羊乳与牛乳理化特性比较

以莎能奶山羊羊乳为样品,利用乳样自动分析仪,氨基酸自动分析仪、等离子发射光谱、色谱分析对其基本成分、氨基酸组成及含量进行了分析和检测,并与牛乳理化特性进行比较,为科学合理地利用羊乳,生产具有独特功能的羊乳制品提供了理论依据。     

Beneficial effect of goat milk on nutritive utilization of iron and copper in malabsorption syndrome

The search for diets that improve the digestive and metabolic use of iron and copper in malabsorption syndrome led us to study goat milk for particular nutritional characteristics and compare it with cow milk, which is usually supplied. We studied the metabolism of iron and copper in transected rats (control) and in resected rats (resection of 50% of the distal small intestine). The diets used were the standard diet recommended by the American Institute of Nutrition and diets based on goat or cow milk. Intestinal resection reduced the apparent digestibility coefficient (ADC) of iron in the three diets tested. In the transected and resected rats, the ADC of iron was highest with the goat milk diet, followed by the standard diet and lowest with the cow milk diet. The ADC of copper was not affected by intestinal resection in the animals fed the goat milk diet, and was higher than that in the two groups of animals fed the other diets. Intestinal resection reduced the ADC of copper with the standard diet and the cow milk diet. When both groups of animals were fed the goat milk diet, the deposit of iron in the organs was greater than with those fed the cow milk diet and similar to that in those animals given the standard diet. The copper content in the kidneys was lower in the resected than in the transected animals, except in the case of those fed the goat milk diet, in which it was similar to that of the control (transected) rats. This study shows the beneficial effect of goat milk, with respect to cow milk, on the metabolism of iron and copper in control rats, especially those with malabsorption syndrome.     

Effects of polymerized goat milk whey protein on physicochemical properties and microstructure of recombined goat milk yogurt

Goat milk whey protein concentrates were manufactured by microfiltration (MF) and ultrafiltration (UF). When MF retentate blended with cream, which could be used as a starting material in yogurt making. The objective of this study was to prepare goat milk whey protein concentrates by membrane separation technology and to investigate the effects of polymerized goat milk whey protein (PGWP) on the physicochemical properties and microstructure of recombined goat milk yogurt. A 3-stage MF study was conducted to separate whey protein from casein in skim milk with 0.1-µm ceramic membrane. The MF permeate was ultrafiltered using a 10 kDa cut-off membrane to 10-fold, followed by 3 step diafiltration. The ultrafiltration-diafiltration-treated whey was electrodialyzed to remove 85% of salt, and to obtain goat milk whey protein concentrates with 80.99% protein content (wt/wt, dry basis). Recombined goat milk yogurt was prepared by mixing cream and MF retentate, and PGWP was used as main thickening agent. Compared with the recombined goat milk yogurt without PGWP, the yogurt with 0.50% PGWP had desirable viscosity and low level of syneresis. There was no significant difference in chemical composition and pH between the recombined goat milk yogurt with PGWP and control (without PGWP). Viscosity of all the yogurt samples decreased during the study. There was a slight but not significant decrease in pH during storage. Bifidobacterium and Lactobacillus acidophilus in yogurt samples remained above 10⁶ cfu/g during 8-wk storage. Scanning electron microscopy of the recombined goat milk yogurt with PGWP displayed a compact protein network. Results indicated that PGWP prepared directly from raw milk may be a novel protein-based thickening agent for authentic goat milk yogurt making.     

山羊奶与牛奶和人奶营养成分的比较

对山羊奶、牛奶和人奶中蛋白质、脂肪、维生素、矿物质等主要营养成分进行了比较,分析了3种奶中主要营养成分的差别。通过比较发现,山羊奶在总体营养成分方面优于牛奶,更接近人奶。但山羊奶存在铁、叶酸和维生素B12含量较低以及羊奶膻味的问题,应在营养上对这方面加以重视。     

陕西生鲜羊奶及其加工羊奶粉品质调研分析及相关性研究

为调查陕西省生鲜羊奶及羊奶粉品质随月份的变化规律,明确生鲜羊奶和羊奶粉品质之间的相关关系,该研究以2020年4月至11月某乳品企业在陕西不同地区的奶站收购的生鲜羊奶及其加工羊奶粉为试验样品,对其感官、理化和安全指标进行分析.结果表明,生鲜羊奶和羊奶粉在感官指标方面均符合国家标准要求;在理化指标方面,生鲜羊奶脂肪含量为3...     

