酶法改性酪蛋白及婴儿配方乳粉的研究

本文针对国内现有配方乳粉生产工艺中存在的弊病而提出的。通过参考国内外有关资料，研制出酶法改性酪蛋白婴儿配方乳粉新工艺，用固定化蛋白酶对牛乳中的酪蛋白预消化，使之转化为易被消化吸收的类乳清蛋白，通过控制蛋白质的水解度，使酪蛋白与类乳清蛋白的比例达到４０：６０，从而避免添加乳清粉的传统工艺。本文介绍了蛋白酶的选择、酶的固定化工艺、及新型婴儿配方乳粉的生产工艺，并研究了改性酪蛋白与乳清蛋白的有关性质，证明了酪蛋白经蛋白酶水解后变成了分子量较小的多肽，其许多相关性质完全可以与乳清蛋白相媲美，甚至优于乳清蛋白，通过调整脂肪酸含量及强化维生素和微量元素，使整个配方更接近母乳，并符合国家有关婴幼儿配方食品标准。     

Dairy powder rehydration: influence of protein state, incorporation mode, and agglomeration

A simplified method to study rehydration was used on different dairy powders. The method involved dispersing powder in a stirred vessel equipped with a turbidity sensor. The changes of turbidity occurring during powder rehydration highlighted the rehydration stage, and the influence of the proteins’ state on rehydration was clarified. Casein powders had a quick wetting time but very slow dispersion, making the total rehydration process time-consuming. On the other hand, whey powders were found to have poor wettability but demonstrated immediate dispersion after wetting. Mixing casein (80%) and whey (20%) before spray drying greatly improved rehydration time compared with casein powder; whereas mixing whey powder with casein powder at the same ratio after spray drying caused a dramatic deterioration in the rehydration properties. Moreover, agglomeration was found to significantly improve the rehydration time of whey protein powder and to slow down the rehydration time of casein powder. These opposite effects were related to the rate-controlling stage (i.e., wetting stage for whey protein and dispersion stage for casein).     

Feasibility of Spray Drying Concentrated Acid Whey After Nanofiltration

Concentration of acid whey and crystallisation of lactose followed by spray drying in the production of acid whey powder are severely restricted by the presence of lactic acid (LA) and calcium (Ca). These compounds cause stickiness during spray drying. The present study examined the effects of removing LA and Ca by membrane processing to varying extents in order to improve the feasibility of the spray drying of an acid whey stream. Spray drying of unaltered acid whey achieved a powder recovery of ~?18% in the collection vessel and ~?31% in the cyclone. Removal of LA and Ca by 30 and 40%, respectively, by nanofiltration significantly increased the powder recovery to ~?58% in the collection vessel. Powder particles decreased in size giving a D[4,3] of ~?18 μm, with SEM images confirming the presence of well separated spherical powder particles. A solubility of >?75% was also achieved. However, removing Ca >?60% compromised the spray drying process. FTIR analysis suggested that water molecules in the hydration layer of lactose and the structural changes of both lactose and protein molecules at the molecular level appeared to play an important role in governing the extent of the drying feasibility. In addition, the formation of calcium lactate may restrict the diffusion of lactose molecules, once the appropriate stoichiometry was reached. Thus, manipulating LA and Ca concentrations in a particular acid whey stream can improve the spray drying process and production of a non-sticky acid whey powder.     

超滤膜分离技术回收乳清蛋白工艺研究

研究利用超滤膜分离技术,从干酪素乳清废弃液中回收乳清蛋白,通过对不同超滤膜性能的比较,选择最佳的超滤膜材料、工艺流程以及运行参数,并测得分离效果。结果表明:采用PW2540型聚醚砜卷式超滤膜较好,其最佳工艺参数为操作温度35℃,操作压力0.5MPa,且超滤膜透液通量较高,运行稳定。乳清蛋白粉中蛋白质含量72.40%,灰分3.85%。经红外光谱检测证明乳清蛋白粉品质得到较大程度的提高。每吨乳清废弃液中可回收乳清蛋白粉5.13kg,具有较好的经济效益及减排环保效益。     

Optimization of Yogurt Production Using Demineralized Whey

The effect of three independent fermentation variables: demineralized whey powder (0.0; 1.5 and 3.0%), lactic culture concentration (1.0; 2.0 and 3.0%) and mix treatment temperature (85; 90 and 95°C) was studied. Fermentation time to reach pH 4.3, instrumental consistency and appearance, visual consistency and taste of the product were evaluated. Product consistency increased as mix treatment temperature increased and demineralized whey powder decreased. The powder had a stronger influence on instrumental consistency than did temperature. Appearance was better when whey powder was used at 1.4 to 1.6%. Visual consistency decreased as whey powder increased but addition of demineralized whey powder did not negatively affect yogurt flavor.     

