乙基纤维素/蓝莓花青素浸泡型标签对牛奶新鲜度的指示

目的 旨在研发一款可浸泡在液体中的食品级牛奶新鲜度指示标签,让消费者简单方便且直观地了解牛奶的实时品质。方法 以乙基纤维素为聚合物基材,蓝莓花青素为pH敏感染料,吐温80和甘油为增塑剂制备出标签。通过比色分析、溶胀率、迁移测试、接触角、傅里叶变换红外光谱分析、扫描电镜(SEM)对指示标签进行表征,再将标签用于牛奶新鲜度监测,探究牛奶菌落总数、pH与指示标签总色差的关系。结果 花青素添加量为乙基纤维素质量分数10%的指示标签在pH缓冲液中的指示效果最佳;乙基纤维素和花青素通过氢键较好地结合使标签耐水性较好,可浸泡于液体中;迁移测试证明标签与牛奶接触不会造成安全问题;牛奶菌落总数、pH值与指示标签总色差存在相关性。结论 花青素添加量为乙基纤维素质量分数10%的指示标签在新鲜牛奶中显示为浅紫色,在变质牛奶中显示为粉色。该浸泡型指示标签在指示牛奶新鲜度上有良好应用价值和开发前景。     

乳品工业中的乳糖酶

主要介绍了乳糖酶的种类特性及其在乳品工业中的应用以及常见的生产工艺和注意事项。     

推广冰缸贮奶 提高乳品质量

本文回顾了二十年来中国乳业的风雨历程和奶源质量对乳业发展的重大影响。指出速冷奶罐是适合收奶站的理想设备,冰缸是乳品专业的最佳冷藏设备,它能给乳品厂和奶牛专业户带来可观的经济效益。推广冰缸是适合我国国情,提高乳品质量的有效途径。     

Growth and health of Holstein calves fed milk replacers supplemented with antibiotics or Enteroguard

Forty-five Holstein calves were fed milk replacers containing either antibiotics [MRA (oxytetracycline at 138 mg/kg and neomycin at 276 mg/kg), n = 22)] or Enteroguard [MRE, a blend of fructooligosaccharides, allicin, and gut-active microbes at (129 mg/kg, n = 23)] from birth to 5 wk of age to compare effects on average daily gain and on incidence of scours. Performance was evaluated by measuring weight gain, feed efficiency, and fecal scores. The overall body weight gains and severity of scours were not different between treatments, nor were there differences in starter intake or mean body weight gain. During wk 2, the average gain of calves fed MRA was less than that of calves fed MRE (0.07 vs. 0.09 kg/d, P = 0.09), and greater during wk 5 (0.62 vs. 0.51 kg/d, P < 0.01); however, total gain for calves fed MRE was not different from calves fed MRA. Likewise, average feed efficiencies (gain/dry matter intake) were not different. Severity of scours, as measured by fecal scores, and concentrations of serum proteins, an indirect measure of immunoglobulins, were similar for calves fed MRA and MRE. The results suggest that antibiotics in milk replacers can be replaced with compounds such as fructooligosaccharides, probiotics, and allicin to obtain similar calf performance.     

Comparison of free amino acids and volatile components in three fermented milks

Free amino acids (FAAs) and volatile components were analysed in commercial samples of yoghurt and Actimel^® drink as well as laboratory‐made kefir. The lysine and cysteine were the principal amino acids and accounted for about 70% of the total FAAs in all the samples. However, the amino acid profiles in the different fermented milk products differed: on the whole values for most of the amino acids were observed to be significantly higher in the Actimel^® samples. A total of 50 volatile components were identified. The largest number of volatiles were found in the kefir. Ethanol, 2,3‐ butanodione and 3‐hidroxybutan‐2‐one were the most prevalent volatile components, with ethanol significantly higher in the kefir samples.     

