Studies On Antioxidant Properties Of Fresh-cut And Processed Sweet Potatoes

Recently,there has been a considerable research interest in antioxidant capacities of phytochemicals from various materials.Several epidemiological studies suggest that a high intake of food rich in natural antioxidants can increase the antioxidant capacity of the plasma and reduce the risk of certain,but not all,cancers,heart diseases,and stroke. It was reported that sweet potatoes are rich in nutrition,higher total content,and showed a stronger antioxidant activity.However,there are fewer research on the antioxidant property of sweet potato products.In order to evaluate the antioxidant properties of sweet potato products,in the current study,antioxidant properties of fresh-cut sweet potatoes which stored in different temperature were studied;as well as analyzed the effects of different cooking on antioxidant properties of sweet potatoes;and also discussed the effect of different drying treatment on the antioixidant properties of sweet potatoes.Storage temperature have obviously effect on antioxidant properties of fresh-cut sweet potatoes.In this study,4℃and 10℃were used in the storage of fresh-cut sweet potatoes,and DPPH assay was used as antioxidant activity assay and include compounds such as total phenolic,flavonoids andβ-carotene were determined.The total phenolic and antioxidant activity increased during storage period,10℃presented a higher data than 4℃.However,4℃can keep color and water capacity much better.Cooking methods may cause increase or decrease in antioxidant activity and include compounds.Water boiled,steam boiled,microwave boiled and roast were used for cooking.The antioxidant properties of cooked sweet potatoes were determined with several antioxidant assays,total phenolics,β-carotene and ascorbic acid content of cooked sweet potatoes were measured,and correlations among them were analyzed. The result showed that the total phenolic content of all cooked sweet potaoes were increased when compared to the raw,andβ-carotene and ascorbic acid declined in varying degrees.There were very significant positive correlation between total phenolics and antioxidant capacity,and significant negative correlation between total phenol and ascorbic acid.The result indicated that total phenols maybe the main compound contributed to the antioxidant activity of cooked sweet potato and steam boiled may be the best cooking method based on the antioxidant properties,and the microwave boiled is better.Effects of hot-air drying,microwave drying and vacuum-freeze drying on the antioxidant activity and antioxidants in sweet potato(Ipomoea batatas L.Lam.) tubers were investigated to determine the potential drying process.Sweet potato tubers were cut into 5 mm thick slices,steamed at 100℃for 10 min,cooled tp the room temperature, and then dried in hot-air,microwave,or vacuum-freeze,respectively.Microwave dried sweet potatoes possessed the highest antioxidant activity,while the lowest activity was obtained in hot-air dried samples.The phenolic content was positively correlated with DPPH~+ scavenging activity and reducing power.Microwave drying presented the highest antioxidant activity and the highest content of phenolic compounds in dried sweet potatoes,however,lost the mostβ-carotene and ascorbic acid content.