宠物食品辐照灭菌及工艺剂量研究

本文以皮卷、绿爽洁牙骨、鸡肉排骨、鸡胸肉为试验材料,开展了宠物食品辐照灭菌工艺剂量的研究。结果表明：辐照剂量为4kGy时杀菌率达到了92%以上,辐照剂量为6 kGy时杀菌率已达99%以上,检测的各项微生物指标均符合国家食品卫生标准要求,10 kGy即可达到完全灭菌的效果。辐照前后4种样品中均未检出沙门氏菌。4～10 kGy辐照后,宠物食品中水分、脂肪、蛋白质、粗纤维、碳水化合物、矿质元素（除钙）及17种氨基酸的含量与对照相比差异均不显著,说明辐照对宠物食品的营养品质影响很小;在此剂量范围内,样品辐照前后的色泽、风味与滋味也没有明显变化。由此,确定宠物食品适宜的辐照工艺剂量范围为4～10 kGy。     

Formation of Resistant Starch by a Twin-Screw Extruder

The objective of this study was to evaluate the potential to increase the level of resistant starch (RS) in extruded products by optimizing extruder conditions. Three experiments were conducted as randomized complete block designs with two replicates. In the first experiment, corn starch, wheat starch, and potato starch were added at a level of 30% (w/w) to degerminated yellow corn meal to investigate the influence of starch type. In the second experiment, citric acid (CA) monohydrate was added to corn meal at levels of 0, 2.5, 5, and 7.5% (w/w). The third experiment was a full-factorial arrangement to evaluate the effect of high-amylose corn starch (HACS) level (0, 15, 30%, w/w) and CA level (0, 5, 7.5%, w/w) at two screw speeds (200 and 300 rpm). In the first experiment, the means for RS plus dietary fiber for the different starch formulations ranged from 1.27 to 2.28%. In experiment 2, adding CA increased RS plus dietary fiber content to a maximum of 5.23% at 7.5% CA. In the third experiment, the means for RS plus dietary fiber ranged from a low of 1.75% for 100% corn meal at 300 rpm to 14.38% for 7.5% CA and 30% HACS at 200 rpm. The results indicated a highly significant positive relationship between CA and RS formation and the same for amylose content. The RS formation had a negative relationship with screw speed, but the influence of screw speed was small when compared with that of CA and HACS.     

Evaluation of 2-alkylcyclobutanones in irradiated cured pork products during vacuum-packed storage

The 2-Alkylcyclobutanones (2-ACBs) content was determined in three Italian cured pork products (salame Milano, coppa, and pancetta) irradiated at different targeted irradiation doses (2, 5, and 8 kGy) during vacuum-packed storage. Among 2-ACBs, three different compounds were investigated, namely, 2-dodecylcyclobutanone, 2-tetradecylcyclobutanone, and 2-(tetradec-5'-enyl)cyclobutanone. 2-ACBs were absent from the nonirradiated samples, whereas their content increased with irradiation dose. Their presence was recorded occasionally at 2 kGy and constantly at higher irradiation doses (5 and 8 kGy). The plot of 2-ACBs content against targeted irradiation doses showed an exponential relationship. The effect of vacuum-packed storage time on the 2-ACBs content was dependent on the irradiation dose. During vacuum-packed storage for up to 60 days, the 2-ACBs content remained unchanged in the cured pork products irradiated at 2 and 5 kGy, whereas a significant increase was observed in the pork products irradiated at 8 kGy.     

