切达干酪加工工艺研究

以鲜牛乳为原料,通过单因素实验和正交实验对切达干酪的加工工艺进行了初步研究,分析了凝乳酶添加量、发酵酸度、氯化钙添加量对切达干酪品质出品率的影响。结果表明,当凝乳酶添加量为7250SU,原料乳酸度为260T,氯化钙添加量为0.02%时可得到较佳的效果。     

响应面法优化切达干酪出品率

采用响应曲面法(response surface methodology,RSM)建立了切达干酪出品率的二次多项数学模型,验证了模型的有效性,并考察凝乳酶添加量、酸度和氯化钙添加量对干酪出品率的影响,优化出混合干酪出品率的最优工艺参数为凝乳酶添加量7250 SU,酸度28 °T,氯化钙添加量0.02%,出品率可达10-36%.     

凝乳条件对干酪凝乳质构及成品的影响分析

本文对干酪凝乳的主要因素进行研究,包括热处理条件、凝乳温度、凝乳酶添加量及氯化钙添加量,利用质构仪对凝乳质构进行测定,并对成品进行感官评价。试验结果表明:热处理条件为72℃/15 s,凝乳温度为35℃,凝乳酶添加量为0.07 g/L,氯化钙添加量为0.2 g/L时,新鲜干酪的品质最佳。     

褐牛牛乳卡门贝尔干酪关键工艺技术研究

以新疆褐牛牛乳为原料,通过单因素筛选影响卡门贝尔干酪生产的主要因素,并进行正交试验,确定出最佳工艺参数。结果显示:当原料乳符合企业标准要求,杀菌温度控制在72～75℃,杀菌时间为15～20s,凝乳温度降低至38～40℃,乳酸菌发酵剂添加量为0.02%,氯化钙添加量为0.03%,发酵pH为6.1,凝乳酶添加量为1140IU/kg,凝乳40～60min,干盐渍后生产出感官和口味良好的卡门贝尔霉菌干酪。在成熟过程中,不同温度条件下水分变化趋势相似,随着成熟时间的增加,温度越高水分、灰分变化幅度越大,而干物质脂肪含量减少。成熟后的干酪具有香醇浓郁,老少皆宜的特点。     

羊奶奶酪制作核心技术的初步研究

[目的]本研究以羊乳为原料，结合奶酪工艺初步探讨了羊奶酪的主要技术参数。[方法]通过对羊奶的杀菌温度、发酵剂添加量、CaCl₂添加量、凝乳酶添加量等因素进行正交试验，以产品质构、综合感官评价为指标，得到最佳用量配比。[结果]羊奶奶酪的最佳工艺为：杀菌条件75~78 ℃，15 s，发酵剂添加量为1.4 %，CaCl₂的添加量为0.03%，凝乳酶添加量为0.01%，在传统奶酪制作工艺的基础上以此技术参数生产的羊奶奶酪口感、风味良好。[结论]本研究为完整羊奶奶酪技术的开发加工奠定了基础，为探寻适合中国羊乳原料及口味要求的羊奶奶酪工业化生产提供了技术依据。     

一种水牛乳硬质干酪的工艺研究

以水牛乳为原料,研究了一种水牛乳硬质干酪的生产工艺,以干酪的校正产率、凝乳情况、感官评分以及凝乳时间作为评价指标,通过正交试验确定最佳工艺条件。结果表明：菌种添加量3%,凝乳酶添加量0.003%,氯化钙添加量0.02%,凝乳升温温度39℃,凝乳升温时间30min,加盐量1.5%,能获得产率高,口感佳,凝乳情况好,凝乳时间较短的水牛乳硬质干酪。     

