Water sorption and glass transition properties of spray dried lactose hydrolysed skim milk powder

The moisture sorption behaviour and glass transition temperature of spray dried skim milk powder with hydrolysed lactose (SMPHL) were determined. Spray drying of skim milk with hydrolysed lactose resulted in very low cyclone recovery of 25% and a large amount of powder remained stuck inside the spray dryer. The equilibrium moisture content of SMPHL was lower than that of lactose for each range of water activity when humidified for 21 days at 23 °C using saturated salt solutions. Unlike lactose, SMPHL did not lose water when the water activity exceeded 0.432 and no crystallization was noticed at water activity ?0.753. The sorption isotherm data for SMPHL fitted well with the BET and GAB models with monolayer moisture contents of 7.55 and 8.27 g/100 g, respectively. The glass transition temperature of anhydrous SMPHL was 49 °C. The critical water activity and moisture content for SMPHL were 0.15 and 2.4 g/100 g dry solid, respectively. The low critical values indicated hydrolysis of lactose necessities maintenance of very low moisture of powder for its long-term stability.     

全脂乳粉和脱脂乳粉在1kHz～10MHz下的介电特征研究

分别研究了各4种不同品种的全脂乳粉和脱脂乳粉在1kHz～10MHz波段的介电特性。结果发现:随着频率的增加,全脂乳粉和脱脂乳粉的ξ’和ξ″值呈单调递减趋势;全脂乳粉的ξ’和ξ″值都高于脱脂乳粉,相同类型乳粉各品种间的ξ’和ξ″差异不大;全脂乳粉的ξ″值在103～105Hz频率段减小趋势明显,且ξ″值的对数与频率的对数成线性反比关系,而脱脂乳粉无此规律;全脂乳粉和脱脂乳粉的穿透深度Dp随频率的提高而减小,两类乳粉的介电特性差异可能与它们各自的脂肪和乳糖含量有关。     

不同奶茶体系共存物对大豆分离蛋白性质的影响

为解决大豆分离蛋白在奶茶体系中稳定性较差的问题,本文探究了奶茶体系中共存物(酪蛋白、单甘脂、奶油、茶多酚、糖类、盐类、奶粉、红茶粉)对大豆分离蛋白乳化性(乳化活性和乳化稳定性)的影响。并通过乳状液ζ-电位和粒径的测量,探讨奶茶体系共存物与大豆分离蛋白相互作用及对其乳化性的影响规律。结果表明:在酪蛋白、茶多酚、乳糖添加量分别为0.2%、0.06%、0.1%时大豆分离蛋白乳化活性最小;在单甘脂、卡拉胶、氯化钠、脱脂奶粉添加量分别为0.15%、0.02%、0.02%、2%时大豆分离蛋白乳化稳定性最大;在乳糖添加量为0.1%时大豆分离蛋白乳化稳定性最小;在酪蛋白、茶多酚、乳糖添加量分别为0.2%、0.06%、0.1%时乳状液ζ-电位绝对值最小;在单甘脂、卡拉胶、碳酸镁添加量分别为0.15%、0.02%、0.01%时乳状液ζ-电位绝对值最大;在柠檬酸钠添加量为0.02%时,乳状液平均粒径最大,在碳酸镁、脱脂奶粉添加量分别为0.01%、2%时,乳状液平均粒径最小。奶茶体系中不同的共存物影响了乳状液的双电层结构,进而改变了大豆分离蛋白的乳化性。     

Influence of skimmed milk concentrate replacement by dry dairy products in a low‐fat set‐type yoghurt model system. Use of caseinates,co‐precipitate and blended dairy powders

Yoghurt fortification with caseinates, co‐precipitate and blended dairy powders in a low‐fat yoghurt model system was studied. These dairy products were characterised for pH, moisture, lactose, mineral and protein fractions. Milk proteins were characterised by polyacrylamide gel electrophoresis (SDS‐PAGE) and isoelectric focusing (IEF). Minerals such as Na, Ca, K and Mg were analysed by atomic absorption spectroscopy. Yoghurts were formulated using a skimmed milk concentrate as a milk base enriched with different dry dairy products up to 43 g kg⁻¹ protein content. The percentage of skimmed milk concentrate replaced with dry dairy products in the mix was between 1.37 and 6.35%. Yoghurts enriched with caseinates had higher viscosity and syneresis index (56.81 Pa s and 548.8 g kg⁻¹ respectively) than yoghurts based on concentrated skimmed milk fortified with co‐precipitate (39.00 Pa s and 392.9 g kg⁻¹) or blended dairy products (33.25 Pa s and 431.8 g kg⁻¹). One blended dairy product was tested to manufacture low‐fat yoghurt on an industrial scale, yielding good rheological properties (high viscosity‐consistence, 37.77 Pa s, and low syneresis index, 450 g kg⁻¹) and lower cost than traditional enrichment with skimmed milk powder. © 2000 Society of Chemical Industry     