大豆蛋白粉的辐照灭菌研究

研究了60Coγ射线辐照大豆蛋白粉的杀菌效果与对大豆蛋白粉的主要营养成分、尿素酶(脲酶)活性以及感官品质的影响。结果表明,2.0kGy辐照对大豆蛋白粉中菌落总数、大肠菌群的杀菌率达70%,对霉菌的杀菌率达53%;4.0kGy辐照杀菌率达95%;经6.0kGy辐照处理后,杀菌率达到97%以上,辐照的大豆蛋白粉样品中微生物指标均达到食品卫生国家标准;8.0kGy辐照杀菌率达到100%。与对照相比,剂量为2.0~8.0kGy的辐照对大豆蛋白粉中蛋白质、粗纤维、总糖、氨基酸(除Leu)含量的影响不明显;而粗脂肪及卵磷脂的含量有极显著变化(P<0.01),尤其是卵磷脂的含量显著增加,异黄酮的含量则显著降低(P<0.05);辐照对大豆蛋白粉中尿素酶活性没有显著影响;6.0kGy以下剂量辐照对大豆蛋白粉色泽、气味、口感无明显改变。综合试验结果,确定了大豆蛋白粉辐照杀菌的适宜工艺剂量范围为3.0~5.0kGy。     

辐照对黄原胶分子量及抗氧化活性的影响

以0~500kGy 60Co γ射线对固态黄原胶进行辐照,研究辐照对黄原胶分子量及还原力、清除1,1-二苯基-2-苦基肼自由基（DPPH·）、超氧自由基（O2-·）及羟自由基（·OH）能力等抗氧化活性的影响。研究表明,10kGy的辐照可使黄原胶粘均分子量从1.71×106增加到2.23×106,超过10kGy后,黄原胶粘均分子量随辐照剂量的增大逐渐减少,500kGy时降为1.59×104。低于10kGy辐照,黄原胶的还原力、对DPPH·和对O2-·的清除率与剂量呈负相关,与对照相比,还原力降低了3.16%,对DPPH·和O2-·的清除率分别从17.37%和18.18%减少到16.87%和8.51%,增大辐照剂量,黄原胶的还原力和对DPPH·和O2-·的清除率与剂量呈正相关,500kGy时黄原胶的还原力比对照增加164.22%,对DPPH·和O2-·的清除率升高至60.79%和30.06%;对·OH清除能力与辐照剂量呈负相关,清除率从0kGy时的9.29%降低到500kGy时的3.63%。辐照可以引起黄原胶聚合或降解,从而导致其分子量及抗氧化活性发生显著变化。     

辐照对泡椒凤爪感官品质的影响

辐照可以有效的控制泡椒凤爪中的乳酸菌含量,从而延长其货架期。本文根据相关的标准和调研,以色泽及形态（权重30%）、香气（权重30%）、质地及滋味（权重40%）为评价指标,制定了泡椒凤爪的感官分析标准,并用此标准对辐照处理后的泡椒凤爪进行了感官品质分析。结果表明贮藏3d后的3、5、8、12kGy辐照的样品,其感官评价结果与对照相比无显著差异,辐照剂量为10 kGy的样品感官评价结果还显著优于对照组。贮藏11d后,样品的感官品质也未降低。由此得出结论：辐照不会影响泡椒凤爪的感官品质,适当剂量的辐照还有助于提高泡椒凤爪的被接受程度。     

直接荧光过滤技术/平板计数法(DEFT/APC)检测辐照食品

以4种香辛料和2种干制海鱼为材料,通过直接荧光过滤技术/平板计数法（DEFT/APC）比较辐照前后DEFT计数和APC计数的差异,判断食品是否经过辐照处理。试验结果表明,当log(DEFT/APC)>40时,表明产品至少已进行过10kGy剂量的辐照处理,DEFT/APC法的检测灵敏度与样品初始菌数及D10值相关。     

