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.     

Rheological Properties of High-Methoxyl Pectin and Locust Bean Gum Solutions in Steady Shear

The Cross and Carreau flow models described well the shear rate-apparent viscosity data. The coil overlap parameter, c[η], correlated well with the zero-shear rate specific viscosities of these mixtures. Experimental values of intrinsic viscosities of the mixtures were in good agreement with the prediction based on an additive model of the individual contributions of the gums. From the results obtained for the mixtures of both polysaccharide solutions at similar viscosity, pH and ionic strength, no significant interactions were detected. Hypotheses for this lack of polymer interaction were developed. Results with such model systems are useful in understanding the relation of composition to the properties of complex food systems.     

Texture as a reflection of microstructure

The perception of texture has been correlated to the microstructure of particulate whey protein gels. A full, two-level, factorial experimental design was used in which the processing conditions, pH, heating rate and addition of salt were used as design factors. The texture of the gels was analysed by a sensory panel, and the microstructure was analysed by light and electron microscopy. The microstructure was quantified by using different types of image analysis.

In this study of particulate whey protein gels, the test principles of analysing texture were divided into two groups: destructive tests and non-destructive tests. The microstructural parameters can also be divided into two groups: overall network dimensions (pore size and particle size) and strand characteristics. The texture as measured with destructive methods was sensitive to overall network dimensions, whereas texture as measured with non-destructive methods was sensitive to the strand characteristics of particulate protein gels.     

Viscoelastic Properties of Heat-Set Whey Protein-Stabilized Emulsion Gels with Added Lecithin

Our objective was to determine how lecithin affects the small-deformation shear rheology of heat-set emulsion gels made from whey protein concentrate (WPC). Fine oil-in-water emulsions were prepared with WPC, lecithin or WPC + lecithin present during homogenization. Storage and loss moduli were measured in situ during thermal processing at temperatures up to 90°C and afterwards at 30°C. The positive influence of pure egg lecithin added after emulsification on the elastic modulus of the WPC emulsion gel was attributed to lecithin-protein complexation. Crude egg lecithin gave a broadly similar increase in gel strength, but pure soybean lecithin was not so effective in reinforcing the network, and crude soybean lecithin was ineffective. Using lecithin as sole emulsifier, with WPC added after homogenization, gave a lower modulus for the heat-set WPC emulsion gel. With protein + lecithin present during emulsification, the considerable loss of gel strength was attributable to some WPC displacement from the emulsion droplet surface.     

壳聚糖凝胶体系研究进展及其展望

概述了壳聚糖凝胶体系研究发展状况和壳聚糖凝胶体系的一些主要影响因素.并对壳聚糖凝胶体系作为新型屯食品添加剂的发展前景和可行性进行了分析.     

食用胶对西式火腿物性特性的影响

探讨以猪肉为原料的西式火腿加工过程中,食用胶加入的种类、加入方式和加入量对产品物性的影响,并采用正交试验研究不同食用胶在西式火腿中的应用效果。结果表明,卡拉胶的加入对西式火腿的黏着性、凝聚性、弹性均有较好影响,当以单一的食用胶添加在西式火腿中时,使用卡拉胶且以粉状的方式添加以及添加量为0.3% 时的效果为最佳。     

Rheological,thermal and microstructural properties of whey protein isolate‐modified cassava starch mixed gels at different pH values

The objective of this study was to investigate the rheological, thermal and microstructural properties of whey protein isolate (WPI)‐hydroxypropylated cassava starch (HPCS) gels and WPI‐cross‐linked cassava starch (CLCS) gels at different pH values (5.75, 7.00 and 9.00). The rheological results showed that the WPI‐modified starch gels had greater storage modulus (G?) values than the WPI‐native cassava starch gels at pH 5.75 and 7.00. Differential scanning calorimetry curves suggested that the phase transition order of the WPI and modified starch changed as the pH increased. Scanning electron microscopy images showed that the addition of HPCS and CLCS contributed to the formation of a compact microstructure at pH 5.75 and 7.00. A comprehensive analysis showed that the gelling properties of the WPI‐modified starch were affected by the difference between the WPI denaturation temperature and modified starch gelatinisation temperature and by the granular properties of the modified starch during gelatinisation. These results may contribute to the application of WPI‐modified starch mixtures in food preparation.     

Properties of Algin/Calcium and Salt/Phosphate Structured Beef Rolls with Added Gums

Ten polysaccharide gums at two levels (0.5 and 1.0%) were individually incorporated into algin/calcium (AC) and salt/phosphate (SP) structured beef rolls (<6% fat) prepared with 15 and 30% added water. Cook yield, pH, bind and textural properties were evaluated. Each gum had specific effects on properties of beef rolls. For example, kappa-carrageenan improved (P<0.001) cook yields and maintained or improved bind and texture of raw and cooked samples of both meat binding systems. Cook yields of AC products were improved with gellan gum, while yields of SP products were improved with iotacarrageenan. Other gums (xanthan, guar, pectin, carboxymethyl cellulose) improved water holding (cook yields) but had detrimental effects on product texture.     

Effect of sesame protein isolate in partial replacement of milk protein on the rheological,textural and microstructural characteristics of fresh cheese

Soft cheeses were manufactured from bovine milk with the addition of 0–12% sesame protein isolate (SPI) were utilised to investigate rheology, texture and microstructure at different stages of cheese making. SPI addition reduced the speed of milk fermentation, kappa‐casein proteolysis of rennet and elongated the time of cheese curd formation. Renneted milk storage modulus G′_60min was decreased and coagulation time increased with increasing SPI content. Low SPI supplements (4% and 8%) enhanced the hardness, cohesiveness, adhesiveness and gumminess of the soft cheese, while high SPI addition (12%) deteriorated the texture. In the cheese curd gel matrix, SPI distributed as specific SPI‐gel clusters on the surface of curd fractures, stacked or fused with ball‐shaped casein micelles and wrapped up to casein gel strands. In summary, SPI actively interacted with casein colloid throughout the cheese making process.