Texturization of soy protein via twin-screw extrusion
Ning, Luping
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Permalink
https://hdl.handle.net/2142/21658
Description
Title
Texturization of soy protein via twin-screw extrusion
Author(s)
Ning, Luping
Issue Date
1993
Doctoral Committee Chair(s)
Wei, Lun-Shin
Department of Study
Food Science and Human Nutrition
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Language
eng
Abstract
Extrusion texturization is one of the most economic means of converting vegetable proteins into textured products with a wide range of applications as meat supplements or extenders. In this study, a Werner & Pfleiderer twin-screw extruder Model ZSK-30 was used to texturize defatted soy flour and soy protein concentrate. A cooled sheeting die was designed to enhance the texture integrity of the finished product. Rheological properties of extrudates were measured by using an Instron. Scanning electron microscopy and light microscopy were employed to observe the ultrastructure of extrudates and the degree and order of protein fiber alignment. Differential scanning calorimetry was used to investigate the influence of texture modifiers and protein cross-linking agents on the denaturation behavior of 7S and 11S globulins. Protein solubility in different chemical reagents was measured to reveal the nature and extent of molecular interactions in the extruded soy protein.
7S and 11S proteins within soy were found to interact with each other during extrusion. The 11S protein enriched extrudates had higher expansion and water holding capacity. An 11S/7S ratio of 1.5 in the feed formulation resulted in a product with the best textural characteristics. Anionic polysaccharide, such as carrageenan, formed complex with soy protein, which significantly affected the extrusion performance of soy protein. Addition of lambda-carrageenan (2%) improved the quality of extruded of soy protein. A significant variation in extrusion behavior and physico-chemical properties of textured soy protein was observed when different salts were added. Calcium chloride and sodium acid pyrophosphate appeared to be the successful protein cross-linking agents. A positive correlation existed between the completion of protein denaturation and the degree of texture formation.
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