Effects of gamma irradiation on quality of Pakistani blood red oranges (Citrus sinensis L. Osbeck)

Effect of gamma irradiation and washing on physicochemical and sensory quality of blood red oranges was investigated. The citrus fruits were packed in cellophane bags and stored at room temperature for 42 days. Two gamma irradiation doses 0.25 and 0.5 kGy alone and in combination with washing were applied to the fruits. Weight loss decreased with gamma irradiation and increased with washing during storage. Acidity and ascorbic acid values were higher for the oranges irradiated at 0.5 kGy and minimum for the washed oranges. Generally, total soluble solids (TSS) increased during the storage period. However, washed samples had the highest concentration and 0.5 kGy-irradiated samples had the lowest TSS at the end of the storage period. Sensory quality qualify by appearance, odour and taste are decreased during storage in both treatments. However, the fruits were still acceptable by the trained observers. It can be inferred from this study that irradiation at 0.5 kGy or in combination with washing is an effective post-harvest technique in keeping the changes in physicochemical and sensory quality to a minimum level during storage.     

电子束辐照对芒果品质的影响

为研究电子束辐照处理对芒果品质的影响,筛选适用于芒果辐照保鲜的最佳剂量,分别采用0.5、1.0、1.5和2.0 kGy剂量电子束辐照芒果,测定室温贮存条件下辐照处理后芒果发病率、失重率以及营养指标的变化情况.结果表明:不同剂量的电子束辐照处理对芒果的硬度、可溶性固形物、抗坏血酸、总酸和还原糖等营养成分含量没有显著性影响...     

~(60)Co γ射线辐照对平菇采后生理及贮藏品质的影响

为探讨60Coγ射线辐照在平菇贮藏保鲜中的应用效果,以黑平1号为试材,分别采用0.5、0.8、1.0、1.3、1.6 kGy和2.0 kGy 60Coγ射线对平菇进行辐照,研究其在6℃贮藏过程中的生理生化及贮藏品质的变化规律。结果表明,采用0.5~1.0 kGy 60Co γ射线辐照处理,可以改善平菇的贮藏品质,贮藏第12天时1.0 kGy处理平菇的保鲜度为0.5,贮藏效果最佳;0.5~1.0 kGy辐照处理可以有效抑制平菇褐变及多酚氧化酶(PPO)活性的增强,统计分析表明褐变度(browing degree,BD)与PPO活性呈显著正相关,回归方程为:BD=0.0183 PPO活性-0.1527(R2=0.753 9,P0.05);0.5~1.0 kGy 60Co γ射线辐照能延缓平菇体内超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)等修复酶活性的降低,减少丙二醛(MDA)和超氧阴离子自由基(O2-·)的积累,降低质量损失率。因此,采用0.5~1.0 kGy 60Co γ射线辐照处理平菇,可以延缓平菇的褐变及衰老,保持其贮藏品质,延长其货架期至10~12 d。     

Effect of edible coating and gamma irradiation on inhibition of mould growth and quality retention of strawberry during refrigerated storage

The aim of this study was to investigate the effect of edible coating and gamma irradiation treatment on mould growth and storage quality of strawberry. Strawberry fruit after harvest were treated with 0.5–1.0% (w/v) carboxymethyl cellulose (CMC) coating followed by irradiation at 2.0 kGy and subsequent storage under refrigerated conditions for 21 days. The investigations revealed that CMC coating alone at levels 0.5% and 0.75% w/v was not effective in delaying the decay and inhibiting the appearance of mould growth in strawberry fruit. Treatment of irradiation in combination with 1.0% w/v CMC coating was found significantly (P ≤ 0.05) effective compared with other treatments in maintaining the quality and delaying the decay and appearance of the mould growth in strawberry up to 18 days of refrigerated storage. Combinatory treatment of irradiation and coating can help to a greater extent in facilitating the marketing of the strawberry fruit to distant markets other than the local market, thereby benefiting growers and consumers.     

