Enzymatic debittering of cheese flavoring and bitterness characterization of peptide mixture using sensory and peptidomics approach.

Peptides in cheese flavoring produced through proteolysis plus fermentation generated bitterness. Bitterness of individual peptide can be quantified using quantitative structure-activity relationship, where molecular mass (M), hydrophobicity, residues, C-terminal hydrophobic amino acids (C-HAAs), and N-terminal basic ones (N-BAAs) are crucial. However, their accumulative influence on the overall bitterness of peptide mixture remains unknown. This study delved into extensive proteolysis to debitter and to correlate the multi-influencing factors of peptides and the collective bitterness. As hydrolysis increased from 7.5 % to 28.0 %, bitterness reduced from 5.0 to 0.3-2.7 scores, contingent on proteases used, in which FU was optimal. The overall bitterness cannot be predicted through the summation of individual peptide bitterness, which depended on M (0.5-3 kDa) and 5-23 residues, followed by N-BAAs and C-HAAs. Analysis of enzymatic cleavage sites and substrate characteristics revealed, to more effectively debitter bovine milk protein hydrolysates, proteases specifically cleaving Pro, Leu, Phe, and Val were desired.

The Possibility of Replacing Wet-Milling with Dry-Milling in the Production of Waxy Rice Flour for the Application in Waxy Rice Ball.

Due to the large consumption and discharge of water in wet milling, dry-milling is an alternative to produce waxy rice flour. The physical properties and sensory characteristics for preparing waxy rice balls in dry-milled waxy rice flour were compared in this study. The results showed that the damaged starch content increased significantly with the particle size of dry-milled flour, which decreased from 160 to 30 µm. The reduction in particle size increased the pasting viscosity of waxy rice flour, which further improved the stretch ability of dough and increased the viscoelasticity of the rice ball. The increase in damaged starch content directly led to a significant increase in the solubility of dry-milled flour, thereby increasing the freeze cracking rate of the rice ball and reducing its transparency, resulting in a decline in quality. In comparison with wet-milled waxy rice balls, dry-milled waxy rice balls made from rice flour in the range of 40 µm to 60 µm particle size had a similar texture and taste to that of wet-milled ones, moderate freeze cracking rate and better storage stability, as well as a stronger aroma of waxy rice that the consumer favored. GC-MS analysis showed that the content of key aroma compounds, such as grassy and fruity, noted nonanal in dry-milled flour, was 15-30% higher than that in the wet-milled depending on the difference of waxy rice variety. In conclusion, dry-milled waxy rice flour with a particle size in the range of 40 µm to 60 µm could be a candidate to replace wet-milled flour in the preparation of a waxy rice ball.

Study on the Pasting Properties of Indica and Japonica Waxy Rice.

In this study, the physicochemical properties of indica (IWR) and japonica (JWR) waxy rice were investigated to find the critical factor that differentiates the pasting behaviors among the two cultivars. The results showed that the peak viscosity of 5 IWR flours was in the range of 1242 to 1371 cP, which was significantly higher than 4 JWR flours (667 to 904 cP). Correlation analysis indicated that all pasting parameters were not correlated (p < 0.05) with physicochemical properties of rice flours and the fine structure of isolated starches. The pasting profiles of IWRs were still significantly higher than those of JWRs after removing lipid, while there were no significant differences between the two cultivars after removing protein sequentially. Meanwhile, the addition of extracted protein from JWR to the isolated starch significantly decreased the viscosity compared to the addition of protein extracted from IWR. The protein composition results found that the IWR protein contained about 18% globulin and 64% glutelin, while the JWR protein contained 11% globulin and 73% glutelin. The addition of glutelin to isolated starch significantly decreased viscosity compared to the addition of globulin. Therefore, the differences in the content of globulin and glutelin might be the main reasons that differentiate the pasting behaviors of the two cultivars.