Mild preheating improves cholesterol-lowering benefits of soy protein via enhancing hydrophobicity of its gastrointestinal digests: An in vitro study

作者：Zhu, Wen-Wen; Tang, Chuan-He^*

来源：Food Hydrocolloids, 2022, 124: 107282.

DOI：10.1016/j.foodhyd.2021.107282

• Soy proteins
• Cholesterol-lowering activity
• Thermal aggregation
• In vitro digestion model
• Ethanol precipitation

Although the cholesterol-lowering benefits of soy proteins have been well recognized for a long time, the importance of protein structural characteristics to their cholesterol-lowering activities is little understood. In the work, we reported that a mild preheating at 95 degrees C for 20 min could remarkably improve the cholesterol-lowering activities of soy protein isolate (SPI) after an in vitro simulated pepsin-pancreatin digestion, including cholesterol and bile acids binding capacities (CBC and BBC), and inhibition of micellar cholesterol solubility (MCI), while an extensive preheating at 121 degrees C contrarily impaired its potential. The improvement of the cholesterol-lowering activities of the pepsin-pancreatin digest by the mild preheating was largely associated with the facilitated formation of digestion-induced peptide aggregates with high surface hydrophobicity (H-o) in the digest. The final pepsin-pancreatin digest of the mildly preheated SPI could be fractionated using a gradient ethanol precipitation technique at ethanol concentrations of 20-80% (v/v). The H-o and cholesterol-lowering activities of peptides in the resultant precipitate or supernatant fractions considerably varied. The ethanol-precipitated fractions at ethanol concentrations of 40-80%, with high H-o but low solubility (in water), largely contributed to the CBC of the digest, while all the precipitates obtained at ethanol concentrations of 20-80% dominated the BBC of the digest. In contrast, the soluble peptides in 80% ethanol were mainly responsible for the high potential of the digest to inhibit micellar cholesterol solubilization. In general, a good positive relationship between the CBC (or BBC) and H-o could be well observed for the pepsin-pancreatin digests of SPI, or their fractions. The MCI of the mildly preheated SPI digest was largely ascribed to the action of soluble peptides in 80% ethanol. The results demonstrated that the choice of preheating conditions (especially temperature) is of vital importance for optimal cholesterol-lowering benefits of soy proteins. The findings are also of interest for understanding the molecular mechanisms of the cholesterol-lowering activities of soy proteins.