电子束辐照对鱿鱼发酵食品及其配料微生物和感官特性的影响

为使电子束辐照在Jeotkal食品产业中得到广泛利用,对鱿鱼Jeotkal发酵食品及配料实施电子束辐照后,分析了鱿鱼Jeotkal发酵食品及配料的微生物和官能特性。结果表明,电子束处理前鱿鱼Jeotkal好氧菌数为2.88logCFU/g,经5kGy处理后,下降为1.76logCFU/g;酵母和霉菌及大肠杆菌初期污染度分别为3.04logCFU/g和4.20logCFU/g,经5kGy辐照后,下降到1.27和1.34logCFU/g,降低2～3log cycle。辣椒粉辐照处理前好氧菌数为4.07logCFU/g,酵母菌和霉菌为3.91logCFU/g,大肠杆菌为4.34logCFU/g。辣椒粉经5kGy辐照后,好氧菌及酵母菌和霉菌显示为ND。蒜糜中初期好氧菌数为4.41logCFU/g,酵母及霉菌为4.48logCFU/g,大肠杆菌为4.32logCFU/g;经5kGy电子束辐照后好氧菌、酵母及霉菌、大肠杆菌都显示为ND。电子束不仅对鱿鱼Jeotkal微生物具有显著的杀菌效果,而且没有引起鱿鱼Jeotkal的pH和官能特性的变化。因此,电子束杀菌技术在低盐或发酵食品储藏工艺中具有很好的应用前景。     

Effect of gamma-irradiation on degradation of alginate

The aqueous solution of alginate was irradiated by 60Co gamma-rays in the dose range of 10-500 kGy. To assess the effect of irradiation on the degradation of alginate, the irradiation-induced changes in the viscosity, molecular weight, color, monomer composition, and sequence were measured. The molecular weight of raw alginate was reduced from 300000 to 25000 when irradiated at 100 kGy. The degradation rate decreased and the chain breaks per molecule increased with increasing irradiation dose. The viscosity of irradiated alginate solution reached a near minimum as low as at 10 kGy. No appreciable color changes were observed in the samples irradiated at up to 100 kGy, but intense browning occurred beyond 200 kGy. The 13C NMR spectra showed that homopolymeric blocks, MM and GG, increased and the M/G ratio decreased with irradiation. Considering both the level of degradation and the color change of alginate, the optimum irradiation dose was found to be 100 kGy.     

辐照对桂圆干的杀菌效果及营养成分的影响

以桂圆干为原料,研究2、4、6、8及10kGy辐照对其微生物的杀灭作用及营养成分的影响.结果表明:6kGy辐照的桂圆干中,菌落总数、霉菌及大肠杆菌的含量都均符合国家标准的要求;辐照对桂圆于中粗脂肪、灰分、Fe、P、Na和VB2的含量的影响不显著,对蛋白质、粗纤维、碳水化合物、水分、Ca、K和VC的含量影响显著.6～10...     

辐照杀菌对核桃粉品质的影响

研究了60Co γ辐照杀菌对核桃粉主要营养成分变化及感官品质的影响。结果表明：剂量为2.0～8.0kGy时,辐照对核桃粉中的总糖、粗蛋白和粗脂肪含量无显著影响;辐照后的粗纤维含量有一定的增加,但不显著;辐照对核桃粉中的月桂酸和肉豆蔻酸含量基本没有影响,对棕榈酸、棕榈油酸、硬脂酸、亚油酸、花生酸和亚麻酸含量有一定的影响,但不显著;辐照后核桃粉中的油酸含量随辐照剂量的上升而显著增加,剂量达到8.0kGy时,油酸含量增加了4.3%。8.0kGy以下辐照对核桃粉色泽、气味、口感无明显改变。可以得出结论低于8.0kGy的辐照不会对核桃粉的营养品质和感官品质有不良影响。     

Study of photostimulated- and thermo-luminescence characteristics for detecting irradiated kiwifruit

Photostimulated luminescence (PSL) and thermo-luminescence (TL) analyses were conducted to detect irradiated kiwifruits. Samples were irradiated with Co-60 gamma-rays at 0-2 kGy. The freeze-dried kiwifruit peel showed 309 photon counts (PCs) for nonirradiated samples that accounted for less than the lower threshold value (700 counts/60 s, negative) and above 9306 PCs for 1 and 2 kGy-irradiated samples, which was higher than the upper threshold value (5000 counts/60 s, positive). However, PSL signals of irradiated samples remarkably decreased after 6 weeks of storage. The TL measurement using minerals isolated from the whole kiwifruit surface revealed a glow curve (TL 1) with a low intensity at 200-300 degrees C in nonirradiated samples but with a higher intensity at around 180 degrees C in irradiated samples at 1 kGy or more. The TL ratios, integrated areas of TL 1/TL 2 that was measured after 1 kGy re-irradiation for the TL 1-tested minerals, were less than 0.1 in nonirradiated samples and higher than 0.1 in irradiated ones and could verify TL 1 results. The inorganic dust minerals used were mainly composed of feldspar and quartz.     

