The quality issues of ultra-high-temperature (UHT) milk, such as protein hydrolysis and aging gels throughout shelf life, are caused by proteases from psychrophilic bacteria. However, existing enzyme activity detection techniques have low sensitivity and cannot accomplish the detection of product deterioration caused by low enzyme activity. In this study, an attempt was made to analyze the relationship between enzymatically cleaved peptides and product quality using peptidomics techniques. The impact of psychrophilic bacteria proteases on the quality of UHT milk was investigated based on peptidomics by exogenously adding proteases. The results indicated that the protease activity and protein hydrolysis increased significantly in UHT milk over the storage period. Through peptidomic analysis, 2479 peptides were identified, in which 32 proteins linked to the identified peptides. 17 potential marker peptides, including αS 1 -casein 143–156 , β -lactoglobulin 99–108 , and β -casein 39–66 , were screened. The correlation of all identified peptides with protease activity and protein hydrolysis was explored by the weighted gene co-expression network analysis (WGCNA) method. The peptidomics technology helps to study the release or degradation of peptides in UHT milk during storage, which can be applied to monitor the shelf life of UHT milk and predict spoilage.
Xiao-Mei Sha,Zi-Zi Hu,Yun-Hua Ye,Huang Xu,Zong-Cai Tu
High-performance liquid chromatography (HPLC) and linear-ion trap (LTQ)/Orbitrap high-resolution mass spectrometry were used to identify porcine gelatins extracted at different temperatures. Moreover, shear stress rheological detection techniques and a texture analyzer were applied to evaluate the gelling properties of various porcine gelatins. The results showed that, with an increased in the extraction temperature, the gel strength, gelation point and melting point of the porcine gelatin gradually decreased, indicating that the temperature significantly affected the gelling properties of gelatin. HPLC- LTQ/Orbitrap high-resolution mass spectrometry indicated that porcine gelatins prepared at different extraction temperatures also showed internal uniqueness, namely, diverse marker peptides for gelatin identification. Compared with the established theoretical sequence fragment database of porcine gelatin and bovine gelatin, 64, 74 and 71 tryptic porcine peptides in gelatins were extracted at 55 °C, 65 °C and 75 °C, respectively. Notably, regardless of the extraction temperature, 47 common peptides were detected in the tryptic hydrolysates of porcine gelatins. Using these common tryptic peptides can effectively improve the accuracy of the porcine gelatin identification.
危险品化学品经营许可证（带存储）