辐照对核桃果实冷藏生理与品质的影响

以‘辽核2号’核桃果实为材料,经0（对照）、0.1、0.3、0.5、1.0 kGy不同剂量60Coγ射线辐照处理后,采用青皮果实60 d＋脱皮鲜坚果30 d两步法贮藏于（0±1）℃的冷库中,监测其在贮藏期间色差、褐变指数、裂果率、乙烯释放量、气体成分、蛋白质含量、脂肪含量、脂肪酸含量、过氧化值与羰基价的变化。结果表明,辐照处理显著降低了核桃果实贮藏期间的裂果率和乙烯峰值,保持了较低的过氧化值和羰基价,延缓了脂肪氧化速度;0.3 kGy和0.5 kGy处理的感官品质较好,以0.3 kGy延缓核桃果实衰老的作用突出。该剂量条件下核桃果实裂果率和乙烯峰值最低,必需脂肪酸总量维持在较高水平,贮藏末期脂肪含量最高,过氧化值最低,确定0.3 kGy为核桃果实冷藏适宜辐照剂量。     

Effect of integrated application of gamma irradiation and modified atmosphere packaging on physicochemical and microbiological properties of shiitake mushroom (Lentinus edodes)

Shiitake (Lentinula edodes) mushrooms were packed in biorientated polypropylene (BOPP) bags and exposed to different doses of gamma irradiation (1.0, 1.5, and 2.0 kGy) within the packaging, heat sealed and stored at 4 °C for 20 d. Of the three doses, 1.0 kGy was most effective in maintaining a high level of firmness. Samples treated with 1.0 kGy also exhibited smaller initial declines in soluble protein, higher increases in total sugar content and lower levels of malondialdehyde accumulation. Furthermore, 1.0 kGy promoted the accumulation of phenolics compound and showed higher antioxidant ability during storage. At higher doses, 2.0 kGy resulted in a higher microbial reduction, but showed negative effects on texture, chemical properties and functional components. All the gamma irradiation were effective in retarding mushroom sensory deterioration. Thus, application of gamma irradiation in combination with MAP can extend the storage life of shiitake mushroom up to 20 d.     

Effect of freezing, irradiation, and frozen storage on survival of Salmonella in concentrated orange juice

Six strains of Salmonella (Anatum F4317, Dublin 15480, Enteritidis 13076, Enteritidis WY15159, Stanley H0588, and Typhimurium 14028) were individually inoculated into orange juice concentrate (OJC) and frozen to -20 degrees C. The frozen samples were treated with 0 (nonirradiated), 0.5, 1.0, or 2.0 kGy of gamma radiation and held frozen for 1 h, and the surviving bacterial population was assessed. The strains showed significant variability in their response to freezing and to freezing in combination with irradiation. The response was dose dependent. Relative to the nonfrozen, nonirradiated control, the reduction following the highest dose (2.0 kGy) ranged from 1.29 log CFU/ml (Salmonella Typhimurium) to 2.17 log CFU/ml (Salmonella Stanley). Samples of OJC inoculated with Salmonella Enteritidis WY15159 and irradiated were stored at -20 degrees C for 1, 2, 7, or 14 days, and the surviving population was determined. Relative to the nonfrozen, nonirradiated control, after 14 days, the population was reduced by 1.2 log CFU/ml in the nonirradiated samples and by 3.3 log CFU/ml following treatment with 2.0 kGy. The combination of frozen storage plus irradiation resulted in greater overall reductions than either process alone.     

γ射线辐照对香菇采后贮藏过程中水分特性及理化指标的影响

以新鲜香菇‘808’为研究对象,考察1.0 kGy 60Co γ射线辐照对香菇贮藏（（4±1）℃、相对湿度（80±5）%）过程中理化指标（色度、质构、显微结构）、水分迁移规律和感官品质的影响。结果表明：在贮藏过程中,经辐照处理的香菇亮度（L*值）由90.06下降至87.77,而对照组L*值由90.54下降至80.71,表明辐照延缓了褐变,防止了鲜香菇色泽劣变;辐照组的硬度显著高于对照组,辐照处理减缓了香菇菌丝组织网络结构的降解;由低场核磁共振分析可知,在贮藏过程中,对照组香菇的水分状态极不稳定,自由水横向弛豫时间T23峰面积在贮藏初期有小幅度上升,随后急剧下降,结合水T21峰面积先升高后降低,并且在贮藏后期T21峰右移;而辐照组香菇自由水T23峰面积均匀下降,结合水T21峰面积并无大幅度变化,两组不易流动水T22峰面积均呈现先升高后降低的趋势,因此辐照处理提高了鲜香菇不同状态水分的稳定性,而且辐照处理延缓了鲜香菇感官品质的劣变进程。结论：1.0 kGy 60Co γ射线辐照处理可以较好地维持鲜香菇的理化特征,减少水分流失,延长香菇的货架期。     

Effect of Co γ-irradiation on postharvest quality and selected enzyme activities of Pleurotus nebrodensis

