Effect of gamma irradiation on microbial load and quality characteristics of minced camel meat

The effect of gamma irradiation on microbial load, chemical and sensory characteristics of camel meat has been evaluated. Camel meat was irradiated at doses of 0, 2, 4 and 6 kGy of gamma irradiation. Irradiated and non-irradiated meat was kept in a refrigerator (1–4 °C). General composition and sensory evaluation of camel meat was done two days after irradiation, whereas, microbiological and chemical analysis was done immediately after irradiation and throughout the storage periods. The results indicated that all doses of gamma irradiation reduced the total mesophilic aerobic plate counts (TPCs) and total coliforms of camel meat. Thus, the microbiological shelf-life of camel meat was significantly extended from less than 2 weeks (control) to more than 6 weeks (samples irradiated with 2, 4 or 6 kGy). No significant differences in moisture, protein, fat, thiobarbituric acid (TBA) values, total acidity and fatty acids of camel meat were observed due to irradiation. There were slight effects of gamma irradiation in both total volatile basic nitrogen (VBN) and lipid oxidation values in camel meat. Sensory evaluation showed no significant differences between irradiated and non-irradiated camel meats.     

Effect of gamma irradiation and frozen storage on chemical and sensory characteristics of rainbow trout (Oncorhynchus mykiss) fillet

The present study was conducted to evaluate the combined effect of low‐dose gamma irradiation (1, 3 and 5 kGy) and frozen storage (5 months at ?20 °C) on chemical and sensory characteristics of rainbow trout (Oncorhynchus mykiss) fillet. Our statistical analysis showed that irradiation process and frozen storage time had a significant effect (P < 0.05) on total volatile nitrogen (TVN), peroxide value (PV), thiobarbituric acid (TBA) and pH. The level of all of these factors increased with increasing frozen storage time. At the end of the fifth month of frozen storage, the lowest and the highest level of TVN, PV and TBA were corresponding to the irradiated samples at 3 and 5 kGy, respectively. In terms of the overall acceptability of their texture, odour, colour and taste, irradiated samples at 3 kGy had the best quality and remained acceptable after 5 months frozen storage. The optimum dose of gamma radiation of rainbow trout fillets according to chemical and sensory analysis was obtained at 3 kGy.     

Effect of gamma irradiation on microbial analysis, antioxidant activity, sugar content and color of ready-to-use tamarind juice during storage

Gamma irradiation is highly effective in inactivating microorganisms in various foods and it offers a safe alternative method of food decontamination. In the present study, the effect of gamma irradiation on microbial analysis, antioxidant activity, sugar content, color and sensory evaluation of ready-to-use tamarind juice was investigated during storage. A fresh tamarind juice was prepared by dissolving 5 g of pulp/100 ml of deionized distilled water and irradiated at 0, 1, 3 and 5 kGy at room temperature. Microbiological assay of the fresh and stored ready-to-use tamarind juice showed better quality after gamma irradiation. Antioxidant ability was studied by using 1,1-diphenyl-2-picrylhydrazyl (DPPH), FRAP (ferric reducing/antioxidant power) and total phenolic contents, and gamma irradiation had a significant increase or maintenance on the antioxidant potential of the ready-to-use tamarind juice. Contents of glucose and fructose also showed minimal alterations both in the fresh and stored samples. There was a significant improvement in the Hunter color value in both the fresh and stored tamarind juice. To conclude, gamma irradiation improves the microbial decontamination and the antioxidants as well as the color of the ready-to-use tamarind juice without any adverse change in sensory qualities.     

Effect of gamma irradiation on fungal load, chemical and sensory characteristics of walnuts (Juglans regia L.)

