Thiamin, Riboflavin and α-Tocopherol Retention in Processed and Stored Irradiated Pork

Combination treatments for preservation of irradiated pork were investigated with respect to vitamin loss. Ground pork was prepared under nitrogen and packaged in anaerobic foil. The samples were enzyme denatured by heating before and after irradiation, then cooked and stored. Irradiation resulted in thiamin loss, but neither riboflavin nor α-tocopherol was affected. Neither thiamin nor riboflavin was affected by heat denaturation, cooking or storage, but heating and cooking increased the measured α-tocopherol. The lack of loss of the vitamins was attributed to the exclusion of oxygen.     

Low-dose Gamma Irradiation and Refrigerated FStorage in vacua Affect Microbial Flora of Fresh Pork

Vacuum-packaged ground fresh pork samples absorbed gamma radiation doses of 0. 0.57. 1.91. 3.76. 5.52. or 7.25 kGv at 2°C. Samolcs were analyzed after 1, 7, 14, 21, 28,‘or 35 days itorage at 2°C’for presence and number of aerobic and anaerobic mesophiles and endospore formers, and aerobic psychrotrophs. Conventional plate counts did not detect surviving microflora in any sample that received an absorbed dose of 1.91 kGy or higher, even after refrigerated storage for up to 35 days. The microflora in the control were predominantly Gram-positive for the first 21 days; however, Serratia predominated at 28 and 35 days. Staphylococcus, Micrococcus, and yeast species predominated in samples that received 0.57 kGy.     

Color Characteristics of Irradiated Vacuum-Packaged Pork, Beef, and Turkey

Changes in color of irradiated meat were observed to be species-dependent. Irradiated pork and turkey became redder due to irradiation but irradiated beef a* values decreased and yellowness increased with dose and storage time. The extent of color change was irradiation dose-dependent and was not related to myoglobin concentration. Visual evaluation indicated pork and turkey increased in red ness whereas beef decreased in redness as dose levels increased. Reflectance spectra showed that irradiation induced an oxymyoglobin-like pigment in pork and that both oxymyoglobin and metmyoglobin developed in beef as a result of irradiation.     

辐照对Pen a1抗原表位免疫原性的影响

辐照处理刀额新对虾中主要过敏原Pen a1,采用SDS-PAGE,MOLDI-TOF MS方法分析辐照处理对虾致敏蛋白Pen a1分子质量的影响,同时利用表位抗体进行免疫印迹及间接竞争ELISA法评估Pen a1中5种抗原表位免疫原性的变化情况。结果显示:与未处理相比,6.7 k Gy辐照处理能够破坏部分Pen a1蛋白结构,导致裂解和聚合现象的发生。5种抗原表位免疫原性均未降低,并有不同程度的增加,其中Epitope1,2,3,4的IC50值约为对照的4/5,Epitope5的IC50值变化不大,说明其对辐照处理较稳定。低剂量的辐照处理不能降低Pen a1抗原表位的免疫原性。     

Color Characteristics of Irradiated Aerobically Packaged Pork, Beef, and Turkey

Color changes in irradiated meat were species-dependent. Irradiated pork and beef became less red as a result of irradiation and display time. The redness values of turkey increased after irradiation but decreased during display time. The yellowness of the irradiated samples, for all species, increased as a result of irradiation and display. Visual evaluation of irradiated pork and beef indicated an increase in brownness, whereas turkey increased in redness as dose increased. The surface color of irradiated pork became less uniform than unirradiated pork. Reflectance spectra indicated that irradiation induced a metmyoglobin-like pigment in pork and beef, whereas the pigment in turkey was unchanged.     

Acceptance and Species Identification of Turkey Steaks Prepared with Beef, Pork, Lamb, and Turkey Fat

Fabricated extruded steaks were prepared from turkey meat, salt, phosphate, and water plus 15% beef, pork, lamb, or turkey fat. The grilled samples recieved relatively high hedonic scores from a sensory panel. The flavor, juiciness, and overall quality of the samples made with pork, beef, and turkey fat were preferred significantly over the samples made with lamb fat. Panel members tended to consider all samples as being pork flavored. Beef, pork, or turkey fat could be used as the fat in a fabricated, extruded steak without affecting the relative acceptability of the cooked product.     