Freshly harvested Pleurotus nebrodensis fruit bodies were exposed to four different doses (0.8-2.0 kGy) of ⁶⁰Co γ-irradiation and various physiological changes associated with postharvest deterioration, as well as the activities of selected enzymes (proteinase, polyphenoloxidase, superoxide dismutase, catalase) thought to play a role in the process of deterioration, were monitored during 22 days of subsequent storage at 4 °C and 65-70% relative humidity. An irradiation dose of 1.2 kGy significantly delayed (by 6-9 days) the onset of fruit body softening, splitting and browning compared with non-irradiated controls and test samples subjected to lower or higher irradiation doses. Irradiation with 1.2 and 1.6 kGy also had a positive effect on other indicators of mushroom tissue senescence, resulting in smaller decreases in soluble protein levels and more protracted increases in proteinase activity. Peak levels of polyphenoloxidase activity, widely recognized as causing postharvest browning of mushroom tissue, were also significantly lower (P < 0.05) in fruit bodies exposed to 1.2 kGy compared with non-irradiated controls. Our data increase our understanding of the effects of γ-irradiation on the biochemical changes associated with postharvest deterioration in P. nebrodensis, and improve the prospects of more targeted strategies for extending the shelf life of both this and other mushrooms.     

Combination effect of sodium lactate and irradiation on color,lactic acid bacteria,lipid oxidation and residual nitrite in Chinese sausages during storage at 25 °C

Chinese sausages, with the addition of 0 or 2% sodium lactate, were vacuum‐packaged and stored overnight at 4°C. Refrigerated sausages were gamma‐irradiated at 0, 3 or 5 kGy absorbed dose. Meat samples were stored at 25°C for up to 30 days. Color, lactic acid bacteria, pH, lipid oxidation and residual nitrite were determined during storage. Irradiated samples were reduced in redness as a result of irradiation and storage time. Irradiation at 5 kGy alone or in combination with 2% sodium lactate and irradiation at 3 kGy could completely inhibit lactic acid bacterial growth. Thiobarbituric acid reactive substances (TBARS) values decreased as the pH values of samples increased. Sodium lactate decreased TBARS values of all samples and protected against a decrease of residual nitrite during storage. Irradiation reduced residual nitrite in Chinese sausage, and residual nitrite decreased with increased time. Copyright © 2004 Society of Chemical Industry     

Effects of electron-beam generated X-ray irradiation on the postharvest storage quality of Agaricus bisporus

The objective of this study was to investigate the effects of electron-beam generated X-ray irradiation on the postharvest storage quality and antioxidant capacity of Agaricus bisporus. All mushrooms were treated with different doses of electron-beam generated X-ray irradiation (0, 0.5, 1.0, 1.5 and 2.0 kGy) followed by stored at 4 °C for 21 days. Results showed that when compared with the control group at the end of storage, the firmness of Agaricus bisporus treated with 1.0 kGy was increased by 43.68%, the cell membrane permeability and malondialdehyde (MDA) content were decreased by 14.48% and 32.27% respectively, and the polyphenol oxidase (PPO) activity was reduced by 44.30%. One-kGy treatment was better than the control group to maintain superoxide dismutase (SOD) and catalase (CAT) activity. The finding suggested that the dose of 1.0 kGy generated by electron beam was suitable for keeping the postharvest quality for 21 days of Agaricus bisporus.Industrial relevanceThis study stated that electron-beam generated X-ray pretreatment could be a green and safe technology to improve the overall quality of Agaricus bisporus at 4 °C for 21 days.     

Absorbed‐dose estimation and quality attributes of gamma‐irradiated fresh shiitake mushrooms

BACKGROUND: The general use of food irradiation requires reliable identification methods as well as extensive quality characterization. Shiitake (Lentinus edodes) mushrooms, packed in polystyrene trays and covered with polyvinylchloride film, were investigated for dose‐dependent identification and quality characterization upon gamma irradiation (0, 1, 2, and 3 kGy). RESULTS: Thermoluminescence (TL) analysis of separated minerals provided excellent results to characterize the irradiated mushrooms. Low‐dose re‐irradiation (200‐600 Gy), medium‐dose re‐irradiation (1‐3 kGy) and high‐dose re‐irradiation (2‐6 kGy) were performed and compared using an additive dose method. An electronic‐nose analysis showed a difference in the volatile profiles of mushrooms following irradiation. One‐kGy‐irradiated mushrooms showed similar or better quality attributes to those of the control samples. Scanning electron microscopy revealed the dose‐dependent degradation in microstructure of mushrooms upon irradiation. CONCLUSION: An absorbed dosed estimation was possible using TL analysis in which 1‐3 kGy re‐irradiation technique gave most promising results. An E‐nose analysis effectively distinguished the samples based on irradiation history. The best quality attributes were observed at 1 kGy irradiation. However, the drastic effects of irradiation were prominent in 2 and 3 kGy‐irradiated mushrooms. © 2012 Society of Chemical Industry     