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.     

牦牛乳清固体饮料的配方设计及优化

为了充分利用牦牛乳清,开发出一种良好口腔刺激感的片状固体饮料。以牦牛乳生产甜干酪时排出的副产物乳清液为基础原料,45 ℃旋转蒸发,-55 ℃真空冻干成粉。采用感官加权总分为评价指标,通过单因素试验、L₉(34)正交试验和Box-Behnken响应面优化,确定饮料片的最佳工艺配方。结果表明,乳清粉添加量、阿斯巴甜添加量和崩解剂添加量对饮料片感官加权评分影响极显著(P<0.001)。最佳工艺参数为:28.75%的乳清粉,43.75%的崩解剂,2.75%的阿斯巴甜,8%的聚乙二醇6000,酸碱比为1.24:1,感官加权总分为4.04。产品直径约10 mm,重约0.50 g/片,崩解时间小于120 s,发泡量大于8 mL,料液pH为6.42,色泽透亮,香味怡人,口感清爽。该结果可作为指导乳清固体饮料生产的理论依据,为功能性乳清的开发提供应用潜能。     

Spray-dried whey protein/lactose/soybean oil emulsions. 2. Redispersability, wettability and particle structure

In the present paper redispersion and wettability experiments of spray-dried whey protein-stabilized emulsions are presented. Emulsion droplet size after redispersion gives information about eventual coalescence between emulsion droplets in the powder matrix during drying or storage, resulting in an increase in emulsion droplet size after redispersion. Results from redispersion experiments are combined with previously presented knowledge about powder surface composition and particle structure to elucidate internal processes in the powder matrix and external processes on the powder surface during drying and storage of whey protein powder. The results show that with addition of lactose to whey protein-stabilized emulsions, emulsion droplet structure remains intact in the powder matrix during drying since the emulsion droplet size in the redispersed spray dried emulsion is unchanged. In the absence of lactose there is a growth in emulsion droplet size after redispersion of the spray-dried whey protein-stabilized emulsion, showing that a coalescense of emulsion droplets occurs during the drying or redispersion process. Storage of the whey protein-stabilized powders in a humid atmosphere (relative humidity 75%, 4 days) induces changes in some powders. When the powder contains a critical amount of lactose there is a remarkable increase in emulsion droplet size after redispersion of humid stored powders compared with the emulsion before drying and with the redispersed dry stored powder. In addition, there is a release of encapsulated fat after humid storage of lactose-containing powders detected by electron spectroscopy for chemical analysis. For powders which do not contain any lactose there is no increase in emulsion droplet size after storage in a humid atmosphere compared with the redispersed dry stored emulsion. Addition of only a small amount of lactose prevents coalescence of emulsion droplets and the subsequent increase in droplet size during drying. If the lactose content is kept rather low neither an effect on the droplet size after storage under humid conditions nor a release of fat onto powder surfaces is detected. Furthermore, wettability of the spray-dried whey protein-stabilized emulsions by water is presented. It is concluded that it is beneficial to wettability in water to have as high a coverage of lactose on the powder surface as possible. In addition, a review of particle structure for powders of various composition is presented.     

Functional and technological aspects of whey powder and whey protein products

Commercial whey powder, whey protein concentrates and whey protein isolates (WPIs) were evaluated for certain functional properties and for their application in full‐fat and nonfat yoghurts. The functional properties of whey products varied, and the highest functionality was recorded in samples with high protein levels. Whey powder had the lowest foaming performance and emulsifying capacity, while WPIs possessed the best functional properties of all the other samples. Curd tension (CT), viscosity and syneresis were improved in yoghurts made using fortified cow's milk or reconstituted skim milk with any whey products, while whey powder had no impact on CT.     

低热脱脂奶粉的生产现状

综述了我国脱脂奶粉的的市场和生产现状,提出了向低热脱脂奶粉发展的方向,论述了加工条件对脱脂奶粉蛋白变性程度的影响以及国际上对奶粉热分级的规定和乳粉加工中乳清蛋白热变性及聚合物产生机理的研究进展。     

DNA-based qualitative and quantitative identification of bovine whey powder in goat dairy products

