乳脂分离机：选购、使用有讲究——访北京俄氏富凯分离机械技术有限公司孟涛经理

一个世纪以前，有人发明了第一台用于乳制品的离心分离机，其工作原理和洗衣机甩干衣物有些类似，通过离心力的作用，将不同的乳成分分离；一个世纪以后的今天，我刊有幸采访到北京俄氏富凯分离机械技术有限公司孟涛经理，他给我们讲述了乳脂分离机的选购和使用技巧。     

Properties of Acidic Whey Protein Gels Containing Emulsified Butterfat

Changes in physical properties of whey protein gels following addition of emulsified fat were investigated. Gels were made by heating mixtures of dialyzed whey protein isolate at pH 4.60 with and without emulsified fat droplets. Addition of emulsified fat improved the gel-like qualities of these systems. Gel strength progressively increased upon addition of emulsified fat up to 30.00% by weight. Mean droplet size 1.85 km produced the greatest reinforcement of gel strength. Gels made with intermediate concentrations of protein were most sensitive to the effect. The elastic moduli and viscosities of whey protein gels at pH 4.60 increased with fat content, whereas syneresis decreased upon addition of fat.     

Microstructure of Whey Protein Isolate Gels Containing Emulsified Butterfat Droplets

The effects of concentration and droplet size of anhydrous butterfat globules on the microstructure of heat-induced whey protein isolate gels (pH 4.60) were studied by scanning and transmission electron microscopy (TEM). All fat globules were emulsified with whey protein isolate and incorporated into the system prior to gelation. Protein aggregates became more closely packed as whey protein concentration was increased from 8 to 15% by weight in gels without added fat. There was no notable change in overall gel microstructure upon addition of fat globules, up to 25% by weight, when viewed by scanning electron microscopy. However, it appeared fat globules were intimately associated with the gel protein matrix. A twofold difference in fat globule size was obvious by TEM. Clusters of droplets became more predominant as butterfat content increased.     

Phase Behavior and Mechanical Properties of TripaImitin/Butterfat Mixtures

The functionality of butterfat can be improved by fractionation, a process that can be considered as enrichment of butterfat with long-chain saturated fatty acids. Model hard fractions were produced by adding tripalmitin to butterfat, in ratios from 0.9:0.1 through 0.1:0.9. The model system had very similar thermal behavior and mechanical properties to true fractions. The phase behavior of tripalmitin/butterfat mixtures was determined. Such butterfat fractions have potential as a moisture barrier in edible films and coatings. Tripalmitin-enriched butterfat is an alternative to hard butterfat fractions in some applications.     

Mono- and Diglycerides Prepared by Chemical Glycerolysis from a Butterfat Fraction

A solid butterfat fraction was prepared by controlled crystallization of the melt. Products of glycerolysis and rate of reaction were analyzed by size exclusion chromatography and gas-liquid chromatography and compared to those of a tricaprilin model system. Physical and functional properties of the resulting mixture of mono- and diglycerides were compared to commercial monoglyceride-based emulsifiers. The emulsifier from the butterfat fraction consisted of ～60% mono- and 40% diglycerides and presented a very different FA profile from the commercial emulsifiers. The butterfat-derived emulsifiers had a lower melting range and imparted a significantly lower surface tension at oil/water and oil/ skim milk interfaces.     

Butterfat in rations for pigs fed skimmed whey: Growth rate, feed conversion, economics, carcass evaluation and fat quality

An experiment was carried out, using 81 castrated male pigs, to estimate the effect of adding butterfat (70% fat, 30% buttermilk), as an energy supplement, to the rations of pigs fed skimmed whey ad libitum. The rations were fed daily in a restricted amount and butterfat added to rations at two levels: T-2 and T-3, 140 and 280 g/day/animal, respectively. In treatment T-1, no butterfat was added. The pigs were weighed every 21 days until they reached average liveweights of 100 (group 1) or 120 kg (group 2), when they were killed for carcass studies. There were significant differences in liveweight gains and feed conversion for the pigs supplemented with butterfat. A negative result, from an economical point of view, was obtained due to the relatively high price of the butterfat. A higher yield of carcass weight on field liveweight was obtained in treatments T-2 and T-3, reflecting the higher degree of fatness. The relative carcass length, muscle depth and percentage of defatted ham were higher in T-1. Conversely, the relative depth of fat was more marked in the groups and treatments that consumed butterfat with their rations. Both groups of T-1 yielded the highest percentage of muscle and the lowest of fat in their carcasses, the differences from T-2 and T-3 being significant. T-2 and T-3 did not differ significantly from one another. There were significant differences in the fatty acid composition due to sampling location. The differences due to treatment were statistically significant in respect of the concentrations of 14:0, 16:1, 17:0, 17:1, 18:0 and 18:1 fatty acids. The unusually low concentration of 18:2 in the dissected fat tissues produces high quality porcine fats, for use in manifactured and prepared foods.     

Peptides: Production,bioactivity, functionality,and applications

ABSTRACT

Production of peptides with various effects from proteins of different sources continues to receive academic attention. Researchers of different disciplines are putting increasing efforts to produce bioactive and functional peptides from different sources such as plants, animals, and food industry by-products. The aim of this review is to introduce production methods of hydrolysates and peptides and provide a comprehensive overview of their bioactivity in terms of their effects on immune, cardiovascular, nervous, and gastrointestinal systems. Moreover, functional and antioxidant properties of hydrolysates and isolated peptides are reviewed. Finally, industrial and commercial applications of bioactive peptides including their use in nutrition and production of pharmaceuticals and nutraceuticals are discussed.