低温酱牛肉贮藏期的品质变化规律

以美好酱牛肉为原料,采用0～4℃、7～11℃二个温度贮藏样品,每10d对酱牛肉pH、肉色、保水性、水分含量、弹性和菌落总数、大肠菌群等指标进行测定。结果表明:感官品质处于下降趋势,且高温贮藏变化较大;pH变化不大,一直处于缓慢下降;水分含量上升,保水性下降;菌落总数处于上升趋势,但都未超过卫生标准。     

低温酱牛肉贮藏期的品质变化规律

以美好酱牛肉为原料,采用0～4℃、7～11℃二个温度贮藏样品,每10d对酱牛肉pH、肉色、保水性、水分含量、弹性和菌落总数、大肠菌群等指标进行测定。结果表明:感官品质处于下降趋势,且高温贮藏变化较大;pH变化不大,一直处于缓慢下降;水分含量上升,保水性下降;菌落总数处于上升趋势,但都未超过卫生标准。      

贮藏期UHT奶中蛋白质组成结构及其糖基化的变化

通过测定UHT奶在贮藏过程中蛋白水解,蛋白在胶束相和乳清相的分布,乳蛋白糖基化位点变化,探究乳蛋白在贮藏过程中性质的变化.结果表明贮藏过程中UHT奶中菌落总数增大,纤溶酶含量增大.UHT奶在内外源酶的作用下乳蛋白发生不同程度的水解.热处理导致从胶束表面脱落的κ-CN和乳清蛋白以热诱导聚合物的形式,在贮藏过程中重新结合到...     

超高温奶的品质控制

从原料控制、生产控制、CIP清洗等方面讨论UHT奶的质量保证体系。并从UHT常见质量问题着手，分析产生问题的主要原因和解决方法。     

不同贮藏条件下菜籽油品质变化的研究

本文采用不同贮藏容器(玻璃油壶、塑料油壶PET)、不同贮藏方式(油壶密封、油壶开盖)来研究菜籽油(无抗氧化剂、添加TBHQ)在食用过程中酸价和过氧化值的变化规律。结果表明：菜籽油在不同的贮藏容器中和不同的贮藏方式下的酸价和过氧化值均随着贮藏时间的延长呈现上升的趋势,而过氧化值的上升速度远大于酸价。密封条件下,玻璃油壶中菜籽油的酸价和过氧化值在6周之内均合格,塑料油壶则是5周;开盖条件下,所测指标均比密封时提前1周超过国家标准;添加TBHQ可以使菜籽油的酸价和过氧化值晚2周超过国家标准。当家庭购买充氮包装的食用菜籽油进行分装时,分装贮藏容器应选择玻璃油壶,用完之后立即密封,并且在6周之内食用完毕。     

市售卤牛肚贮藏过程中的品质变化研究

分析市售卤牛肚贮藏过程中品质指标的变化,探讨理化指标和微生物指标的相关性,为客观评价卤牛肚的品质,通过一定的措施来延长卤牛肚的货架期提供基础理论依据和技术支持。实验模拟超市中的情形,测定了4℃冷柜中贮藏的卤牛肚在0,2,4,6,8,10,12,14天的菌落总数、水分、pH、硫代巴比妥酸(TBA)值和感官评分值。结果表明:在贮藏过程中,菌落总数、水分含量、pH和TBA值均呈现逐渐上升的趋势,而感官评分值不断下降。卤牛肚的各品质指标之间均呈现极强的相关性(p0.01),其中又以菌落总数与TBA的相关性最大。新鲜的卤牛肚模拟超市中的情形在4℃冷柜下贮藏4天时,菌落总数就接近国家标准中的限量值。因此,超市中新鲜的卤牛肚应在5天内售完,若要延长贮藏时间,应尽量使温度恒定在4℃,或者考虑降低冷柜的温度。     