As one of the main ingredients in some milk powders, whey powder is sometimes added to pure goat milk products, which can cause health risks, economic fraud, and unfair competition of food industries. This study is the first to explore qualitative and quantitative methods to identify adulteration of bovine whey powder in goat dairy products based on DNA. We extracted DNA from whey powder using a modified DNA extraction method; this exhibited good quality and integrity, with purity of 1.53 to 1.75 and concentration of 122 to 179 ng/μL. Conventional PCR and real-time PCR were compared for qualitative detection of bovine whey powder; real-time PCR demonstrated sensitivity of 0.01 ng/μL, which was higher than the 0.05 ng/μL detected by the conventional PCR method. Furthermore, real-time PCR was conducted for DNA quantitative detection, with good linearity (R² = 0.9858) obtained for bovine whey powder contents from 0.1% to 30%. Relative error decreased with increase of the mixing proportion of whey powder; the coefficient of variation above 0.1% of the mixing ratio was close to or less than 5%; and the relative standard deviation of repeatability results was less than 5%. Considering the economic costs of testing, conventional PCR could be performed first, and samples with obvious intentional adulteration detected can be further accurately quantified by real-time PCR. Overall, this research provides a realistic and effective method for qualitative and quantitative identification of bovine whey powder in goat dairy products, thus laying a good foundation for verification of goat dairy product label claims and industrial control.     

Current trends in whey processing and utilization in Greece

Whey treatment began in Greece in 1998; in previous years, whey was considered only as effluent from cheese production, a part of which yielded whey cheeses. In 1998, the first whey powder plant started to operate successfully. The main physicochemical characteristics of whey from feta cheese production are illustrated, together with those of the 'cooked' whey, ie the serum remaining after whey cheese production. Quality standards for both types of whey are proposed. The drive for efficient whey processing is the unrelenting demand for whey products in the local market and the current status is described.     

Economic aspects of cheese making as influenced by whey processing options

Economic consequences of the cheese making process are illustrated through several sample calculations concerning processing of whey in relation to cheese making throughput and several whey processing alternatives. Small cheese plants with daily milk throughput of approximately 100 000 kg cannot economically justify the capital for water removal equipment. For small plants that have to convert whey to a dry product, alternatives include pre-concentrating with a reverse osmosis unit or a small plate evaporator and drying on a double roller dryer. The economics are evaluated at several price levels. At the upper scale of cheese plant size (2–3 million kg d⁻¹ of milk), the investment for whey processing is about half the total investment. Cash flows are calculated for electricity, natural gas and whey powder prices. Increased investment for further processing into whey protein concentrate and dried whey solubles or lactose is evaluated at several price levels.     

Demineralisation of whey by a combination of nanofiltration and anion‐exchange treatment: a preliminary study

Demineralisation is an important process for the utilisation of whey in the food industry. Sodium (Na⁺) and potassium (K⁺) ions pass through nanofiltration (NF) membranes in ion pairs with chloride (Cl^?) to maintain electroneutrality, but NF processing can only partially remove these ions from whey, because the total Na and K content of whey generally exceeds the Cl content. In this work, a preliminary study of a new demineralisation method was made. A reconstituted sweet whey powder solution was first treated by Cl‐form anion‐exchange resin to increase the molar ratio of Cl to Na and K from ~0.5 to ~1.0. Subsequently, NF removed >90% of Na and K from the anion‐exchange treated whey compared with <60% from the control whey. This new process could be useful for producing 70% demineralised whey with very low levels of the monovalent ions Na⁺, K⁺ and Cl^?.     

Spray-dried whey protein/lactose/soybean oil emulsions. 1. Surface composition and particle structure

Emulsions made of whey protein, lactose and soybean oil were spray-dried and the chemical surface composition of the dried powders estimated by electron spectroscopy for chemical analysis. In particular, the ability of whey protein to encapsulate fat was highlighted. Additionally, the structure of the spray-dried powder particles was studied by scanning electron microscopy. The powders were examined after storage in both dry and humid atmospheres (relative humidity 75%, 4 days). It was found that the ability of whey protein to encapsulate soybean oil is rather low compared with sodium caseinate, with a large part of the powder surface covered by fat after spray-drying. After storage in humid atmosphere there is a release of encapsulated oil onto the powder surface in most cases, and an increase in fat coverage. The release offat onto the powder surfaces causes the particle structure to change dramatically for powders containing a critical amount of lactose. Such powders agglomerate and lose structure completely. In comparison, powders containing no lactose storage under humid conditions also cause a release of fat onto the powder; however, in this case particle structure remains intact. Powders containing only a small amount of lactose, up to ~25% of emulsion dry weight, do not exhibit the release of fat onto the powder surfaces after storage under humid conditions and the structure of these powder particles does not change. The presence of lactose in whey protein-stabilized emulsions, however, does not increase fat encapsulation by whey protein, as reported earlier for sodium caseinate-stabilized emulsions that were spray-dried. During spray-drying of whey protein/lactose solutions there is a strong overrepresentation of surface-active whey protein on the powder surface. Whey protein coverage increases even further when the powders are stored under humid conditions, also making them lose structure.     

