High Pressure Processing of Mixed Pea Protein-Starch Systems: Effects on Structure and in-vitro Digestibility
Pea proteins offer a relatively inexpensive and sustainable plant protein source that can be used to meet the increased consumer demand for protein. A major challenge in using pea protein ingredients to create novel food products is the undesirable “cooked” flavor formed during traditional thermal processing. Hence, a nonthermal method such as high pressure processing (HPP) may be key to expanding the range of pea-based products and their consumption. A review of the literature in Chapter One shows that the structures of protein and starch can be individually modified by HPP to create foods with unique textures and digestibility. However, it is not known how this occurs in protein-starch mixtures, which is important as starch is a major component in pea protein systems. Therefore, this dissertation describes work performed to understand how novel structures can be created using HPP treatment of pea protein-starch mixed systems, the mechanisms responsible for the formation of these structures, and the effect of HPP treatment on protein and starch digestibility. The effects of pressure level and protein concentration on the pressure-induced structural changes in pea protein concentrates (PPC) were evaluated and compared to heat treatments in Chapter Two. HPP induced gel formation in PPC, with gel strength increasing with both pressure level and protein concentration, due to a greater extent of protein denaturation, aggregation and network formation. Heat-treated samples exhibited greater gel strength than pressure-treated samples at the same protein concentration, due to the different type of structural transformations caused by the two processes. Starch granules present in PPC retained their structure and were not gelatinized even after HPP treatment at the highest pressure level, but were gelatinized by heat. Since starch is a major component in pulses, the contributions of pea starch to pressure-induced structure formation in mixed protein-starch systems were examined in Chapter Three, using PPC and pea starch of varying protein and starch concentrations. Starch acted mainly as a filler in the pressure-induced protein gel matrix, and the increase in gel strength was more dependent on protein concentration than starch concentration. Starch granules were observed to be embedded in the protein network, and remained intact and ungelatinized after HPP. As starch in the mixed systems remained ungelatinized after HPP, this was expected to have implications on its digestibility. At the same time, protein digestibility is also likely to be affected by the pressure treatment. The effects of HPP and heat on the protein and starch digestibility of mixed pea protein-starch systems were explored in Chapter Four. Pressure treatments led to higher protein and lower starch digestibility than heat treatments. Untreated controls had the highest protein and the lowest starch digestibility compared to the HPP and heat-treated samples. The implication of these results is that HPP-treated pea protein-starch mixtures could lead to the creation of novel pea-based products with lower glycemic-index and enhanced protein digestibility. Overall, the findings of this work provide the knowledge foundation to develop novel pulse and pea protein foods using HPP, with significance both for their texture and digestibility.
Food science; High Pressure Processing; Pea Protein Concentrate; Pea Starch; Protein Gelation; Pulse Protein; Starch Gelatinization
Moraru, Carmen I.
Brenna, James Thomas; Mattson, Neil S.
Food Science and Technology
Ph.D., Food Science and Technology
Doctor of Philosophy
dissertation or thesis