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生牛奶作为乳品加工企业的主要原料,其品质好坏与产品质量直接相关。由于生牛奶含有丰富营养,含水量较高,加之pH值接近中性,导致各种微生物都可在其中生长和繁殖。生牛奶中含有大量的微生物,主要分成病原微生物、有害微生物以及有益微生物三大类。有些微生物会导致牛奶的风味更加理想,有些会导致牛奶发生腐败变质,有些甚至能够造成人类感染疾病。现介绍牛奶中的主要微生物、检测方法及控制方法。 相似文献
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众所周知,牛奶富含脂肪、蛋白质等多种营养成分,各种微生物容易繁殖、生长,破坏牛奶中所含的正常营养成分,为此,必须对生产过程中牛奶所接触的设备进行彻底、规范的清洗,才能确保牛奶避免“二次污染“。有效清洗,就是按照一定的操作规范,科学的运用 相似文献
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牛奶具有突出营养品质。但牛奶既是环境微生物理想的培养基,也是引起各种疾病的有效媒介物。世界各国间牛奶生产和分布情况是不同的。从生物学观点看,气候条件是影响牛奶供应及卫生质量的重要因素之一牛奶卫生的微生物学在牛奶卫生方面,或在牛奶加工过程中控制微生物都是最根本和最重要的问题。微生物的传播和污染来源既在奶牛本身、操作工人,也在于含有污染水 相似文献
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谭建宁 《青海畜牧兽医杂志》2001,31(6):32-32
由于受设备条件的制约 ,青海省目前乳品加工企业及个体牛奶营销户仍将牛奶的酒精检验 ,作为牛奶检测的主要手段 ,但是由于此检验法自身的缺陷 ,加之奶牛饲喂管理不当及环境等各种应激因素影响 ,造成牛奶酸度在正常值范围而作酒精检验时却呈阳性反应 ,给牛奶生产者造成一定的经济损失 ,鉴于此 ,现就牛奶的酒精检验作一浅谈。由于酒精对乳酪蛋白有脱水作用 ,同时酒精与牛奶混合过程中又产生化合热 ,这种化合热被认为有加强牛奶中酪蛋白的凝固力 ,以此来观察脱水后的酪蛋白对热的稳定性反应。由于这些作用 ,酒精对酸度偏高的牛奶 ,因细菌繁殖而… 相似文献
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牛奶中乳蛋白和乳脂肪含量的高低直接关系到牛奶的品质和风味。牛奶中乳蛋白主要可以分为酪蛋白和乳清蛋白两种类型,其合成代谢过程均受到mTOR信号分子通路、JAK-STAT信号分子通路、GCN2-eIF2a信号分子通路的影响。牛奶中乳脂肪主要为三酰基甘油酯、磷脂等,对于牛奶的营养和风味均有重要影响,其受到脂肪酸相关酶ACACA、FAS、SCD1的调控。饲料营养是影响牛奶中乳蛋白和乳脂肪的关键因素之一,包括精粗饲料配比及饲料添加剂的应用等方面。本文对牛奶中乳蛋白和乳脂肪的合成调控机理,及日粮组成对其的影响机制进行阐述,为改善乳品质提供参考。 相似文献
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谈谈牛奶中微生物的来源及污染预防 总被引：5，自引：1，他引：4
谈谈牛奶中微生物的来源及污染预防￥福建省南平市乳牛良种繁殖场＠龚太棋谈谈牛奶中微生物的来源及污染预防○福建省南平市乳牛良种繁殖场（３５３０００）龚太棋牛奶营养丰富，是微生物生长繁殖的良好培养基。了解牛奶中微生物的来源及污染渠道，对防止和控制牛奶中微生物的污... 相似文献
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The combined action of proteinases/peptidases and acid phosphatases on phosphorylated proteins/peptides could be important for cheese quality. It seems that acid phosphatase activity in cheese originates from milk and microorganisms. Bovine milk contains more than one acid phosphatase, which are distributed between the cream and skim milk. The properties of two enzymes isolated from butter milk and skim milk are different. In general, acid phosphatase, especially that from starter organisms is very heat stable. The dephosphorylation of casein and phosphopeptides is of interest in cheese ripening. It has been suggested that acid phosphatases from both skim milk and lactic acid bacteria contribute to dephosphorylation of phosphopeptides in cheese, which are produced from casein by coagulant, indigenous milk proteinase and microbial proteinases during cheese ripening. 相似文献
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A significantly lower alkaline phosphatase activity was recorded in the arterial blood of cows with higher milk efficiency. They also had higher sugar contents in their blood: highly significantly in arterial blood and significantly in venous blood after milking. As to the other blood components, the differences are low and insignificant. A significant positive relationship between the daily milk yield and the content of ash in blood (mainly in venous blood before milking), highly significant positive relationship between protein content in arterial blood and daily milk yield, and significant to highly significant negative relationship between the activity of alkaline phosphatase in arterial and venous blood before milking and the level of gamma-globulins in arterial blood were recorded in the group of cows with higher milk output. In the group of cows with lower milk production, significant to highly significant negative relationships were obtained between protein content in blood and the daily milk yield (in arterial and venous blood before milking). 相似文献
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选取我国东南某乳品企业特优级(A+)生乳,采用不同巴氏杀菌温度74℃、75℃、76℃、77℃、78℃、79℃和80℃(15 s保持时间),检测杀菌乳中的热敏感物质糠氨酸、碱性磷酸酶、乳过氧化物酶和乳中生物活性物质免疫球蛋白、乳铁蛋白、ɑ-乳白蛋白、β-乳球蛋白的含量。试验结果显示,优质乳在74℃和75℃杀菌条件下活性物质变化不大,杀菌温度从76℃提高至80℃的过程中,随着杀菌温度的升高,乳中活性成分急剧降低。综合分析,优质巴氏杀菌乳的生产推荐采用75℃/15 s的温度时间组合,为行业同类产品生产参数的选取提供了参考。 相似文献
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Walawski K Kaczmarczyk E Sowiński G Czarnik U Zabolewicz T Białłowicz E 《Archivum veterinarium Polonicum / Polish Academy of Sciences, Committee of Veterinary Sciences》1993,33(3-4):165-176