Isolation and characterization of whey phospholipids

A freeze-dried whey powder was produced by microfiltration of Cheddar cheese whey. A 0.2-micron ceramic membrane in a stainless steel housing unit was used to concentrate components > 400 kDa present in the whey. The experimental whey powder, derived from Cheddar cheese whey, and a commercial whey powder were subjected to proximate analysis, lipid classes, phospholipid classes, and fatty acid compositional analyses. Commercial whey powder and commercial soybean lecithin were subjected to an alcohol fractionation procedure in an effort to alter the ratio of phosphatidyl choline to phosphatidyl ethanolamine and the functionality of dairy phospholipids. The fractionation procedure produced an alcohol-insoluble fraction containing 84% phosphatidyl ethanolamine, whereas the alcohol-soluble fraction resulted in a decrease in the phosphatidyl choline to phosphatidyl ethanolamine ratio. The commercial whey contained a higher ratio of phospholipids to neutral lipids compared with the experimental whey. The classes of phospholipids present within the two wheys were similar, whereas the experimental whey contained a phosphatidyl choline content twice that of the commercial whey, and the phospholipids composition of both wheys differed from the milk fat globule membrane. Comparison of the phospholipids and fatty acid composition of the wheys with the soy lecithin revealed that although the wheys were similar to each other, they differed from the soy lecithin in both the classes of phospholipids present and in the fatty acid composition. These compositional differences may influence the functionality of whey phospholipids.     

Spray drying in the cheese industry

Advances in the application of spray drying in relation to the cheese industry are discussed. The technology of producing cheese powder is briefly covered, together with the production of skim milk powder suitable for subsequent conversion into cheese and the technology of processing whey into various dry products. A new process, called TIXOTHERM™, is described. TIXOTHERM™ is suitable for the processing of permeate, produced as a by-product from the ultrafiltration of whey or milk, into a non-hygroscopic powder. After evaporation to 60% total solids (TS), the permeate concentrate is subjected to a three-step process comprising concentration to 86% in the Rosinaire™ paddle dryer; holding, stabilization and curing in a screw conveyor with two augers; and finally drying and cooling in a combined back-mix/plug-flow fluid bed drier. In comparison with the traditional processes, TIXOTHERM™ provides significant savings in both energy (about 30%) and building costs (up to 75%).     

Crosslinking of whey protein by transglutaminase

Guinea pig liver transglutaminase (EC 2.3.2.13) was used to enzymically crosslink the whey protein alpha-lactalbumin, beta-lactoglobulin, blends of these protein fractions, whey proteins in powdered whey, and whey proteins in modified powdered whey. Transglutaminase actively crosslinked whey proteins over a wide pH range (6.5 to 8.0). Crosslinking gradually increased with increased incubation time to 4 h. Crosslinking was negligible with transglutaminase after 4 h of incubation. Reconstituted commercial whey and modified whey powders contained sufficient Ca2+ for crosslinking by .92 units transglutaminase/ml of reconstituted whey powder (2% protein) and modified whey powder solutions (1 to 5% protein). Reconstituted whey and modified whey powder (35% protein) served as protein sources for crosslinking by transglutaminase without further adjustment of pH or Ca2+. Dithiothreitol was required to crosslink the whey protein.     

Effectiveness of sweet ovine whey powder in increasing the shelf life of Amaretti cookies

The effect of sweet ovine whey powder on physical-chemical and textural changes during storage of Amaretti cookies is reported. The aim of the study was to study the impact of the ovine whey powder on the shelf life of cookies. Two batches of Amaretti cookies were prepared, with and without whey powder. Freshly baked Amaretti cookies were individually packaged with a high water vapour barrier film and stored for 120 days under controlled temperature/humidity conditions. Physico-chemical, textural and sensory changes were inspected at regular intervals during storage.The water-binding properties of ovine whey powder, as revealed by sorption isotherms and magnetic resonance imaging, resulted in delayed firming and increased shelf life of cookies with whey powder with respect to control cookies and did not influence the sensory properties. MRI allows visualizing differences in internal structure and proton distribution of the two batches of Amaretti cookies, pointing out the more homogeneous internal structure of the cookies where whey powder is added.     

Buttermilk as milk powder and whey substitute in compound milk chocolate: Comparative study and optimisation

The aim of this study was to investigate the optimal concentration of milk, whey and buttermilk powder by using mixture design for the formulation of compound milk chocolate. The influence of buttermilk as a milk and whey substitute on the main physicochemical parameters of compound milk chocolate was investigated. The optimisation of the variables indicated that using 35.660% milk powder, 27.957% whey powder and 36.383% buttermilk produced the optimum milk chocolate with the highest desirability without undesirable changes in the quality properties. Chocolates containing equal amounts of buttermilk and milk powder and also equal amounts of whey powder and buttermilk powder demonstrated high consumer acceptability.