Czech J. Food Sci., 2013, 31(6):568-574 | DOI: 10.17221/469/2012-CJFS

Effect of microwave thawing on microstructure and physicochemical stability of low fat white sauces made with soy proteinOriginal Paper

Luis M. GuardeÑO¹, Amparo Quiles¹, Empar Llorca¹, José Pertusa², Isabel Hernando¹

¹ Research Group of Food Microstructure and Chemistry, Department of Food Technology, Polytechnic University of Valencia, Valencia, Spain

² Department of Functional Biology and Physical Anthropology, Faculty of Biological Sciences, University of Valencia, Valencia, Spain

The microstructural and physicochemical stability of white sauces made with soy protein and modified waxy maize starch was evaluated after subjecting them to a freezing-thawing process in a conventional or microwave oven. The microstructure of sauces revealed a structured matrix of soy protein and starch polymers where fat globules and swollen starch granules remain dispersed. Both thawing methods affected the fat globule size and morphology but they did not affect the starch granules. The SDS-PAGE analysis did not show any apparent changes between sauces thawed by both methods. Moreover, a similar pattern was found in the soy protein isolate used as a raw material indicating that this type of protein was also stable to the cooking process. There were no significant differences (P > 0.05) in the reducing power of the sauces regardless of the thawing method used. However, the acidity index and the k₂₃₂ parameter were significantly higher (P < 0.05) in conventionally thawed sauces. Finally, syneresis was negligible and no significant differences (P > 0.05) were found among different frozen storage periods. In conclusion, the formulation of the sauce is appropriate to develop low fat, vegetarian meals which can be subjected to frozen storage and microwave reheating.

Keywords: Confocal laser scanning microscopy (CLSM); microwave heating; SDS-PAGE; soy protein isolate; starch

Published: December 31, 2013  Show citation