Commercial Mineral Enhanced Dairy By‐Products as Sodium Replacers,Antioxidants and Calcium Fortifiers in Sausages

Sausages are perceived as high in Na and with a too high Na:K ratio. Frankfurter type sausages are regarded as important contributors of sodium in the diet and thereby of health risks. Surplus products from the dairy industry are various mineral powders enriched in either potassium, calcium, or phosphate and include various amounts of lactose. Sausages were produced at 3 sodium levels (equivalent to 13, 15, and 17 g NaCl/kg sausage) using 4 different milk ingredients (a dried skimmed milk powder, a calcium enriched milk powder, a potassium enriched powder, and a lactose enriched powder). The sausages with added calcium and potassium enriched milk powders resulted in the hardest sausages when compared at the same sodium level. Milk mineral addition also produced whiter and less red sausages. No effect on rancidity after 6 wk at chill (4 °C) storage was observed by adding milk minerals, when compared with adding dried skimmed milk powder. A significant advantage of using these milk minerals in sausages is that the Na:K ratio can be reduced from an unhealthy (in this study 36) to a far healthier ratio ( ? 2) with limited or no taste changes. High additions of milk calcium (6 g/kg), where Ca‐phosphates prevail, added as milk mineral, had no influence on sensory bitterness or aftertaste as typically observed for CaCl₂ additions. Ca additions to sausages are presently presumed to be an advantage with respect to human nutrition.     

抹茶牛奶饮料配方优化

采用模糊数学分析法对抹茶原料进行筛选,以奶粉、抹茶为主要原料制成蛋白含量为2.0 g/100 g的抹茶牛奶饮料。通过单因素实验研究全脂奶粉和脱脂奶粉添加比、白砂糖添加量、抹茶添加量、稀奶油添加量、复配增稠稳定剂添加量对感官评价的影响。通过响应曲面法得到最佳配方:全脂奶粉和脱脂奶粉添加比为4.3:1,白砂糖添加量为6.16%,抹茶添加量为0.81%,稀奶油添加量为0.5%,复配增稠稳定剂添加量0.19%,验证实验的感官评分为85.1分。对最优配方所得抹茶牛奶饮料进行139 ℃ 4 s的超高温杀菌,微生物检测结果合格,蛋白质含量为2.0 g/100 g,固形物含量为12.5%,pH为6.85。所得抹茶牛奶饮料颜色淡绿,香味醇厚,甜度适宜,口感细腻。货架期口感品评和稳定性观察结果表明,产品可以满足6个月保质期。     

低乳糖益生菌乳粉制备研究

本实验以全脂牛奶为原料,探究低乳糖高益生菌乳粉的制备工艺,考察水解温度、pH、时间和乳糖酶添加量对水解率的影响.同时通过海藻酸钠-大豆分离蛋白复配壁材微胶囊包埋益生菌,各自制备完成后分别真空冷冻干燥低乳糖牛乳和益生菌微胶囊,干燥结束将低乳糖乳粉与益生菌微胶囊粉按质量比7:1的比例混合制得低乳糖益生菌乳粉.结果表明,牛乳...     

Viability, efficacy, and storage stability of freeze-dried biocontrol agent Candida sake using different protective and rehydration media

Viability, efficacy against Penicillium expansum on Golden Delicious apples, and storage stability of freeze-dried Candida sake strain CPA-1 were studied. The effect of several protective agents and rehydration media was investigated in the freeze drying of C. sake. Skimmed milk at 10% concentration was a good rehydration medium for all protectants tested. In general, good viability results were obtained when the same solution was used as a protectant and as a rehydration medium. The best survival was obtained when C. sake cells were protected with 10% lactose + 10% skimmed milk and rehydrated with skimmed milk (85% viability). The potential for biocontrol of the best freeze-dried treatments against P. expansum on apples was compared with that of fresh cells. Freeze-dried treatments at 1 x 10(7) CFU/ml reduced the incidence of decay by 45 to 66%. The best biocontrol effect was obtained with cells that had been freeze dried using 10% lactose + 10% skimmed milk as a protectant and 1% peptone as a rehydration medium, with a 66% reduction in rot incidence. However, in all treatments, the efficacy of freeze-dried cells was significantly lower than fresh cells. The stability of freeze-dried samples decreased during storage and was influenced by storage temperature. In the best treatment, storage of C. sake cells for 60 days at 4 degrees C resulte in final concentrations of 2.5 x 10(8) CFU/ml, which was a 10-fold reduction in relation to the initial starting concentration of cells prior to freeze drying.     

