Hot air impingement drying kinetics and quality attributes of orange peel

Abstract

In the recent work, hot air impingement drying was employed to orange peel processing under different temperatures and its effects on drying kinetics and quality attributes of the orange peel were investigated. Results showed that the drying time of peels decreased from 150 to 75 min as the temperature increased from 50 to 70°C, and the Weibull model precisely described the drying kinetics. The total polyphenols, flavonoids, ascorbic acid (AA), and antioxidant capacity markedly decreased after drying. The total polyphenols, flavonoids, ascorbic acid (AA), and antioxidant capacity of the orange peel markedly decreased after drying. In the case of total flavonoids and color, no significant effect (p > .05) was observed for different drying temperatures. While, the water retention capacity decreased with increasing of drying temperature. The findings contribute to a better understanding of air impingement drying characteristics of orange peel and help to optimize drying conditions for the maximum preservation of its phytochemicals and antioxidant capacity. Practical applications As the primary by-product of orange juice processing, orange peel is an excellent source of physiochemical compounds, which take an important role in health promoting. However, it is often discarded as garbage as it rots easily and hard to preserve due to its high moisture content. Drying is an essential step for the preservation and utilization of peel waste. Several drying techniques have been applied for the dehydration of citrus by-products, such as sun drying, hot air drying, freezing drying, etc. But they are difficult to achieve the rapid and reliable industrial processing of peel waste. The findings of this work indicate that hot air impingement drying is a promising drying technique for orange peel and drying temperature of 65°C allowed the best preservation of polyphenols and ascorbic acid as well as the antioxidant capacity.