Effect of sulphiting and drying methods on physico-chemical and sensorial quality of dried apricots during ambient storage

Fresh mature and ripe apricots after preparations were pre-treated with potassium meta-bisulphite (KMS) at concentrations of 2–8% for 30, 45 and 60 min followed by drying in solar tunnel dryer and in open air. After completion of drying, the samples were packed in polyethylene pouches and evaluated for various quality parameters at 0, 6 and 12 months of ambient storage. KMS pre-treatment at concentration of 6% for 60 min prior to drying helped significantly in improving and maintaining the quality of dried apricots for up to 12 months of ambient storage. Solar tunnel drying resulted in hygienic product and reduced the drying time to 3–4 days compared with 14–16 days in open air drying. Residual free sulphur dioxide of apricots pre-treated at KMS concentration of 6% for 60 min was within the prescribed limits of the Fruit Product Order (1955) specifications for dried products.     

The potential use of irradiation to extend the shelf-life of clams (Ruditapes decussatus) during live storage: effect on bacterial and biochemical profiles

Changes in microbiological and biochemical quality of clams ( Ruditapes decussatus ) subjected to low doses of gamma irradiation (0.5 and 1 kGy) were investigated during alive storage, at 5 °C. The mortality rate was significantly lower for irradiated clams compared with the control. In the same way, ammonia content was lower for irradiated clams (especially 1 kGy irradiated group). Considerable levels of total mesophiles, coliforms, staphylococcus, faecal streptococcus and Escherichia coli were detected in the control and irradiation had immediately reduced these charges; all bacteria studied experienced a 1- to 3-log reduction following 1 kGy irradiation. At the last day of storage, irradiated groups showed a noticeable reduction in the bacterial counts, whereas the mesophiles, staphylococcus and coliform germs were abundant in the control group (6.3, 2 and 1.7 log CFU g⁻¹, respectively). Irradiation doses up to 1 kGy had not an immediate effect on fatty acids composition ( P  > 0.05) and lipid profile was better in irradiated samples, where polyunsaturated fatty acid fraction was maintained throughout storage using irradiation. Also, sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed minor changes in proteins bands between different samples. These results demonstrated that 1 kGy irradiation appeared to be the optimum dose for treating alive clams ( R. decussatus ), through improving the microbial quality and alleviating biochemical changes during refrigerated storage.     

Effect of Gamma Irradiation of Whole Chicken Carcasses on Bacterial Loads and Fatty Acids

Broiler chickens were irradiated by Cobalt-60 at a commercial irradiation facility at dose levels of 0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 kGy at 3.0°C. Regression analyses indicated more than 99% of the microbial load on the whole carcass was eliminated at doses ranging from 1.5 to 2.0 kGy. Fatty acids were not affected except for palmitic which showed a decrease and oleic acid which showed an increase. Both of those changes were significant. Results indicate gamma irradiation of chicken at 2.0 kGy or more using commercial irradiation substantially reduced bacterial loads.     

EFFECTS OF GAMMA RADIATION ON NUTRITIVE AND SENSORY QUALITIES OF SWEET POTATO STORAGE ROOTS

Jewel and Georgia Jet sweet potato storage roots were treated with gamma radiation doses of 0.1, 0.5, 0.8, 1.5 and 2.0 kGy and compared to the untreated control. Analyses showed that ascorbic acid and starch decreased at 1.5 and 2.0 kGy. Total carotenoids in both cultivars were unaffected by radiation treatment. Gamma radiation caused softening of Jewel and Georgia Jet sweet potato roots and the texture score decreased at 1.5 and 2.0 kGy. Color was not affected by radiation in either cultivar and differences in L, a and b values were not observed. The total sugar content of the Jewel sweet potato was higher at 0.8 kGy than at other doses but for Georgia Jet it tended to increase as the radiation dose increased. The sensory evaluation test indicated that acceptability of baked sweet potatoes was severly affected by gamma radiation at doses of 0.5 kGy and above.     

