超滤浓缩乳清蛋白并分离乳糖的研究

采用管式超滤装置,选用切割分子量为20000的聚丙烯腈膜,对乳清进行了超滤浓缩试验。结果表明,降低乳清pH值可提高透液通量,把乳清调整至pH7．0,再离心除去不溶性钙盐,可获得最大透液透量。中性乳清经离心沉降后,在进口压力0.24MPa,温度45℃条件下浓缩180min,平均透液通量达到29．1kg／m2·h,蛋白质含量提高到2.85％,透过液中乳糖浓度变化不大。     

Cultured dairy products: an overview of their gelation and texture properties

There has been considerable research in recent years on the texture and sensory properties of cultured dairy products. This article gives an overview of the formation of structure in cultured products (primarily in relation to yoghurt, cottage cheese and sour cream) and suggests approaches to controlling their textural properties. Two important themes concerning this topic are first that the casein micelles are the building blocks of acid gels so casein chemistry and casein interactions are important, and second that an understanding of the gelation process is the key to controlling the physical properties of cultured products. The impact of several processing steps on the structure of cultured dairy products is discussed. Textural properties and the possible causes of defects such as whey separation and lumpiness are also discussed.     

Microbiological aspects and challenges of whey powders – I thermoduric,thermophilic and spore-forming bacteria

For dairy processors, spoilage and pathogenic spore-forming bacteria are key sources of concern, not only due to their ability to remain dormant in a desiccated state in powders and to survive heat treatments, but also their ability to form biofilms in the vegetative state that lead to contamination of foods. These include members of the genera Bacillus, Geobacillus, Anoxybacillus, Brevibacillus, Paenibacillus and Clostridium, many of which are associated with food poisoning and spoilage. Here, we review the common bacterial species that form spores in whey powders and their sources and provide insights into their risks and strategies to control them.     

Pre-treatment methods of Edam cheese milk. Effect on the whey composition

Edam cheese milk was subjected to high-heat treatment (HH), ultrafiltration (UF) and microfiltration (MF). The effect on the recovery yield and the composition of whey was studied. Traditional Edam process was used as a reference. HH reduced the whey protein concentration of milk and whey, but the recovery from milk to whey was not affected. Reduction of whey proteins was the highest (28%) with MF treatment, during which 15% was lost in the MF permeate and 13% was co-precipitated with the cheese curd. Co-precipitation of the whey proteins was the highest (84%) with ultrafiltered milk. MF and UF treatments produced 22% less whey with increased whey protein concentration. Elevation of the cheese milk protein concentration by microfiltration or ultrafiltration decreased the recovery of fat in whey. None of the treatments decreased the residual casein concentration in whey. The protein composition was altered by UF and MF treatments, which significantly increased the caseinomacropeptide content of total protein in whey. The whey was processed into whey protein concentrate powders. The amino acid composition of the whey protein concentrate produced from microfiltration process was significantly different from the others.     

Optimal operation of a protein hydrolysis reactor with enzyme recycle

A cyclic batch enzyme membrane reactor (CBEMR) incorporating an 8000-Da polyethersulphone membrane was intended for enhancing the enzyme use in the production of a whey protein hydrolysate. The operation of the CBEMR comprises three consecutive stages: (i) proteolysis, (ii) ultrafiltration and (iii) enzyme recycle and re-use. A mechanistic mathematical model comprising zero-order kinetics for the hydrolysis and second-order deactivation for the enzyme was proposed and validated through experiments. Two alternative operation modes were proposed for the CBEMR: isothermal versus non-isothermal operation. The performance of both modes was assessed in terms of enzyme consumption and number of enzyme uses versus the productivity required. Furthermore, the optimisation of both modes was carried out, comparing their optimal operation as enzyme consumption.     

Composition and nutritional value of commercial dried whey products from feta cheese manufacture

Various commercial dried whey products—WHEYPRO20, WHEYPRO35 and WHEYPRO65 (with approximately 20, 35 and 65% protein, respectively) and LACTINA (a permeate powder)—were studied in terms of chemical composition and nutritional value. These products were produced industrially from the whey of feta cheese manufactured with ovine and caprine milk by ultrafiltration and subsequent evaporation and spray-drying. As the protein content in these products increased, the nonprotein nitrogen and fat contents increased while the lactose and ash contents decreased. Generally the concentration of minerals (Ca, P, Na, K, Cl) in these products decreased with increasing protein content. With the exception of valine and methionine + cysteine, all essential amino acids were in excess in the whey protein concentrates (WHEYPRO35 and WHEYPRO65) as compared with the Food and Agriculture Organization reference protein and with human milk protein.     

Clarification of high-added value products from olive mill wastewater

The objective of the current study is to investigate the clarification of two high-added value products (pectin containing solution and phenol containing beverage) recovered from olive mill wastewater. For this purpose, both liquids were processed with four types of ultrafiltration (100, 25, 10 and 2 kDa) and one nanofiltration membranes under optimum transmembrane pressure. Retention coefficients and performance parameters were monitored for each experiment. The membranes of 25 and 100 kDa showed very satisfying results with regard to the concentration of pectin solutions as they were able to separate it from cations and phenols. The membrane of 25 kDa was also able to partially remove the heavier fragments of hydroxycinnamic acid derivatives and flavonols, and simultaneously to sustain the antioxidant properties of the phenol containing beverage in the permeate stream. Finally, nanofiltration clarified the beverage from cations that passed in the permeate stream, but this process resulted in loss of antioxidant compounds, too.     

