Thermal and surface active properties of citric acid-extracted and alkali-extracted proteins from Phaseolus beans

• Published in: Journal of agricultural and food chemistry Vol. 41; no. 1; pp. 24 - 29
• Main Authors: DiLollo, Antonio, Alli, Inteaz, Biliarderis, Costas, Barthakur, Nayana
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.01.1993
• Subjects: Animal, plant, fungal and microbial proteins, edible seaweeds and food yeasts; Biological and medical sciences; CONTENIDO PROTEICO; ESPUMACION; Food industries; Fundamental and applied biological sciences. Psychology; GRAINE; HIDROFOBICIDAD; HYDROPHOBICITE; MOUSSAGE; PHASEOLUS VULGARIS; PROTEINAS; PROTEINE; SEMILLA; SEPARACION; SEPARATION; TENEUR EN PROTEINES; TENSION DE LA SUPERFICIE; TENSION SUPERFICIELLE; Proteins; Sodium Hydroxides; Surface properties; Extraction; Hydrophobicity; Citric acid; Thermal stability; Bean
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf00025a006

Acid-extracted crystalline protein isolates and alkali-extracted amorphous proteins from four Phaseolus beans were investigated for thermal and surface properties. Differential scanning calorimetry (DSC) analysis of crystalline isolates gave denaturation enthalpy (delta H) values ranging from 12.4 to 31.0 J/g; for amorphous isolates of the same beans AH ranged from 10.3 to 11.9 J/g, suggesting that the crystalline proteins were less denatured than the corresponding amorphous isolates. Differences in protein content, nitrogen solubility index (NSI), surface hydrophobicity (S0), and foam expansion were observed between the alkali- and acid-extracted isolates. The alkali-extracted isolates showed protein contents ranging from 69.62 to 81.61%, NSI of 24.23-66.75%, S0 of 2128-17000 FI%-1, and foam expansions of 30.0-49.0%. The acid-extracted isolates showed higher protein contents (75.84-96.09%) and NSI (52.19-92.37%) but much lower S0 (1966-7479 FI%-1) and low foam expansion (3.0-26.0%). Surface tension of crystalline and amorphous proteins solutions ranged from 54.8 to 58.5 and from 54.2 to 56.3 mN/m, respectively. However, the rate of decay of tension in the crystalline isolates was lower than that of the corresponding amorphous isolates. Regression analysis revealed that protein surface activity was dependent on protein content and surface hydrophobicity