Walnuts of the Baladi variety were treated with 0, 0.5, 1.0, 1.5 and 2.0 kGy of gamma irradiation. The irradiated and unirradiated nuts were stored at room temperature (15-18°C) and 50-70% r.h. Fungal load, proximate composition (moisture, protein, fat and ash contents), chemical changes and sensory properties of nuts were evaluated immediately after irradiation and after 12 months of storage. The results indicated that gamma irradiation reduced fungal load. The doses applied did not cause any significant change in proximate composition of walnuts. Gamma irradiation increased total acidity and decreased iodide value and volatile basic nitrogen (VBN) immediately after treatment. After 12 months of storage, gamma irradiation decreased total acidity and peroxide value and increased iodide value and VBN. No significant differences were observed between irradiated and nonirradiated samples in flavor and aroma immediately after irradiation. After 12 months of storage, higher doses (1.5 and 2.0 kGy) had a negative effect on sensory characteristics.     

Effects of low dose gamma irradiation on microbial inactivation and physicochemical properties of fried shrimp (Penaeus vannamei)

Changes in microbiological, physicochemical and sensory properties of shrimp gamma irradiated with ⁶⁰Co at doses of 0, 1, 3, 6, 9 kGy were investigated. Irradiation at 6 kGy eliminated most of the spoilage microorganisms and did not affect sensory quality. The L* value increased as irradiation dose increased, while a* value decreased as irradiation dose increased. Irradiation had no significant effect on the texture of shrimp samples; however, increasing the dose up to 9 kGy significantly increased the amount of volatile compounds, such as, alcohols, ketones, aldehydes, furans, and oxides. According to the total sensory points, the appearance and flavour of the shrimp product was considered as acceptable by sensory evaluation when irradiated at doses of 0–6 kGy. These results showed that gamma irradiation processing (<6 kGy) had the potential to extend the shelf life of fried shrimp.     

Effect of gamma irradiation on the physico‐chemical and sensory properties of raw shelled peanuts (Arachis hypogaea L.) and pistachio nuts (Pistacia vera L.)

Backround The present study evaluated the quality of raw peanuts and pistachio nuts as a function of irradiation dose in order to determine dose levels causing minimal undesirable changes to these products. Physico‐chemical (colour, peroxide value, hexanal content, fatty acid composition, volatile compounds) and sensory (colour, texture, odour, taste) properties of raw peanuts and pistachio nuts were determined after irradiation at doses up to 7 kGy. Results Results showed an eight‐ and seven‐fold increase in peroxide value and a twelve and five‐fold increase in hexanal content after irradiation at a dose of 7 kGy for peanuts and pistachio nuts, respectively. An increase was also observed in saturated fatty acids (20.51–28.28% and 15.24–24.87%) with a parallel decrease in unsaturated fatty acids (79.49–71.72% and 84.76–75.13%) for peanuts and pistachio nuts, respectively. Likewise, volatile compounds such as aldehydes, alkanes, ketones and alcohols comprising secondary oxidation products of peanut and pistachio nut lipids increased after irradiation. Pistachio nut colour parameter a* and to a lesser extent parameters, L* and b* decreased after irradiation leading to a slight but noticeable darkening in product colour while colour parameter L*, b* and a* of raw peanut remained unchanged by irradiation up to 7 kGy. Conclusion Based on sensory evaluation, peanuts and pistachio nuts become unacceptable for consumption when irradiated at doses higher than 3 kGy. Copyright © 2009 Society of Chemical Industry     

Effects of electron-beam and gamma irradiation treatments on the microbial populations, respiratory activity and sensory characteristics of Tuber melanosporum truffles packaged under modified atmospheres

The effects of electron-beam or gamma irradiation (doses of 1.5 kGy and 2.5 kGy of either one) on the microbial populations, respiratory activity and sensory characteristics of Tuber melanosporum packaged under modified atmospheres were monitored immediately after treatment, and subsequently every seven days during 35 days of storage at 4 °C. Treatments with 1.5 and 2.5 kGy reduced the total mesophilic aerobes counts respectively by 4.3 and 5.6 log cfu/g for electron-beam treatment, and by 6.4 and 6.6 log cfu/g for gamma irradiation. Other microbial groups studied (Pseudomonas genus, Enterobacteriaceae family, lactic acid bacteria, mesophilic aerobic spores, molds and yeasts) were not detected after the treatments. A decrease in the respiratory activity was detected in all the irradiated batches, indicating that the carbon dioxide levels were lower and the oxygen levels higher than those of the non-irradiated ones. Two species of yeasts, Candida sake and Candida membranifaciens var. santamariae, survived the irradiation treatments and became the dominant microbial populations with counts of up to 7.0 log cfu/g. The growth of these microorganisms was visible on the surface of irradiated truffles from day 21 onwards, affecting the flavor and the general acceptability of the ascocarps. Moreover, a watery exudate was detected in the treated truffles from the third week onwards, so the application of irradiation treatments in doses equal to or above 1.5 kGy did not preserve the quality characteristics of T. melanosporum truffles beyond 28 days.     

