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。     

Short communication: influence of transglutaminase on the heat stability of milk.

Skim milk powders were prepared from control and transglutaminase-treated skimmed milk. The heat stability of reconstituted transglutaminase-treated skimmed milk (9.0% total solids) was markedly increased in the pH region of minimum stability (pH 6.8 to 7.1) compared with control milk, while the heat stability of reconstituted concentrated transglutaminase-treated skimmed milk (22.5% total solids) increased progressively as a function of pH relative to control milk. The effect of transglutaminase treatment on the heat stability of skimmed milk may have commercial applications, but extensive research is necessary to gain a better understanding of the mechanism by which transglutaminase improves heat stability.     

Risk evaluation for staphylococcal food poisoning in processed milk produced with skim milk powder

The growth of S. aureus and the production of staphylococcal enterotoxin A (SEA) in skim milk concentrates stored at inappropriate temperatures in a recovery milk tank (tank for excess concentrated skim milk) used in the manufacture of skimmed milk powder were investigated. Also, it was estimated if a possible outbreak of food poisoning would occur if the contaminated skimmed milk powder was used in the manufacture of processed milk. Skim milk concentrates with milk solid content of 15, 25, and 35% were inoculated with S. aureus at 1-2 log CFU/ml and incubated at 15, 25, or 35 degrees C for 0 to 24 h with or without shaking. Bacterial growth and the level of SEA production were measured. At 35 degrees C with shaking, there was a significant difference (p<0.05) in one way layout analysis of variance, and it was demonstrated that the growth of S. aureus and SEA production could be milk solid content-dependent. Shaking accelerated the growth of S. aureus and SEA production at 35 degrees C. Generally, skim milk powder is produced by mixing a set percentage of skim milk concentrates (recovery milk) from the recovery milk tank into raw milk. If recovery milk contaminated with S. aureus at levels of 1-2 log CFU/ml is kept at 15 to 35 degrees C due to a power failure, it was estimated that processed milk consumption of 670-1200 ml, 420-1500 ml and 18-83 ml would trigger the onset of food poisoning symptoms when skim milk concentrates (recovery milk) are stored at 25 degrees C for 24 h, 35 degrees C for 10 h, and 35 degrees C for 24 h, respectively, during the production of the skim milk powder. Based on these consumption levels, it was concluded that, if recovery milk cannot be refrigerated and is stored at room temperature (25 to 35 degrees C), it must be used within 8 h and preferably within 6 h.     

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。     

脱脂凝固型酸奶的研制

研究了脱脂奶粉的复原方法、蛋白质含量、发酵剂接种量、发酵温度、牛奶粉末香精、稳定剂用量等对脱脂凝固型酸奶产品感官品质的影响,结果表明,采用优化条件为:脱脂奶粉在50℃下复原30 min,复原乳的蛋白含量为3.3％,发酵剂接种量为2％,稳定剂的添加量为0.8％,发酵温度为43℃,添加牛奶粉末香精乳特浓3#,可开发出风味口...     

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.     

Quarg production methods - past, present and future

The characteristics of quarg are described, with standard methods of manufacture of conventional quarg from skimmed milk. Various methods for increasing the yield of quarg are discussed, and it is concluded that the most promising alternative is the ultrafiltration of the skimmed milk to 17%–20% TS before coagulation. This would reduce processing costs as well as increasing yield. However, problems of abnormal organoleptic properties need to be resolved.     

Effect of milk fat and total solids concentration on the kinetics of moisture uptake by ready-to-eat breakfast cereal

Summary When immersed in milk, breakfast cereal easily take up moisture, lose their brittle texture and become soggy. Earlier comparative analysis of the moisture sorption by breakfast cereal immersed in water and milk indicated that milk solids might play an important role on the sorption kinetics. In this work, the moisture uptake by ready-to-eat corn breakfast cereal immersed in milk solutions, reconstituted from whole and skimmed milk powder, was measured under isothermal conditions at 5, 30 and 55 °C. Dilutions between 0.25 and 1.5 were tested, with the factor of dilution 1 corresponding to the standard recommended by the milk powder manufacturer. The Weibull probabilistic model adequately fitted the experimental data by appropriate choice of its variable parameters. The dependence of the model parameters on temperature and total solids concentration was assessed for both skimmed and whole milk. Fat was found to play a major role on the process mechanism, which was attributed to the deposition of a fat layer at the solid matrix surface, hindering water and solids uptake. Yet, for short times, moisture uptake proceeded at a similar rate both in skimmed and whole milk.     