黑鱼香肠冰温贮藏期品质的变化

目的:研究冰温对即食黑鱼香肠贮藏特性的影响。方法:利用冰温脱水技术控制黑鱼香肠水分在50%左右并将鱼肉香肠冰点降低至5.6 ℃,在4 ℃环境下贮藏,以冷藏(4 ℃)为对照。通过对贮藏期间黑鱼香肠菌落总数(TVC)、颜色、持水力、总挥发性盐基氮(TVB-N)、质构特性、生物胺等理化指标的测定以及扫描电子显微镜的观察,分析黑鱼香肠品质以及微观结构的变化情况。结果:冰温组各指标均显著低于对照组(P＜0.05),其在贮藏42 d时的TVC对数值为(5.37±0.06),TVB-N值为(17±0.03) mg/100 g,总胺含量为(324.93±1.89) mg/kg。TVC和TVB-N分析结果表明,相比于冷藏,冰温贮藏可以将黑鱼香肠保质期延长1倍。低场核磁共振结果表明黑鱼香肠在冰温贮藏期间的水分分布优于冷藏组。扫描电镜显示,冰温组的凝胶网络对脂肪颗粒的结合程度更高。结论:冰温贮藏黑鱼香肠的保鲜效果要优于冷藏。     

薏仁米贮藏过程中品质的变化

以贵州兴仁薏仁米作为试验材料,研究了薏仁米贮藏过程中品质的变化。结果表明,在为期1年的贮藏过程中,薏仁米的颜色、气味、主要成分及关联指标变化明显,表明薏仁米品质随贮藏时间的延长而下降。薏仁米色泽随着贮藏时间的延长,由最初的乳白色、有光泽,逐渐变暗偏黄且带有灰色;气味也由最初的甜香气,最终呈哈败味。在贮藏期间,薏仁米的蛋白质、淀粉和灰分含量的变化无显著差异,但水分含量逐渐降低(降低37.06%),脂肪含量减少明显(减少15.00%);薏仁米贮藏过程中脂肪酸值、过氧化值、电导率、丙二醛含量升高,分别增加了272.56%,416.21%,123.78%,99.91%,脂肪酶活性呈先升后降的趋势。薏仁米的脂肪氧化是其品质变化的主要原因,关联指标如肪酸值、过氧化值、丙二醛值、脂肪酶活动度和电导率的变化,均灵敏地反映其品质的下降。     

乙醇对两个品种桃贮藏期品质变化的影响

以中熟品种"大久保"和晚熟品种"绿化9号"桃为试材,用0、1、2ml/kg(桃重)的95%乙醇处理,研究了果实在不同贮藏温度(10±1℃、0±1℃)下品质的变化。结果表明,在两个温度下乙醇处理对两个品种桃保持较高的硬度,对保持可滴定酸含量有益,其中,1ml/kg乙醇处理显著提高了绿化9号桃冷藏后货架期间可滴定酸含量。乙醇处理有效改善了绿化9号桃果面色泽,2ml/kg乙醇处理提高了冷藏桃货架期间果实亮度、促进果面转红、抑制底色变黄,1ml/kg处理效果次之。10℃条件下乙醇处理提高了绿化9号桃可溶性固形物含量。1、2ml/kg乙醇处理降低了两品种桃冷藏后货架期间的腐烂率及褐变率。感官评价表明,1ml/kg处理较好保持了2种桃的风味。     

乳脂乳球菌复配发酵乳贮藏期品质变化研究

探讨了分离自新疆酸奶疙瘩的一株乳脂乳球菌,在乳制品应用中具有的潜在益生价值。通过测定多肽、滴定酸度、丁二酮、乙醛、黏度、活菌数等指标,研究了乳脂乳球菌复配菌株发酵乳在贮藏期间的发酵特性。结果表明,在贮藏期发酵乳各指标均显著高于对照组,酸度升高了29.59 °T,后酸化能力较强。丁二酮含量在整个贮藏过程中较稳定,乙醛、多肽、黏度、胞外多糖的含量在贮藏7 d后达到最大值。多肽含量最高达3.34 mg/mL,胞外多糖含量与测定的黏度值呈现正相关。活菌数呈下降趋势,贮藏21 d后,为7.8×107 CFU/mL,仍高于发酵乳标准中活菌数1×106 CFU/mL的要求。     

冰藏三文鱼品质变化及菌相分析

以感官、物理(质构、色差)、化学(TVB-N、TMA-N、K值)及微生物(菌落总数、嗜冷菌落数、致病菌数)为指标,研究三文鱼冰藏期间的品质变化,并对三文鱼冰藏期间的菌相变化及优势腐败菌进行分析。结果表明:三文鱼在冰藏期间品质变化明显,第4天到达高品质期终点,第10天感官即已不可接受。冰藏过程中,色差变化很小,质构变化中剪切力与咀嚼性逐渐减小,硬度与弹性先增加后减小,黏附性在贮藏后期上升,前期波动较大。TVB-N、TMA-N、TVC和K值变化明显,冰藏到第10天已分别达到17.36 mg/100 g、7.62 mg/100 g、7.64 lg(CFU/g)和68.7%。菌相分析表明假单胞杆菌属(Pseudomonas spp.)为冰藏三文鱼的特定腐败菌。     