The effect of raw milk microbial flora on the sensory characteristics of Salers-type cheeses

The sensory characteristics of Salers Protected Denomination of Origin raw-milk cheeses are linked to the biochemical composition of the raw material (milk) and to the resultant microbial community. To evaluate the influence of the microbial community on sensory characteristics, Salers-type cheeses were manufactured with the same pasteurized milk, reinoculated with 3 different microbial communities from 3 different filtrates from microfiltered milks. Each cheese was subjected to microbial counts (on selective media), biochemical tests, and volatile and sensory component analyses at different times of ripening. Adding different microbial communities to specimens of the same (biochemically identical) pasteurized milk lead to different sensory characteristics of the cheeses. Cheeses with fresh cream, hazelnut, and caramel attributes were opposed to those with fermented cream, chemical, and garlic flavors. The aromatic compounds identified (esters, acids, alcohols, and aldehydes) in these cheeses were quite similar. Nevertheless, one milk was distinguished by a higher content of acetoin, and lower 2-butanone and 3-methylpentanone concentrations. Over the production period of 1 mo, the different cheeses were characterized by the same balance of the microbial population assessed by microbial counts on different media. This was associated with the stability of some sensory attributes describing these cheeses. Nevertheless, there was no linear correlation between microbial flora data and sensory characteristics as measured in this study.     

Low dose gamma irradiation of raw meat. I. Bacteriological and sensory quality effects in artificially contaminated samples

Filet américain, consisting of raw, ground meat (beef) mixed with mayonnaise sauce, and the corresponding raw beef (without sauce) were experimentally contaminated with different strains of Salmonella. Yersinia enterocolitica and Campylobacter jejuni and irradiated with doses up to 1.5 kGy.Radiation resistance (D value) was determined immediately after irradiation. For the evaluation of the irradiaion effect on Y. enterocolitica in relation to storage, a number of samples were stored for a few days at 3°C and the microbiologically examined.D values of S. typhimurium, S. anatum, S. panama and S. stanley (strains isolated from retail filet américain) irradiated in filet américain were found to be 0.37, 0.45, 0.41 and 0.61 kGy and in raw beef 0.55, 0.67, 0.66 and 0.78 kGy, respectively. D values of Y. enterocolitica serotypes 0:3, 0:5, 27 and 0:9 irradiated in filet américain were 0.043, 0.065, and 0.080 kGy and in raw beef, 0.10, 0.16 and 0.21 kGy, respectively. D values of C. jejuni (three strains) irradiated in filet américain were 0.11, 0.08 and 0.09 and in beef 0.15, 0.14 and 0.16 kGy, respectively.It is concluded that doses as low as 1 kGy are effective in reducing Salmonella by approximately 1.6–2.7 log cycles in filet américan and 1.3–1.8 log cycles in ground meat. Numbers of Y. enterocolitica and C. jejuni are always reduced by more than 4 log cycles with this dose.On sensory evaluation 38% of samples of filet américain irradiated directly with 1 kGy were not acceptable for a taste panel; preference was for the unirradiated sample in 82% of the cases. However, when beef was irradiated with the same dose prior to the addition of mayonnaise sauce no significant taste differences could be observed between nonirradiated and irradiated samples.     