涂抹型牦牛乳软质干酪的研制

本试验采用单因素试验对涂抹型牦牛乳软质干酪制作过程中使用的发酵剂、凝乳酶进行了选择,采用L9(34)正交实验研究了菌种添加量、杀菌条件、凝乳酶添加量和凝乳切割p H值等各因素水平对产品品质的影响,确定了最佳工艺参数,结果表明:菌种QH-3的产率和固形物回收率都比较高,产品的组织比较细腻,酸味适中;进口凝乳酶的凝乳时间最短,固形物回收率最高。A3B1C2D2为生产涂抹型牦牛乳软质干酪的最佳工艺参数即菌种添加量为5%、杀菌条件为65℃,30min、酶的添加量为400IU/100L、凝乳切割时的p H值为4.6。     

用牦牛奶生产Gouda奶酪工艺技术的研究

采用四因素三水平正交试验,分析了以新鲜牦牛乳为发酵原料,进行Gouda奶酪制作工艺中,不同剂量凝乳酶、氯化钙、食盐以及温度等因素对成品口感和色泽质地的影响。经分析用牦牛奶制作Gouda奶酪的最佳条件为：凝乳酶0.003%、氯化钙0.02%、食盐20%,发酵温度为30℃。     

氯化钙的添加量对半硬质干酪品质影响研究

研究氯化钙的添加量对半硬质干酪品质的影响,以确定其最佳添加量。采用单因素试验设计,氯化钙的添加量分别为0、5、10、15、20g/100kg牛奶。在其它工艺条件相同的情况下,分别加工一批干酪,然后测定成熟干酪的性能指标。结果表明,随着氯化钙添加量的增加,干酪的感官评定值逐渐降低;干酪的硬度、pH4.6可溶性氮含量、游离氨基酸总量和水分含量逐渐增加,而pH值变化不大。以感官评定值为主指标,结合其它性能指标,确定氯化钙的最佳添加量为0-5g/100kg。     

Mozzarella干酪与模拟干酪成熟过程中菌群及pH的变化

干酪凝块中含多种微生物和酶，这些微生物和酶在没有采用有效防治措施的条件下易发生作用，可发生生物、生化和化学变化。通过制作正常干酪（即加乳酸菌、凝乳酶）、两份模拟干酪（一份不加乳酸菌改用盐酸直接酸化、另一份不加凝乳酶改加葡萄糖酸内酯将乳凝结），再将其进行对比，研究菌群在成熟过程中的变化，结合蛋白水解、风味变化、微观结构，以找出菌群在干酪成熟中的确切作用。     

Closantel plasma and milk disposition in dairy goats: assessment of drug residues in cheese and ricotta

Closantel (CLS) is currently used in programs for the strategic control of gastrointestinal nematodes. CLS is extralabel used in different dairy goat production systems. From available data in dairy cows, it can be concluded that residues of CLS persist in milk. The current work evaluated the concentration profiles of CLS in plasma and milk from lactating orally treated dairy goats to assess the residues pattern in dairy products such as cheese and ricotta. Six (6) female Saanen dairy goats were treated orally with CLS administered at 10 mg/kg. Blood and milk samples were collected between 0 and 36 days post‐treatment. The whole milk production was collected at 1, 4, 7, and 10 days post‐treatment to produce soft cheese and ricotta. CLS concentrations in plasma, milk, cheese, whey, and ricotta were determined by HPLC. The concentrations of CLS measured in plasma were higher than those measured in milk at all sampling times. However, the calculated withdrawal time for CLS in milk was between 39 and 43 days postadministration to dairy goats. CLS residual concentrations in cheese (between 0.93 and 1.8 μg/g) were higher than those measured in the milk used for its production. CLS concentrations in ricotta were sixfold higher than those in the milk and 20‐fold higher than those in the whey used for its production. The persistent and high residual concentrations of CLS in the milk and in the cheese and ricotta should be seriously considered before issuing any recommendation on the extralabel use of CLS in dairy goat farms.     

