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.     

Effects of Calcium Ascorbate and Ionizing Radiation on the Survival of Listeria monocytogenes and Product Quality of Fresh-cut 'Gala' Apples

The interactive effects of calcium ascorbate (CaA) and ionizing radiation on viability of Listeria monocytogenes inoculated in solutions and on ‘Gala’ apple slices were investigated. The D10 values (radiation doses that inactivate 90% of bacterial population) for L. monocytogenes inoculated in water, 3.5%, and 7.0% CaA solutions were 0.32, 0.61, and 0.58 kGy, respectively. The D₁₀ values of the pathogen on the surface of apple slices treated with water, 3.5%, and 7.0% CaA were 0.24, 0.32, and 0.32 kGy, respectively. To determine the impact of CaA and irradiation on quality of apple slices, apple slices treated with 0%, 3.5%, and 7.0% CaA were exposed to 1.6 kGy gamma radiation (a dose that produced a 5‐log reduction of L. monocytogenes) and stored under modified atmosphere at 4 °C for 14 d. CaA at levels of both 3.5% and 7.0% prevented the browning of the apple slices. The apple aroma intensity, however, decreased as the concentration of CaA increased. Irradiation at 1.6 kGy did not significantly affect color, soluble solid content, titratable acidity, or apple aroma intensity. The only negative effect of irradiation on apple slices appeared to be a loss of firmness. Our results suggest that CaA, used as an antibrowning agent, protected L. monocytogenes from radiation both in solution and on apple slices, but radiation at doses sufficient to inactivate 5‐log of the bacterium did not significantly influence product quality attributes except for the loss in firmness.     

Changes in quality, liking, and purchase intent of irradiated fresh-cut spinach during storage

The use of ionizing radiation to enhance microbial safety of fresh spinach at a maximum dose of 4 kGy has been approved by the U.S. Food and Drug Administration (FDA). However, whether spinach can tolerate those high doses of radiation is unclear. Therefore, this study was conducted to investigate the effects of irradiation and storage on quality, liking, and purchase intent of fresh-cut spinach. The oxygen radical absorbance capacity values and total phenolic content were not consistently affected by irradiation. However, the ascorbic acid content of irradiated sample decreased rapidly during storage, resulting in these samples being lower in ascorbic acid content than controls after 7 and 14 d of storage at 4 °C. Sensory evaluation by a 50-member panel revealed that purchase intent and ratings for liking of appearance, aroma, texture, flavor, and overall were not affected by irradiation at doses up to 2 kGy. Therefore, irradiation at doses up to 2 kGy may be used to enhance microbial safety without affecting consumer acceptance or overall antioxidant values of irradiated spinach.     

MICROBIAL QUALITY OF FRESH‐CUT ICEBERG LETTUCE WASHED IN WARM OR COLD WATER AND IRRADIATED IN A MODIFIED ATMOSPHERE PACKAGE*

ABSTRACT

The microbial keeping quality of fresh‐cut iceberg lettuce was determined after being washed in either cold water (5C) for 3 min or warm water (47C) for 2 min followed by a cold water rinse (5C) and packaged in a modified atmosphere film bag. The lettuce samples were treated with gamma radiation to 0, 1 or 2 kGy while maintaining a refrigerated temperature (4C). The samples were analyzed for total aerobic, total coliform and Enterobacteriaceae counts after refrigerated storage up to 12 days. No difference in aerobic counts was observed between the hot‐ and cold‐washed samples immediately after washing. The coliform and Enterobacteriaceae counts were reduced by 2 log after the warm water wash and no difference for the cold water‐washed sample. The irradiation treatment at 1 kGy reduced the aerobic, coliform and Enterobacteriaceae counts by 2 log for the warm‐washed samples. At the 2‐kGy treatment level, the aerobic and coliform counts were reduced by 3 log for the cold‐washed lettuce, whereas the Enterobacteriaceae counts were reduced by only 2 log. The observed log reductions in bacterial counts after irradiation were maintained for 12 days when stored at 4C. The combination of a cold water wash and irradiation to 2 kGy had the best microbial keeping quality.

