新疆疆岳驴乳研究进展

介绍了新疆疆岳驴乳研究进展情况.包括:驴乳的化学成分和理化指标、蛋白质和脂肪酸组成、矿物元素和维生素质量分数、功能性物质及其质量分数、驴乳中的微生物以及驴乳的抗茵作用、抗疲劳作用、抗肿瘤作用和免疫功效.文章还对今后驴乳研究工作的重点提出了建议.     

不同发酵剂对发酵驴乳酸奶在冷藏期间品质的影响

目的 研究不同发酵剂发酵的驴乳酸奶在冷藏期间的品质变化。方法 对使用3种发酵剂发酵的驴乳酸奶在冷藏期间微生物指标、理化指标和风味滋味进行检测及感官评价。结果 在冷藏26 d中,LR-A、LR-B乳酸菌活菌数显著降低,LR-C乳酸菌活菌数逐渐增多,细菌菌落总数均呈现先上升后下降的变化趋势;随着冷藏时间的延长,LR-A、LR-B和LR-C的pH值持续降低,总酸度持续上升,持水力降低,感官评价分析3种驴乳酸奶在第14 d时口味最佳,之后都有所下降。结论 LR-A、LR-B在冷藏至26 d时各项指标符合国标要求,仍可以正常饮用,LR-C在冷藏14 d后酸度上升太高,超出接受范围无法饮用。     

不同发酵剂对发酵驴乳酸奶在冷藏期间品质的影响

目的研究不同发酵剂发酵的驴乳酸奶在冷藏期间的品质变化。方法对使用3种发酵剂发酵的驴乳酸奶在冷藏期间微生物指标、理化指标和风味滋味进行检测及感官评价。结果在冷藏26 d中, LR-A、LR-B乳酸菌活菌数显著降低,LR-C乳酸菌活菌数逐渐增多,细菌菌落总数均呈现先上升后下降的变化趋势;随着冷藏时间的延长, LR-A、LR-B和LR-C的pH值持续降低,总酸度持续上升,持水力降低,感官评价分析3种驴乳酸奶在第14 d时口味最佳,之后都有所下降。结论 LR-A、LR-B在冷藏至26 d时各项指标符合国标要求,仍可以正常饮用, LR-C在冷藏14 d后酸度上升太高,超出接受范围无法饮用。     

不同季节原料乳中主要微生物和理化指标分析

研究了冬季、春季和夏季原料乳的主要理化指标和微生物指标。3个季节内,蛋白质、乳脂、乳糖和干物质的变化范围分别是3.38%～3.52%,3.98%～4.26%,4.80%～4.85%和12.78%～13.19%。理化指标检测结果表明冬季牛乳的营养成分高于春夏两季,并且3个季节的乳成分均高于生鲜牛乳的收购标准;此外,对原料乳中主要的微生物:总菌数、乳酸菌、大肠菌群、沙门氏菌、蜡样芽孢杆菌、单增李斯特菌和嗜冷菌的菌数进行了检测。结果中未检测到沙门氏菌、蜡样芽孢杆菌和单增李斯特菌,其他微生物质量分数均在可接受范围内,但是大肠菌群的出现说明需要建立相关的卫生质量标准。     

驴乳营养成分和生物活性研究进展

中医古籍记载,驴乳具有清热解毒、润燥止渴等功效.欧洲和南美,驴乳流行作为人乳的替代品.研究表明,驴乳含有蛋白质、必需脂肪酸、矿物质、维生素等丰富的营养成分,而且其含量与人乳接近,有利于人体吸收和利用.生物活性研究表明,驴乳的蛋白质构成特点使驴乳致敏性低,可用于对牛乳过敏的婴儿.驴乳富含溶菌酶,具有抗菌功能.随着我国驴产业链的发展,驴乳资源将越来越丰富,市场和应用前景广阔.     