简析凝乳酶凝乳机理及羔羊凝乳酶自制方法

本文重点介绍了凝乳酶的种类和凝乳机理,以及自制羔羊凝乳酶及其活力测定的方法,对引导我国家庭牧场和小型羊乳企业突破凝乳酶自制核心技术,创新开展羊奶酪生产研发,填补国产羊奶酪市场空白与丰富羊乳制品种类,具有重要的指导意义。     

混合果肉羊乳扣碗酪的加工工艺研究

研制全新的具有民族特色并且适合大多数人口味的奶酪食品。采用单因素多水平试验及正交试验方法,研究出混合果肉羊乳扣碗酪的加工工艺。为:白砂糖、琼脂熬汁→过滤→杀菌→添加到过滤杀菌的羊奶中调配→冷却→加江米酒→分装→冷凝→纯化→成品。产品配方为:新鲜山羊奶400g,8%桃果肉,8%梨果肉,9%葡萄干,果肉用30%的砂糖液煮制8min最佳,7.5%白砂糖,0.5%琼脂以及1.5%江米酒。该果肉扣碗酪具有水果的保健功效,营养全面,丰富我国的乳品市场和促进羊奶产业的发展。     

Isolation of Listeria monocytogenes from Goat Cheese Associated with a Case of Listeriosis in Goat

Listeria monocytogenes was isolated from the brain of a goat, which was euthanized due to listeriosis. A few weeks later a similar subtype of L. monocytogenes was isolated from an on-farm manufactured fresh cheese which did not contain any milk from the goat which had suffered from listeriosis. A similar subtype was also found on 1 of the shelves in the refrigerator where cheeses were stored. Prior to the onset of listeriosis, 1 fresh cheese had been made of milk from the actual goat, which may have excreted L. monocytogenes in her milk. Thus, the cheese made of this milk may have contaminated the shelves in the refrigerator which then has served as a Listeria reservoir for new cheeses during several weeks.     

Survival of Listeria monocytogenes in cheese made of unpasteurized goat milk

Food-born infections with Listeria monocytogenes have been reported during recent years, cheese being mentioned as one of the foods responsible. A classical opinion is that cheese represents a very inhospitable environment for pathogens due to antagonism by the starter culture of lactic-acid-producing organisms. In order to study the survival of L. monocytogenes in goat cheese, cheeses were made with the addition of L. monocytogenes cultures. The maximum survival time for L. monocytogenes was 18 weeks in two of the cheeses. It is concluded that L. monocytogenes has the ability to survive in semi-soft cheese made of unpasteurized goat milk during normal curing (2–3 months).     

Flavour of goat's milk: A review of studies on the sources of its variations

The specific flavour of goat's milk is undesirable for direct consumption but for cheese production its presence can be advantageous.Norwegian trials have shown that unclean handling of the milk reduces the true flavour. The flavour was not influenced by the presence of a buck.The flavour is influenced by the free fatty acid content, especially the C₆ to C₁₀ acids, and also may be affected by the KCl content and the presence of three different cresols. The flavour is negatively correlated to the organic substances in the milk. A strong flavour in the milk causes a strong flavour in the product when making brown whey cheese as well as ordinary white cheese.In the Norwegian goat population there is a positive phenotypic, and maybe also a positive genetic, correlation between yield and strong flavour. The heritability for flavour is estimated to be about 0.25. A significant difference has been found between Norwegian and Saanen goat's milk, both in flavour intensity and free fatty acid content.The flavour was less pronounced at the start and the end of lactation. Small differences were found in the flavour when comparing milk produced by goats fed on pasture and indoors. High feeding intensity by means of concentrates generally increased the flavour of the milk. In general the method of feeding and different feedstuffs have little influence on the true flavour of the goat's milk.     

