奶啤饮料稳定性的研究

通过分析乳蛋白质和乳脂肪的结构特点，根据Stokes定律，经实验研究确定了影响奶啤饮料外观稳定性的因素及提高饮料稳定性采取的措施，配合整个工艺过程，有效地解决了奶啤饮料的外观稳定性问题。     

奶啤的研制

以牛奶、麦芽和酒花为主要原料,通过二次生物发酵研制出具有奶香和啤酒风味的奶啤饮料。通过实验确定奶啤的最佳配方及生产工艺流程并对奶啤的稳定性进行探讨,从而研制出即有啤酒的低酒精度、泡沫丰富和适度的二氧化碳,又具有酸乳饮料的酸甜可口、营养全面的奶啤饮料。     

奶啤稳定性的研究

以牛奶、麦芽和酒花为主要原料经过二次生物发酵研制出具有奶香和啤酒风味的奶啤饮料.从乳化剂、稳定剂、盐类、均质条件等方面分析探讨了影响奶啤稳定性的各因素,得出了使奶啤保持稳定性的最佳工艺条件.     

仙人掌奶啤的研制

探讨了以仙人掌、牛奶、麦芽和酒花为主要原料经过二次生物发酵研制既有啤酒的低酒精度,泡沫丰富和适度的二氧化碳,又具有酸乳饮料的酸甜可口,营养全面且具有保健功能的绿色饮料—仙人掌奶啤。通过实验确定仙人掌奶啤的最佳配方及仙人掌汁的添加方式,并对奶啤的稳定性进行了探讨。     

芦荟奶啤的研制

以芦荟、牛奶、麦芽和酒花为主要原料,经过二次生物发酵,研制出既有啤酒的低酒精度,泡沫丰富和适度的二氧化碳,又具有酸乳饮料的酸甜可口,营养全面且具有保健功能的绿色饮料-芦荟奶啤。本文通过实验确定芦荟奶啤的最佳配方及芦荟汁的添加方式,并对奶啤的稳定性进行了探讨。     

奶啤饮料的研制

以鲜奶为主要原料，通过发酵试验和感官评定，筛选出发酵风味好的菌株，探究奶啤饮料的工艺配方并进行奶啤稳定性研究。结果表明：利用啤酒酵母发酵，奶啤风味最好；当酵母接种量为4％，蔗糖添加量为8％，发酵温度为30℃，发酵时间为15h时生产的奶啤饮料风味最佳，而当CMC添加量为0．5％，黄原胶添加量为0．2％时，稳定性较好。     

复合增稠剂在奶啤饮料中的应用研究

通过单因素试验、多因素正交试验研究复合增稠剂、乳化剂、增重剂等添加剂对凝固型酸奶及奶啤饮料稳定性的影响,确定出最优的复配增稠剂配方:CMC0.05%、黄原胶0.10%、蔗糖脂肪酸酯0.15%,以此复配增稠剂制作的奶啤饮料稳定性最佳。     

低糖奶啤饮料生产工艺与质量控制研究

运用分离、纯化技术筛选出最佳乳酸菌、酵母菌菌株,对牛奶进行二段发酵,不经蒸馏,合理添加碳水化合物,强化营养素,生产出低糖奶啤饮料,此饮料具有某些保健功能。研究了菌种制备、工艺流程、技术指标、质量控制等,并对影响奶啤产品质量的因素进行了探讨。     

新概念饮料——奶啤

奶啤饮料是介于奶饮料与啤酒之间的新概念饮料.奶制品因其丰富而均衡的营养成分,越来越被人们所认可,提倡饮奶被列为提高全民健康水平的重要措施之一.但是仍有一部分消费者因乳糖不适症或不习惯奶的风味,而不饮用牛奶.     

