Soluble Hydrolysate Research Articles

Bitterness intensity of soybean protein hydrolysates—chemical and organoleptic characterization

Soluble and isoelectric soluble soybean protein hydrolysates were prepared by Alcalase treatment to a degree of hydrolysis of 3–15%. The bitterness intensity of the hydrolysates obtained was assessed on a five-point scale. The average relative molecular masses of peptides in the soluble hydrolysates (2250-1400) and isoelectric soluble hydrolysates (1313-800) and their hydrophobic peptide fractions (575-400) were determined by the trinitrobenzenesulphonic acid method. The molecular mass distribution of peptides in soluble and isoelectric soluble soybean hydrolysates and their hydrophobic peptide fractions was determined by gel permeation HPLC using a Zorbax Bio Series GF-250 column. The results suggest that the main reason for the bitterness of soybean protein hydrolysates prepared by Alcalase treatment are hydrophobic bitter peptides of relative molecular mass less than 1000.

Effects of Aging and Xerosis on the Amino Acid Composition of Human Skin

Amino acid compositions of skin samples from young and old subjects and from age-matched donors with dry skin syndrome (xerosis) were examined. The amino acid contents of the free amino acid (FAA) fraction, soluble hydrolysate (SH) fraction, and whole cell hydrolysate (WCH) were determined. The greatest differences were observed between the FAA compositions of the young and old normal subjects. Xerosis did not appear to affect the amino acid compositions of samples from young subjects as much as old subjects. Overall, the effect of aging on the amino acid contents was more pronounced than the effect of xerosis. The amino acid composition of the FAA showed a high degree of similarity to filaggrin, whereas the WCH showed a similarity to keratin.

Protein hydrolysates from meat industry by-products

Hydrolysates were prepared from bovine lung, bovine rumen and from partially defatted tissue by treatment at 50°C with either pepsin at pH 3·0, papain at pH 5·5, neutrase at pH 7·0 or alcalase at pH 8·5. For all substrates papain was the most effective hydrolysing agent of those studied whilst neutrase was the least effective. Yields of soluble hydrolysate were high with 45–85 % of the protein being solubilised. In addition, the tissue is, to some extent, defatted during hydrolysis. All enzymes, with the exception of alcalase, readily solubilised the collagen of heated by-products although undenatured (unheated) collagen was, to some extent, resistant to enzymic digestion. Amino acid analysis of the soluble hydrolysates indicated that there was no major loss of any amino acid following prolonged enzymic hydrolysis. In addition, no increase in tyramine concentration occurred during hydrolysis.