驴乳营养成分和生物活性研究进展

中医古籍记载,驴乳具有清热解毒、润燥止渴等功效。欧洲和南美,驴乳流行作为人乳的替代品。研究表明,驴乳含有蛋白质、必需脂肪酸、矿物质、维生素等丰富的营养成分,而且其含量与人乳接近,有利于人体吸收和利用。生物活性研究表明,驴乳的蛋白质构成特点使驴乳致敏性低,可用于对牛乳过敏的婴儿。驴乳富含溶菌酶,具有抗菌功能。随着我国驴产业链的发展,驴乳资源将越来越丰富,市场和应用前景广阔。     

基于双重聚合酶链式反应技术检测掺假驴乳中的牛乳

目的 建立双重PCR技术检测驴乳中掺假的牛乳的鉴别方法。方法 将牛乳按比例掺入驴乳制备掺假乳,经热处理提取DNA,以驴和牛的12S-RNA、16S-RNA为靶标设计特异性引物,进行相应的PCR,优化双重PCR退火温度,同时考察该方法在巴氏杀菌、高温灭菌和冷冻干燥条件下的适用性及灵敏度。结果 牛和驴的引物特异性均良好,与非目标物种DNA不发生交叉反应,DNA检测限最低为10 ng;优化后的双重PCR最佳退火温度为55.7℃;单重PCR由于干扰因素少,对驴乳中牛乳的掺假检出限均为0.1%,而双重PCR也表现出较好的适用性及灵敏性,在原料乳中检出限为0.5%,巴氏杀菌乳、高温灭菌乳和冷冻干燥驴乳中检出限均为2%。相较于单重PCR,双重PCR大大缩短了检测时间成本。结论 本研究为驴乳中牛乳的掺假检测提供了一种准确、灵敏和经济的方法,具有实际参考价值。     

响应面法优化风味驴乳酸奶发酵工艺的研究

在驴乳中添加牛乳粉制作酸奶,通过单因素试验和响应面优化法研究了风味驴乳酸奶最佳发酵工艺。结果表明,以牛乳粉添加量、发酵温度和发酵时间为自变量,以感官评价为因变量,响应面法优化出风味驴乳酸奶的最佳发酵工艺为：牛乳粉添加量10%、发酵温度42 ℃、发酵时间5.5 h。在此优化条件下,风味驴乳酸奶口感细腻爽滑,酸甜适口,有浓郁的驴乳香味与滋味,感官评分达到92分,与预测值（90.85分）相差较小。产品的理化及微生物指标均符合相关国标要求。     

西藏地区牦牛乳理化和微生物指标的检测分析

研究了西藏地区牦牛乳的理化指标和微生物指标。从西藏3个不同地区共取48份牦牛乳样品．通过理化和微生物指标的检测及其统计分析，研究发现牦牛乳的营养成分为：脂肪7．14％（体积分数）、粗蛋白5．06％（质量分数）、干物质18．45％（质量分数）、乳糖5．00％（质量分数）和灰分0．81％（质量分数），并且不同地区各成分的质量分数也不同。牦牛乳的微生物检测结果为（对数值）：细菌5．63mL^-1，芽孢菌1．76mL^-1，乳酸菌5．19mL，真菌3．03mL^-1，肠道菌3．27mL^-1，大肠杆菌2．09mL^-1和金黄色葡萄球菌3．52mL^-1，并且存在明显的地区差异性。     

贮藏条件对驴初乳理化性质的影响

对新疆岳普湖驴乳37℃贮藏的理化性质进行研究。研究表明,随放置时间的延长,pH、相对密度呈下降趋势,而酸度则呈上升趋势;蛋白质、非脂乳固体含量均呈下降趋势;而乳糖含量及微生物数量则随放置时间的延长逐渐上升。     

模糊数学评价法优化驴乳奶啤稳定性的预处理参数及香气成分分析

基于模糊数学评价法对驴乳奶啤稳定性预处理参数初步优化,结合气相色谱-质谱联用（GC-MS）技术确定驴乳奶啤的最佳预处理参数,通过与牛乳奶啤香气成分差异化对比,探究驴乳奶啤的香气组成。结果表明,最佳预处理参数为单甘脂添加量0.10%、海藻酸丙二醇酯添加量0.15%、果胶添加量0.20%。在此最佳条件下,5号驴乳奶啤综合评分最高（84.20分）,稳定性系数、离心沉淀率、黏度分别为（98.23±0.17）%、（5.21±0.14）%、（37.13±0.08） mPa·s。从牛乳奶啤及5号、9号驴乳奶啤中共检测出79种香气化合物,包括醇类11种、酯类25种、醛类8种、酸类12种、酮类6种、苯类2种、烷烃类12种、萜烯类2种、其他类1种,其中醇类、酯类和酸类挥发性化合物相对含量较高,对牛乳奶啤及5号、9号驴乳奶啤共有的18种香气成分进行主成分分析,经综合评价得出5号驴乳奶啤香气品质最佳,GC-MS分析结果与综合模糊评判结果一致。     