红枣雪梨汁复合奶啤的研制

为了丰富乳制品的种类,开阔奶啤的消费市场,以脱脂奶粉、红枣汁、雪梨果汁和啤酒原浆为主要原料,添加白砂糖和稳定剂,分别将啤酒原浆和通过乳酸菌发酵所得到的红枣雪梨酸乳液按一定的设计比例进行配比,制备出一款兼具天然的酸乳香、浓郁的醇香和保健功能的红枣雪梨汁复合奶啤饮料。通过单因素试验筛选出影响奶啤质量和感官的重要参数,然后通过响应曲面回归设计确定最佳水平,并对研制出的奶啤的稳定性进行一定的研究。当红枣汁和雪梨果汁的添加量均为10.40%、啤酒原浆和红枣雪梨酸乳液的添加比例为0.90︰1、白砂糖的添加量为8.22%、CMC-Na的添加量为0.2%以及卡拉胶的添加量为0.15%时所制作出的复合奶啤的感官性能最佳,稳定性能最好。     

Cycled high hydrostatic pressure processing of whole and skimmed milk: Effects on physicochemical properties

In this study, we compare the effects of single- and double-cycle HP treatments at 600 MPa on inactivation of the natural microflora and physicochemical properties of whole and skimmed milk of high bacterial load. The results show that two-cycled HP (2 × 2.5 min) was more effective (P < 0.05) on microbial inactivation, and caused similar or slightly less changes (P > 0.05) in physicochemical properties of milk in comparison to single cycled HP (1 × 5 min). In addition to the expected milk protein structure changes, HP at 600 MPa caused only slight effects on milk fat and lactose. Minor decreases in levels of short chain fatty acids were observed with the cycled treatments, and the volatiles in general decreased after HP treatment, depending mostly on the pressure time but also on cycling in skimmed milk. The study confirmed the superior effect of two-cycle HP on microbial inactivation, and shows a slightly better preservation of the physical-chemical milk quality.Industrial relevanceMulti-cycling HP has been shown to be advantageous for microbial inactivation, but limited information is available regarding the effect on milk components in whole milk or skimmed milk. The present study compares the psychochemical properties of whole and skimmed milk processed by multi-cycling in comparison to single cycle HP treatment. Double cycled HP presented a superior effect on microbial inactivation and slightly better preservation of milk quality than one continuous HP.     

Effects of continuous versus periodic milk availability on behavior and performance of dairy calves

Dairy calves fed milk ad libitum engage in feeding activity throughout the day and night. However, providing calves with continuous access to milk can present practical problems with milk quality, particularly during warm weather. One way to maintain milk quality in ad libitum feeding regimens is to limit the time that milk is available, but no research to date has addressed how this might affect calves. The objectives of this study were to quantify the effects of continuous access to milk (24 h/d) vs. access during only part of the day on milk feeding behavior and performance. Twenty-eight female Holstein calves were randomly assigned to treatments at 5 ± 3 d of age and monitored for 28 d. All calves had milk delivered through a teat. Treatments were 1) access to milk for 24 h/d; 2) access to milk for 2 feedings per day (each of 2 h), with water available through the teat the remainder of the day (4-h wet treatment); and, 3) access to milk for 2 feedings per day (each of 2 h), but with no water available through the teat (4-h dry treatment). Calves given 24-h access to milk consumed 11.2 ± 0.5 kg/d on average. Milk intake tended to be lower for the 4-h wet and 4-h dry treatments, averaging 10.0 ± 0.3 kg/d, with no difference between these 2 treatments in this or any other variable. Average daily gain over the course of the experiment did not vary with treatment and averaged 1.1 ± 0.04 kg/d. Calves in the 24-h treatment spent more time on the teat than those calves on the 4-h treatments, but during the 4 h/d when milk was available to all calves, calves in the 4-h treatments spent more time on the teat. These results show that individually housed calves fed milk ad libitum for only 4 h/d compensate by changing their milk feeding behavior and are able to achieve similar weight gains to animals fed milk continuously.     