不同风味羊奶皮配方及加工工艺研究

本试验旨在研究一种新型营养更全面的适合大众口味的奶皮子。在传统奶皮子加工的基础上,选用可可粉、草莓、桑椹、山羊奶和白砂糖为原料,采用对比试验和正交试验等方法研究了不同风味羊奶皮的加工工艺和配方。其工艺流程为:山羊奶过滤→加热灭菌→加白砂糖、可可粉或果汁→搅拌翻扬→保温→冷却→取出奶皮→晾晒→成型;其产品配方为:(1)可可味奶皮最佳配方:20g可可粉,80 g糖/5 kg奶;(2)草莓奶皮最佳配方:400 mL草莓汁,50 g糖/5kg奶;(3)桑椹奶皮最佳配方:400 mL桑椹汁,60 g糖/5 kg奶。研制的奶皮子的营养更加丰富,口感更加纯香,衍生产品更加多样,能满足更多消费者的需求。     

世界及我国奶山羊产业发展现状及趋势分析

近年来,世界山羊养殖数量持续增长,据联合国粮农组织(FAO)统计显示,2018年全球山羊养殖数量已超10.4亿只,其中奶山羊养殖数量超2.16亿只,约有90%以上的奶山羊和山羊奶产自亚洲和非洲。欧洲的奶山羊存栏和产奶量均在亚洲和非洲之后,但其单产水平远高于其他各大洲,在世界奶山羊每只平均年产奶量100 kg以上的国家中,前十位均为欧洲国家。我国奶山羊产业发展迅速,2018年我国奶山羊实际存栏约518万只,年产羊奶量约100万t,约占全国鲜奶产量的3.3%。本文对全球及我国奶山羊产业进行了纵向和横向比较,客观分析我国奶山羊产业的地位、发展现状以及未来发展趋势,旨在为我国奶山羊产业的发展提供参考。     

Influence of the calf presence during milking on dairy performance,milk fatty acid composition,lipolysis and cheese composition in Salers cows during winter and grazing seasons

The milking of Salers cows requires the presence of the calf. The removal of the calf would simplify the milking routine, but it could also modify the milk yield and the milk and cheese composition. Therefore, the aim of this experiment was to evaluate the effect of calf presence during milking during sampling period (winter or grazing periods), on dairy performance, milk fatty acid (FA) composition, lipolysis and cheese yield and composition. Nine and 8 Salers lactating cows were milked in the presence (CP) or absence (CA) of their calves respectively. During winter, the cows were fed a hay‐based diet and then they only grazed a grassland pasture. Calf presence during milking increased milk yield and milk 16:0 concentration and decreased milk fat content and milk total odd‐ and branched‐chain FA (OBCFA) concentrations. Calf presence only increased initial lipolysis in milk collected during the winter season. Milk from CP cows compared to CA cows resulted in a lower cheese yield and ripened cheeses with lower fat content. Milk from the grazing season had lower saturated medium‐chain FA and OBCFA concentrations and higher 18:0, cis‐9‐18:1, trans‐11‐18:1 and cis‐9, trans‐11‐CLA concentrations than that from the winter season. Initial milk lipolysis was higher in the winter than in the grazing season. These variations could be due to seasonal changes in the basal diet. Furthermore, the effect of calf presence during milking on milk fat composition was lower than that on dairy performance, cheese yield and composition. Removing the calf during the milking of Salers cows seems feasible without a decrease in milked milk, and with a positive effect on cheese yield and fat content, under the condition that we are able to select cows having the capacity to be milked easily without the calf.     

Housing of Norwegian goat herds and associations with milk yield and milk quality

Abstract

Data from a questionnaire regarding housing factors were merged with data from the milk recording databases (herd mean annual milk yield per goat, somatic cell count (SCC) and bulk milk bacterial count), and the material included 235 herds. Associations with housing factors were tested at herd level and at individual goat level. Housing in insulated buildings with no access to outdoor areas during the winter season, expanded metal grating and no use of bedding predominated. None of the housing factors evaluated were significantly associated with milk yield. In herds using water nipples, SCC was lower compared to herds using water bowls. SCC was also lower in herds with milking facilities in separate milking stalls as compared with combined feeding milking stalls in common pens. No significant associations were found between housing factors and bacterial counts, but the counts were lower in herds with high average milk yields per goat.