同时蒸馏萃取法和固相微萃取法提取羊奶粉挥发性风味物质

采用固相微萃取法和同时蒸馏萃取法提取羊奶粉中的挥发性成分,再经气相色谱-质谱联用仪分析,共检出风味化合物55种,SPME法检出41种,SDE法检出22种,其中共同检测到8种,分别是辛酸、壬酸、癸酸、月桂酸、十二内酯、十四烷、十五烷、2-壬酮。SPME法和SDE法结合使用能较为全面的反映出羊奶粉的挥发性风味物质,且羊奶粉的挥发性风味物质以挥发性酸类成分为主。      

苹果渣、复原羊乳无蔗糖发酵工艺研究

以苹果渣和复原羊乳为主要原料,生产固体复合发酵乳饮料。在单因素的基础上,通过正交实验,确定苹果渣复合发酵乳的优化工艺条件为:复原羊乳量30%,43℃发酵8h,接种量5%,木糖醇5%。营养评价结果证明,此工艺参数生产的固体复合发酵乳饮品营养丰富、均衡,风味纯正,是一种风味纯正的饮料。      

Influence of storage and preservation on fossomatic cell count and composition of goat milk

This study was designed to evaluate the effects of different test conditions on the somatic cell count (SCC) and composition of goat milk. To this end, 3600 tests were performed on 1800 aliquots taken from 40 goat milk samples using a combined instrument set-up based on flow cytometry for SCC and Fourier transform infrared analysis for fat, total protein, lactose, total solids, and freezing point determinations. The conditions tested were storage temperature (refrigeration and freezing), use of a preservative [no preservative (NP), azidiol (AZ), and bronopol (BR)], and age of the milk samples at each storage temperature (24 h to 42 d at refrigeration temperature and 21 to 105 d at freezing temperature). Significant effects on logSCC variation were shown by the storage temperature, the preservation treatment, the interaction of storage temperature × preservation treatment, and milk age within the interaction of storage temperature × preservative. Highest counts were recorded in the BR-preserved milk samples (logSCC = 5.877), and lowest counts were recorded in milk samples preserved using AZ (logSCC = 5.803). The use of frozen/thawed samples led to a significantly decreased logSCC for the treatments AZ and NP; the logSCC was not modified when BR-preserved frozen/thawed samples were analyzed. During storage, variations in the SCC observed for BR-preserved samples stored at refrigeration temperature for up to 25 d and at freezing temperature for all times tested were always <10%. The preservation treatment was the main factor affecting the milk composition variables examined. Highest values of most variables were obtained in the BR-preserved samples, and the lowest values were obtained in the AZ-preserved samples. The freezing point was lower in the preserved samples than in the NP samples. The levels of milk constituents recorded in the BR-preserved samples were independent of both the storage temperature and age of milk sample. Our findings indicate that the freezing point of goat milk must be interpreted according to the preservative used.     

发酵羊乳中乳酸菌低产粘菌株的筛选

对从商业乳酸菌发酵剂分离纯化的11株保加利亚乳杆菌和11株嗜热链球菌在发酵羊乳中的粘度进行了研究。结果表明,保加利亚乳杆菌L.b-124菌株和L.b-346菌株、嗜热链球菌S.t-222菌株和S.t-346菌株具有较低的产粘能力,凝乳时间也较短;将L.b-346菌株与S.t-346菌株按杆菌和球菌1:1比例混合后在43℃下发酵羊乳时,可获得较低的发酵粘度。     

羊奶脂肪酶特性的研究

对影响羊乳脂肪酶活性的温度、pH以及金属离子进行了研究。结果表明,羊奶中脂肪酶在37℃时活性最高,在40⁵0℃时具有较高的热稳定性;羊奶脂肪酶最适pH为6.5,在pH5.0⁶.5时稳定性较高;Ca2+和Fe2+对脂肪酶具有激活作用,而K+、Zn2+、Cu2+、Mn2+和Mg2+对脂肪酶具有抑制作用,低浓度的Al3+和Fe3+对脂肪酶活性具有抑制作用,而高浓度的Al3+和Fe3+对脂肪酶具有激活作用。      

Grazing season and forage type influence goat milk composition and rennet coagulation properties