Investigation of the migration of triclabendazole residues to milk products manufactured from bovine milk,and stability therein,following lactating cow treatment

Triclabendazole (TCB) is a flukicide used in the treatment of liver fluke in cattle; however, its use is currently prohibited in lactating dairy cows. In this study, following administration of 10% Fasinex (triclabendazole, Novartis Animal Health UK Ltd., Camberley, UK) the milk of 6 animals was used to manufacture dairy products, to ascertain if TCB residues in milk migrate into dairy products. The detection limit of the ultra-high-performance liquid chromatography-tandem mass spectrometry method used was 0.67 μg/kg. The highest concentrations of TCB residue measured, within the individual cow milk yield, was 1,529 ± 244 µg/kg (n = 6), on d 2 posttreatment. Days 2 and 23 posttreatment represented high and low residue concentrations, respectively. At each of these 2 time points, the milk was pooled into 2 independent aliquots and refrigerated. Milk products, including cheese, butter, and skim milk powder were manufactured using pasteurized and unpasteurized milk from each aliquot. The results for high residue milks demonstrated that TCB residues concentrated in the cheese by a factor of 5 (5,372 vs. 918 µg/kg for cheese vs. milk) compared with the starting milk. Residue concentrations are the sum of TCB and its metabolites, expressed as keto-TCB. Residues were concentrated in the butter by a factor of 9 (9,177 vs. 1,082 μg/kg for butter vs. milk) compared with the starting milk. For milk, which was separated to skim milk and cream fractions, the residues were concentrated in the cream. Once skim milk powder was manufactured from the skim milk fraction, the residue in powder was concentrated 15-fold compared with the starting skim milk (7,252 vs. 423 µg/kg for powder vs. skim milk), despite the high temperature (185°C) required during powder manufacture. For products manufactured from milk with low residue concentrations at d 23 posttreatment, TCB residues were detected in butter, cheese, and skim milk powder, even though there was no detectable residue in the milk used to manufacture these products. Triclabendazole residues were concentrated in some milk products (despite manufacturing treatments), exceeding residue levels in the starting milk and, depending on the storage conditions, may be relatively stable over time.     

Potentials to differentiate milk composition by different feeding strategies

To investigate the effect of the dietary intake of the cow on milk composition, bulk-tank milk was collected on 5 occasions from conventional (n = 15) and organic (n = 10) farms in Denmark and on 4 occasions from low-input nonorganic farms in the United Kingdom, along with management and production parameters. Production of milk based on feeding a high intake of cereals, pasture, and grass silage resulted in milk with a high concentration of α-linolenic acid (9.4 ± 0.2 mg/kg of fatty acids), polyunsaturated fatty acids (3.66 ± 0.07 mg/kg of fatty acids), and natural stereoisomer of α-tocopherol (RRR-α-tocopherol, 18.6 ± 0.5 mg/kg of milk fat). A milk production system using a high proportion of maize silage, by-products, and commercial concentrate mix was associated with milk with high concentrations of linoleic acid (LA; 19.7 ± 0.4 g/kg of fatty acids), monounsaturated fatty acids (27.5 ± 0.3 mg/kg of fatty acids), and a high ratio between LA and α-linolenic acid (4.7 ± 0.2). Comparing these 2 production systems with a very extensive nonorganic milk production system relying on pasture as almost the sole feed (95 ± 4% dry matter intake), it was found that the concentrations of conjugated LA (cis-9,trans-11; 17.5 ± 0.7 g/kg of fatty acids), trans-11-vaccenic acid (37 ± 2 g/kg of fatty acids), and monounsaturated fatty acids (30.4 ± 0.6 g/kg of fatty acids) were higher in the extensively produced milk together with the concentration of antioxidants; total α-tocopherol (32.0 ± 0.8 mg/kg of milk fat), RRR-α-tocopherol (30.2 ± 0.8 mg/kg of milk fat), and β-carotene (9.3 ± 0.5 mg/kg of milk fat) compared with the organic and conventional milk. Moreover, the concentration of LA (9.2 ± 0.7 g/kg of fatty acids) in milk from the extensive milk production system was found to approach the recommended unity ratio between n-6 and n-3, although extensive milk production also resulted in a lower daily milk yield.     

