Journal
COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY
Volume 20, Issue 5, Pages 4841-4880Publisher
WILEY
DOI: 10.1111/1541-4337.12797
Keywords
catechins; condensed tannins; degree of polymerization; depolymerization; epimerization; flavan-3-ols; oxidation; proanthocyanidins
Categories
Funding
- China Scholarship Council (CSC)
- l'Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE)
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Flavanols, a subgroup of polyphenols with antioxidant properties, are naturally produced in plants and have significant effects on human health. However, their changes during physical processing, such as oxidation, polymerization, degradation, and epimerization, are often underestimated due to analytical challenges. Research on the effects of physical processing techniques on flavanol content and structural changes is important for improving nutritional value, but further studies are needed to better understand the role of flavanols in food processing.
Flavanols, a subgroup of polyphenols, are secondary metabolites with antioxidant properties naturally produced in various plants (e.g., green tea, cocoa, grapes, and apples); they are a major polyphenol class in human foods and beverages, and have recognized effect on maintaining human health. Therefore, it is necessary to evaluate their changes (i.e., oxidation, polymerization, degradation, and epimerization) during various physical processing (i.e., heating, drying, mechanical shearing, high-pressure, ultrasound, and radiation) to improve the nutritional value of food products. However, the roles of flavanols, in particular for their polymerized forms, are often underestimated, for a large part because of analytical challenges: they are difficult to extract quantitatively, and their quantification demands chemical reactions. This review examines the existing data on the effects of different physical processing techniques on the content of flavanols and highlights the changes in epimerization and degree of polymerization, as well as some of the latest acidolysis methods for proanthocyanidin characterization and quantification. More and more evidence show that physical processing can affect content but also modify the structure of flavanols by promoting a series of internal reactions. The most important reactivity of flavanols in processing includes oxidative coupling and rearrangements, chain cleavage, structural rearrangements (e.g., polymerization, degradation, and epimerization), and addition to other macromolecules, that is, proteins and polysaccharides. Some acidolysis methods for the analysis of polymeric proanthocyanidins have been updated, which has contributed to complete analysis of proanthocyanidin structures in particular regarding their proportion of A-type proanthocyanidins and their degree of polymerization in various plants. However, future research is also needed to better extract and characterize high-polymer proanthocyanidins, whether in their native or modified forms.
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