Factors impeding enzymatic wheat gluten hydrolysis at high solid concentrations

Flavor Precursors and Volatile Compounds Improvement of Unfermented Cocoa Beans by Hydrolysis Using Bromelain

Cocoa fermentation is an essential process that produces flavor precursors. However, many small farmers in Indonesia directly dry their cocoa beans without fermentation due to low yield and long fermentation time, resulting in fewer flavor precursors and cocoa flavor. Therefore, this study aimed to enhance the flavor precursors, particularly free amino acids and volatile compounds, of unfermented cocoa beans by hydrolysis, using bromelain. Unfermented cocoa beans were previously hydrolyzed with bromelain at concentrations of 3.5, 7, and 10.5 U/mL for 4, 6, and 8 h, respectively. An analysis of enzyme activity, degree of hydrolysis, free amino acids, reducing sugar, polyphenols, and volatile compounds was then conducted using unfermented and fermented cocoa beans as negative and positive controls, respectively. The results showed that the highest degree of hydrolysis was 42.95% at 10.5 U/mL for 6 h, although it was not significantly different from the hydrolysis at 3.5 U/mL for 8 h. This indicates a higher reducing sugar and lower polyphenols content than unfermented cocoa beans. There was also an increase in free amino acids, especially hydrophobic amino acids, such as phenylalanine, valine, leucine, alanine, and tyrosine, and desirable volatile compounds, such as pyrazines. Therefore, this suggests that hydrolysis with bromelain increased the flavor precursors and cocoa-bean flavors.

Plastein from hydrolysates of porcine hemoglobin and meat using Alcalase and papain

Plastein is defined as a protease-induced peptide aggregate and has been explored for over a century. This study investigated the effects of Alcalase and papain on plastein formation in protein hydrolysates of porcine hemoglobin and meat by measuring turbidity, particle size distribution, free amino groups and chemical interactions, as well as identifying the soluble peptides remaining in solution by LC-MS/MS. The results showed that Alcalase induced more peptide aggregation than papain in terms of increases in turbidity and particle size. Porcine hemoglobin was better than meat in inducing plastein formation in a short reaction time. Besides, covalent bonds involving peptide bonds and disulfide bonds were not crucial in the plastein reaction, instead a high proportion of hydrophobic interactions dominated the plastein. Not all peptides of both hydrolysates took part in plastein formation, and the regions of sequence that were prone to aggregation were visualized by Peptigram.