Effect of thermal treatment on the enzymatic hydrolysis of chicken proteins

The proteins of chicken breast meat were thermally treated in this work. Treatment temperature and time were chosen to evaluate the effect of thermal treatment. By determination of SH and S-S group levels, the results indicated that the SH and S-S group levels in the chicken proteins without thermal treatment were 65.06 and 12.29 mu mol/g. With the increase of treatment temperature, the SH group level decreased, while S-S group level increased gradually. Enzymatic hydrolysis by Alcalase was done to evaluate the nitrogen levels of hydrolysates. A temperature-dependent effect was observed for Soluble and formaldehyde nitrogen levels. A slight increase of peptide nitrogen level was found with the increase of temperature. Treatment time had a similar effect to treatment temperature. The molecular weight of chicken protein hydrolysates was analysed by gel permeation chromatography. The chicken protein hydrolysates Without thermal treatment showed an apparent peak at 27.5 ml of elution volume and a weak peak at 4.0 ml, which represented fractions with molecular weight of >10,000 Da and <2640 Da, respectively. Thermal treatment led to decreases of the fractions with molecular weight of >10,000 Da, 3500-2640 Da and <2640 Da, compared with hydrolysate fractions without thermal treatment. Treatment with a temperature higher than 60 degrees C for 20 min would completely eliminate the >10.000 Da fraction from chicken protein hydrolysates. The percentage of fraction with molecular weight of 4500-3500 Da increased with the extension of treatment time to 20 min, thereafter decreased. Industrial relevance: The annual yield of chicken meat in China ranks the second of the world. However, the extensive development of this resource is still limited. In this work, chicken breast meat was thermally treated and then hydrolysed by Alcalase. Effects of treatment temperature and time on the hydrolysates were investigated. The results indicated that thermal treatment could change the levels of soluble nitrogen, formaldehyde nitrogen and peptide nitrogen. The area percentages of fractions with different molecular weight were also changed. This work was helpful to understand the characteristics of bioactive peptides produced from chicken proteins. (C) 2008 Elsevier Ltd. All rights reserved.