Water Concentration/Activity and Loss of Vitamins B1 and E in Pork Due to Gamma Radiation

When irradiated, increasing the water content of pork by partial rehydration of freeze-dried L. dorsi muscle resulted in increasing rate of thiamin loss from zero in dry tissue to ca 6%/kGy of irradiation in tissue with 70% water. Conversely, the rate of loss of α-tocopherol decreased, from 44%/kGy at 0% to 32%/kGy at 70% water. Decreasing water activity in buffers or in ground or freeze-dried pork by salt or sucrose had no effect on rate of loss of either vitamin following irradiation. Salt decreased the loss of both vitamins in pork due to competition for the hydroxyl radical by chloride ions.     

Application of Gamma Irradiation on Breakdown of Hazardous Volatile N-Nitrosamines

ABSTRACT: Gamma irradiation was applied for the breakdown of the volatile N-nitrosamines (VNAs), nitrosodimethylamine (NDMA), and nitrosopyrrolidine (NPYR). NDMA and NPYR were dissolved in distilled water, dichloromethane, or ethanol, and irradiated at 2.5, 5.0, 7.5, 10, 15, 20, and 25 kGy by gamma ray. Samples were analyzed by GC-TEA. NDMA and NPYR in distilled water and dichloromethane were easily broken at 5 kGy or above. NPYR was the most sensitive to irradiation, while the NDMA is relatively resistant to irradiation. NDMA and NPYR dissolved in ethanol was the most resistant to irradiation and the breakdown was 90% or above at 20 kGy. VNA formation was not observed by in vitro test from decomposed compounds without nitrite, while the VNAs were found by exposure of irradiated products to nitrite. Results indicated that the gamma irradiation technology may be effective to reduce carcinogenic VNA contents in food and other industry.     

肉类保藏技术(六) 辐照技术及其在肉类食品保藏中的应用

辐照技术是一种新型的冷杀菌技术,具有无残留、无污染、高效、节能等优点,因此在食品保藏中广泛应用。辐照处理不仅能有效提高肉品的卫生安全性、延长其保质期,并可最大程度地保持肉品的原有营养价值和感官特征,因此备受人们关注。本文主要介绍了食品辐照技术的原理、优点及辐照对肉品营养成分的影响、辐照肉品的安全性、辐照技术的在肉品保藏中的应用,并对辐照技术在肉品保藏中应用的前景进行了展望。     

Effects of Low-dose Gamma Irradiation and Conventional Treatments on Shelf Life and Quality Characteristics of Diced Celery

ABSTRACT: The effects of 0.5 and 1.0 kGy gamma irradiation on microbial and sensory characteristics of diced celery were compared to conventional treatments such as acidification, blanching, and chlorination. Aerobic plate counts for the irradiated celery did not exceed 10⁷ CFU/g, in contrast, the acidified, blanched, chlorinated, and control samples surpassed aerobic microbial counts of 10⁸ CFU/g in 22, 19, 12, and 8 d, respectively. Importantly, the 1.0-kGy treatment eliminated inoculated Listeria monocytogenes and E. coli. While the acidified and blanched samples had significantly different sensory profiles compared to the other treatments, the irradiated samples maintained their color, texture, and aroma longer and were preferred in the sensory tests. The sensory shelf life of the 1.0-kGy-treated celery was 29 d compared to 22 d for the control, chlorinated, and 0.5 kGy, and 15 d for the acidified and blanched celery.     

Effect of Gamma Irradiation on Molecular Structure and Physicochemical Properties of Corn Starch

ABSTRACT:  Carboxyl content and amylose leaching of gamma-irradiated corn starch increased and swelling factor decreased with increasing radiation dose. The apparent amylose content decreased gradually from 28.7% for native starch to 20.9% for 50 kGy irradiated starch. The proportion of short amylopectin branch chains (DP 6 to 12) increased, while the proportion of longer branch chains (DP ≥ 37) decreased with increasing radiation dose. The relative crystallinity and the degree of granule surface order decreased from 28.5% and 0.631 in native starch to 26.9% and 0.605 in 50 kGy irradiated starch, respectively. Pasting viscosity and gelatinization temperatures decreased with an increase in radiation dose. At a high dose (50 kGy), melting of amylose–lipid complex in DSC thermogram was not observed. The rapidly digestible starch (RDS) content slightly decreased up to 10 kGy but increased at 50 kGy. The resistant starch (RS) content slightly decreased at 2 kGy and then increased up to 50 kGy. The slowly digestible starch (SDS) content showed the opposite trend to RS content. Slower irradiation dose rate reduced carboxyl content, swelling factor, and amylose leaching. The apparent amylose content and amylopectin chain length distribution were not significantly affected by dose rate of gamma irradiation. However, the relative crystallinity and gelatinization enthalpy increased with slower dose rate. Slower dose rate decreased RDS and SDS contents, and increased RS content.     