PRACTICAL APPLICATIONS

Fresh‐cut lettuce, when washed in either cold or warm water, shows neither an appreciable removal of the microbial load nor a significant increase in the keeping quality when compared with unwashed fresh‐cut controls. Placing the washed lettuce into modified atmosphere packaging (MAP) did not lessen the overall bacteriologic load, and after 12 days of storage at 4C, the microbial counts increased. However, gamma irradiation of the washed, MAP‐stored lettuce to a dose of 2 kGy significantly reduces the overall microbe count, thereby increasing both the shelf life and the safety of the produce. A 2‐kGy dose of gamma irradiation provides a pathogen‐free, long shelf life, fresh‐cut lettuce that is bacteriologically safer and sensorially indistinguishable from bagged, nonirradiated, fresh‐cut lettuce.     

Retention of quality and nutritional value of 13 fresh-cut vegetables treated with low-dose radiation

Improving the microbial safety while maintaining quality of fresh fruits and vegetables will increase consumer confidence in fresh produce. This study was conducted to investigate the effects of irradiation at 1 kGy, a dose that potentially inactivates E. coli O157:H7 by 5 logs, on the quality of 13 common fresh-cut vegetables: iceberg, romaine, green and red leaf lettuce, spinach, tomato, cilantro, parsley, green onion, carrot, broccoli, red cabbage, and celery. The results showed that the appearance of irradiated samples was similar to the nonirradiated ones except that irradiated carrots, celery, cilantro, and green onions had higher appearance scores than corresponding nonirradiated vegetables. There was no difference in the instrumental texture between irradiated samples and nonirradiated ones. The aroma of several irradiated vegetables was significantly better than controls after 14-d storage, because these control samples decayed or senesced. The 1 kGy irradiation did not affect vitamin C content of most vegetables; however, irradiated green and red leaf lettuce had 24% to 53% lower vitamin C contents than the controls. Our results suggest that most fresh-cut fruits and vegetables tested can tolerate up to 1 kGy irradiation without significant losses in any of the quality attributes.     

PHYSICOCHEMICAL AND SENSORY ANALYSES ON EGG POWDER IRRADIATED TO INACTIVATE SALMONELLA AND REDUCE MICROBIAL LOAD

Egg powder was treated with 0, 2, 5 and 10 kGy of gamma radiation at 20C to inactivate Salmonella and to stabilize its microbial load. Microbial, physicochemical and sensory determinations were performed during 4 months of storage to select the optimal radiation dose to attain the objective without significantly reducing egg quality. Microbial results show that 2.0 kGy inactivated Salmonella and reduced microbial load to levels below those stipulated by the Argentine regulations. Physicochemical determinations of egg powder extracts for peroxide number, spectrophotometric measurements in the visible and ultraviolet regions, functional properties on sponge cakes made with egg powder (height, comprssion-relaxiation cycle parameters), foam stability and viscosity showed that gamma radiation at the dose of 2 kGy, did not cause significant changes in these parameters. Higher radiation doses (5 and 10 kGy) did increase rancidity, pigment loss and protein chain scission. Sensory determinations performed on egg powder, and on cakes manufactured with it, agreed with the physicochemical results. After 110 storage days, 2 kGy was the most suitable of the tested doses .     

电子束辐照对泥蚶杀菌保鲜效果的影响

目的：研究电子束辐照对泥蚶微生物数量及其感官质量的影响。方法：泥蚶经不同剂量电子束处理,测定辐照后及冷藏期间菌落总数、大肠菌群及其感官评分。结果：电子束辐照能有效地杀灭泥蚶中的微生物,经过0、1、3、5、7、9kGy 不同剂量处理,泥蚶的菌落总数逐步下降,当泥蚶的初始菌落总数为3.10 × 105CFU/g时, D10=3.12kGy;泥蚶的感官质量与辐照剂量有关,经过7、9kGy 剂量处理后样品产生令人不愉快的异味。结论：结合辐照后及冷藏期泥蚶的微生物和感官指标,泥蚶电子束冷杀菌的适宜剂量为3～5kGy,经3～5kGy 处理后,泥蚶的货架期由对照组的5d 延长至15～19d。     

Shelf life extension of minimally processed cabbage and cucumber through gamma irradiation