Two different types of pasture (cultivated and rangeland) and 2 different hay qualities (high and low quality) were examined for their effects on goat milk composition and rennet coagulation properties. Furthermore, the effect of dietary treatments in both the early and late grazing season was studied. As lactation stage is known to influence milk composition, the goats in the early and late grazing season were in the same lactation stage at the start of the experiment. The milk composition was influenced both by dietary treatment and season. Milk from goats on pasture was superior to those on hay by containing a higher content of protein and casein, and the goats on cultivated pasture had the highest milk yield. Casein composition was significantly influenced by forage treatment. Goats grazing on cultivated pasture had higher contents of α_s1-casein and also of κ-casein compared with the other treatments, whereas goats grazing on rangeland had the highest content of β-casein. Factors such as milk yield, casein micelle size, α_s2-casein, and calcium content were reduced in late compared with early season. More favorable rennet coagulation properties were achieved in milk from the early grazing season, with shorter firming time and higher curd firmness compared with milk from the late grazing season, but the firming time and curd firmness were not prominently influenced by forage treatment. The content of α_s2-casein and calcium in the milk affected the firming time and the curd firmness positively. The influence of season and forage treatment on especially milk yield, casein content, and rennet coagulation properties is of economic importance for both the dairy industry and goat milk farmers.     

花生功能成分及营养价值的研究进展

花生是全球最重要的四大油料作物之一,是我国食用油脂和蛋白质的重要来源.花生含有丰富的功能成分和很高的营养价值,应重视对我国花生资源开发利用的研究,大力开发花生营养保健食品,满足国人健康消费需求.     

山羊乳与绵羊乳的物理化学性质比较

阐述了山羊乳与绵羊乳在物理化学方面的不同特性，比较了它们在色泽、风味以及化学组成方面的不同，如它们的脂肪、非脂固形物、蛋白质、乳糖、灰分、维生素含量等。对蛋白质和脂肪而言，还进一步讨论了它们的氨基酸和脂肪酸组成。     

Sensory evaluations and stability determinations of goat milk containing galactooligosaccharides

The objectives of this study were to evaluate the feasibility of producing goat milk containing galactooligosaccharides (GOS) by β‐galactosidase and to determine the sensory attribute and stability of goat milk containing GOS. The results indicated that the maximum GOS obtained were approximately 13.9% of total sugars at pH 4.5 and temperature 40 °C. The sensory attribute of the obtained GOS was determined using a 5‐point hedonic scale in terms of taste, flavour, appearance and overall acceptability. There were significant increases in taste and overall acceptability of goat milk containing higher GOS concentration when compared to regular goat milk (control). Also, goat milk containing GOS presented a good stability over the acidic conditions. GOS in goat milk were also stable after the high heat treatment and shelf life conditions.     

Effect of processing on nutritive values of milk protein

Milk is an essential source of nutritionally excellent quality protein in human, particularly in vegan diet. Before consumption, milk is invariably processed depending upon final product requirement. This processing may alter the nutritive value of protein in a significant manner. The processing operations like thermal treatment, chemical treatment, biochemical processing, physical treatments, nonconventional treatments, etc. may exert positive or negative influence on nutritional quality of milk proteins. On one side, processing enhances the nutritive and therapeutic values of protein while on other side intermediate or end products generated during protein reactions may cause toxicity and/or antigenicity upon consumption at elevated level. The review discusses the changes occurring in nutritive quality of milk proteins under the influence of various processing operations.     

Profile of gelatinolytic capacity of raw goat milk and the implications for milk quality

Both endogenous and exogenous proteinases occur in milk, and they can have beneficial or detrimental effects on dairy production. Because the lactation length of dairy goats is shorter and the somatic cell count (SCC) of goat milk is generally greater compared with dairy cows, the objectives of the present study were to investigate the prevalence of major proteinases in raw goat milk, their association with SCC and production stage, and their effects on milk quality. Milk samples were collected from individual goats in consecutive weeks for different durations, covering regular lactation, late lactation, and post-milk stasis. Long-term (monthly) or short-term (weekly) fluctuations of milk fibrinolytic and gelatinolytic capacities of individual goats were revealed chronologically on fibrin and gelatin zymograms, respectively. In a separate trial involving milk samples from 23 goats at random production stages, the percentage of ultracentrifuge force-precipitable casein of total milk protein was calculated to represent milk quality and was assessed to evaluate its correlation with the corresponding proteolytic capacities. The results for regular milk indicate that gelatinase B was more abundant than gelatinase A when they first appeared at SCC of ∼1 × 10⁶/mL. During the last month before milk stasis, both gelatinases A and B were found to be prevalent and prominent in milk regardless of the broad SCC range recorded there. Fibrinolytic activity and the active form of gelatinase A were only regularly detected in post-stasis secretions and were scarce before stasis. The results of the milk quality trial indicate that milk of relatively high proteinase capacity tended to have a low casein ratio. Correlation analysis confirmed a significant relationship between gelatinase capacity of goat milk and production stage, SCC, or casein ratio. It is suggested that an elevation of gelatinolytic capacity of goat milk coincides with an increase in somatic cell number accompanying the extension of lactation length, which is unfavorable for the production of a more desirable quality of goat milk.     