电子束辐照进口冷冻牛腩的剂量分布及感官特性研究

目的 确认电子束辐照冷冻牛腩的剂量分布特性,研究不同剂量电子束辐照对冷冻牛腩的杀菌效果及辐照后产品色泽、风味、质构等感官指标的变化.方法 对不同厚度的冷冻牛腩块分别用8 kGy进行单面及双面电子束辐照,检测其内部剂量分布,确定辐照适宜的产品厚度,在此基础上用0、2、4 kGy不同剂量对商品包装(1 kg/袋,最大厚度不...     

Effects of gamma irradiation and electron beam irradiation on quality,sensory, and bacterial populations in beef sausage patties

This study compared effects of gamma ray (GR) and electron beam (EB) irradiation on quality (TBARS value, hardness, color), sensory characteristics, and total bacterial populations in beef sausage patties during accelerated storage at 30 °C for 10 days. Beef sausage patties were vacuum-packaged and irradiated by GR and EB at 0, 5, 10, 15, and 20 kGy at room temperature. The results of quality evaluation showed that the effects of GR irradiation were similar (p ? 0.05) to EB irradiation on lipid oxidation, hardness, color and sensory scores of the beef sausage patties. However, GR-irradiated samples had lower (p < 0.05) total bacterial counts than EB-irradiated samples after irradiation, and during storage regardless of irradiation dose. The results indicate that use of GR irradiation up to 10 kGy on patties should be useful in reducing bacterial populations with no adverse effect on quality and most of sensory characteristics (color, chewiness, and taste).     

Effect of low‐energy X‐ray irradiation on physical,chemical, textural and sensory properties of Dates

The effect of X‐ray irradiation as postharvest treatment on physical, chemical, textural and sensory attributes of Khalas dates (Phoenix dactylifera L.) was investigated. The surface of dates was subjected to low‐energy X‐ray irradiation at 3, 5 and 7 KGy. While some physical and chemical properties of dates were significantly different between treatments (fruit hardness, crude protein, total fat, tannins, total fibre and insoluble fibre), there was no detrimental effect on the quality (crude fibre, soluble dietary fibre, sucrose, glucose, fructose, moisture, total soluble solids, pH, water activity, colour and sensory evaluation). The sensory acceptability of X‐ray irradiated dates was significantly lower at 5 and 7 KGy than for untreated control. Irradiation at 3 KGy did not contribute to significant changes in physical, chemical or textural properties of dates. Adaptation to low‐energy X‐ray irradiation can be used as a potential commercial treatment for retaining the quality and ensuring the safety of dates.     

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.     

The effect of ethephon and clone on physical characteristics and sensory quality of Crimson Seedless table grapes after 1 month storage

Colour is one of the most important quality parameters of table grapes. Ethephon can be applied to improve the colour of table grapes. Trials were conducted in Western Australia to investigate the effect of ethephon on low berry colour and other quality parameters of two new clones (306 and 314) of Crimson Seedless table grapes developed in Western Australia. The ethephon effect was studied in comparison with clone 5560, which was the standard clone imported from California. The grape clones were established at two locations in Western Australia having different types of soil and environmental conditions. Ethephon was applied (300 ppm Ethrel^®) to improve the colour development. Physical measurements demonstrated that clones 306 and 314 were better than the imported standard clone in terms of berry weight, length and width. Sensory evaluation by 70 panellists revealed that clone 314 with ethephon application received significantly higher sensory scores for sweetness, crispness, flavour and overall acceptability compared with the standard clone. The acidity level was higher in clone 314 than the standard clone at the same °Brix level and had a positive effect on flavour and overall acceptability. Ethephon treatment reduced the berry crispness in the standard clone and clone 306 but had no effect on the crispness of clone 314.     

Effects of electron-beam irradiation on the shelf life, microbial populations and sensory characteristics of summer truffles (Tuber aestivum) packaged under modified atmospheres