Subject: 'Skim milk' Technology of skimmed milk evaporation

The paper seeks to show how the requirements of skimmed milk concentration are met in modern evaporators and how the type of plant used has developed over the years, the falling film tubular evaporator now being virtually standard. Very economical operation is now possible with sophisticated multiple-effect plants with thermocompression, and further economies are possible with mechanical vapour recompression. The importance of adequate wetting of heat transfer surfaces is discussed with regard to length of run and achievable concentration, and methods of maintaining correct wetting conditions are illustrated. Preheating is an important feature of such evaporators for both economy and control of final powder properties, and the methods adopted are described, Finally, the control of modern skimmed milk evaporators is considered briefly.     

马铃薯冲调营养粉配方优化

为探索一种适于高血脂、高血压人群食用的马铃薯冲调营养粉,采用正交试验进行配方优化。以感官评价为指标,考察马铃薯全粉、脱脂奶粉、核桃粉、黑芝麻粉、白砂糖的最佳配比。试验结果表明,马铃薯冲调营养粉的最佳配方为：马铃薯全粉15g、脱脂奶粉30g、核桃25g、黑芝麻粉10g及白砂糖12g。所得的产品呈均匀的灰白色,冲调性良好,口感细腻,气味清雅,香甜可口。     

芦荟山药酸奶的研制

芦荟山药酸奶是以库拉索芦荟、新鲜山药和脱脂奶粉为原料,用保加利亚乳杆菌和嗜热链球菌以1:1混合作为发酵剂进行乳酸发酵,制得的一种集芦荟、山药和酸奶于一体的新型保健乳品。通过单因素和正交试验对芦荟山药酸奶的配方和发酵工艺条件进行了优化。研究表明,芦荟山药酸奶的最佳发酵工艺条件为:乳酸菌接种量4%,发酵温度42℃,主酵时间5h;最佳配方为:粉水比为1:9,其中粉由山药粉和脱脂奶粉以4:6配比而成,白砂糖7%,芦荟汁10%,稳定剂为黄原胶0.20%、CMC-Na0.16%和海藻酸钠0.25%三者混合而成。在此工艺条件下制备的芦荟山药酸奶具有感官品质佳、稳定性好和营养丰富等特点。     

Instant infusion pasteurisation of bovine milk. II. Effects on indigenous milk enzymes activity and whey protein denaturation

Direct heat treatment of two milk types, skimmed and nonstandardised full‐fat, was performed by instant steam infusion and compared with indirect heating. Infusion conditions were temperatures of 72–120°C combined with holding times of 100–700 ms, and indirect heat conditions were 72°C/15 s and 85°C/30 s. The activity of indigenous enzymes such as alkaline phosphatase, lactoperoxidase, xanthine oxidase and γ‐glutamyl transpeptidase was evaluated. Infusion temperature was the main determinant of inactivation. Whey protein denaturation represented by β‐lactoglobulin increased significantly with infusion temperature. The nonstandardised milk had a higher denaturation rate than skimmed milk. The effect of instant infusion on pH and milk fat globule size in relation to whey protein denaturation and association is discussed.     

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.     

Influence of Preheating Skimmilk on Water-holding Capacity of Sodium Salts of Caseinates and Coprecipitates

The effect of different preheat treatments of milk on the water-holding capacity of the corresponding sodium caseinates made under laboratory conditions was investigated. Unheated skimmed milk, and milks heated under conditions ranging from 60°C to 120°C for 1 min, respectively, were used for the manufacture of the caseinates. Water-holding capacity was estimated using a method involving equilibration of the powder with excess water and measurement of the volume of released water. Water-holding progressively increased with heating, whereby with 120°C/1 min more than two-thirds of the dispersion volume tested was retained. The whey protein content of the caseinates also varied according to temperature and water-holding capacity.     