The influence of irradiation of minimally processed cabbage and cucumber on microbial safety, texture, and sensory quality was investigated. Minimally processed, polyethylene-packed, and irradiated cabbage and cucumber were stored at refrigeration temperature (5 degrees C) for 2 weeks. The firmness values ranged from 3.23 kg (control) to 2.82 kg (3.0-kGy irradiated samples) for cucumbers, with a gradual decrease in firmness with increasing radiation dose (0 to 3 kGy). Cucumbers softened just after irradiation with a dose of 3.0 kGy and after 14 days storage, whereas the texture remained within acceptable limits up to a radiation dose of 2.5 kGy. The radiation treatment had no effect on the appearance scores of cabbage; however, scores decreased from 7.0 to 6.7 during storage. The appearance and flavor scores of cucumbers decreased with increasing radiation dose, and overall acceptability was better after radiation doses of 2.5 and 3.0 kGy. The aerobic plate counts per gram for cabbage increased from 3 to 5 log CFU (control), from 1.85 to 2.93 log CFU (2.5 kGy), and from a few colonies to 2.6 log CFU (3.0 kGy) after 14 days of storage at 5 degrees C. A similar trend was noted for cucumber samples. No coliform bacteria were detected at radiation doses greater than 2.0 kGy in either cabbage or cucumber samples. Total fungal counts per gram of sample were within acceptable limits for cucumbers irradiated at 3.0 kGy, and for cabbage no fungi were detected after 2.0-kGy irradiation. The D-values for Escherichia coli in cucumber and cabbage were 0.19 and 0.17 kGy, and those for Salmonella Paratyphi A were 0.25 and 0.29 kGy for cucumber and cabbage, respectively.     

Quality and Microbial Population of Cornish Game Hen Carcasses as Affected by Electron Beam Irradiation

ABSTRACT:  We evaluated the chemical and microbiological quality of Cornish game hen carcasses irradiated up to 7 kGy with a 10 MeV linear accelerator (dual beam configuration). Eighty frozen and vacuum packaged (approximately 0.45 kg) Cornish game hens ( Gallus domesticus ) were irradiated and stored in low-density polyethylene bags at 4 ± 1 °C for 21 d; nonirradiated chickens served as controls. Fat oxidation (in terms of malonaldehyde content) increased with storage time and dose for all chicken parts analyzed (breast, thigh, and skin). As expected, the skin had the highest level of fat oxidation while the breast samples had the lowest. Oxidation level in all samples exposed to 2 kGy reached a maximum on day 14. Sensory evaluation showed that irradiation caused significant textural toughening, and increased the redness of raw chicken meat. In terms of overall quality and aroma, lipid oxidation was not a major problem since it was not detected by the panelists. Irradiation significantly reduced the total viable microbial counts (TVC) in the breast and thigh samples. Exposure to 3-kGy dose decreased the TVC by 0.3-log cycles on the surface of the skin. In less than 14 d, the nonirradiated chicken carcasses had counts greater than 6 log CFU/50 cm², while the 2 and 3 kGy irradiated samples reached these numbers only after 21 d of storage. Samples irradiated at 7 kGy had consistently the lowest counts (2.5 log CFU/50 cm²) throughout storage time.This study shows that irradiation up to 7 kGy and refrigerated storage (4 °C) inhibits microbial growth and extends shelf life of Cornish game hens without affecting consumers' acceptability.     

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.     

Optimization of radiation dose and quality parameters for development of ready-to-cook (RTC) pumpkin cubes using a statistical approach

Full factorial design was employed to study the effect of gamma irradiation (0–2.5 kGy) and storage (up to 28 d) at 10 °C on quality of RTC pumpkin. Data obtained from microbial, color, texture and sensory analysis were fitted into a cubic model. Resulting equations were solved to assess radiation dose and maximum storage period for acceptable microbial quality (< 10⁵ CFU g^− 1) and sensory scores (overall acceptability > 5). Radiation dose of 1 kGy resulted in a product with desired microbial and sensory quality up to storage period of 21 d. The processed product (1 kGy) had significantly (p < 0.05) higher total antioxidant and vitamin C content as compared to non-irradiated control after storage of 21 d. HPLC analysis demonstrated that there were no qualitative changes in phenolic and carotenoid constituents due to radiation processing. Thus radiation processing was successfully employed to develop RTC pumpkin with improved shelf-life.Industrial relevanceThe present study demonstrates the efficacy of the statistical approach of the experimental design for optimization of radiation dose and storage time for ready-to-cook (RTC) pumpkin cubes with acceptable microbial and sensory quality. Complex interactions among radiation dose, storage duration and quality attributes of RTC pumpkin were successfully mathematically modeled. The mathematical modeling can be useful for commercial production as the required processing conditions can be suitably obtained based on the desired quality characteristics of the final product.     

