Novel insights into bound Phenolics: Conversion and release of phenolic compounds in lychee pulp by heat pump drying
Fangli Hou1, Tong Su2, Yun Chen2
1Teaching and Experimental Center, Guangdong Pharmaceutical University, Zhongshan 528458, China.
Abstract:
The bioactivities of lychee pulp (LP) phenolics have been extensively documented. However, the impact of processing techniques on the phenolics remains unclear. The objective of this study was to investigate the conversion and metabolism of phenolics in LP that was first heat pump-dried and then fermented by lactic acid bacteria. HPLC-DAD analysis revealed that a portion of the free phenolics were converted to bound phenolics during the drying process. It is noteworthy that 4-hydroxybenzoic acid, procyanidin B2, and syringic acid were identified as novel compounds. The HPLC-MS/MS analysis demonstrated that Lactobacillus fermentation facilitated the additional release of polyphenols from dried LP. Seven previously unidentified phenolic compounds, including protocatechuic acid, 4-hydroxyphenylpropionic acid, dihydrocaffeic acid, 3-phenylpropionic acid, 4-hydroxyphenylacetic acid, isorhamnetin-3-O-rutinoside, and isoferulic acid, were discovered in samples of mixed strain Lactobacillus fermentation. These findings provide a theoretical foundation for the lychee processing industry.
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