was used to wrap chicken meat samples, with and without skin, contained in a polystyrene tray. Samples were then irradiated with γ-radiation [⁶⁰Co] at doses equal to 4 kGy and 9 kGy corresponding to “cold pasteurization”. Irradiation was carried out at 8–10 °C and samples were subsequently stored at 4–5 °C. Contaminated chicken meat samples were analysed for DOA at intervals between 7 h and 240 h of contact, using an indirect GC method. Identical non-irradiated (control) samples were also analysed for their DOA content. Results showed no statistically significant differences in migrated amounts of DOA between irradiated and non-irradiated samples. Neither were differences observed between samples irradiated at 4 kGy and 9 kGy. This was supported by identical IR spectra recorded for irradiated and non-irradiated samples and leads to the conclusion that, at such intermediate radiation doses (?kGy), the migration characteristics of PVC film are not affected. DOA migration was found to be time dependent, approaching equilibrium after approximately 170 h for the chicken flesh plus skin samples and 120 h for the chicken flesh samples. The amount of DOA migrated into chicken flesh plus skin samples was significantly greater (3.2–22.3 mg/dm²) than that for chicken flesh samples (0.9–8.9 mg/dm²). After 240 h of sample/ film contact under refrigeration, loss of DOA was approximately 35.6% for chicken flesh plus skin samples and 14.3% for chicken flesh samples. Sample spoilage, as demonstrated by off-odour development, occurred after approximately 120 h of refrigerated storage. Diffusion coefficients for DOA were calculated and were found to be lower for chicken flesh (1×10^?13) than for flesh plus skin (4.4×10^?13) samples.     

Comparison of radiation‐induced hydrocarbons for the identification of irradiated perilla and sesame seeds of different origins

BACKGROUND: Perilla and sesame seeds, a rich source of energy, are commonly utilized in different forms in many countries. During the post‐harvest period, they are contaminated with insects as well as microbes that may have importance for keeping quality and quarantine, and thus they can be treated with ionizing radiation for insect disinfestation and microbial decontamination. Reliable and routine methods to identify whether or not a food has been irradiated are needed to help consumers' understanding of irradiated food and promote international trade. In the present study, fat‐derived hydrocarbons from irradiated perilla seeds and sesame seeds of Korean and Chinese origin were analyzed in order to identify irradiation treatment by comparing their properties during the post‐irradiation period. RESULTS: Gas chromatographic–mass spectrometric analysis showed that several saturated hydrocarbons, such as tetradecane, pentadecane, hexadecane and heptadecane, were found in the non‐irradiated control samples, while four radiation‐induced unsaturated hydrocarbons (R² = 0.647–0.997), such as 1,7,10‐hexadecatriene (C_16:3), 1,7‐hexadecadiene (C_16:2), 6,9‐heptadecadiene (C_17:2) and 8‐heptadecene (C_17:1), were detected in all irradiated samples at 0.5 kGy or higher, with variations according to sample and origin. Concentrations of all hydrocarbons were reduced during storage and could not be detected in 0.5 kGy irradiated Chinese sample of either seed after 8 months. CONCLUSION: Radiation‐induced hydrocarbons (C_{16:3, 16:2, 17:2, 17:1}) could be used as markers to identify irradiated perilla and sesame seeds of both Korean and Chinese origin at 1 kGy or higher for 8 months' storage at room temperature. Copyright © 2009 Society of Chemical Industry     

Gamma irradiation as a means to eliminate Listeria monocytogenes from frozen chicken meat

Cells of Listeria monocytogenes ATCC 35152 were sensitive to gamma irradiation in phosphate buffer, pH 7.00 (D₁₀, dose required for 10% survival—0.15 kGy) at 0–5°C. The cells showed higher radiation survival when irradiated under frozen condition, with a D₁₀ of 0.3 kGy. The protection offered by shrimp/chicken/kheema homogenates (100 g litre^?1) was evidenced by even higher D₁₀ values (0.5 kGy) at both 0–5°C and cryogenic temperature. Boneless chicken meat samples were artificially inoculated with L monocytogenes ATCC 35152 cells at low (5 × 10³) colony-forming unit (cfu) g^?1 and high (5 × 10⁶ cfu g^?1) concentrations and irradiated at 1, 3, 4, 6 kGy doses under cryogenic conditions. The efficacy of the radiation process was evaluated by detecting L monocytogenes during storage at 2–4°C in the irradiated samples. These studies, when repeated with three other serotypes of L monocytogenes, clearly suggested the need for a dose of 3 kGy for elimination of 10³ cfu cells of L monocytogenes g^?1 from air-packed frozen chicken meat.     