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.     

Effects of Gamma-Irradiation on Flatulence-Causing Oligosaccharides in Green Gram (Phaseolus Areus)

Effects of gamma-irradiation (l–10 kGy) on flatulence-causing oligosaccharides of green gram were investigated. Irradiation at 2.5 kGy of hydrated seeds caused nearly 20% loss in their total content; but, 50% each of stachyose and raffinose, the two most gas-forming sugars, was reduced. However, oligosaccharides disappeared completely from germinated (48 hr) seeds, irradiated at 2.5–10 kGy; though α-galactosidase activity was not changed. When irradiated green gram flour was subjected to enzymic hydrolysis, significantly more reducing sugars were liberated. Quantitative analysis of the breakdown products of raffinose also suggested that radiation treatment stimulated the glycosidic cleavage of higher sugar molecules to simpler, easily digestible sugars. Thus radiation treatment of green gram is effective for elimination of oligosaccharides during germination.     

Effect of low‐dose irradiation on shelf life and microbiological safety of sliced carrot

Minimally processed non‐irradiated carrots (sliced) exhibited diverse microflora at initial level. During storage, bacterial number increased with the presence of pathogenic bacteria accompanied by a loss of total solids. On the other hand γ‐irradiation at an optimal dose of 2 kGy offered a pathogen‐free, hygienic product with insignificant losses in nutrients such as in sucrose, total carotenes and ascorbic acid content in comparison to controls and 2‐ to 4‐fold increased in shelf‐life at refrigeration temperature. The D₁₀ values of pathogens like Escherichia coli and Yersinia enterocolitica in carrot paste were in a lower range (0.12–0.26 kGy) compared with that of Listeria monocytogenes (0.3–0.5 kGy). The validity of the processing treatment (2 kGy) was challenged by artificially inoculating Listeria monocytogenes in the product. Thus, minimally processed carrots (sliced) are amenable to radiation treatment for extended storage stability and microbial safety. Copyright © 2005 Society of Chemical Industry     

QUALITY RESPONSE OF 'BING' AND 'RAINIER' SWEET CHERRIES TO LOW DOSE ELECTRON BEAM IRRADIATION

'Bing' and 'Rainier' sweet cherries were irradiated at doses of 0.00, 0.15, 0.30, 0.60 and 0.90 kGy using a linear accelerator. Cherries were evaluated for quality immediately after treatment and again after 14 days storage at 1C. No variation in soluble solids, titratable acidity or flavor were noted at any of the irradiation doses. Defects were increased for 'Rainier' cherries at irradiation doses above 0.60 kGy, but no change in defects of 'Bing' cherries were present regardless of irradiation doses. Objective color of 'Bing' cherries was lighter with more red at irradiation doses greater than 0.30 kGy, but this change in color was not evident visually. Objective color of 'Rainier' cherries was reduced at irradiation doses of 0.60 kGy and greater. This reduction in 'Rainier' red color was evident visually at an irradiation dose of 0.90 kGy. No change in 'Bing' green stem color was evident, but 'Rainier' stem color improved at irradiation doses above 0.60 kGy. Firmness of both 'Bing' and 'Rainier' cherries was reduced at irradiation doses of 0.60 kGy and greater. By using the linear accelerator at doses of 0.60 kGy or less, 'Bing' and 'Rainier' cherries can be irradiated with no major quality loss to meet quarantine requirements.     

Effect of Irradiation on Microbial Safety and Nutritional Quality of Minimally Processed Bitter Gourd (Momordica charantia)

ABSTRACT: The feasibility of gamma radiation in combination with low temperature was studied to ensure microbiological safety and maintaining physicochemical and sensory characteristics of minimally processed bitter gourd. Radio sensitivity (D₁₀ values, that is, irradiation dose required for 90% reduction of microorganisms) for Salmonella paratyphae A and Escherichia coli were 0.28 kGy and 0.23 kGy, respectively. On the basis of D₁₀ values, 5D₁₀ values were determined and samples of minimally processed bitter gourd were irradiated up to 5D₁₀ values, stored for 14 d at 5 ± 1 °C, and analyzed for total bacterial, fungal, and coliform counts. Ascorbic acid, acidity, texture, and sensory qualities were also studied. Results showed that an irradiation dose of 2.0 kGy significantly reduced the microbial count to keep the samples microbiologically safe for 7d. Sensory evaluation revealed that the samples received maximum scores for appearance and flavor (7.8 and 7.9, respectively) with radiation dose of 2.0 kGy and minimum score for control (6.5). Firmness and ascorbic acid content decreased significantly with increase in storage time and irradiation dose. All the samples were discarded during the 2nd wk of storage due to high bio-burden.     