Cocoa-enriched diet enhances antioxidant enzyme activity and modulates lymphocyte composition in thymus from young rats

Cocoa is a rich source of flavonoids, mainly (-)-epicatechin, (+)-catechin, and procyanidins. This article reports the effect of continuous cocoa intake on antioxidant capacity in plasma and tissues, including lymphoid organs and liver, from young rats. Weaned Wistar rats received natural cocoa (4% or 10% food intake) for three weeks, corresponding to their infancy. Flavonoid absorption was confirmed through the quantification of epicatechin metabolites in urine. Total antioxidant capacity (TAC) and the activity of antioxidant enzymes, superoxide dismutase (SOD) and catalase, were examined. Cocoa intake enhanced TAC in all tissues especially in thymus. Moreover, thymus SOD and catalase activities were also dose-dependently increased by cocoa. It was also analyzed whether the enhanced antioxidant system in thymus could influence its cellular composition. An increase in the percentage of thymocytes in advanced development stage was found. In summary, cocoa diet enhances thymus antioxidant defenses and influences thymocyte differentiation.     

Effect of gas environment and sorbate addition on flavor characteristics of irradiated apple cider during storage

Apple cider, with (0.1%) and without potassium sorbate, was packaged in polystyrene containers and exposed to three different gas environments: oxygen flush, nitrogen flush, and atmospheric air. To evaluate the effects of irradiation (2 kGy) and storage on flavor and microbial quality, these irradiated apple cider samples were compared to a control, unirradiated sample exposed to atmospheric air. Volatile compounds, soluble solids, titratable acidity, and microbiological counts were determined weekly throughout 7 weeks of refrigerated (4 degrees C) storage. Cider irradiated and stored in atmospheric air or nitrogen-flush environments had lower rates of loss for characteristic flavor volatiles compared to unirradiated apple cider and cider irradiated and stored in an oxygen-flush environment. The addition of potassium sorbate to the apple cider resulted in lower counts of yeasts and aerobic microorganisms, reduced fermentation of sugars to organic acids, and improved retention of volatile compounds characteristic of apple cider.     

电子束辐照对美国红鱼杀菌保鲜效果的研究

以美国红鱼为对象,利用不同剂量电子束处理,对冷藏期内鱼肉菌落总数、总挥发性盐基氮（TVB-N）、过氧化值（POV）及鲜度指标K值进行测定,分析不同剂量电子束辐照对美国红鱼肉的杀菌效果及品质影响。结果表明：电子束辐照能有效降低美国红鱼肉的菌落总数,其中D10=161kGy,D=540kGy,冷藏期间辐照组样品菌落生长缓慢,且辐照剂量越大,杀菌效果越强;电子束处理后美国红鱼肉TVB-N值、POV均有不同程度增加,但在冷藏期内对照组TVB-N值、POV、K值的上升速度大于辐照组样品;辐照对美国红鱼肉感官影响不明显,但6kGy辐照组鱼肉色泽略微变红。综合考虑,美国红鱼肉经4kGy 电子束辐照,能有效杀灭其中的微生物,冷藏条件下保质期可达到14d,比对照延长5d左右。     

