Effect of Gamma Irradiation on Whole-cell Glucose Isomerase

Gamma-rays induced inactivation of Actinoplanes missouriensis and Streptomyces olivaceus glucose isomerase has been studied. This enzyme exhibits high resistance against ionizing radiation. The D₃₇ value was found to be equal to 131 kGy for Actinoplanes missouriensis cells and 88 kGy for Streptomyces olivaceus cells when irradiated in the dry state in the presence of air. Mg²⁺ ions do not affect the radiosensitivity of the enzyme in cells, while the addition of Co²⁺ ions to the cell suspension increases its stability against ionizing radiation.     

Effect of Gamma Irradiation on Egyption Sweet Potato Starch

Results showed that treatment of sweet potato starch with different doses of gamma irradiation caused increase in starch acidity and reducing sugars as well as molecular degradation, occurred as a result of the marked decrease in viscosity and intrinsic viscosity and water absorption while the solubility increased.     

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。     

从红酵母中提取胡萝卜素

本文对从红酵母中提取胡萝卜素的生产方法进行了初步研究,得出了一条简便、适宜工业化生产的工艺路线。整个生产过程分为细胞培养、细胞破碎及色素提取三个阶段。该工艺相对天然植物提取法具有成本低、质量稳定的优势,较化工合成法简便且无毒性,是一个很有前途的方法。该方法在国内尚未见报道。     

Combined Effects of Gamma Irradiation and Blanching Process on Acrylamide Content in Fried Potato Strips

Potato tubers were irradiated in ⁶⁰Co gamma station at different doses in order to investigate the effect of gamma irradiation on acrylamide formation in fried potato strips. Acrylamide content due to the irradiation treatment was reduced by 20–54% compared to a control after frying the irradiated tubers. While apply a blanching process, using warm tap water, to potato strips before frying has decreased acrylamide by 61%. A combination of gamma irradiation and a blanching process, which was applied in this work, showed a maximum decrease in acrylamide formation to reach 78% in fried potatoes.     

辐射对淀粉作用的研究概况

介绍了近年来国内外研究辐射对淀粉作用的概况，总结了电离辐射对淀粉理化性质的影响，简单阐述了辐射对淀粉作用的机制。研究表明：淀粉经辐射后，淀粉链断裂，聚合度下降，对酶的作用敏感，辐射对淀粉的破坏程度与辐射剂量成正相关。     

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.     

低剂量γ辐照对牛肉肌内脂肪酸组成及牛肉质量的影响

取8头黄牛的半腱肌,在60Co源下辐照,剂量分别1.13,2.09及3.17kGy,牛肉在7℃环境下储存10d,评估不同辐照剂量和储存时间(0d或10d)条件下肌内脂肪酸组成及牛肉质量的变化.肉样储存10d后,未辐照的肉样中SFA和MUFA含量比未储存未辐照的牛肉(0d,0kGy)显著上升,而辐照过的肉样SFA和MUFA含量基本不变.辐照后多不饱和脂肪酸(PUFA)、n-3PUFA、n-6PUFA含量和P/S显著下降(0d或10d).不同辐照剂量对脂肪酸的影响差异不显著.辐照后0d,牛肉样滴水损失及TBARS与辐照剂量呈正相关,随着辐照剂量的增加(从0kGy到3.17kGy),滴水损失及TBARS逐步升高;而10d储存后,滴水损失和TBARS则与辐照剂量呈负相关.辐照后牛肉样细菌总数随辐照剂量的增大显著下降.牛肉肌内脂肪脂肪酸组成和比值因辐照而产生变化,而辐照剂量的增加(1.13kGy到3.17kGy)对脂肪酸组成没有显著的影响.3kGy左右的低剂量辐照可以很好的确保牛肉质量,而不会引起脂肪营养较大的损失.     

热和紫外辐照对红莓花色苷稳定性的影响

研究了热和紫外辐照对红莓花色苷提取物稳定性的影响。结果表明,红莓花色苷受热(45～75℃)影响发生降解,其含量及红值均发生显著下降,75℃受热10h条件下,花色苷残留率仅为74 93% ,红值保留率为83 0 3% ,色泽变化(△E)为2 4 6 16。并发现红莓花色苷受热降解的反应符合一级反应动力学,其相关系数为0 984 7。通过对降解自由能的比较发现,红莓花色苷(E0 =8 33×10 4kJ/mol)比杨梅花色苷(E0 =343 4 6 4kJ/mol)有更好的热稳定性。2 5 4nm下的紫外辐照也会影响红莓花色苷的稳定性,但其表现的降解趋势与受热降解不同。     

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.     

Physicochemical Properties of Dry Red Kidney Bean Proteins and Natural Microflora as Affected by Gamma Irradiation

Gammaγ-irradiation affected (p≤0.05) the physicochemical properties of dry red kidney beans (Phaseolus vulgaris.) Protein deamidation, solubility and hydrophobicity increased and the number of sulfhydryl groups was reduced after irradiation. Irradiation also affected the outgrowth of natural mold contaminants. A dose of 1.5 kGy reduced the number of molds by 2 log cycles immediately after the treatment. However, incomplete inhibition was observed with the highest irradiation dose (3 kGy). Species of Aspergillus and Penicillium. were completely inhibited at 1.5 and 3 kGy respectively.     