Respiratory parameters of onion bulbs (Allium cepa) during storage. Effects of ionising radiation and temperature

The O₂ and CO₂ respiration rates of untreated and irradiated onion bulbs (Allium cepa) at 0.15 and 0.30 kGy were measured at 4, 10 and 20 °C. The O₂ respiration rate increased for 24 h after treatment from 0.19 mmole kg⁻¹ h⁻¹ at 20 °C for control samples up to 0.26 and 0.39 mmole kg⁻¹ h⁻¹ for 0.15 and 0.3 kGy irradiated onions respectively. Respiratory quotient (RQ) increased with temperature. The Q₁₀ of the respiration of the control samples (1.61) was lower than that of any other plant tissue, but it increased with storage duration and irradiation dose. The respiration rate of control onions increased steadily over 25 weeks of storage at 4 °C, while that of the irradiated samples decreased during the same period after a peak observed after irradiation treatment. The apparent K_m for the Menten–Michaelis equation was determined on a new respirometer and averaged 1.6 kPa at 10 °C and 6.3 kPa at 20 °C. However, at this higher temperature (20 °C) apparent K_m varied with O₂ partial pressure, proving that the respiration of onion bulbs does not follow a Menten–Michaelis‐like process. The Fermentative Index (FI) of onions was measured under anoxic conditions as CO₂ production rates in mmole kg⁻¹ h⁻¹ at 4, 10 and 20 °C. © 2000 Society of Chemical Industry     

Influence of gamma irradiation on growth and survival of Escherichia coli O157:H7 and quality of cig kofte, a traditional raw meat product

Cig kofte is a traditional Turkish food containing raw ground meat. Samples inoculated with Escherichia coli O157:H7 were irradiated at 0.5–6 kGy with a ⁶⁰Co source and stored at 4 and 25 °C. Total aerobic mesophilic count decreased with increasing irradiation doses, D₁₀ value was 0.83 kGy. Escherichia coli O157:H7 count decreased from 5.1 log₁₀ CFU g^?1 to an undetectable level (<1 log₁₀ CFU g^?1) after 1‐day storage at 4 °C following irradiation at 2 kGy, D₁₀‐value was 0.29 kGy. Irradiation doses up to 2 kGy did not affect sensory quality after 1 day. There was colour loss in samples irradiated at 2 kGy or above and stored for longer periods. Storage of the irradiated products at abused temperature must be avoided for safety assurance. Irradiation at 2 kGy has a great potential for extending the shelf‐life of cig kofte and assuring safety by decreasing the number of E. coli O157:H7 and other bacteria, but further studies with suitable package designs are needed to decrease quality degradation during extended storage.     

The effect of temperature and storage time on the resonance signals of irradiated pea (Pisum sativum L.)

In the present work, the effects of storage time and temperature on the resonance signals of unirradiated and irradiated dry pea (Pisum sativum L.) were investigated using electron spin resonance (ESR) spectroscopy. As other legumes, unirradiated pea contains Mn²⁺ binded proteins and very small amount natural free radicals. They give rise to an ESR spectrum consisting of an equally spaced sextet and a singlet resonance line, respectively, both appearing at g=2.0050±0.0007. Irradiation of pea by gamma radiation did not produce any pattern changes in the ESR spectrum of pea except a significant change in the intensity of the singlet resonance line which increased exponentially with absorbed dose in the studied dose range (1.25–15.0 kGy). Cooling the irradiated samples down to room temperature caused a reversible increase in Mn²⁺ and a reversible decrease in free radical signal intensities. However, heating the sample above room temperature created irreversible decreases in the intensities of both species. At room temperature, the free radical signal decayed very fast, but the signal due to Mn²⁺ ion did not exhibit any intensity changes over the storage period of 75 days. While, annealing of irradiated samples at high temperatures (308–373 K) produced continuous decrease in the signal intensity of Mn²⁺, it caused a decrease at the beginning and then an increase in the free radical signal intensity. Arrhenius plot constructed using rate constants determined from the variations of the signal intensities at high temperatures was used to calculate activation energies related with oxidation of Mn²⁺ and free radical species responsible from singlet resonance line.     