The effects of two doses of electron-beam irradiation (1.5 kGy and 2.5 kGy) on the microbial populations (total mesophilic aerobes, Pseudomonas genus, Enterobacteriaceae family, molds and yeasts) and sensory characteristics of Tuber aestivum packaged under modified atmospheres were monitored immediately after treatment, and weekly during 42 days of storage at 4 °C. Treatment with 1.5 and 2.5 kGy reduced the pseudomonads populations by 4.3 and 5.5 logs, respectively. Enterobacteriaceae counts decreased by 5.4 logs with the 1.5 kGy dose and counts below the detection limit (<1.0 log cfu/g) were obtained with the 2.5 kGy dose. Lactic acid bacteria and yeasts were less affected by the ionizing radiation treatments and they became the dominant microbial populations throughout storage with microbial counts up to 7.1 log cfu/g. The carbon dioxide levels inside the packages containing irradiated truffles were lower than those of the non-irradiated ones, suggesting a decrease in the respiration rate of the treated ascocarps. The treatments with 1.5 and 2.5 kGy e-beam did not negatively affect the sensory characteristics of truffles, but a visible superficial yeast growth was detected in truffles irradiated with 1.5 kGy at the end of their shelf life (day 28). Treatment with 2.5 kGy e-beam has prolonged the shelf life to 42 days, compared with 21 days for the untreated samples.     

The effect of green ham pH and NaCl concentration on cathepsin activities and the sensory characteristics of dry-cured hams

There is a tendency to reduce the amount of NaCl in the manufacturing process of Spanish dry-cured ham. NaCl, pH and temperature determine the stability of this product. This study was concerned with the evaluation of green ham pH and sodium chloride concentration on cathepsin activities, physico-chemical parameters and sensory characteristics of dry-cured hams. Two different amounts of salt (55 and 80 g kg⁻¹) and two different pH levels (pH at 24 h post mortem <5·8; pH at 24 h post mortem >6·2) were used. Physico-chemical composition, cathepsin activity and a number of sensory parameters were evaluated. Hams with high pH displayed lower cathepsin activity, NPN, saltiness and hardness whereas the levels of brightness, crumbliness, pastiness and adhesivity were found to be higher than in normal hams. A high level of salt produced greater cathepsin B and B+L activity and lower pastiness and adhesivity than the samples with a low NaCl level. © 1998 SCI.     

Effect of gaseous ozone on microbial inactivation and sensory of flaked red peppers

Flaked red peppers inoculated with Escherichia coli , Bacillus cereus and B. cereus spores were exposed to gaseous ozone at 20 °C and 70% relative humidity (RH). Ozone concentrations of 0.1, 0.5 and 1.0 ppm up to 360 min were used to reduce E. coli and B. cereus, whereas 1.0, 5.0, 7.0 and 9.0 ppm ozone concentrations for 360 min were used to treat B. cereus spores. When flaked red peppers were treated with 1.0 ppm ozone concentration for 360 min, B. cereus and E. coli counts were decreased by 1.5 and 2.0 log numbers, respectively. Bacillus cereus spores were reduced by 1.5 log numbers at ozone concentrations of 7.0 ppm or above for 360 min. There were slight changes in flavour, appearance and overall palatability of flaked red peppers treated with ozone between 5.0 and 9.0 ppm. Ozone concentration (1.0 ppm) for 360 min can be used to decrease E. coli and B. cereus, whereas ozone concentrations ≥5.0 ppm can be used to reduce B. cereus spores.     

The irradiation of spices, packaging materials and luncheon meat to improve the storage life of the end products

Spices and packaging materials were exposed to γ‐irradiation at a dose of 10 kGy. Luncheon meat was prepared with irradiated or non‐irradiated spices and packaged in irradiated or non‐irradiated packaging materials. Packaged luncheon meat was treated with 2 kGy. Irradiated and non‐irradiated packaged luncheon meat were kept in a refrigerator (1–4 °C) for 12 months. Microbiological, nutritive and chemical characteristics of luncheon were evaluated after processing and during storage; whereas, sensory quality was evaluated only after irradiation. γ‐Irradiation decreased the microbiological counts of spices, packaging materials and packed products and increased its shelf‐life. No significant differences in moisture, protein, fat, pH value, total acidity, lipid peroxide and volatile basic nitrogen were observed as a result of irradiation. Sensory evaluation showed that all the combinations of treated luncheon meats were acceptable. However, the taste, odour, appearance and texture scores of irradiated packaged products were significantly lower than those of non‐irradiated samples.