The purpose of this project was to conduct an investigation into the development of a soy cheese with acceptable texture. The effects of heat treatment, different oils/fat and reducing and non-reducing sugars on the soy protein isolate (SPI) and SPI curd were studied. The physico-chemical, biochemical and textural properties of three types of soy cheese were compared: (1) glucono-8-lactone (GDL) induced, (2) bacterially fermented and (3) GDL-induced and fermented. The results indicate that the fermentedGDL- cheese had the most acceptable texture. Heat treatment of SPI at neutral pH caused it to denature partially and increased the storage modulus and hardness of subsequently GDL-induced gels. Subsequent heat treatment of the acidic gels further significantly enhanced the storage modulus and gel hardness. The SPI emulsion containing palm stearin showed higher emulsifying stability, emulsifying activity, protein adsorption and denaturation degree than the emulsions containing sunflower and soy oil at neutral pH. The acidified emulsion gel containing palm stearin was significantly harder than the control (without fat), whereas emulsion gels containing sunflower and soy oil were softer than the control. Glucose, lactose and sucrose increased the onset denaturation temperature of SPI, resulting in decreased gel hardness and stiffness at acidic pH. At neutral pH, both reducing and non-reducing sugars increased the emulsifying activity of SPI emulsions and decreased the emulsifying stability and protein adsorption at oil/water interface. The Maillard reaction took place between SPI and glucose and lactose, resulting in increased gelation of SPI and decreased emulsifying activity at neutral pH. Chemical analysis indicated that disulfide bonds were involved in maintaining the structure ofthe gels. Furthermore, evidence was found of other types of covalent bonds besides disulfide bonds in acidic gels formed by glycated SPI.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:491281 |
| Date | January 2008 |
| Creators | Gu, Xin |
| Publisher | Heriot-Watt University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10399/2039 |
Page generated in 0.0017 seconds