益生菌发酵枣粉喷雾干燥条件的优化

以植物乳杆菌（Lactobacillus plantarum）、凝结芽孢杆菌（Bacillus coagulans）混菌对大枣进行液态发酵,通过单因素试验研究喷雾干燥进口温度、雾化流量、蠕动泵转速和脱脂乳粉添加量对益生菌发酵枣粉出粉率、感官评定、含水量、堆积密度及活菌数的影响,确定喷雾干燥进口温度、雾化流量、蠕动泵转速和脱脂乳粉添加量4个因素为自变量,感官评分为响应值进行响应面优化。结果表明,喷雾干燥制备益生菌发酵枣粉的最优参数为喷雾干燥进口温度150 ℃,雾化流量473 L/h,蠕动泵速20%,脂乳粉添加量2.5%。在此优化条件下,益生菌发酵枣粉出粉率为39.15%、感官评分为95.6分、含水量3.82%、堆积密度为0.251 g/mL、活菌数为1.78×109 CFU/g。     

莱茵-埃农氏法和高效液相色谱-示差折光法检测奶粉中乳糖和蔗糖的比较研究

选用市售同种品牌不同年龄段的奶粉,采用莱茵-埃农氏法和高效液相色谱-示差折光检测法对其乳糖和蔗糖进行测定,分析乳糖和蔗糖的差异,并对两种分析方法的结果进行比较,为奶粉中乳糖和蔗糖的检测方法提供依据。结果表明,莱茵-埃农氏法和高效液相色谱-示差折光检测法相比,高效液相色谱-示差折光检测法测定乳糖和蔗糖含量的准确度更高,蔗糖和乳糖的线性范围均为2～12 mg/mL,相关系数分别为0.999 3、0.999 6,精密度实验结果表明,相对标准偏差分别为2.53%、3.81%,平均加样回收率分别为99.70%、101.06%。高效液相色谱-示差折光检测法结果准确、分析时间短、前处理简单,适用于快速测定奶粉中蔗糖和乳糖含量。     

Process for calcium retention during skim milk ultrafiltration

Lactose is separated from milk or other fluid dairy products for a variety of reasons. Ultrafiltration is a known process of removing lactose from these products. However, during ultrafiltration, valuable minerals, such as calcium in soluble form, are also lost into permeate. In this study, a process was developed in which first the lactose reduction in skim milk was achieved by ultrafiltration (4x volumetric concentration) using a 10-kDa membrane. Then, the calcium present in permeate was precipitated using one of three methods: 1) heat treatment, 2) pH adjustment, or 3) a combination of pH adjustment and heat treatment to permeate, then recovered by refiltering permeate. The process was first developed at laboratory scale, and then its applicability was tested at the pilot scale. Skim milk, retentates, permeates, and the treated permeates were analyzed for total solids, ash, protein, or total nitrogen, calcium, and lactose content. About 76% of the total lactose and about 16% of the calcium present in skim milk permeated through the membrane during ultrafiltration. The three treatments applied produced white precipitates and turned the clear permeates turbid. On refiltering the treated permeates approximately 42, approximately 50, and approximately 70% of the total calcium present could be recovered from 1) heat-treated, 2) pH-adjusted, and 3) pH-adjusted and heat-treated permeates, respectively. There was no marked change in the lactose content due to any of the three treatments and subsequent refiltering of the treated permeates.     

Influence of skimmed milk concentrate replacement by dry dairy products in a low fat set‐type yoghurt model system. I: Use of whey protein concentrates,milk protein concentrates and skimmed milk powder