Alternatives to spray irrigation of starch waste based distillery effluent

The distillery effluent from a starch waste based ethanol plant has been disposed of by spray irrigation for some time. The alternative methods of disposal are reviewed and their then costs compared for a 50 Ml/year plant. Anaerobic digestion can reduce pollution load significantly but it requires more investment and increased annual cost. Partial solids recovery by ultrafiltration (UF) does not reduce the pollution as much, but results in a byproduct for sale and a payback period of under six years for the extra investment. Further solids recovery by UF and nanofiltration requires a much longer payback period for the extra investment. Further research is required for more economical solids recovery and better value added byproducts.     

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.     

Functional milks and dairy beverages

During the last decade, consumers' approach to healthy foods has changed dramatically, and today enhancing the health span of consumers through consumption of healthy food is more important than simply enhancing their life span. Rising medical costs are the prime factor forcing people to find cheaper and effective means of protecting their health. This fact has led to an increase in consumers' interest in functional foods. Dairy products occupy a significant space in the functional foods market and dairy-based functional beverages are a growing segment of this sector. This article reviews recent scientific, technological and commercial developments in the functional dairy-based beverage sector.     

Effects of phytate and minerals on the bioavailability of oxalate from food

Phytate and mineral cations are both considered as important dietary factors for inhibiting the crystallisation of calcium oxalate kidney stones in susceptible individuals. In this paper, the phytate and mineral composition of whole bran cereals (wheat, barley and oat) and legumes were determined together with their soluble and insoluble oxalate concentrations in order to investigate the effects on oxalate solubility. The oat bran sample had the highest soluble oxalate concentration at 79 ± 1.3 mg/100 g, while total and soluble oxalate concentrations in the food samples studied range from 33 to 199 mg/100 g and 14 to 79 mg/100 g, respectively. The phytate concentration was in the range from 227 to 4393 mg/100 g and the concentrations of cations were in the range 54–70 mg/100 g for calcium, 75–398 mg/100 g for magnesium, 244–1529 mg/100 g for potassium and 4–11 mg/100 g for iron. Soluble oxalate concentration did not increase in proportion to total oxalate, and the phytate concentration in all foods was sufficient to contribute to an increase in soluble oxalate concentration by binding calcium.     

食品法典标准与我国乳制品标准的比较分析

乳和乳品是中国近年来农产品生产、消费中比例较大的产品,但乳品工业在我国是一个新兴产业,由于整体基础薄弱,因此存在许多亟待解决的问题,其中尤其值得关注的是乳制品的标准问题。根据世界贸易组织(WTO)的协议,国际食品法典委员会(CAC)制定的法典规范或准则被视为衡量各国食品是否符合卫生、安全要求的尺度。本文通过将CAC法典中的第12卷《乳及乳制品法典标准》与我国乳制品标准进行五个方面的对比,分析了目前我国乳制品标准与CAC乳与乳制品标准的差异和其中存在的问题,并对我国乳制品标准的修改和制定提出建议。     

Proposal of a new reference method to determine the water content of dried dairy products

The water content of milk powders is “officially” determined by drying. The result of drying techniques is, however, the mass loss the sample undergoes under the conditions applied. No differentiation between water and other volatile substances is made. A particular problem is the lactose that is present in all dried dairy products. The α-form contains one mole of water of crystallisation per mole. This water fraction is not determined completely by ordinary drying methods. How much of the crystallised water is detected depends very much on the conditions applied. The entity determined by drying is not defined. It is only a tradition to regard the mass loss thus detected as water content. More and more, however, the expression moisture content is used for the result of drying techniques, although this term is also unsatisfactory and misleading. The discrepancy between mass loss on drying and water content becomes more pronounced when the product has high crystalline lactose content, such as whey powders or lactose itself. In these cases the difference between mass loss and water content can be quite significant. The existing reference method for moisture determination in dried milk is therefore not reasonably applicable on dairy products with high crystalline lactose content. It could be shown that the water content of dried dairy products can be determined using the Karl Fischer titration independently of the level of crystallisation water. The results are not only more accurate but also more precise than those obtained by the reference drying method. It is therefore proposed to introduce the Karl Fischer titration as reference method for dried dairy products.     

The antioxidant properties of whey permeate treated fresh-cut tomatoes

The aim of this research was to analyse the effects of three types of cheese whey permeate treatment on the antioxidant properties of fresh-cut tomatoes. Tomatoes were treated with whey permeate concentrate (PC), delactosed permeate (DP) and delactosed concentrate (DC), stored at 4 °C for 10 days and compared to samples treated with the industry standard, chlorine (120 ppm). Samples treated with DP retained significantly higher antioxidant activity (FRAP) and total phenols (TP), when compared with those treated with PC and DC. DP showed significantly higher results than chlorine for DPPH, FRAP and TP. In DPPH assay, all whey permeate-treated samples showed similar antioxidant activity, while ascorbic acid and lycopene were unaffected by treatment. Among the three whey permeates, delactosed permeate showed the best results in maintaining the antioxidant properties of tomato, suggesting it could be used to enhance the antioxidant activity of fresh-cut tomato and retain the antioxidant components during storage.