Physicochemical analysis of full-fat, reduced-fat, and low-fat artisan-style goat cheese

The objective of this study was to examine the physicochemical properties of cheese elaborated via traditional artisan methods using goat milk containing 5, 1.5, or 0.4% fat and ripened for 1, 7, 14, or 28 d. Seventy-two cheeses were produced (2 batches × 3 fat levels × 4 ripening times × triplicate). Proximal composition, pH, texture analysis, and color were recorded in each cheese. Protein and moisture were increased in cheese, and fat and fat in DM were decreased with decreasing fat in milk. Internal and external pH was higher in low-fat and reduced-fat cheese, and pH values decreased during the first 2 wk of ripening but increased slightly on d 28. Cheese fracturability, cohesiveness, masticability, and hardness increased with decreasing fat, whereas elasticity and adhesiveness decreased. Cheese lightness and red and yellow indexes decreased with decreasing fat content; during ripening, lightness decreased further but yellow index increased.     

掺假羊乳及其制品中牛乳的检测技术研究进展

羊乳具有营养价值高、蛋白质组成更接近人乳、脂肪球直径小及致敏性低等优点,更利于人体消化吸收,受到消费者和乳品企业的青睐.近年来我国羊乳产业发展迅速且潜力巨大,但由于受羊乳产量和养殖规模的限制,羊乳价格昂贵,市场中存在羊乳及其制品掺假牛乳的现象,且掺假手段多样,难以辨别.为了保证消费者的健康和权益,保障羊乳市场良性发展,...     

巴氏杀菌对原料羊乳卫生质量的影响

本文就巴氏杀菌条件对原料羊乳和贮存过程中巴氏杀菌羊乳的菌落总数和大肠菌群变化规律进行研究。不同污染程度的原料羊乳分别在63℃/30min、72℃/30s和85℃/15s下处理,乳样中菌落总数和大肠菌群变化差异极为显著（p<0.05）。随着巴氏杀菌强度的增大,污染程度相同乳样的巴氏杀菌效率依次增高,污染程度不同乳样的巴氏杀菌效率却依次降低。巴氏杀菌后轻度污染和中度污染的乳样在5℃贮存7d后,其菌落总数和大肠菌群变化不显著（p>0.05）,均未超过巴氏杀菌乳国标GB19645-2010;重度污染的巴氏杀菌羊乳乳样在5℃贮存7d之后其菌落总数和大肠菌群已经显著超过巴氏杀菌乳国标GB19645-2010。因此原料羊乳在生产和贮存运输过程中要避免被微生物所污染,轻度和中度污染乳样的巴氏杀菌条件应选63℃/30min,贮存温度和时间应该控制在5℃/7d以内,以提高巴杀羊乳的品质和货架期。      

Effects of ultra-high pressure homogenization on microbial and physicochemical shelf life of milk

The effect of ultra-high pressure homogenization (UHPH) on microbial and physicochemical shelf life of milk during storage at 4°C was studied and compared with a conventional heat preservation technology used in industry. Milk was standardized at 3.5% fat and was processed using a Stansted high-pressure homogenizer. High-pressure treatments applied were 100, 200, and 300 MPa (single stage) with a milk inlet temperature of 40°C, and 200 and 300 MPa (single stage) with a milk inlet temperature of 30°C. The UHPH-treated milks were compared with high-pasteurized milk (PA; 90°C for 15 s). The microbiological quality was studied by enumerating total counts, psychrotropic bacteria, lactococci, lactobacilli, enterococci, coliforms, spores, and Pseudomonas. Physicochemical parameters assessed in milks were viscosity, color, pH, acidity, rate of creaming, particle size, and residual peroxidase and phosphatase activities. Immediately after treatment, UHPH was as efficient (99.99%) in reducing psychrotrophic, lactococci, and total bacteria as was the PA treatment, reaching reductions of 3.5 log cfu/mL. Coliforms, lactobacilli, and enterococci were eliminated. Microbial results of treated milks during storage at 4°C showed that UHPH treatment produced milk with a microbial shelf life between 14 and 18 d, similar to that achieved for PA milk. The UHPH treatments reduced the L* value of treated milks and induced a reduction in viscosity values of milks treated at 200 MPa compared with PA milks; however, these differences would not be appreciated by consumers. In spite of the fat aggregates detected in milks treated at 300 MPa, no creaming was observed in any UHPH-treated milk. Hence, alternative methods such as UHPH may give new opportunities to develop fluid milk with an equivalent shelf life to that of PA milk in terms of microbial and physicochemical characteristics.