A herd of cows of the same age, kept in a stable system under controlled environmental conditions, was used to estimate the repeatability of diagnostic blood and milk indices in several stages of the I, II and III lactation. Attention was paid to genetic and non-genetic sources of phenotypic variation. Statistically significant values of the regression coefficient were found for the following milk parameters: fat and protein content, milk density, calcium, potassium and lysozyme levels, as well as the following blood parameters: leucocytes' number, lymphocytes and neutrophils number, uric acid content, leucocytes acid phosphatase activity, lysozyme and blood serum alkaline phosphatase activity. Examined indices were analysed which proved to be suitable for prognostic and breeding application. 相似文献
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Selected public health criteria of pasteurised milk available to the consumer from milk-shops in a pre-defined area of Pretoria compared with a national distributor's milk was evaluated. Of the 135 milk samples purchased from milk-shops, 87% were not fit for human consumption on the basis of the minimum standards prescribed in the Foodstuffs, Cosmetics and Disinfectants Act, 1972 (Act 54 of1972). The national distributor's milk (n = 79) did not contain any pathogens, toxins nor inhibitory substances and passed all the criteria laid down in the Act. Even though milk-shop milk was sold as having been pasteurised, 38.5% of samples were alkaline phosphatase positive, indicating probable inadequate pasteurisation. Milk-shop milk quality varied between milk-shops and between sampling days and differed significantly (P < 0.05) from the national distributor's milk. Total aerobic plate and coliform counts were generally high for all milk-shop milk samples. Somatic cell counts of milk-shop milk differed significantly (P < 0.05) from the national distributor's milk. Escherichia coli was detected in 1 ml of 17% of milk-shop milk, 95% of which originated from milk which was alkaline phosphatase positive. Salmonella spp. could not be detected in 1 ml in any of the E. coli-positive milk tested. Staphylococcus aureus was isolated from 40% of milk-shop milk samples, and S. aureus enterotoxins from 7.8% of 51 cultures. Inhibitory substances were detected in 54.1% of milk-shop milk. The presence of inhibitory substances and the isolation of E. coli and S. aureus (some of which were able to produce enterotoxins) indicated potentially unsafe milk and poses a serious public health risk to consumers. 相似文献
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During the evaluation of the biochemical components of the arterial and venous blood of cows before and after milking, an insignificantly higher content of ash was found in the blood of the cows of Black-Pied Lowland breed, as compared with the Slovak Pied breed. The difference in the activity of alkaline phosphatase was found to be significant: the higher alkaline phosphatase activity was recorded in the blood of the cows of Slovak Pied breed than in the cows of Black-Pied Lowland cattle of the same age and in the same stage of lactation. A positive relationship was found between the milk yield and albumin level in the blood of the dairy cows of Black-Pied Lowland cattle; in the same breed a negative relationship was found between venous blood before milking and the level of gamma-globulins. 相似文献
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S van Dijk T Wensing P van Beukelen H J Breukink 《American journal of veterinary research》1983,44(4):674-676
Serum activities of sorbitol dehydrogenase (SDH), lactate dehydrogenase (LDH), gamma-glutamyltranspeptidase (gamma-GT), and alkaline phosphatase (ALP) were measured before, during, and after milk fat depression in 9 cows fed a high-concentrate ration during 2 experiments. In 7 of the 9 cows, increases in serum SDH and LDH activities were observed during milk fat depression. The gamma-GT activity showed only moderate changes, whereas the ALP activity remained unchanged. During recovery from milk fat depression, decreases of SDH, LDH, and gamma-GT activities were found in nearly all cows. Association of this phenomenon with changes found in beef cattle, such as ruminal lesions and liver abscesses, are discussed. 相似文献