Shelf‐life extension of vacuum‐packaged sea bream (Sparus aurata) fillets by combined γ‐irradiation and refrigeration: microbiological,chemical and sensory changes

The combined effect of γ‐irradiation and refrigeration on the shelf‐life of vacuum‐packaged sea bream (Sparus aurata) fillets was studied by monitoring the microbiological, chemical and sensory changes of non‐irradiated and irradiated fish samples using low‐dose irradiation doses of 1 and 3 kGy. Fish species such as sea bream and sea bass are very popular in the Mediterranean countries due to their high quality characteristics, and their preservation is a constant challenge given their extreme perishability. Irradiation (3 kGy) dramatically reduced populations of bacteria, namely, total viable counts (3 vs 7 log cfu g^?1) for the non‐irradiated samples, Pseudomonas spp (<2 vs 7.6 log cfu g^?1), H₂S‐producing bacteria typical of Shewanella putrefaciens (<2 vs 5.9 log cfu g^?1), Enterobacteriaceae (<2 vs 6.0 log cfu g^?1) and lactic acid bacteria (<2 vs 3.5 log cfu g^?1) after 10 days of storage. The effect was more pronounced at the higher dose (3 kGy). Lactic acid bacteria, Enterobacteriaceae and H₂S‐producing bacteria typical of Shewanella putrefaciens showed higher sensitivity to γ‐radiation than did the rest of the microbial species. Of the chemical indicators of spoilage, Trimethylamine (TMA) values of non‐irradiated sea bream increased very slowly, whereas for irradiated samples significantly lower values were obtained reaching a final value of 7.9 and 6.3 mg N per 100 g muscle at 1 and 3 kGy respectively (day 42). Total volatile basic nitrogen (TVB‐N) values increased slowly attaining a value of 67.3 mg N per 100 g for non‐irradiated sea bream during refrigerated storage, whereas for irradiated fish, lower values of 52.8 and 43.1 mg N per 100 g muscle were recorded (day 42). Thiobarbituric acid (TBA) values for irradiated sea bream samples were higher than respective non‐irradiated fish and increased slowly until day 21 of storage, reaching final values of 1.1 (non‐irradiated), 2.0 (1 kGy) and 2.2 mg malonaldehyde kg^?1 muscle (3 kGy), respectively (day 42). Sensory evaluation showed a good correlation with bacterial populations. On the basis of overall acceptability scores (sensory evaluation) a shelf‐life of 28 days (3 kGy) was obtained for vacuum‐packaged sea bream, compared with a shelf‐life of 9–10 days for the non‐irradiated sample. Copyright © 2004 Society of Chemical Industry     

Effect of γ-radiation on migration behaviour of dioctyladipate and acetyltributylcitrate plasticizers from food-grade PVC and PVDC/PVC films into olive oil

