Study of the Molecular Structures and Functional Properties of Proteins from Seven Pea (Pisum sativum L.) Genotypes with Different Levels of Protein Content

  • Author / Creator
    Lopes Lorenzetti, Rani
  • The food industry has seen shifting trends towards the use of plant proteins due to a variety of factors including consumer´s perception of health, ethical and religious purposes, as well as environmental considerations. Pulses are good sources of proteins and other nutrients such as resistant starch, dietary fiber, vitamins, minerals, and polyphenols, and therefore have gained particular interest. Among the pulse family, field pea (Pisum sativum) is a widely produced legume that has high nutritional value and low allergenicity.
    Though a lot of research has been focused on the applications of pea protein, the effect of genotype on the protein structure and functional properties has not been clearly investigated. This research intended to fill the gap by extracting and characterizing pea proteins from seven pea genotypes, consisting of high and regular protein genotypes. After extracting the pea protein, the protein molecular structures were systematically studied such as protein compositions, amino acid profiles, secondary structure, molecular weight by an array of advanced analytical tools including SDS–PAGE, Fourier-transform infrared (FTIR) spectroscopy, HPLC-Size exclusive chromatography (SE) and Differential Scanning Calorimetry (DSC). The protein solubility and functional properties including water and oil holding capacity, foaming and emulsifying properties and gelling capacity were compared between high and regular protein genotype.
    Pea protein concentrates were successfully extracted from pea grains of all 7 genotype with the protein content ranging from 76.5 % to 86.2 %. Globulins are major storage proteins in pea grains with legumin (11S) and vicilin (7S) as the major globulin fractions. It is interesting to notice that the protein extracts from different pea genotype possess a wide range of 11S/7S ratio from 1.5 to 8.7. While the high protein genotype P0540-41 and P1142-6195 show relatively low 11S/7S ratio (1.5-1.9), the other high protein line P1141-5085 demonstrated an extremely high 11S/7S ratio of 8.6 5± 0.65, which is also high when compared to regular protein containing line. In this study, it was observed that the 11S/7S ratio significantly impact the pea protein denaturation temperature. For example, protein extracts from P0540-41 and P1142-6195 with lower 11S/7S ratios had relatively lower denaturation temperatures.
    When analyzing nutritive value, protein concentrates from Earlystar, Greenwater and P0540-41 show higher sulfur-containing amino acids than other pea genotype, which is a known limiting essential amino acid in pea protein. The protein concentrates from Lacombe and P0540-41 have higher digestibility values of 86.3 % and 88.45 %, respectively compared to those from other pea genotype.
    In general, the pea protein extracts show good foaming and emulsifying properties, and their foaming stability values are especially high. Among the protein extract samples, those from Cooper and P1142-6195 had relatively low foaming capacity at all tested pHs and the lowest 11S/7S ratio as compared to other samples. It is interesting to notice that the pea protein gelling properties are influenced by the genotypesgenotypes. The protein samples from Earlystar and P0540-41 possess better gelling capacity and their gels showed significantly increased mechanical strength. Among all the pea genotype tested, the high protein line P0540-41presents a better source to generate pea protein concentrate with good overall functional properties to support food applications.

    This research is the first of its kind to compare not only the protein content of different pea genotype, but also the protein structure and functional properties between high protein genotype and regular protein genotype. Although, it is an initial study with few samples, the results demonstrate that high protein genotype are comparable, and in some instances, superiors to regular protein genotype in terms of protein functionality and nutritive value. This opens the possibility of breeding genotypesgenotypes in order to achieve not only high protein content, but also to target specific protein physical-chemical and functional properties for desirable industry processing and food applications.

  • Subjects / Keywords
  • Graduation date
    Fall 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.