Effect of lactation number, year, and season of initiation of lactation on milk yield of cows hormonally induced into lactation and treated with recombinant bovine somatotropin

Records representing data from 1,500 barren Holstein cows over an 8-yr period from a large commercial dairy farm in northern Mexico were analyzed to determine the effects of lactation number and season and year of initiation of lactation on milk production of cows induced hormonally into lactation and treated with recombinant bovine somatotropin (rbST) throughout lactation. Peak and 305-d milk yields were also assessed as predictors of total milk yield in cows induced into lactation. A significant quadratic relationship was found between 305-d milk yield and number of lactation [7,607 ± 145 and 9,548 ± 181 kg for first- and ≥6-lactation cows, respectively; mean ± standard error of the mean (SEM)] with the highest production occurring in the fifth lactation. Total milk yields of cows with ≤2 lactations were approximately 4,500 kg less than milk yields of adult cows (the overall average ± standard milk yield was 13,544 ± 5,491 kg per lactation and the average lactation length was 454 ± 154 d). Moreover, 305-d milk production was depressed in cows induced into lactation in spring (8,804 ± 153 kg; mean ± SEM) and summer (8,724 ± 163 kg) than in fall (9,079 ± 151 kg) and winter (9,085 ± 143 kg). Partial regression coefficients for 305-d milk yield and peak milk yield indicated an increment of 157 kg of milk per lactation per 1-kg increase in peak milk yield (r² = 0.69). Neither peak milk yield (r² = 0.18) nor 305-d milk yield (r² = 0.29) was accurate for predicting total milk yield per lactation. Year, parity, and season effects had significant influence on milk yield of cows induced into lactation and treated with rbST throughout lactation, and peak milk yield can assist in the prediction of 305-d milk yield but not total milk yield. This study also showed that hormonal induction of lactation in barren high-yielding cows is a reliable, practical, and affordable technique in countries where rbST treatment and prolonged steroid administration of dairy cows are legally permitted.     

Effect of heating on the distribution of transforming growth factor-��2 in bovine milk

The objective of this study was to characterize the impact of heat treatments on the distribution of transforming growth factor-beta (TGF-??2) between cream and skim milk and between the casein and whey fractions of skim milk. Skimming removed 45% and 62% of the TGF-??2 from raw and pasteurized milks and only 8% of the total TGF-??2 in skimmed pasteurized milk was found in whey, compared to 37% in whey from raw skimmed milk. The TGF-??2 content of whey decreased as the heat treatment of the milk increased in intensity (thermization > pasteurization > UHT sterilization). Using milk held for 1 or 2 min at temperatures ranging from 57 to 84 °C, it was shown that TGF-??2 in the whey portion decreases at temperatures above 66 °C and becomes undetectable at temperatures higher than 76 °C. Altogether, these data on the heat-induced changes in TGF-??2 content of cream, skim milk, casein and whey reveal a potentially negative impact of certain heat treatments in developing TGF-??2-enriched fractions from milk.     

Dietary molasses increases ruminal pH and enhances ruminal biohydrogenation during milk fat depression

Feeding high-concentrate diets has the potential to cause milk fat depression, but several studies have suggested that dietary sugar can increase milk fat yield. Two experiments were conducted to evaluate the ability of dietary molasses to prevent milk fat depression in the presence of a 65% concentrate diet. In trial 1, molasses replaced corn grain at 0, 2.5, or 5% of diet dry matter in diets fed to 12 second-lactation Holstein cows (134 ± 37 d in milk) in a 3 × 3 Latin square design. Trial 1 demonstrated that replacing up to 5% of dietary dry matter from corn with molasses had positive effects on de novo fatty acid synthesis, increasing the yield of short- and medium-chain fatty acids during diet-induced milk fat depression. Increasing inclusion rate of molasses increased milk fat concentration, but decreased milk yield and milk protein yield. Trial 2 used 7 ruminally cannulated, multiparous, late-lactation Holstein cows (220 ± 18 d in milk) to evaluate effects of dietary molasses on ruminal parameters and milk composition, and also to assess whether increased metabolizable protein supply would alter these responses. Cows were randomly assigned to a dietary treatment sequence in a crossover split plot design with 0 and 5% molasses diets. Dietary treatments were fed for 28 d, with 16 d for diet adaptation, and the final 12 d for 2 abomasal infusion periods in a crossover arrangement. Abomasal infusions of water or AA (5 g of l-Met/d + 15 g of l-Lys-HCl/d + 5 g of l-His-HCl-H₂O/d) were administered 3 times daily for 5 d, with 2 d between infusion periods. Administration of AA had no effect on concentration or yield of any milk components. Addition of molasses increased milk fat concentration (2.71 vs. 2.94 ± 0.21%), but had no effect on yields of milk fat or protein. Dietary molasses decreased total volatile fatty acid concentration (141 vs. 133 ± 4.6 mM), decreased the molar proportion of propionate, and increased the molar proportion of butyrate in ruminal fluid. Molasses also increased ruminal pH (5.73 vs. 5.87 ± 0.06), decreased the yield of trans-10 C18:1, and increased the yield of trans-11 C18:1 in milk fat. These data provide evidence that molasses may promote mammary de novo fatty acid synthesis in cows fed high-energy rations by moderating ruminal pH and altering ruminal fatty acid biohydrogenation pathways.     