Food-grade PVC and PVDC/PVC films containing 28.3% dioctyladipate (DOA) and 5.0% acetyltributylcitrate (ATBC) plasticizers, respectively, were brought into contact with olive oil and were irradiated with γ-radiation [⁶⁰Co] at doses equal to 4 kGy and 9 kGy corresponding to “cold pasteurization”. Irradiation was carried out at 8–10 °C and samples were subsequently stored at 4–5 °C. Contaminated oil samples were analysed for DOA and ATBC at intervals between 7 h and 97 h of contact, using an indirect GC method. Identical nonirradiated (control) samples were also analysed for DOA and ATBC content. Results showed no statistically significant differences in migrated amounts of DOA and ATBC between irradiated and non-irradiated samples. Neither were differences observed between samples irradiated at 4 kGy and 9 kGy. This was supported by identical IR spectra recorded for irradiated and non-irradiated samples and leads to the conclusion that at such intermediate radiation doses (≤9 kGy) the migration characteristics of both PVC and PVDC/PVC films are not affected. The amount of DOA that migrated into olive oil was dependent on time, reaching equilibrium after approximately 47 h of contact (302.8 mg/l). The amount of ATBC that migrated into olive oil was non-detectable (<1 mg/1) for all samples stored at 4–5 °C after 97 h. In non-irradiated samples (PVDC/PVC in contact with oil) stored at 20 °C, small amounts of migrated ATBC were determined (3.3 and 5.1 mg/l after 29 h and 94 h of contact respectively). Furthermore, in thermally treated samples heated to 80 °C for 30 min and 60 min, the respective amounts of migrated ATBC determined were 2.9 mg/l and 19.3 mg/l.     

Effect of irradiation on properties and storage stability of Som-fug produced from bigeye snapper

Effects of irradiation at different doses (0, 2 and 6 kilogray (kGy)) on the microbiological, chemical and physical properties of Som-fug, a Thai fermented fish mince, were investigated. Lactic acid bacteria (LAB), yeast and mould counts in samples irradiated at 6 kGy were not detectable throughout the storage of 30 days at 4 °C, whereas no growth was found in the sample irradiated at 2 kGy within the first 10 days. Generally, greater carbonyl contents of lipid and protein, as well as thiobarbituric acid-reactive substances (TBARS), were noticeable in the irradiated samples, than in the non-irradiated sample (p < 0.05). The carbonyl contents and TBARS increased with increasing storage time and the rate of increase was more pronounced in samples irradiated at higher dose (p < 0.05). With increasing storage time, Som-fug irradiated at 6 kGy showed greater decreases in hardness, adhesiveness, springiness and cohesiveness, than did non-irradiated samples and those irradiated at 2 kGy (p < 0.05). L^∗ value of all samples decreased, whereas a^∗ and b^∗ values increased throughout storage (p < 0.05). Lower acceptance in all attributes was observed in the samples irradiated at 6 kGy, than in other samples, particularly when storage time increased (p < 0.05). However, samples irradiated at 2 kGy showed no changes in acceptability within 20 days. The results revealed that irradiation at high dose (6 kGy) might induce lipid and protein oxidation, though the growth of microorganisms was inhibited. Therefore, the irradiation at low dose (2 kGy) could be used to control the overfermentation of Som-fug up to 20 days at 4 °C without adverse effects on quality and acceptability.     

Sterilization of Ground Prepacked Indian Spices by Gamma Irradiation

Prepacked ground Indian spices which included pepper. turmeric, chilli, and coriander were found to be heavily contaminated with bacteria and molds. The total bacterial counts ranged between 10⁵–10⁷. whereas total fungal counts ranged between 10²–10⁶. Red chilli was found to be the most contaminated spice. The bacterial population consisted mainly of spores. A dose of 10 kGy was found to be effective in destroying these microbes in prepacked spices without affecting their quality attributes. To eliminate mold contamination a dose of 5 kGy was sufficient. During a six-month storage study of irradiated and unirradiated spices, the irradiated spices were found to retain their quality.     

Physicochemical Stability of Fluid Soybean Lecithin Gamma Irradiated for Decontamination Purposes

Soybean lecithin is a food additive mainly used for its emulsifying properties. As many other natural ingredients, it can contain microorganisms capable of causing spoilage to the food products to which it is incorporated that cannot be eliminated by the usual methods due to the damage they can cause to the product. Commercial samples were gamma irradiated at the⁶⁰ Co Facility of the Ezeiza Atomic Center with doses suitable for attaining microbial decontamination (1, 2, 3 and 5 kGy). The technological properties were then evaluated every 2 mo, for a total period of 8 mo (lecithin commercial storage time). Control and irradiated samples were analysed at least by triplicate in viscosity, acid value, acetone insoluble matter (phosphatides), peroxide value, ultraviolet spectra, refraction index, iodine value, thin layer chromatography, test for hydrolysis and emulsifying capacity. The results revealed no significant differences between control and irradiated samples. Gamma irradiation of fluid soybean lecithin can be used for attaining the sanitary specifications while preserving its technological properties.     