Pasteurization of Fresh Orange Juice Using Gamma Irradiation: Microbiological, Flavor, and Sensory Analyses

Recent concern about the presence of disease‐causing bacteria in unpasteurized juice has highlighted the need to develop alternative means of pathogen control that preserve sensory properties and nutrient content. The objectives of this study were to determine the effects of different doses of gamma irradiation on reducing the microbial pathogens L. monocytogenes and Salmonella enterica in fresh orange juice, and to determine whether significant reduction could be achieved without compromising sensory qualities. While irradiation was effective in destroying pathogens, the development of off flavors precludes its use as an alternative processing technology.     

Influence of Gamma Irradiation on Enzyme, Microorganism, and Flavor of Cantaloupe (Cucumis melo L.) Juice

ABSTRACT:  The production of freshly squashed juice is a best way to raise the merchandise rate of cantaloupe and to prolong its industrial chain, and as a low acid and heating sensitive juice how to ensure its safety and quality is a key point. In this study, enzyme activity and microorganism survival in Golden Empress cantaloupe juice after ⁶⁰Co irradiation were measured and analyzed, and the irradiation off-odor intensity was evaluated with the Kramer sensory evaluation method. Sensory evaluation indicated that the juice had a slight irradiation off-odor after treatment at 1 kGy, and had strong off-odor at 2 kGy and above; therefore the dosage should be less than 1kGy in order to keep the off-odor in acceptable scope. Enzyme activity determination indicated that lipoxygenase was the easiest one to be inactivated by irradiation, followed by polyphenoloxidase and peroxidase, but the 3 enzymes still remained activities even at 5 kGy. Microorganism survival determination indicated that Escherichia coli was sensitive to irradiation, and can be reduced by 7 log-cycles at 1 kGy, whereas total colony and target spore bacteria in the juice had stronger endurance to the irradiation, suggested by D ₁₀ values of 0.9908 and 1.1923 kGy, respectively, indicating both total colony and target spore bacteria were difficult to inactivate as compared to E. coli . The study indicated that gamma irradiation can not completely inactivate the enzymes, total colony, and target spore bacteria in cantaloupe juice on the premise of acceptable off-odor.     

冷却肉低剂量辐照后的理化和感官特性变化

研究真空包装冷却猪肉经保鲜液处理和未经过保鲜液处理,再分别经1kGy、2kGy和3kGy低剂量辐照后的理化和感官特性变化,进而确定最佳的辐照处理方式以延长冷却猪肉的货架期。结果表明:经过2kGy辐照的处理组,在贮藏的过程中,鲜红色泽保持相对的稳定。冷却猪肉经过保鲜液处理 2kGy剂量辐照 冷藏(4±1℃),可以有效的延长冷却猪肉的货架期。     

辐照处理对魔芋葡甘聚糖肠道益生作用的影响

为探究辐照改性技术对魔芋葡甘聚糖（konjac glucomannan,KGM）肠道益生性的影响,以60Co为辐射 源制备0、10、20、30 kGy辐照剂量的KGM样品,采用健康志愿者粪便体外厌氧发酵,比较不同辐照剂量KGM 体外发酵液pH值、短链脂肪酸含量、有益菌及有害菌数目、双歧杆菌数量/大肠杆菌数量（B/E值）、益生元指数 （prebiotic index,PI）的差异。结果表明：相对于葡萄糖阳性对照,不同辐照剂量KGM均能有效降低发酵液pH 值,维持酸性环境,促进短链脂肪酸生成,同时改善发酵液微生物构成,提高B/E值及PI。在0～30 kGy辐照范围 内,随辐照剂量增大,KGM发酵液短链脂肪酸生成量增加,PI升高,0、10、20、30 kGy KGM的PI分别为0.48、 0.61、0.76、0.78。综上,KGM具有良好的肠道益生元作用,γ-辐照改性有助于进一步提高KGM的肠道益生性,综 合考虑辐照效率及KGM肠道PI,推荐20 kGy作为制备KGM低聚糖的适宜辐射剂量。     