广西北部湾主要贝类在冻藏过程中品质变化的研究

测定冻藏过程中牡蛎(Crassostrea rivularis)、文蛤(Meretrix meretrix Linnaeus)和波纹巴非蛤(Paphia Undulata)的水分含量、pH、氨基态氮含量、挥发性盐基氮含量和色差。研究不同的冻藏温度(-18℃和-60℃)和预处理方式(新鲜的和预煮的)对贝肉冻藏品质的影响。结果表明,新鲜的牡蛎、文蛤和波纹巴非蛤在-18℃和-60℃下冻藏3个月,肌肉的水分含量在总体上均呈现下降的趋势;pH的变化起伏不定;氨基态氮和挥发性盐基氮的含量随着冻藏时间的延长而逐渐升高;肌肉亮度降低,总体颜色变暗淡。经过预煮的牡蛎、文蛤和波纹巴非蛤在-18℃或-60℃下冻藏3个月,贝肉的水分含量、pH、氨基态氮和挥发性盐基氮以及亮度变化不大,其品质变化小于未经预煮处理的样品。     

Application of fluorescence spectroscopy for monitoring changes in nonfat dry milk during storage

The objective of this study was to determine if fluorescence spectroscopy could be used to characterize the biochemical characteristics of nonfat dry milk (NDM) caused by manufacturing and storage conditions. Nine low-heat NDM samples were collected from 3 manufacturers and stored at 4 temperatures (4, 22, 35, and 50°C) for 8 wk. The spectra of Maillard products, tryptophan, and riboflavin were recorded and analyzed with principal components analysis. Colorimetric indices L*, a*, and b* were also determined. The before-storage NDM samples collected from each manufacturer had different fluorescent characteristics. Inconsistency was observed for the NDM samples collected from 1 manufacturer, whereas the samples from the other 2 manufacturers displayed consistent fluorescence characteristics. Biochemical reactions, such as Maillard reaction, modification of the tryptophan environment, and degradation of riboflavin occurred during the manufacturing process. For each of the data collections, discrimination of the NDM samples stored at 50°C from the samples stored at 4, 22, and 35°C was observed in the similarity maps. The factor loadings of the first 2 principal components for the fluorescence spectra of the samples before storage were similar to the principal components analysis results of the samples during storage. It appears that similar factors are responsible for the variation in the samples before storage and their changes during storage. Additionally, storage of the samples at 50°C accelerated these reactions. The results demonstrate that front-face fluorescence spectroscopy, coupled with multivariate statistical methods, can be utilized as an analytical technique to monitor variation in NDM samples from different manufacturers and changes during storage.     

黄瓜汁鱼丸的研制及冷藏过程中品质变化规律的研究

通过3因素3水平的正交实验,优化了黄瓜汁、鸡蛋清、淀粉的添加量对鱼丸质构特性及感官品质的影响,并研究了其在冷藏条件下的品质变化规律。结果显示,在最佳配料比为:黄瓜汁17%、鸡蛋清16%、淀粉21%的条件下,真空包装的黄瓜汁鱼丸在冷藏过程中随着贮藏时间的延长,3d以后pH出现一定程度的下降,白度呈不规律变化,细菌总数、硬度显著增加,其中弹性和硬度呈良好的负相关;核磁共振分析结果显示,黄瓜汁鱼丸具有4种流动性不同的水分,其对应的弛豫时间分别为T21、T22、T23,T24(0ms相似文献   

糙米储藏过程中品质变化研究进展

糙米中含有硒、谷维素、甾醇、γ-氨基丁酸等多种营养物质,相对精米而言具有更高的营养价值。随着人们对食品中营养价值追求的提升,糙米逐渐被大众所接受。然而,糙米的耐储藏性能较差,随着储藏时间和储藏条件的改变,糙米的各种品质也会发生明显的变化。本文综述了糙米在储藏过程中各项生化指标的变化趋势,包括蛋白质、脂质逐渐氧化,脂肪酸值增加,不溶性直链淀粉含量增加,支链淀粉含量相对减少,陈米臭味增加,色泽变深等。米饭食用品质的变化表现为黏度下降、口感变劣、香味不纯,本研究可以为糙米的仓储提供参考。     

