Effect of drying methods on physicochemical properties and antioxidant activities of okra pods

Abstract

The effects of hot air drying (HD), freeze‐drying (FD), microwave drying (MWD), natural convective drying (NCD), and vacuum drying (VD) on the physicochemical, nutritional, and https://www.sciencedirect.com/topics/food-science/antioxidant properties of okra pods were investigated. Changes in the surface morphology, color, rehydration ratio, protein, pectin, ascorbic acid, and phenolics, as well as antioxidant activities of okra pods measured by 2,2′‐azinobis (3‐ethylbenzo thiazoline‐6‐sulphonic acid) diammonium salt (ABTS), 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH), and Ferric Ion Reducing Antioxidant Power (FRAP) assays were evaluated. In general, FD products exhibited a better retention of the texture characteristics, nutritional, and antioxidant activities, and was suitable for okra pods drying, although FD was the longer time‐consuming method among the five drying methods. Furthermore, NCD products were poorer in color, texture, and nutrition. Future studies should continuously focus on various combinations of different types of drying methods to supply okra pods products with the most affordable cost and the highest quality. Practical applications Physicochemical properties and antioxidant capacities of okra pods are affected by the drying process. The drying process with nonthermal, low temperature, and low content of oxygen is beneficial to the retention of nutrients and functional components. In general, freeze‐drying exhibited a better texture characteristics and good antioxidant activities, although higher energy and longer time consumption was the current challenge. How to combine the different types of drying methods has become an inevitable trend and research focus.

Influence of Different Types of Drying Methods on Color Properties, Phenolic Metabolites and Bioactivities of Pumpkin Leaves of var. Butternut squash (Cucurbita moschata Duchesne ex Poir)

“…Furthermore, openly sun-dried cowpea leaves lost 82-86% ascorbic acid (22), whereas, in this study, sun drying caused a 39.67% loss. In this study, the solar-drying cabinet significantly reduced the loss of ascorbic acid by 36.22% in pumpkin leaves.…”

Ultrasound freeze-thawing style pretreatment to improve the efficiency of the vacuum freeze-drying of okra (Abelmoschus esculentus (L.) Moench) and the quality characteristics of the dried product

“…Thereby, this life amelioration provided a broad prospect for development of the dried products [5] . In recent years, the common methods of drying okra slices were, e.g., open-sun, hot air drying (HD), vacuum freeze‐drying (VFD), microwave drying (MWD), natural convective drying (NCD), and vacuum drying (VD), Microwave assisted hot air drying [6] , [7] , [8] , [9] , [10] . Each drying method has its advantages and drawbacks, such as microwave drying has a high heating efficiency; however, the disparity in the absorption of microwave energy caused by the unequal internal moisture of the material at the late drying stage, is likely to lead to local scorching and poor quality of the dried material [11] .…”

Comprehensive evaluation of physicochemical properties and antioxidant activity of B. subtilis‐fermented polished adlay subjected to different drying methods

“…The highest fat content was presented in MVD samples, but VD samples showed low fat content. Similarly, significant differences in proximate composition were found among different treatments, and FVD samples had higher contents of proximate composition (Gong et al, 2019; Li, Jin‐Jia, Ling, & Hao, 2019). Samples treated by FVD at low temperature condition, and the cell injury was generally negligible; thus the contents of protein, starch, and fat were higher in FVD samples (Öztürk & Gündüz, 2018).…”