Content of Zinc in Selected Muscles from Beef, Pork, and Lamb

Zinc concentration was measured in four muscles from beef, pork, and lamb: longissimus dorsi (LD), biceps femoris (BF), gluteus medius (GM), and triceps brachi (TB). Within a species, BF, GM, and LD had similar zinc concentrations but TB was significantly (P<0.01) higher in zinc. The means for the four muscles ranged from 39.8–53.5, 13.9–28.0, and 28.2–36.9 μg Zn/g wet weight for beef, pork, and lamb, respectively. The zinc concentration of muscle may relate to protein synthesis and the predominant type of energy metabolism occurring in the muscle. The mean zinc concentration of the four muscles between species was significantly (P< 0.01) different.     

Modeling Thermal and Mechanical Effects on Retention of Thiamin in Extruded Foods

ABSTRACT: A model was proposed to predict separate thermal and mechanical effects of extrusion cooking on thiamin retention. Thermal effects were determined by heating small samples of wheat flour mixed with 0.30% (wt/ wt) thiamin hydrochloride isothermally at 140 °C, 151 °C, and 161 °C for different times. The calculated activation energy and rate constants at each temperature were 67.28 kJ/g mol and 0.00869/min, 0.0145/min, and 0.0224/min, respectively. The "extruder constant" was estimated as 27.7/rev, based on a matching-viscosity method. Wheat flour with 0.30% (wt/wt) thiamin was extruded at different screw speeds. Mechanical effects caused 89.7% to 94.4% of total thiamin loss. This research provides a generalized method to "fingerprint" the extrusion process.     

The Effect of Gamma Irradiation as a Phytosanitary Treatment on Physicochemical and Sensory Properties of Bartlett Pears

A major concern in exporting agricultural commodities is the introduction or spread of exotic quarantine pests to the new area. To prevent spread of insect pests, various phytosanitary measures are used. Worldwide commercial use of irradiation as a phytosanitary treatment has increased greatly in recent years; however, trade has been limited to tropical fruits. Bartlett pear is a major summer variety of California pears with great potential and market for export. In this study, the effect of gamma irradiation at dose levels of 400, 600, and 800 Gy on physicochemical properties and sensory attributes of early and late harvest Bartlett pears was investigated. Firmness and color changes indicate that irradiation delayed the ripening of pears by 1 d. For the early harvest pears, scarring, bruising, and off flavor were significantly increased at the highest irradiation dose (800 Gy). The appearance of early harvest 800 Gy irradiated pears was the only attribute that received significantly (P ≤ 0.05) lower scores than the control in consumer testing. For the late harvest pears, the 400 Gy fruit had lowest levels of scarring and bruising as rated by trained panelist but consumers did not score the control and 800 Gy fruit differently for any attribute. Titratable acidity, total soluble solids, and chroma were significantly (P ≤ 0.05) decreased and hue increased by irradiation for the early harvest pears. These results suggest that there was a difference in radiotolerance of early and late harvest pears, but in both cases, irradiation at 400 to 600 Gy seemed to maintain best quality.     

60Co-γ辐照对储藏糙米理化品质和食用品质的影响研究

糙米经不同剂量的60Co-γ辐照后,恒温(15±0.5)℃储藏1年,每3个月进行1次品质测定,并分析辐照剂量对储藏糙米各指标的影响。结果表明,储藏1年后,糙米表面颜色b值升高,储藏期间b值有波动,1.0 k Gy和2.0 k Gy的辐照后,糙米表面颜色b值显著增加(P0.05),大米呈现发黄趋势;L值随着辐照剂量的增加而降低(储藏时间对L值没有显著影响);经1.0 k Gy和2.0 k Gy辐照的糙米感官评定颜色项得分显著低于对照组(P0.05);脂肪酸值随着储藏时间延长持续上升,辐照剂量与脂肪酸值无明显相关性(P0.05);溶解度和膨胀力都随着储藏时间延长而升高,第9个月达到峰值,随辐照剂量的增大,溶解度和膨胀力增大,米饭质构软化,米饭软硬度得分升高;糙米菌落总数含量随着储藏时间延长逐渐上升,但辐照剂量与菌落总数极显著负相关(P0.01)。低剂量(0.2~0.5 k Gy)水平的辐照可显著优化储藏糙米理化指标,提高感官品质。