非活性双蛋白乳酸菌饮料配方的优化

以大豆分离蛋白和脱脂乳粉为原料,研制具有独特风味和营养价值的非活性双蛋白乳酸菌饮料。采用单因素和正交实验法对非活性双蛋白乳酸菌饮料的配方进行优化,以感官评分为指标,考察了脱脂乳粉、大豆分离蛋白粉、白砂糖及柠檬酸添加量对饮料感官评分的影响。实验结果表明:脱脂乳粉添加量2%、大豆分离蛋白粉添加量1%、白砂糖添加量8%以及柠檬酸添加量0.25%时,感官评分为97分,在此条件下研制出的非活性双蛋白乳酸菌饮料酸甜适口、风味独特、口感饱满,且具有丰富的营养价值。     

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     

巧克力非活性乳酸菌饮料的研制

研究了以脱脂奶粉、可可粉为主要原料,生产巧克力非活性乳酸菌饮料的生产工艺,通过试验确定了工艺参数。     

乳酸菌菌种的简便分离和培养

嗜热链球菌和保加利亚杆菌是酸乳制品的常用菌种,因其有共生关系,较难分离。用特殊的培养基如M17和MRS酸化培养基可以将此共生苗分离。本文介绍的培养基同样能起到分离的作用,且成分简单,取材方便。     

真空冷冻干燥法制备益生菌粉的冻干保护剂配方优化

为提高益生菌冻干粉存活率。本文采用真空冷冻干燥法,分别以植物乳杆菌SC1、凝结芽孢杆菌XP2、酿酒酵母菌SA1为实验菌株,研究冻干保护剂脱脂乳粉、低聚木糖、可溶性淀粉和V_C钠盐对三种益生菌冻干存活率的影响。通过单因素和正交试验筛选出最优组合。结果表明经-70℃预冷冻2 h,-50℃,10 Pa条件下冷冻干燥38 h,保护剂最佳配方组合分别为,植物乳杆菌:可溶性淀粉10%,V_C钠盐3%,脱脂乳粉12%,低聚木糖14%;凝结芽孢杆菌:低聚木糖8%,V_C钠盐4%,可溶性淀粉14%,脱脂乳粉8%;酿酒酵母菌:低聚木糖10%,V_C钠盐2%,脱脂乳粉12%,可溶性淀粉12%。添加最优保护剂组合,三株菌的冻干存活率分别为83.2%、83.7%和86.7%,活菌数均高于1.0×108 CFU/g,具有较好的应用价值。     

Kinetics of alkaline phosphatase and lactoperoxidase inactivation,and of beta-lactoglobulin denaturation in milk with different fat content

In the context of identifying intrinsic time temperature integrators (TTIs) for evaluating heat processing of milk, the extent to which milk fat content has an effect on alkaline phosphatase (ALP) and lactoperoxidase (Lpo) inactivation and on beta-lactoglobulin (beta-Ig) denaturation kinetics was studied. Inactivation and denaturation kinetics were analysed in whole, semi-skimmed and skimmed milk. In previous experiments (isothermal and non-isothermal heating conditions), heat inactivation of ALP and Lpo and heat denaturation of beta-Ig were found to follow first order kinetics. This allowed experimental design to be simplified. Data analysis was performed by non-linear regression and results were evaluated by construction of joint confidence regions. The possible effect of milk fat was illustrated by temperature time tolerance (TTT-) diagrams. Although initial ALP activity was lower in skimmed milk compared with semi-skimmed or whole milk, kinetics were comparable and fat content did not seem to substantially affect the ALP test result for pasteurized milk. Unlike ALP, Lpo inactivation and beta-Ig denaturation kinetics differed significantly in milk with different fat content. Differences between Lpo inactivation kinetics were relatively small and acceptable in the context of quantifying the process impact. Denaturation of beta-Ig, on the other hand, seemed to be enhanced at higher milk fat content (> 72 degrees C).