辐照处理提高猪肉火腿肠保鲜效果

辐照是一种非常有效的食品杀菌保鲜技术,近年来在即食肉制品保鲜方面的应用逐渐引起了人们的关注。为了探讨γ辐照技术对猪肉火腿肠的杀菌保鲜效果,试验采用1、3、5、7、9 k Gy 5个剂量分别对火腿肠进行辐照处理,辐照结束后样品在4℃条件下冷藏,然后跟踪测定其在冷藏过程中脂肪和蛋白质氧化、颜色、p H值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)以及菌落总数的变化,分析不同剂量辐照处理对火腿肠保鲜效果的影响。结果表明,辐照可以显著降低火腿肠脂肪和蛋白质的氧化稳定性,促进其在储藏过程中的氧化。1 k Gy剂量辐照对火腿肠的色泽影响不显著;3~9 k Gy剂量辐照,可以使样品的红度值(a*值)显著降低、亮度值(L*值)显著升高(P0.05),而在冷藏过程中a*值与L*值均随储藏时间的延长而降低,且高剂量辐照组要比低剂量组降低更快一些。火腿肠p H值受辐照影响不显著(P0.05),且在冷藏过程中所有处理组火腿肠的p H值变化也不显著,均在6.0~6.5范围内。5 k Gy剂量辐照即可对猪肉火腿肠中的微生物起到有效抑制作用。     

电子束辐照对花生过敏原免疫原性及生化性质影响的研究

研究了电子束辐照降低花生过敏原免疫原性的效果及辐照对花生生化性质的影响。选择2、4、6、8、10、15和20kGy剂量的电子束对花生过敏原液、脱脂花生粉进行辐照处理,辐照后花生主要过敏原(Ara h 1, Ara h 2, Ara h 3)蛋白分子质量的变化通过SDS-聚丙烯酰胺凝胶电泳测定,免疫原性的变化通过免疫印迹和间接竞争ELISA法测定;辐照后花生过敏原溶液的浓度、浊度及疏水性的变化通过紫外分光光度计和荧光光度计分别进行测定。结果表明,花生过敏原在溶液状态比固体状态对辐照更为敏感。当辐照剂量低于10kGy时处理的过敏原液的免疫原性稍有增强,剂量大于10kGy时免疫原性降低,剂量为20kGy时过敏原液的IC₅₀值是未处理的11倍。辐照使过敏液的浓度和浊度随着剂量的加大而增加,疏水性与对照组相比增强,但当剂量大于15kGy时降低。电子束辐照改变了过敏原的生化性质,降低了其免疫原性,比较而言,辐照对液体状态下过敏原的影响更显著。     

Warm water treatment in combination with modified atmosphere packaging reduces undesirable effects of irradiation on the quality of fresh-cut iceberg lettuce

Fresh-cut iceberg lettuce dipped in either 5 or 47 degrees C water for 2 min was packaged in modified atmosphere film bags and then exposed to 0, 0.5, 1, or 2 kGy gamma-radiation. Dipping cut lettuce in 47 degrees C water for 2 min prior to irradiation reduced antioxidant and phenolic accumulations induced by irradiation. Irradiation at 2 kGy increased cellular leakage and sogginess of cut lettuce dipped in both temperatures. Samples irradiated at 0.5 and 1 kGy had similar firmness and vitamin C and antioxidant contents as the controls after 14 and 21 days of storage except 1 kGy samples dipped at 47 degrees C had lower antioxidant contents than controls at 14 days of storage. Lettuce dipped at 47 degrees C and irradiated at 0.5 and 1 kGy had better overall visual quality and less tissue browning than corresponding irradiated samples dipped at 5 degrees C. These results suggest lettuce treated with warm water and irradiated at 0.5 or 1 kGy had the best sensory quality without significant loss in texture, vitamin C, or total antioxidants.     

冷冻虾仁辐照保鲜研究

研究了出口冷冻虾仁的辐照保鲜效果 ,并对辐照冷冻虾仁的微生物指标、主要营养成分、理化指标进行了检测。结果表明 :3～ 5kGy的辐照剂量可以杀灭冷冻虾仁中 99%以上的微生物 ,经 1～ 9kGy剂量辐照 ,虾肉中大多数氨基酸含量均有增加 ,其总量明显高于对照 ,增加幅度在 0 33%～ 2 4 6%之间 ,辐照后挥发性盐基氮的含量降低 ,有害重金属元素含量辐照前后无显著差异 ,辐照后虾仁在 - 7℃下贮存 ,保鲜期比对照延长 6个月。