稻米储藏期间的品质变化与储藏方法

该文主要综述了稻米、糙米在不同的储藏条件下脂肪酸、发芽率、黏性等品质的变化,并介绍了多种较为合适的储藏方法。     

UHT乳贮存期间蛋白变化的研究

在UHT乳贮存期间,对其纤维蛋白酶活力、蛋白沉淀量、下层蛋白粒径、游离氨基氮含量进行测定。结果表明,随着贮存时间的延长,纤维蛋白酶活力、蛋白沉淀量、下层蛋白粒径、游离氨基氮含量变化极显著(P<0.01);贮存时间与纤维蛋白酶活力、蛋白沉淀量、下层蛋白粒径、游离氨基氮含量间均呈极显著正相关(P<0.01)。      

Stability of cyclopiazonic acid during storage and processing of milk

The effect of refrigerated storage (4°C) of raw or processed milk on the stability of cyclopiazonic acid (CPA) in milk was investigated. CPA decreased by 1.4% following 4 days of simulating collecting, storing and transporting of contaminated (1 μg CPA ml⁻¹) raw milk. Storage at 4°C for 21 days, simulating retail milk, moderately reduced the CPA level by 5.8%. A similar trend of CPA decrease was observed in frozen and freeze dried milk stored at −18°C. However, in both products, less than 12% of CPA decreased in spite of a storage period of 140 days. The effect of processing milk on component separation of CPA was also studied. Simulating unsweetened condensed milk production by preheating 4 l contaminated milk to 100°C and concentrating under steam injection to 1.5 l led to a decrease of CPA by 39.7%. In contrast, very little CPA (0.7%) was lost from the production of evaporated milk using low temperature (60°C) heating under vacuum to remove water. CPA was stable in both concentrated and evaporated milks throughout an 8 weeks storage period at 4°C. There was no decrease of CPA during the manufacturing of milk powder by spray drying. Persistence of CPA during the above milk storage and processing methods confirmed the potential of CPA to reach consumers of dairy products when the mycotoxin was carried over into processed milks.     

The effect of different precooling rates and cold storage on milk microbiological quality and composition

The objective of this study was to measure the effect of different milk cooling rates, before entering the bulk tank, on the microbiological load and composition of the milk, as well as on energy usage. Three milk precooling treatments were applied before milk entered 3 identical bulk milk tanks: no plate cooler (NP), single-stage plate cooler (SP), and double-stage plate cooler (DP). These precooling treatments cooled the milk to 32.0 ± 1.4°C, 17.0 ± 2.8°C, and 6.0 ± 1.1°C, respectively. Milk was added to the bulk tank twice daily for 72 h, and the tank refrigeration temperature was set at 3°C. The blend temperature within each bulk tank was reduced after each milking event as the volume of milk at 3°C increased simultaneously. The bacterial counts of the milk volumes precooled at different rates did not differ significantly at 0 h of storage or at 24-h intervals thereafter. After 72 h of storage, the total bacterial count of the NP milk was 3.90 ± 0.09 log₁₀ cfu/mL, whereas that of the precooled milk volumes were 3.77 ± 0.09 (SP) and 3.71 ± 0.09 (DP) log₁₀ cfu/mL. The constant storage temperature (3°C) over 72 h helped to reduce bacterial growth rates in milk; consequently, milk composition was not affected and minimal, if any, proteolysis occurred. The DP treatment had the highest energy consumption (17.6 ± 0.5 Wh/L), followed by the NP (16.8 ± 2.7 Wh/L) and SP (10.6 ± 1.3 Wh/L) treatments. This study suggests that bacterial count and composition of milk are minimally affected when milk is stored at 3°C for 72 h, regardless of whether the milk is precooled; however, milk entering the tank should have good initial microbiological quality. Considering the numerical differences between bacterial counts, however, the use of the SP or DP precooling systems is recommended to maintain low levels of bacterial counts and reduce energy consumption.     

湿米粉存储过程品质的变化及相关性分析

研究了湿米粉于冰箱(4℃、相对湿度90%)以及常温(20℃、相对湿度80%)条件下储存48h过程中,其质构、感官、蒸煮特性的变化及其相关性。结果表明,质构品质中的硬度和耐咀嚼性均与湿米粉的感官品质和蒸煮品质呈极显著相关,可作为湿米粉品质评定的主要指标。