RESUMO
Guar korma and churi protein isolates were assessed for their physicochemical, nutritional, functional, structural, and digestibility properties for their application in the food industry. The water extracted protein isolate of guar korma showed a protein content of 89.7 % and a yield of 48.7 %. Water extracted protein isolate of guar korma showed an excellent protein efficiency ratio, essential amino acid/total amino acids (34.35 %), amino acid score, and protein digestibility corrected amino acid score values, suggesting the existence of high-quality proteins. Water extracted protein isolate of guar korma contains all the essential amino acids except Methionine and Cysteine, according to World Health Organization recommendations for children and adults. The protein profiling of water extracted protein isolate of guar korma was analyzed using 12 % sodium dodecyl sulfate polyacrylamide gel electrophoresis and indicated the presence of eight major protein bands in the range of 17-100 kDa. In vitro digestibility of water extracted protein isolate of guar korma showed the complete digestion of the abundant protein bands within 15 min. Further, the foaming capacity, water/oil holding capacity, and emulsifying stability of water extracted protein isolate of guar korma were comparable with soy protein isolate. Fourier Transform Infrared and Circular Dichroism spectral analysis revealed the presence of several aromatic groups and ß-sheets, random coils respectively in water extracted protein isolate of guar korma. The morphological nature of the guar protein isolate was characterized by Scanning Electron Microscopy. Overall, these findings support that water extracted protein isolate of guar korma has excellent functional and nutritional properties and could be a potential alternative plant protein in food industries.
RESUMO
Pectin methylesterase (PME) is a ubiquitous cell wall enzyme, which de-esterifies and modifies pectins for food applications. Functional properties of pectin rely on molecular weight and degree of esterification, and thus de-esterification by PME influences the pectin functionality. The main aim of the study is to purify and biochemically characterize PME from the outer mesocarp-exocarp tissue of unripe Carica papaya L. fruit. The ion-exchange and gel-permeation chromatography purified enzyme exhibited a specific activity of 2363.1 ± 92.8 units/mg protein, with a fold purification of 10.6, and final recovery of 9.0%. The PME showed a low apparent mass of 27 kDa by SDS-PAGE. The optimal activity of purified PME was found at pH 7.0, and at 60 °C. The enzyme is fairly stable at 60 °C for 10 min, retaining 60% activity. The optimum activity was found with 0.25 mol/L monovalent salts indicating that this PME is salt-dependent. The Km of PME was 0.22 mg/mL, and the Vmax value was 1289.15 ± 15.9 units/mg. The increase in the calcium sensitivity of the PME-treated pectin indicated a blockwise mode of action. The PME significantly differs from other known plant PMEs in their biochemical properties. Manual inspection and MASCOT searching of generated tryptic peptides confirmed no homology to known papaya PME sequences. The preliminary results indicate that the papaya PME can be potentially utilized to modify pectin functionality at elevated temperature. However, further investigation is required to understand the usefulness of this enzyme for the modification of pectins for various food applications. PRACTICAL APPLICATION: In this work, a small, 27 kDa papaya PME was purified by ion-exchange and gel-permeation chromatography and biochemically characterized. The papaya PME significantly differs from other known plant PMEs in their biochemical properties. The preliminary results like fair thermostability coupled with high temperature optimum indicate that the papaya PME can be potentially utilized to modify pectin functionality at high temperature. Modification of pectin functionality at elevated temperatures is advantageous since it evades the detrimental action of other pectinolytic enzymes.