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     

Shelf life of fresh‐cut green beans as affected by packaging systems

To reduce quality loss of fresh‐cut green beans, different packaging systems were studied. In particular, samples were packaged in micro‐perforated and no‐perforated films and stored at 5 °C; unpackaged fresh‐cut green beans were also stored at the same temperature as the control. Headspace gas concentrations, mass loss, sensory quality and microbial proliferation were monitored for about 3 weeks. Results confirmed that selection of proper packaging is of crucial importance to create conditions able to guarantee the maintenance of product quality. Shelf life of fresh‐cut green beans packaged in the no‐perforated film (polyethylene, 25 μm) and in two micro‐perforated films (polypropylene films with 7 and 4 micro‐holes per package) was higher (19.2, 18.13 and 17.7 days, respectively) than that of the control or samples packaged in the micro‐perforated film with 12 micro‐holes per package (16.5 days).     

Combined effects of irradiation and modified atmosphere packaging on minimally processed Chinese cabbage (Brassica rapa L.)

Cut Chinese cabbage with air, CO₂ or CO₂/N₂ packaging was irradiated at doses up to 2 kGy and the microbiological and physicochemical qualities were investigated during a refrigerated storage for 3 weeks. Irradiation significantly reduced the microorganisms, and additionally, the modified atmosphere packaging (MAP) enhanced the reduction of the total aerobic and coliform bacteria during storage. Irradiation effectively inhibited the changes of the titratable acidity and pH, while a significant effect was not shown in the texture by irradiation. Antiradical and antioxidant activity, and the phenolic contents were slightly increased by irradiation at 0.5 kGy, while the phenolic contents were reduced by irradiation over 1 kGy. Our results suggest that irradiation at 1 kGy or above can be used to enhance the microbial safety of cut Chinese cabbage without a significant loss in the quality attributes.     

Post-harvest treatment of cherry tomatoes by gamma radiation: Microbial and physicochemical parameters evaluation

The aim of this study was to evaluate the effects of gamma radiation on cherry tomatoes, to assess the potential of irradiation post-harvest treatment for fruit shelf-life extension. Freshly packed cherry tomatoes (Solanum lycopersicus var. cerasiforme) were irradiated at several gamma radiation doses (0.8 kGy up to 5.7 kGy) in a ⁶⁰Co chamber. Microbiological parameters, antioxidant activity and quality properties such as texture, color, pH, total soluble solids content, titratable acidity, and sensory parameters, were assessed before and after irradiation and during storage time up to 14 days at 4 °C. Inactivation studies of natural cherry tomatoes microbiota and inoculated potential foodborne pathogens (Salmonella enterica; Escherichia coli and Staphylococcus aureus) were performed. A two log reduction on the microbial load of cherry tomatoes was verified after irradiation at 3.2 kGy, and 14 days of storage at 4 °C. Moreover, a maximum reduction of 11 log on the viability of potential foodborne bacteria was obtained after irradiation at 3.2 kGy on spiked fruits. Regarding fruits quality properties, irradiation caused a decrease in firmness compared with non-irradiated fruit, although it was verified a similar acceptability among fruits non-irradiated and irradiated at 3.2 kGy. Therefore, these results suggest that the irradiation treatment could be advantageous in improving microbial safety of cherry tomatoes and shelf-life extension without affecting significantly its quality attributes.Industrial relevanceThere is an ever-increasing global demand from consumers for high-quality foods with major emphasis placed on quality and safety attributes. One of the main demands that consumers display is for minimally processed, high-nutrition/low-energy natural foods with no or minimal chemical preservatives. Extending the shelf-life, while improving the food safety, will have a positive impact on both the industry and consumers (and potential target groups such as immunocompromised patients). The present study indicated that post-harvest gamma radiation treatment of cherry tomatoes can be used as an emergent, clean and environmental friendly process to extend the shelf-life of this fruit with safety and quality.