基于单拷贝核基因的荧光定量PCR技术检测驴奶的含量

本研究建立了一种基于内参基因的标准化实时聚合酶链式反应(real-time PCR)方法,能够定量检测混合掺假的灭菌乳中驴奶的含量。使用单拷贝核基因代替多拷贝线粒体基因,基于Ct值(驴特异性引物/内参引物)与驴奶含量的线性关系,对含量为5%~100% 的驴奶建立了标准曲线。该方法具有良好的线性相关(R2=0.9650)和较高的准确度,对含有20%、50%和80% 驴奶的模拟掺假样品进行定量分析,平均回收率为109.16%,平均CV值为4.68%。因此,该方法可以快速、准确地对驴奶进行定量,从而确定驴奶是否掺假以及掺假比例。     

Composition, physiochemical properties, nitrogen fraction distribution, and amino acid profile of donkey milk

This study investigated the changes in chemical composition, nitrogen fraction distribution, and AA profile of milk samples obtained during lactation from the Jiangyue breed of donkey in Northwest China. Results showed that donkey milk contained 9.53% total solids, 1.57% protein, 1.16% fat, 6.33% lactose, and 0.4% ash on average, which is more similar to mare and human milk than to the milk of other mammals. Throughout the lactation investigated, pH and density were constant, protein and ash content showed an apparent negative trend (an increase in lactose content during 120 d postpartum, followed by a decrease), fat content exhibited wide variability, and variations in the content and percentage of whey protein, casein, and AA were small. The casein to whey protein ratio of 52:37 was between the lower value of human milk and the higher value of cow milk. Sodium dodecyl sulfate-PAGE results demonstrated that donkey milk is rich in β-lactoglobulin and lysozyme. The percentages of 8 essential AA in protein of donkey milk were 38.2%, higher than those of mare and cow milk; donkey milk also had higher levels of serine (6.2%), glutamic acid (22.8%), arginine (4.6%), and valine (6.5%) and a lower level of cystine (0.4%).     

Effects of thermized donkey milk with lysozyme activity on altered gut barrier in mice exposed to water-avoidance stress

Nutrition plays a crucial role in human gut health through the improvement of gut barrier functionality. Donkey milk represents an interesting source of natural antimicrobial factors such as lysozyme. Recently, anti-inflammatory properties of donkey milk lysozyme activity were described in a mouse model of ileitis. The current increase of donkey milk consumption highlights the necessity to propose a healthy milk compliant with microbiological standards. This study aims to define a heat treatment of donkey milk, retaining its high lysozyme activity, and to evaluate its beneficial effects on a gut barrier impairment model due to chronic stress in mice. To perform this experiment, samples of raw donkey milk were collected in 15 distinct French farms. Microbiological analysis and lysozyme content and activity were evaluated for each sample. Then, several heat treatments were carried out to define a time and temperature combination that allowed for both a reduction in the number of total micro-organisms, increasing the shelf-life of the product, and preservation of lysozyme activity. The beneficial effect of heated donkey milk on the gut barrier of mice was evaluated and compared with raw donkey milk. We found that samples of raw donkey milk showed low total mesophilic microbial counts, and no pathogens were detected. Among the different heat-treatment procedures tested, a 2-min, 72°C combination was determined to be the most optimal time and temperature combination to preserve lysozyme activity and increase the shelf-life of donkey milk. Oral administration of this heat-treated donkey milk in mice counteracted chronic stress-induced intestinal damage, illustrated by gut hyper-permeability and low-grade inflammation, similar to raw donkey milk. We have demonstrated for the first time that oral intervention with donkey milk, optimally heat-treated to retain enzymatic lysozyme activity, improves intestinal barrier damage linked to psychological stress in mice.     