Gamma Irradiation Influence on the Storage and Nutritional Quality of Mushrooms

SUMMARY– Growth of freshly harvested mushrooms subjected to 100 krad of gamma irradiation is markedly inhibited, as measured by the small number of broken veils. This could significantly increase the storage life of mushrooms even under suboptimal conditions. Untreated mushrooms were preferred to the treated, but hedonic scores indicated that the treated mushrooms would be acceptable. There was no significant change in rate of moisture loss, or in reducing sugar or dry matter content of the irradiated mushrooms. Respiration of irradiated mushrooms is accelerated up to about 3 days after treatment and then slows markedly. The inclusion of 20% irradiated mushrooms in mouse diets fed in late pregnancy and lactation had no significant effects on the average mouse weight of the offspring 40 days old or on their daily food intake and weight gain in a subsequent 6-wk feeding period.     

低剂量辐射对真空包装冷却羊肉微生物与理化指标的影响

虽然20℃下辐照要求冷却肉在辐照场所放置3～16h,使肉品温度升高,但考虑到较高温度下辐照对微生物的杀死作用更强,并且实际生产中辐照场所的温度未必控制得当,为寻找更加切合我国当前肉品加工实际的辐照方法,对真空包装冷却羊肉在不同温度(0～4℃和20℃)下经不同辐照剂量(0、1、3、5kGy)处理,然后再置于0～4℃下贮存21d。贮期内对理化指标(TVB-N、TBARS)和微生物指标(细菌总数、肠杆菌科菌、假单孢菌属、乳酸菌)进行测定,对比不同辐照温度对辐照效果的影响。结果表明:经5kGy辐照,当辐照温度为20℃时,贮存21d后,冷却羊肉的细菌总数、乳酸菌、肠杆菌科菌、假单胞菌属测定菌数对数值分别为:4.14、3.6、1.00、2.21,TVB-N值为28.9mg/100g,TBARS值为0.89mg/kg;而同样辐照剂量下,当辐照温度为0～4℃时,贮存21d后,冷却羊肉的细菌总数、乳酸菌、肠杆菌科菌、假单胞菌属测定菌数对数值分别为:3.73、3.13、1.00、3.03,TVB-N值为17.8mg/100g,TBARS值为0.34mg/kg。由此可见,0～4℃辐照与20℃辐照相比,微生物指标相互交错,但0～4℃辐照组的理化指标显著优于20℃辐照组。     

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.     

A High Yield of Amylase from Aspergillus niger by the Effect of Gamma Irradiation

When irradiated rice starch was used as a media for Aspergillus niger a noticeable increase of amylase production was observed. Molecular degradation of starch molecules did occure, and an increase in starch acidity and solubility was noticed, whereas a marked decrease in viscosity as well as swelling capacity was observed. Gelatinization time and temperature of irradiated starch became shorter or lower resp. These results showed that internal changes in irradiated starch molecules and an alteration in its molecular configuration occured. They may affect the pathway of the growth of the fungi Aspergillus niger. When the amount of amylase was determined by measuring enzyme activity, it was observed that amylases in the irradiated media were higher than in the control media.     

Modification of Corn Starch and Fine Flour by Acid and Gamma Irradiation. Part 2. Effect of Gamma Irradiation and Acid Treatment on the Chemical Structure of Starch and the Distribution of Protein Fractions

The effect of γ-irradiation and dextrinization on the chain length of the starch molecule was studied. The chain length was decreased from 30.0 to 5.4 G. U. after dextrinization in presence of hydrochlorid acid. The average chain length of the irradiated starch was affected depending on the doses. The results showed that splitting of glucosidic linkage by irradiation occured beside other transformations in the structure of the starch. The formation of little amounts of dialdehyde by irradiation has been proved. Results showed the presence of a fraction containing a monosaccharide and different amino acids. This is partial proof for the presence of a glucoprotein type. In case of irradiation of the fine flour with 700 krad, the percentages of the protein fractions were not affected. In case of acid dextrinized fine flour, there is an increase in the water-soluble fraction and a decrease in the alkali fraction. Irradiation of fine flour with 700 krad decreased the amylase activity to about half the value.     

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,...     

Effect of Dose on Gamma Irradiation Induced Formation of Free Radicals in Freeze-Dried Natural Actomyosin

Freeze-dried preparations of actomyosin from chicken breast muscle were irradiated in liquid nitrogen with gamma radiation from a ce-sium-137 source at 5, 10, 15, 20, 30, 40, and 50 kGy. The ESR spectra at – 130°C were recorded with an EPR spectrometer. Signal intensities increased linearly with radiation. Analysis of data indicated a ten-fold rise in dose resulted in an almost seven-fold increase in number of free radicals generated. Determining the extent of such interaction on a major structural protein can help assess type and extent of reactions which might occur on irradiation of animal products.