Rheological characteristics, microstructure and cheese making properties of mixed soy-milk gels
Incorporating soy proteins into food products can greatly decrease price and increase the nutritional value of the final products. However, very little is known about the behaviour of soy proteins when mixed in foods. This research focused on the properties of the mixture of soy proteins and milk proteins with acid-rennet combined gelation. This mixed system containing soy proteins and milk proteins were characterized using dynamic light scattering, confocal microscopy, rheology, electrophoresis and syneresis. The mixture system had different behaviors on rheology, microstructure and cheese making properties such as syneresis. The study on the rheological properties of the SM/SMP mixture (55:45, protein-based ratio) demonstrated that pH is the determining factor in the gelaton of the acid-rennet combination SM/SMP mixture and rennet playa positive role in increasing the storage modulus G' value. The results by Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) demonstrated that the acid-rennet combined coagulation from the mixture can form a 3-dimensional structure. The syneresis rate of the gels from the mixture was increased probably due to a gel structure with large pore size, lower density and lower water-holding capacity. And the SDS-PAGE pattern indicated that the gel syneresis and its texture may be enhanced if [beta]-lactoglobulin([beta]-Lg) and [alpha]-lactalbumin([alpha]-La) were involved in the gel structure. This study focused for the first time on understanding the rheological properties, microstructure and texture attributes of the acid-rennet combined coagulation from the SM/SMP mixture (55:45, protein-based ratio) using various and novel techniques. It is concluded that the SM/SMP mixture with acid-rennet combination can form a three dimensional matrix structure. This may help develop new soymilk/milk cheese to meet consumer and industrial needs.