The effect of gamma irradiation on the microbial load,mineral concentration and sensory characteristics of liquorice (Glycyrrhiza glabra L)

Ground liquorice roots were exposed to various doses (0, 5, 10, 15 and 20 kGy) of gamma radiation from a ⁶⁰Co source. Irradiated and non‐irradiated samples were stored at room temperature. Microbial population, viscosity, concentrations of some minerals and the sensory properties of the extracts were evaluated after 0 and 12 months of storage. Tests carried out immediately after irradiation showed that the microbial count had been reduced and that the dose required to reduce the count by 1 log cycle (D₁₀) was about 2 kGy. No effect was observed on the total dissolved solids in extracts of liquorice roots. Glycyrrhizinic acid concentration in the extracts and the viscosities of suspensions produced from irradiated roots were lower than those from non‐irradiated ones. Sensory evaluation indicated that there were no significant differences (P < 0.05) in colour, taste or flavour between extracts produced from irradiated and non‐irradiated roots. However, after 12 months of storage, some mineral ion (Na⁺, Ca²⁺ and K⁺) concentrations in extracts produced from irradiated roots were lower than in those from non‐irradiated ones; no significant differences (P < 0.05) in viscosity were found between suspensions of irradiated and non‐irradiated roots. © 2002 Society of Chemical Industry     

Low‐Dose Irradiation Can be Used as a Phytosanitary Treatment for Fresh Table Grapes

Grapes (Vitis vinifera var. Sugraone and Vitis labrusca var. Crimson Seedless) were treated with 400, 600, and 800 Gy and the effects on physicochemical factors were measured alongside sensory testing during 3 wk of storage. Significant changes in texture and color with irradiation and age were measured but little visual difference was seen between control and irradiated grapes. However, age had a greater effect on firmness than irradiation for Sugraone grapes. Irradiation did not significantly (P ≤ 0.05) affect the SSC/TA ratio, which increased during storage. The trained panel detected significant changes in the berry texture and rachis color but rated sweetness and flavor significantly higher (P ≤ 0.05) for irradiated Sugraone as compared to the control. Consumers liked both the untreated and 800 Gy treated Sugraone grapes, but liked the untreated grapes more for texture (P ≤ 0.05). However, there was no difference in liking between irradiated (600 Gy or 800 Gy) and control samples of Crimson Seedless for any attribute. The results show that there are varietal differences in response to irradiation but the overall maintenance in quality of irradiated grapes during 3 wk of storage indicates that irradiation can serve as a viable phytosanitary treatment.     

Radiation Processing of Minimally Processed Pineapple (Ananas comosus Merr.): Effect on Nutritional and Sensory Quality

ABSTRACT:  Radiation processing of minimally processed pineapple at a dose of 2 kGy was investigated. Effect of this treatment on different quality parameters like vitamin C content, total carotenoids content, sensory attributes, texture, and color was determined over a storage period of 12 d at 8 to 10 °C. Results showed that the irradiation treatment showed no significant effect ( P > 0.05) on total vitamin C content of pineapple samples but a significant decrease ( P ≤ 0.05) in vitamin C during storage period in both controls as well as irradiated samples was observed. However, total carotenoids were not affected by irradiation and were stable during the whole storage period as well ( P > 0.05). Sensory evaluation studies revealed that irradiation had no significant effect ( P > 0.05) on the ratings of any of the sensory attributes of pineapple samples. Taste panelists could not differentiate between control and irradiated samples. Textural studies showed no significant effect ( P > 0.05) of irradiation as well as storage period on the firmness of the central edible region of pineapple samples. Color attributes of both control and irradiated samples showed slight variation during the storage period of 12 d. However, irradiation at 2 kGy did not have a significant effect ( P > 0.05) on all color coordinates. Thus, radiation processing with 2 kGy did not affect significantly the nutritional value as well as the sensory quality of minimally processed pineapple samples.     