Adaptation of Escherichia coli O157:H7 to acid in traditional and commercial goat milk amasi

Acid resistance of Escherichia coli O157:H7 strains UT 10 and UT 15 were determined in traditional Amasi fermented for 3 days at ambient temperature (ca 30 °C) and commercial Amasi fermented at 30 °C for 24 h and stored at 7 °C for 2 days. Escherichia coli O157:H7 counts in commercial Amasi were detected at 2.7 log₁₀ cfu/ml after 3 days while those in traditional Amasi could not be detected after the same period. There was no significant difference (p ? 0.05) in the survival of acid adapted (AA) and non-adapted (NA) E. coli O157:H7 in traditional Amasi, while in commercial Amasi, the NA strain survived significantly (p ? 0.05) better than its AA counterpart. Regardless of prior adaptation to acid, E. coli O157:H7 can survive during fermentation and storage of fermented goat milk Amasi. Also, the fermentation time, pH and storage temperature affects the survival of E. coli O157:H7 in the fermented milk.     

共轭亚油酸强化型乳制品的稳定性研究

通过牛乳液中添加共轭亚油酸（CLA）,分析杀菌温度、均质压力、乳化剂类型、CLA添加量对牛乳稳定性的影响.实验结果表明：脱脂乳中添加0.17%的CLA稳定性较好,口感纯正;当灭菌温度超过100℃时,CLA含量明显降低;以单苷酯、三聚苷酯和蔗糖酯的混合乳化剂,按1∶1∶2混合的乳液稳定性好;35MPa以上的均质压力下,乳液中的脂肪球细小,分布均匀,口感细腻。     

牦牛α-乳白蛋白基因单核苷酸多态性分析

为明确牦牛乳中α-乳白蛋白遗传多样性,以α-乳白蛋白基因(LAA)的Ⅰ、Ⅱ、Ⅲ和IV外显子为研究对象,采用聚合酶链反应-单链构象多态性(PCR-SSCP)方法对麦洼牦牛的LAA进行分析,旨在从分子水平揭示LAA在牦牛乳中遗传多样性分布. 牛属不同来源的α-乳白蛋白基因的编码序列被用于构建系统发育树. 结果表明,牦牛乳中LAAⅠ外显子区域以杂合体形式存在,并发现了一个新变异体JN084189. 不同来源LAA的系统发育树分析表明,LAA在进化上存在一定的物种特异性.     

不同贮藏温度对UHT乳品质的影响

UHT乳作为一种经超高温瞬时灭菌、无菌灌装生产的长货架期液态乳,具有品质优良,饮用方便等优点.但是在贮藏过程中,UHT乳经常会因残留酶或微生物作用而产生蛋白质凝块、沉淀或脂肪上浮等缺陷,从而影响UHT乳的品质.本研究通过UHT中试生产线无菌灌装制备PET瓶装UHT乳,将其分别置于7,25,37℃下保温观察,定期测定色泽、酪蛋白胶体粒径、蛋白质水解度及理化指标等变化.结果表明,贮藏过程中UHT乳发生的主要反应为蛋白质水解、脂质氧化和美拉德反应,UHT乳的pH值、游离钙离子含量和酪蛋白胶体粒径呈下降趋势,b＊值、蛋白水解度、脂质氧化程度呈上升趋势.120 d保温试验结束后,除37℃贮藏下的UHT乳色泽从第90 d开始发生明显变化外,各UHT乳样品并未产生明显的脂肪上浮和蛋白沉淀等现象.     

<Superscript>1</Superscript>H NMR characterization of milk lipids: A comparison between cow and buffalo milk

Characterization of the lipid fraction of raw cow and buffalo milk samples, collected in different breeding areas in Apulia, a region of southern Italy, were performed by means of ¹H NMR. The aim of this work was to establish whether FA composition data obtained by ¹H NMR can be used in the differentiation of buffalo and cow milk samples according to species. A complete assignment of the signals present in the spectrum was attempted by COSY, heteronuclear coherence spectra. Quantification of FA was carried out by inserting the integrals of particular peaks in suitable calculations. Multivariate statistical analysis, conducted on the results of the quantification, permitted buffalo and cow milks to be distinguished.