Ten commercial samples of dry dairy products used for protein fortification in a low fat yoghurt model system at industrial scale were studied. The products employed were whey protein concentratres, milk protein concentrates, skimmed milk concentrates and skimmed milk powder which originated from different countries. The gross chemical composition of these dried products were determined, including polyacrylamide gel electrophoresis (SDS‐PAGE) and isoelectric focusing of the proteins, and minerals such as Na, Ca, K and Mg. Yoghurts were formulated using a skim milk concentrated as a milk base enriched with different dry dairy products up to a 43 g kg⁻¹ protein content. Replacement percentage of skim milk concentrated by dry dairy products in the mix was between 1.49 and 3.77%. Yoghurts enriched with milk protein concentrates did not show significantly different viscosity (35.12 Pa s) and syneresis index (591.4 g kg⁻¹) than the two control yoghurts obtained only from skimmed milk concentrates (35.6 Pa s and 565.7 g kg⁻¹) and skimmed milk powder (32.77 Pa s and 551.5 g kg⁻¹), respectively. Yoghurt fortified with the whey protein concentrates, however, was less firm (22.59 Pa s) and had less syneresis index (216 g kg⁻¹) than control yoghurts. Therefore, whey protein concentrates may be useful for drinking yoghurt production. © 1999 Society of Chemical Industry     

Fermentation of specially formulated milk with single strains of bifidobacteria

A number of strains of bifidobacteria have been used to ferment milk to a yoghurt-like product. The milk used for fermentation was fortified with whey protein and threonine. It was prepared by mixing skimmed milk and cheddar cheese whey which had been concentrated using ultrafiltration membranes which allowed lactose to permeate. A 2 percent inoculum was used, and fermentation was carried out at 37° C overnight. The resulting products resembled voghurt, having good consistency. 'walnutty' aroma (acetaldehyde). and pleasant acidity.     

Production and evaluation of some physicochemical parameters of peanut milk yoghurt

The peanut milk for yoghurt production was prepared by fortifying peanut milk (∼12 g/100 g total solids) with 4 g/100 g skimmed milk powder. The final product was subjected to physicochemical analysis using cow milk yoghurt (CMY) as a control throughout the study. Peanut milk yoghurt (PMY) had higher protein content, fat, water holding capacity and lower susceptibility to Syneresis than CMY. PMY had lower lactose level (1.73 g/100 ml) compared to CMY (4.93 g/100 ml). Generally both PMY and CMY had high mineral composition and contained high amounts of essential amino acids. PMY also contained a higher proportion of unsaturated fatty acids than saturated fatty acids as compared to CMY. Therefore, in terms of fatty acid composition, PMY could be considered to be more health promoting than CMY. Sensory evaluation revealed that though PMY had better sensory texture scores than CMY, its sensory appearance, flavor and overall acceptability scores were lower than those of CMY.     

Lactose,glucose and galactose content in milk,fermented milk and lactose-free milk products

Lactose, glucose and galactose contents in milk and fermented milk products and their lactose-free alternatives, were determined. Storage of products up to the best-before dates had no effect on carbohydrate composition. Total galactose content in yoghurt, i.e., free galactose plus the galactose moiety of lactose, was 2.3–2.4 g 100 g⁻¹ (94–95% of that in milk), whereas that in Swedish soured milk and kefir was 1.9–2.0 g 100 g⁻¹ (75–79% of that in milk). Lactose levels in lactose-free milk and fermented milk products were below or close to detection limits for all products. Only small differences in total galactose content existed for the lactose-free alternatives of milk, yoghurt and filmjölk, all with average total galactose contents of 1.3–1.4 g 100 g⁻¹ (55–60% of that in milk). In contrast, lactose-free kefir had the same galactose content as milk, 2.4 g 100 g⁻¹.     

Thickening of molten white chocolates during storage

When white chocolates are kept molten in storage tanks, problems can arise due to uncontrolled thickening and solidifying of the chocolate mass. The thickening of molten white chocolate was simulated on a laboratory scale using a rotational rheometer under static conditions, interrupted by short shear periods to measure the increasing viscosity. Several chocolates having different dairy components and fat contents were investigated for their tendency to thicken. In addition, sorption isotherms for white chocolates were obtained using Dynamic Vapour Sorption at different temperatures. The sorption isotherms showed the presence of amorphous lactose in all the chocolates that were manufactured from milk powders. Moisture that is released during the crystallisation of amorphous lactose causes stickiness and agglomeration of the neighbouring particles and starts the thickening process. This process is highly temperature-dependent. On elevating the temperature the lactose crystallisation occurs at lower relative humidities. In order to reduce the tendency of white chocolate to thicken, a high free fat level should be maintained, based on a high total fat content and on the use of high free fat milk powders, preferably roller-dried whole milk powders or the combination of skimmed milk powder and anhydrous milk fat.     