Effect of the gamma radiation dose rate on psychrotrophic bacteria, thiobarbituric acid reactive substances, and sensory characteristics of mechanically deboned chicken meat

Frozen samples of mechanically deboned chicken meat (MDCM) with skin were irradiated with gamma radiation doses of 0.0 kGy (control) and 3 kGy at 2 different radiation dose rates: 0.32 kGy/h (3 kGy) and 4.04 kGy/h (3 kGy). Batches of irradiated and control samples were evaluated during 11 d of refrigerated (2 ± 1 °C) storage for the following parameters: total psychrotrophic bacteria count, thiobarbituric acid reactive substances (TBARS), evaluation of objective color (L*, a*, and b*) and a sensory evaluation (irradiated odor, oxidized odor, pink and brown colors). No statistical difference (P > 0.05) was found amongst the TBARS values obtained for the MDCM samples irradiated with dose rates of 0.32 and 4.04 kGy/h. There was a significant increase (P < 0.05) in the psychrotrophic bacterial count as from the 7th day of refrigerated storage, for the MDCM samples irradiated at the dose rate of 4.04 kGy/h. With respect to the attribute of oxidized odor, the samples irradiated with a dose rate of 0.32 kGy/h showed a stronger intensity and were significantly different (P < 0.05) from the sample irradiated with a dose rate of 4.04 kGy/h on days 0 and 2 of refrigerated storage. Irradiation with a dose rate of 4.04 kGy/h (3 kGy) was shown to be the best condition for the processing of MDCM according to the evaluation of all the variables, under the conditions of this study. Practical Application: The results obtained for the application of different dose rates of ionizing radiation to mechanically deboned chicken meat will provide the food industry with information concerning the definition of the best processing conditions to maximize the sensory and food quality.     

Bacteriological Quality of Freshly Processed Broiler Chickens as Affected by Carcass Pretreatment and Gamma Irradiation

Chicken carcasses dipped in whey fermented by Streptococcus thermophilus, lactic acid solution or water and irradiated at 2.5 kGy by ⁶⁰Co were evaluated for bacteriological quality on day-1, day-3 and at 3-day intervals for an 18-day storage (4°C) period. Unirradiated carcasses treated similarly were used as control. Gram negative bacteria, Yersinia and Campylobacter counts were significantly (p<0.01) lower in irradiated samples, but no significant (p>0.05) differences were observed among the dipping solutions. Salmonellae were completely eliminated in irradiated samples. Whey fermented by 5. thermophilus reduced the proportion of Salmonella contaminated carcasses from 67% to 20%. As evidenced by the bacterial counts the shelf-life was found to be 15 days for irradiated carcasses compared to about 6 days for the unirradiated samples.     

Gamma Irradiation Effects on Shelf Life and Gel Forming Properties of Washed Red Hake (Urophycis chuss) Fish Mince

Fresh washed red hake (Urophycis chuss) mince without cryoprotectants was irradiated at 0 (control), 0.66 and 1.31 kGy and stored aerobically at 3.3°C. The total aerobic plate counts of the control and the low and high levels irradiated samples remained less than 10⁶ CFU/ g for 4, 10, and 17 days, respectively. Gel strength decreased after irradiation of mince, and such decreases were dose-dependent. Irradiation extended sensory shelf life of unfrozen fish mince 12–18 days and microbiologically (<10⁶ CFU/g) 6–13 days longer than the unirradiated control.     

