Phase behavior, thermodynamic and microstructure of concentrated pea protein isolate-pectin mixture: Effect of pH, biopolymer ratio and pectin charge density

Authors: LAN, YANG - North Dakota State University; Ohm, Jae-Bom; CHEN, BINGCAN - North Dakota State University; RAO, JIAJIA - North Dakota State University

Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2019
Publication Date: 12/3/2019
Citation: Lan, Y., Ohm, J., Chen, B., Rao, J. 2019. Phase behavior, thermodynamic and microstructure of concentrated pea protein isolate-pectin mixture: Effect of pH, biopolymer ratio and pectin charge density. Food Hydrocolloids. 101:105556. https://doi.org/10.1016/j.foodhyd.2019.105556.
DOI: https://doi.org/10.1016/j.foodhyd.2019.105556

Interpretive Summary: Recently, there is growing interest in the consumption of plant proteins, particularly yellow pea (Pisum sativum L.) protein isolate, as an alternative to animal proteins. Pectin which is a typical food-grade polysaccharide is widely used to improve functionality of proteins. Especially, concentrated protein-pectin complex has a number of applications as an encapsulation material, fat-replacer, and texture modifier in food industry. However, there have been few researches on the factors that influence interaction of yellow pea protein and pectin. Proteins and pectins are mixed in a solution to produce concentrated protein-pectin complex. This research provided information on influence of yellow pea protein-pectin mixing ratio (1:1 to 20:1), pH (2-8), and pectin types on interaction of yellow pea protein and pectin to form concentrated yellow pea protein-pectin complex. The information gained from this research will be helpful for enhancing the production of pea protein-pectin complex which is useful in food systems.

Technical Abstract: The impact of pH, pea protein isolate (PPI)–pectin mixing ratio and pectin type on phase behaviors (co-solubility, soluble complex and complex coacervate) of concentrated biopolymer mixture was investigated using phase diagram and '–potential. The microstructure, thermodynamic behavior and non-covalent bonding of PPI to pectin were further explored by confocal laser scanning microscopy (CLSM), isothermal titration calorimetry (ITC) and Fourier transform infrared spectroscopy (FTIR). In general, the pH of soluble complex, complex coacervate formation shifted towards higher pH as PPI–pectin mixing ratio increased. Low methyl pectin (LMP) is favorable for complex coacervate formation over a wider pH range compared with high methyl pectin (HMP) due to its higher overall charge density. The CLSM images revealed that the larger aggregates were formed in PPI-LMP coacervate compared to PPI-HMP coacervate. Both ITC and FTIR analysis indicated that the complexation including soluble complex and complex coacervate was formed through the electrostatic interaction and hydrogen bonding between PPI and pectin.