Physicochemical, structural, and functional properties of hemp protein vs several commercially available plant and animal proteins: A comparative study

Authors: XU, YIXIANG - Virginia State University; SISMOUR, EDWARD - Virginia State University; BRITLAND, JULIA - Virginia State University; SELLERS, ANISA - Virginia State University; ABRAHA-EYOB, ZAID - Virginia State University; ADNAN, YOUSUF - Virginia State University; RAO, QINCHUN - Florida State University; KIM, JIMIN - Columbia University; Zhao, Wei

Submitted to: ACS Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2022
Publication Date: 9/28/2022
Citation: Xu, Y., Sismour, E., Britland, J., Sellers, A., Abraha-Eyob, Z., Adnan, Y., Rao, Q., Kim, J., Zhao, W. 2022. Physicochemical, structural, and functional properties of hemp protein vs several commercially available plant and animal proteins: A comparative study. ACS Food Science and Technology. https://doi.org/10.1021/acsfoodscitech.2c00250.
DOI: https://doi.org/10.1021/acsfoodscitech.2c00250

Interpretive Summary: Plant-based foods have enjoyed rapid growth in recent years because of increasing concern over issues associated with the consumption of animal products such as human health, animal welfare, and environmental sustainability. Hemp protein, a by-product after oil extraction from hemp seed, could be an excellent alternative plant protein source. Following the passage of the 2018 Farm Bill, hemp production has been legalized, which creates a great opportunity to utilize hemp protein as an ingredient in various protein-rich food products. However, the information regarding the structure and functionality of this underexploited “novel” protein is limited. In this study, physicochemical, structural, and functional properties of hemp seed protein were compared with commercially-available animal (whey and egg) and plant (soy and pea) proteins. The results indicate hemp protein has a highly-compact structure with predominant ß-sheet conformation. Hemp protein is rich in arginine and sulfur-containing amino acids that promote beneficial health outcomes. Hemp protein has low solubility and water absorption capacity but highest oil adoption and emulsification capacities. Our results support the potential use of hemp protein in various protein-rich food products. However, appropriate processing technologies to modify its structure and thereby improve its functionality are needed for its potential usage in food applications.

Technical Abstract: Physicochemical, structural, and functional properties of hemp seed protein, a non-traditional and underexploited plant protein source, were compared with commercially-available animal (whey and egg) and plant (soy and pea) proteins. The proximate composition of the hemp protein was 70.9% protein, 5.04% crude oil, and 13.1% ash. Compared to the other proteins, hemp protein exhibited the lowest total (67.1g/100g) and essential amino acid contents (23.1 g/100g) but the highest arginine level (9.17 g/100g). The ß-sheet conformation was the predominant secondary structure in hemp protein since the major protein constituent is the globulin edestin. SDS-PAGE profile of hemp protein demonstrated four major bands located ~18, ~20, ~34-36 kDa corresponding to the basic and acidic subunits of edestin, respectively. Hemp protein had the second highest surface hydrophobicity (H0) of 750 x104 a.u, while its total sulfhydryl group (-SH) content of 34.85 µmol/g was significantly higher than soy and pea but lower than whey and egg albumin. A highly-compact structure along with higher H0 and –SH content of hemp protein may explain the low water absorption capacity (372.41 g/100g) and protein solubility, but the high oil absorption capacity (135.48 g/100g) and emulsification activity index of 48.40 m2/g. Our results support the potential use of hemp protein in various protein-rich food products. However, appropriate processing technologies are still needed to modify its structure, thereby improving its functionality and utility.