Thickening of molten white chocolates during storage

When white chocolates are kept molten in storage tanks, problems can arise due to uncontrolled thickening and solidifying of the chocolate mass. The thickening of molten white chocolate was simulated on a laboratory scale using a rotational rheometer under static conditions, interrupted by short shear periods to measure the increasing viscosity. Several chocolates having different dairy components and fat contents were investigated for their tendency to thicken. In addition, sorption isotherms for white chocolates were obtained using dynamic vapour sorption at different temperatures. The sorption isotherms showed the presence of amorphous lactose in all the chocolates that were manufactured from milk powders. Moisture that is released during the crystallization of amorphous lactose causes stickiness and agglomeration of the neighbouring particles and starts the thickening process. This process is highly temperature-dependent. On elevating the temperature the lactose crystallization occurs at lower relative humidities. In order to reduce the tendency of white chocolate to thicken, a high free-fat level should be maintained, based on a high total fat content and on the use of high free-fat milk powders, preferably roller-dried whole milk powders or the combination of skimmed milk powder and anhydrous milk fat.     

Comparison of Rat Hepatic Cholesterol Biosynthesis During Skim Milk Versus Whey Permeate Ingestion

Whey permeate is an ultrafiltrate of whey that is devoid of protein but contains lactose, salts, and other soluble low molecular weight compounds. These experiments compared cholesterol concentrations of blood plasma, hepatic lipids, and hepatic cholesterol biosynthesis of rats ingesting skim milk powder versus whey permeate powder. Groups of young male rats weighing 90 to 92 g were fed a casein-based diet into which skim milk powder or whey permeate powder was incorporated isocalorically. No effects of skim milk or whey permeate on plasma cholesterol concentrations were observed at any time during 5-wk of feeding. However, 3-hydroxy-3-methylglutaryl coenzyme A reductase activity was increased by either skim milk or whey permeate feeding. Hepatic cholesterol, triglyceride, and phospholipid concentrations at wk 5 were unchanged. Plasma and hepatic cholesterol responses of rats to whey permeate ingestion are similar to those that occur with skim milk consumption, and plasma and hepatic cholesterol concentrations do not reflect necessarily an increase in hepatic cholesterol biosynthesis.     

Replacement of skimmed milk with hydrolyzed fish protein and Nixtamal in milk substitutes for dairy calves

Two experiments were conducted with 3- to 5-d-old Holstein male calves. In Experiment 1, 15 calves were assigned to three dietary treatments. The control diet was based on sodium caseinate, lard, and cerelose. In the other diets, either 50% or all carbohydrates were replaced by lime-treated corn flour (Nixtamal). In Experiment 2, 35 calves were assigned to dietary treatments in which 0, 50, or 67% low heat skimmed milk protein was replaced by hydrolyzed fish protein; for the replacement diets, Nixtamal was incorporated at 25 or 35% of the dry matter. Control diet protein was entirely from skimmed milk. Milk substitutes provided the only feed during the 8-wk experiment. In Experiment 1, body weight gain and feed efficiency declined when Nixtamal completely replaced skimmed milk but remained unchanged at 50% substitution. Substitution of Nixtamal for skimmed milk powder decreased nitrogen and carbohydrate digestibility; but digestibility improved with age. In Experiment 2, replacing up to 67% of skimmed milk protein with partially hydrolyzed fish protein concentrate had no effect on body weight gain but decreased feed efficiency linearly at 8 wk and reduced dry matter, nitrogen, and fat digestibility. Nixtamal can replace up to 50% of skimmed milk carbohydrates without detrimental effect on growth rate, feed efficiency, and diarrhea, but digestibility might be reduced. Concurrent replacement of up to 67% of skimmed milk protein with partially hydrolysed fish protein concentrate would be feasible for newborn calves gaining 450 g/d, despite lower nitrogen digestibility.     

枯草芽孢杆菌Prob1822复合抗热保护剂的研究

以枯草芽孢杆菌（Bacillus subtilis）Prob1822为研究对象,以热诱激处理（55 ℃热处理10 min）稳定期菌体存活率为评价指标,通过单因素试验和响应面法研究枯草芽孢杆菌Prob1822复合抗热保护剂的组成。结果表明,单一抗热保护剂以海藻糖、蔗糖及脱脂奶粉抗热保护效果较好;利用响应面法优化复合抗热保护剂配方为海藻糖9.0%、蔗糖5.0%和脱脂奶粉6.8%。在此最优条件下,菌体存活率为（95.24±0.84）%。糖类与蛋白质联用作为复合抗热保护剂比单一保护剂抗热保护效果更好,可减轻喷雾干燥对菌体亚细胞结构及生物大分子损伤,实现枯草芽孢杆菌的抗热保护。