Comparative effects of two oral rehydration solutions on milk clotting, abomasal luminal pH, and abomasal emptying rate in suckling calves

The effect of adding an oral rehydration therapy (ORT) solution containing bicarbonate, citrate, and acetate to cow's milk on milk clotting, abomasal luminal pH, and abomasal emptying rate was determined in suckling calves. Six male Holstein-Friesian calves with abomasal cannulae, 5 to 13 d of age, were used in a crossover design. Calves were fed 2 L of cow's milk alone, milk with an ORT solution containing a low bicarbonate concentration (25 mmol/L), acetate (12 mmol/L), citrate (12 mmol/L), and glycine (7 mmol/L; group BACG), or milk with an ORT solution containing formate (58 mmol/L) and acetate (15 mmol/L) in randomized order. Clotting of milk was assessed in vivo and in vitro. Abomasal luminal pH was monitored continuously. Abomasal emptying rates were determined by using the change in abomasal luminal pH, acetaminophen absorption, and glucose absorption. The addition of a BACG-ORT solution to cow's milk increased in vitro clotting time by approximately 6 min. All 3 test solutions clotted in vivo by 15 min after the beginning of suckling. The addition of a BACG-ORT solution to cow's milk increased the pH of cow's milk and abomasal fluid by approximately 0.3 pH units. The addition of a BACG-ORT or a formate and acetate-ORT solution to cow's milk increased solution osmolality and slowed the rate of abomasal emptying. We concluded that the addition of BACG-ORT solution to cow's milk did not affect milk clotting in vivo. Recommendations based on the results of in vitro studies that bicarbonate- or citrate-containing ORT solutions should not be fed concurrently with cow's milk do not appear to be relevant to in vivo conditions when 2 L of a low-bicarbonate (25 mmol/L), low-citrate (12 mmol/L) ORT solution is fed.     

Soymilk as a novel milk replacer to stimulate early calf starter intake and reduce weaning age and costs

The primary objective was to determine the effects of partial replacement of whole milk with soymilk on preweaning calf performance and weaning costs. Following 3 d of colostrum and transition milk feeding, 18 male and 9 female neonatal Holstein calves (41.6 ± 1.6 kg of body weight; mean ± SE) were assigned in a completely randomized design to 3 treatments offered at 10% of body weight (wet basis) including 1) whole milk (control), 2) 75% whole milk + 25% soymilk (S25), or 3) 50% whole milk + 50% soymilk (S50). The weaning criterion was defined as the calf age at a daily intake of ≥900 g of starter concentrate. During the first 2 wk of the experiment, treatments did not differ in starter intake and fecal score. Calves fed S25 gained similar amount of body weight as calves fed whole milk diet. By 49 d of age, also, calves on S25 gained similar body weight as did calves on whole milk diet. Calves on S25 and S50 achieved the weaning criterion, respectively, about 10 and 12 d earlier than did peers on whole milk. The soymilk-fed calves consumed less milk than control calves to meet the weaning criterion owing to promoted starter intake. Feed-related weaning costs dropped by about 35% when soymilk was fed because whole milk was about 50% more expensive than both soymilk and starter concentrate. Feeding soymilk at up to 50% of the milk diet maintained health during the first 2 to 4 wk of age when the neonate calf is highly sensitive to nonmilk proteins and plant antinutrients. Results introduce soymilk as an economic partial substitute for whole milk in calf-raising facilities.