Extension of shelf-life of whole-wheat flour by gamma radiation

The effect of low-dose gamma irradiation (0.25–1.00 kGy) on pre-packed whole-wheat flour (atta) was assessed in terms of physico-chemical properties, nutritional quality, chapati-making quality and sensory attributes. Semi-pilot scale storage studies on irradiated pre-packed whole-wheat flour revealed that there was no adverse effect of irradiation and storage up to 6 months of whole-wheat flour treated at doses up to 1.00 kGy on total proteins, fat, carbohydrates, vitamin B₁ and B₂ content, colour index, sedimentation value, dough properties, total bacterial and mould count. Storage of wheat flour resulted in slight increase in moisture, free fatty acids, damaged starch, reducing sugars and slight decrease in gelatinization viscosity.
However, irradiation as such had no effect on any of these parameters. Irradiation at 0.25 kGy was sufficient to extend the shelf-life of atta up to 6 months without any significant change in the nutritional, functional attributes. Chapaties made from irradiated atta (0.25 kGy) were preferred even after 6 months storage, compared with the control.     

Improvement of anthocyanin yield and shelf-life extension of grape pomace by gamma irradiation

This research investigated the effect of gamma irradiation on anthocyanin extraction from grape pomace, and on inhibition of microbial growth and anthocyanin content during subsequent storage. The combination of four variables was investigated: (1) irradiation at doses from 0 to 9 kGy; (2) packaging under vacuum; (3) addition of a low dose of sodium metabisulfite during irradiation; and (4) extraction in the presence of SO₂. Results indicate that the irradiation at 6 kGy, packaging in the presence of 0.1% sodium metabisulfite and extraction in the presence of 2000 ppm of SO₂ yielded the highest value of anthocyanins, and improved shelf-life of grape pomace.     

Use of gamma-irradiation and sulphur dioxide to improve storability of two Syrian grape cultivars (Vitis vinifera)

The feasibility of using gamma-irradiation and sulphur dioxide to control post-harvest diseases and to extend the shelf-life of table grapes in cold storage (1–2 °C) was studied using two cultivars of grapes local to Syria (Baladi and Helwani). The experiment took 2 years. In the first year the clusters of both cultivars were subjected to one of the following treatments, irradiation with 1.0 kGy of gamma-rays, sulphur dioxide (3 g of Na₂S₂O₅ per 5-kg cluster) or a combination of both 1.0 kGy of gamma-irradiation and sulphur dioxide. In the second year clusters of Baladi cv. were treated with 1.5 kGy of gamma-radiation, sulphur dioxide, and a combination of 1.5 kGy of gamma-radiation and sulphur dioxide, whereas clusters of Helwani cv. were treated with 0.5 kGy of gamma-radiation, sulphur dioxide, and a combination of 0.5 kGy of gamma-irradiation and sulphur dioxide. Treated and untreated clusters were kept in cold storage. With the exception of Helwani cv. produced in the first year and treated with sulphur dioxide, the results indicated that separate application of sulphur dioxide and gamma-radiation reduced the rotting induced by Botrytis cinerea . Gamma-irradiation in combination with sulphur dioxide was the best method of preserving the two varieties of table grapes.     

Use of γ-irradiation to reduce Clostridium perfringens on ready-to-eat bovine tripe

The aim of this study was to determine the effect of gamma irradiation at a target dose of 9kGy and storage at 5 and 15°C on the safety of ready-to-eat (RTE) tripe with respect to Clostridium perfringens count (CC) and aerobic plate count (APC), and to determine the effect of boiling (1h) and irradiation (9kGy) on Cl. perfringens ATCC 13124 spore structure. Irradiation significantly reduced APC stored at 5 and 15°C for 7 days. However, 0kGy control samples increased in their APC to >7log(10) cfu/g throughout 7 days of storage. Irradiation eliminated the inoculated Cl. perfringens ATCC 13124 spores on RTE tripe throughout storage at 5 and 15°C. Transmission electron microscopy of Cl. perfringens ATCC 13124 spores showed that boiling caused a reduction in spore material, irradiation caused elongation of the Cl. perfringens ATCC 13124 spores, and boiling in combination with gamma irradiation caused loss of spore material. Therefore, irradiation at 9kGy, together with storage at 5°C, can assure the microbiological safety of RTE bovine tripe, with respect to Cl. perfringens spores for at least 7 days at 5 and 15°C.