Physicochemical, morphological, and digestibility properties of round and wrinkled pea starches

Authors: Daba, Sintayehu; McGee, Rebecca; Finnie, Sean

Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pea seeds can be categorized based on morphological characteristics, such as seed surface texture (smooth/round vs. rough/wrinkled) and seed color variations (yellow, orange, green, and brown). A growing trend in using peas for protein isolation generates a significant amount of the starch-rich fraction as a byproduct, necessitating effective utilization in various food and non-food applications. The physicochemical and morphological properties of starch play a crucial role in determining their functional properties and digestibility. Variations in the functional properties between round and wrinkled pea starches may arise from inherent structural and compositional differences. Therefore, it is essential to comprehensively investigate starch properties from both pea types. This study aims to (1) assess the physical, chemical, and morphological properties of starch extracted from round and wrinkled peas, and (2) assess the in vitro digestibility of starch obtained from both round and wrinkled peas.

Technical Abstract: Pea protein extraction yields an excess of starch-rich byproduct, requiring efficient use in diverse applications. We analyzed the physicochemical, morphological, and digestibility properties of starches from round and wrinkled peas, highlighting their functional differences. For this study, three varieties of round pea (Yellowstone, Hampton, and Aragorn) and three varieties of wrinkled pea (Bistro, Strike, and PLS595) grown across three locations (Pullman, WA; Richland, MT; and Sidney, MT) in 2023. The result indicated that wrinkled peas contained higher protein, but lower starch compared to round peas. Additionally, the starch fraction of wrinkled peas had lower starch concentration, but higher amylose content as compared to their round counterparts. RVA test at 95°C revealed that wrinkled peas showed minimal swelling and viscosity development, whereas round peas exhibited well-defined pasting profiles with higher final viscosity. In an RVA test at 140°C for wrinkled pea entries, they showed considerable granular swelling and viscosity development. However, the pasting profiles were different among the wrinkled varieties, with PLS595 showing the highest final viscosity. Round peas had lower pasting temperatures and higher gel firmness compared to wrinkled peas by at least 40°C. Cluster analysis clearly grouped round and wrinkled peas in separate clusters. With the clustering of measured traits into two separate groups, the correlation coefficient between parameters was generally positive for traits within a group and negative for traits in different groups. Our findings indicated that final viscosity and swelling power at higher temperatures were increased as amylose content and protein concentration in the starch fraction increased, but these parameters increased as the total starch concentration increased. Wrinkled peas exhibited higher early-stage digestibility, but lower total digestible starch after 4 hours of digestion as compared to round peas. The resistant starch content was higher for round peas. SEM images revealed distinct granular morphologies in native form between round and wrinkled pea, with round pea starches exhibiting simple granules and wrinkled pea starches found in compound forms. Overall, the two types of peas showed differences in physicochemical, seed morphology and starch digestibility.