Short communication: Technological and seasonal variations of vitamin D and other nutritional components in donkey milk

Vitamin D is an essential nutrient that plays a crucial role in calcium homeostasis and bone metabolism and also acts as a hormone. Although several studies on the content of vitamin D in bovine milk have been conducted, little information is available regarding donkey milk. In the context of the nutritional assessment of donkey milk, the aim of this study was to assess the vitamin D content in donkey milk and its chemical profile, with particular reference to seasonal and technological modifications after pasteurization. The study was conducted on a dairy farm that produces donkey milk for human consumption located in central Italy. At sampling time, an aliquot of total bulk milk production was sampled before and after pasteurization (63°C for 30 min without homogenization) with a total of 20 raw and 20 pasteurized milk samples. The samples were collected for 10 mo, every 15 d, from May to February 2017. All the samples were analyzed for the chemical composition and vitamin D₂ and D₃ content by HPLC after saponification. The donkey milk analyzed showed a higher average vitamin D content (raw milk: vitamin D₂ = 1.68, vitamin D₃ = 0.60 μg/100 mL; pasteurized milk: vitamin D₂ = 1.38, vitamin D₃ = 0.30 μg/100 mL) than reported for bovine and human milk. The results of the effect of pasteurization on milk did not highlight significant differences in the total content of vitamin D. However, vitamin D₃ has a poor thermal stability, which led to a significant reduction in content in pasteurized milk compared with raw milk. The total vitamin D content of donkey milk did not show significant variations between seasons; however, a higher concentration of vitamin D₃ was found in spring and summer. In conclusion, raw and pasteurized donkey milk showed a high content of vitamin D, which could be useful in meeting the deficiencies of this vitamin in humans. Further investigations are needed to improve the vitamin D content in donkey milk by increasing its endogenous synthesis or its transfer in milk and to clarify other variability factors.     

Investigation of donkey milk bacterial diversity by 16S rDNA high-throughput sequencing on a Cyprus donkey farm

The interest in milk originating from donkeys is growing worldwide due to its claimed functional and nutritional properties, especially for sensitive population groups, such as infants with cow milk protein allergy. The current study aimed to assess the microbiological quality of donkey milk produced in a donkey farm in Cyprus using culture-based and high-throughput sequencing techniques. The culture-based microbiological analysis showed very low microbial counts, whereas important food-borne pathogens were not detected in any sample. In addition, high-throughput sequencing was applied to characterize the bacterial communities of donkey milk samples. Donkey milk mostly composed of gram-negative Proteobacteria, including Sphingomonas, Pseudomonas, Mesorhizobium, and Acinetobacter; lactic acid bacteria, including Lactobacillus and Streptococcus; the endospores forming Clostridium; and the environmental genera Flavobacterium and Ralstonia, detected in lower relative abundances. The results of the study support existing findings that donkey milk contains mostly gram-negative bacteria. Moreover, it raises questions regarding the contribution of (1) antimicrobial agents (i.e., lysozyme, peptides) in shaping the microbial communities and (2) bacterial microbiota to the functional value of donkey milk.     

The nutritional ingredients and antioxidant activity of donkey milk and donkey milk powder

The aim of this work was to shed light on the nutritional ingredients and antioxidant activity of donkey milk and powder. It indicated that basic components of donkey milk were closed to human milk, especially lactose. The fat content of donkey milk was lower than that of cow milk and human milk. The essential amino acids, fatty acids and taurine in donkey milk and powder were richer. The whey protein content of donkey milk was 49.08 g/100 g. The ratio of casein to whey protein in donkey milk and powder was 70.3:100. The cholesterol of donkey milk was 8.6 mg/100 g. Therefore, donkey milk and powder are typical low-fat and low-cholesterol foods. The precious values of donkey milk and powder are suitable calcium and phosphorus proportion, and strongly resistant to oxidation. In conclusion, donkey milk and powder are good supplementary of cow milk and powder, would be better for infant dietary.