2-Dodecylcyclobutanone as an irradiation dose indicator to identify and estimate original dose in irradiated ground beef

2-Dodecylcyclobutanone (2-DCB), as a chemical marker of irradiated lipid-containing foods, was used to detect whether ground beef patties were irradiated and to estimate the original absorbed dose. The ground beef patties (70/30) were irradiated at five targeted absorbed doses of 0.5, 1.0, 3.0, 5.0, and 7.0?kGy and stored for 0, 7, 14, 21, and 28?days, respectively at 4?°C. A rapid analytical method based on direct solvent extraction (DSE)/gas chromatography–mass spectrometry (GC–MS) was developed to analyze 2-DCB in γ-ray irradiated ground beef patties. The samples were extracted with acetonitrile via DSE using a tissue-mashing instrument, and then purified with a 1-g silica cartridge and analyzed via GC–MS. The results indicate a linear relationship between irradiation dose and the amount of 2-DCB produced in the irradiated samples (y?=?0.0608x–0.0004, R2?=?0.9899). In addition, a linear relationship was observed between the loss (%) of 2-DCB and storage time (L?=?1.958d–1.6596, R2?=?0.9597). Thus, a method for estimating the initial dose of irradiated food was developed based on these two line equations; this method explored the establishment of a determination model of the original irradiation dose of lipid-containing foods. The method was used to successfully estimate 2–7?kGy irradiated beef samples within 28?days with minimal deviation within ±15?%.     

Effect of irradiation on Salmonella survival and quality of 2 varieties of whole green onions

Abstract: Two varieties of green onions, Banner and Baja Verde, were inoculated with a cocktail of 3 Salmonella strains using dip and spot inoculation and irradiated at 0, 0.3, 0.6, 0.9, and 1.2 kGy using electron beam. Salmonella survivors were enumerated using a XLD underlay/TSAYE overlay plating method. The D values were in the range of 0.26 to 0.32 kGy depending on variety but not on the method of inoculation. This indicated that a 5‐log reduction of Salmonella can be achieved at a dose of 1.6 kGy. For the quality study, both varieties of green onions were irradiated at 0, 1.5, 2.0, and 2.5 kGy and evaluated for changes in microbial counts, color, texture, and visual quality during storage at 4 °C. Irradiation reduced total plate counts and psychrotrophs by 3 logs. Although the counts increased during storage, they did not exceed the initial counts of control. No significant difference was observed in color and texture between irradiated samples and control. The control maintained good visual quality for about 13 d as compared to 15 d for 1.5 and 2.5 kGy samples. The 2.0 kGy samples maintained good visual quality for 17 d suggesting that irradiation can increase shelf life by reducing spoilage microorganisms but higher doses can be detrimental to quality. At the dose levels required to achieve a 5‐log reduction in Salmonella, the shelf life of whole green onion can be extended. This study shows that irradiation can be used to enhance safety without adverse effects on quality.     

Combined Effect of Chitosan and Oregano Essential Oil Dip on the Microbiological, Chemical, and Sensory Attributes of Red Porgy (Pagrus pagrus) Stored in Ice

The combined effect of chitosan and oregano essential oil dip on shelf life of whole red porgy (Pagrus pagrus) stored in ice under refrigeration was investigated for a period up to 20 days. Quality attributes monitored during storage included microbiological (total viable counts, Pseudomonas spp., H₂S-producing bacteria including Shewanella putrefaciens, Enterobacteriaceae, and lactic acid bacteria), physicochemical (pH, thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), trimethylamine (TMA), and color), and sensory (odor and taste) parameters. Untreated red porgy was used as the control sample. Regarding the chemical indicators of spoilage, TBARS values for all treatments were equal to or less than 0.4 mg MDA?kg^?1 throughout the 20-day storage period. pH values varied between 6.6 (day 0) and 6.9 (day 14) for the various treatments. TVB-N values increased gradually during storage reaching the proposed acceptability limit (30 mg N?100 g^?1) on day 13 for control samples, days 15–16 for samples treated with oregano essential oil, day 20 for samples treated with chitosan, and >20 days for samples treated with chitosan plus oregano essential oil. Likewise, TMA values reached the proposed limit (5–6 mg N?100 g^?1) for red porgy on days 11–12, 14–15, 19–20, and >20, respectively. Finally, sensory evaluation data were in general agreement with microbiological data indicating a product shelf life of ca. 11 days for control samples, 16 days for samples treated with oregano essential oil, 18 days for samples treated with chitosan, and 19–20 days for samples treated with chitosan plus oregano essential oil.