Abstract: Four common processing methods (steaming,boiling,frying,and microwaving) were used to process purple sweet potatoes and carrots.Combined with in vitro simulated digestion,the contents of total phenols,total flavonoids,total anthocyanins,total carotenoids,and the changes of antioxidant activity (DPPH,ABTS free radical scavenging ability) in raw materials before and after processing and at various stages of digestion were measured.Meanwhile,purple sweet potatoes and carrots were compounded in different ratios before and after different heat processing treatments to evaluate the antioxidant interactions of the mixed diets.The results showed that the steam and boil processing could effectively convert the bound phytochemicals in purple sweet potatoes and carrots into the free state for human absorption and use,and the degradation of phytochemicals caused by the steam and boil processing conditions was lower compared to frying and microwaving.Compared to frying and microwave processing,the steamed and boiled purple sweet potatoes and carrots have a better DPPH and ABTS free radical scavenging ability.When purple sweet potatoes and carrots from the same processing methods were combined in different proportions,it was found that when the proportion of water-soluble phytochemicals was higher,the overall antioxidant synergy could be demonstrated significantly.The total phenol and total flavonoid content of purple sweet potatoes in each processing method showed the most significant increase in the gastric digestion stage,and slowed down significantly in the intestinal digestion stage,while the total anthocyanin content continued to decrease during the digestion process,with the best antioxidant ability in the gastric digestion stage.The total carotenoid content of carrots in all processing methods continued to increase during digestion,and the growth trend was greater in the intestinal digestion stage than in the gastric digestion stage,and their DPPH and ABTS free radical scavenging ability were best in the intestinal digestion stage.

Key words: cooking process, antioxidant interaction, antioxidant in vitro, simulated digestion in vitro