Understanding the Molecular Interactions Between the Major Food Polymers, Including Starch, Protein, and Fiber, as Impacted by Extrusion Processing

Jana Katharina Richter

doi:10.7273/000006391

Health and environmental awareness as well as changes in lifestyle go hand in hand with significant changes in human diet. Snackification, the displacement of larger meals by snacks, and vegetarianism or veganism, the abstinence from eating meat or animal-based products, respectively, are two trends that have become increasingly popular over the last twenty years. Extrusion processing allows for the manufacture of direct expanded snack products and plant-based meat alternatives, specifically high moisture meat analog (HMMA) products, and hence, offers excellent potential to respond to such diet changes. To improve the texture of snack products fortified with dietary fiber and the structure of HMMA products, interactions between the major food polymers, including starch, protein, and fiber, as impacted by extrusion processing, need to be understood. Therefore, this dissertation work focused on evaluating potential interactions between starch and fiber during the production of direct expanded products, as well as on the interaction between proteins during protein texturization. Generally, the inclusion of insoluble fiber into direct expanded starch products causes an undesirable reduction in expansion. Potential interactions between starch and fiber were evaluated by the traditional approach of analyzing the raw and the extruded materials using wet-chemical and spectroscopic techniques further by two novel approaches, including the 1H NMR analysis of model compounds representing the complex biopolymers starch and fiber and a simulated small-scale expansion process using a newly developed pressure vessel setup. Even though it has often been assumed that fibers are inert during extrusion processing, the results suggest that starch and fiber interact through hydrogen bonding; however, there was no evidence for covalent bonds formed between the biopolymers during extrusion processing. Despite the extensive conducted work on understanding the mechanism of protein texturization, it is still not fully comprehensive as to why proteins from some plant sources perform better than others. With a focus on disulfide bonds, which are often described as essential during protein texturization, interactions between proteins were analyzed using different techniques, including spectrophotometric measurement of disulfide bonds, solubility tests, and polymeric protein extraction followed by size exclusion chromatographic analysis. The findings indicate that large disulfide linked polymers are formed during HMMA extrusion processing and that the mechanism of texturization differs slightly based on the protein source. Additionally, it was found that reducing agents can help form a fibrous texture by premature splitting of existing disulfide bonds, better protein alignment, and improved flow characteristics.

Understanding the Molecular Interactions Between the Major Food Polymers, Including Starch, Protein, and Fiber, as Impacted by Extrusion Processing

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