Evaluation of the effects of thermal processing on antioxidant activity and digestibility of green tea noodles: Based on polyphenol stability and starch structure

The health benefits of green tea noodles (GTN) are strongly influenced by polyphenols' thermal stability and starch's thermal denaturation. This study aimed to comprehensively assess the influence of different thermal processing methods (i.e., steaming, boiling, roasting and frying) on the antioxidant activity and in vitro starch digestibility of GTN. As a result of thermal processing, the polyphenol content and antioxidant activity decreased, with correlation analysis showing a significant increase in polyphenol retention as antioxidant activity increased. GTN showed the greatest polyphenol stability during steaming compared with other thermal processing. Under the optimal cooking time, steaming and frying processing methods remarkably delayed the starch hydrolysis rate and reduced the estimated glycemic index (eGI). Further analysis proved that polyphenol content and retention rate, starch structure and the state of starch in the gluten network directly affected the in vitro starch digestion properties of GTN. Thus, steam processing will be an effective method for maximizing the functional properties of GTN from a healthy perspective.