A Comparison of Phenolic Compounds, Antioxidant Activity, and Α-Glucosidase Inhibitory Activities of Apple Chips Dried and Fried by Vacuum Combined Infrared Radiation

Abstract

In this study, the effects of different drying (180-325 W and 100-400 mmHg) and frying (250-350 W and 400 mmHg) parameters on phenolic compounds, bioaccessibilities, antioxidant activities, and alpha-glucosidase inhibitory activities of apple chips dried and fried by vacuum-combined infrared radiation were investigated. Catechin (12.15-34.48 mg/kgDM), epicatechin (34.33-137.07 mg/kgDM), procyanidin B1 (14.07-30.05 mg/kgDM), procyanidin B2 (48.10-95.76 mg/kgDM), procyanidin C1 (14.95-42.97 mg/kgDM), chlorogenic acid (262.70-397.97 mg/kgDM), and rutin (0-5.94 mg/kgDM) were identified in apple chips. The phenolic content of apple chips increased with increasing infrared power during the drying and frying process. The phenolic contents of fried apple chips were generally higher than dried apple chips. However, the bioaccessibility rates of total flavan-3-ols in dried apple chips were higher than those of fried apple chips. It was determined that the initial total phenolic, flavonoid, and flavan-3-ol contents and antioxidant activity levels of the samples decreased after in-vitro gastrointestinal digestion. It was determined that all drying and frying samples showed higher alpha-glucosidase inhibitory activities (15.52-28.77 mg/mL) compared to acarbose (30.87 mg/mL). The apple chips dried and fried by infrared radiation had higher phenolic content, antioxidant activity, bioaccessibility, and alpha-glucosidase inhibitory activity than their counterparts (convectional drying and deep-fat frying, respectively). Vacuum-combined infrared drying and frying is a promising method to preserve the phenolic content, antioxidant, and antidiabetic activities of apple chips, especially at high temperature applications. Further research is needed on new designs for the production of fruit chips using infrared radiation and their effects on bioactive components.