Effects of tray drying, vacuum infrared drying, and vacuum microwave drying techniques on quality characteristics and aroma profile of orange peels

Abstract

This study aimed to dry orange peels using tray drying (TD), vacuum infrared drying (VID), and vacuum microwave drying (VMD) techniques and to investigate the effects of different drying techniques on the drying kinetics, physical, chemical characteristics, and volatile compounds. The VMD raised the drying rate and the effective water diffusivity compared to the TD and the VID. It was detected that the TD, VID, and VMD at 50°C required 300, 106, and 20.67 min, respectively. The VMD showed the highest vitamin C, total phenolic substance, total carotenoid content, whereas the TD indicated the lowest color values. A total of 63 volatile compounds which consist of 16 aldehydes and ketones, 4 esters, 34 terpenes, and 9 other types of compounds were determined in dried orange peels. It was determined that the VID technique caused the least destructing in volatile compounds, whereas the TD technique was the most destructive.Practical ApplicationsDrying is a common preservation method used for the long‐term durability of foods. Drying of orange peel conduces not only to decrease environmental problems but also to provide economic benefits. Dried orange peel is used in herbal teas and food products because it is rich in aromatic flavor and odor components. Orange peel was dried using tray drying, vacuum infrared drying, and vacuum microwave drying. The vacuum microwave drying increased the drying rate and effective water diffusivity to others. The vacuum microwave drying and vacuum infrared drying protected quality characteristics, and volatile compounds of orange peels. This study demonstrated that the waste orange peels could be dried with different drying methods and converted into products with high nutritional components.

Combined Hot Air, Microwave, and Infrared Drying of Hawthorn Fruit: Effects of Ultrasonic Pretreatment on Drying Time, Energy, Qualitative, and Bioactive Compounds’ Properties

“…According to the diagram, increasing the drying time increased the pH, which can be attributed to the type of compounds extracted from hawthorn fruit and also the further degradation of cell walls over time. The increase in pH could be due to the Maillard reactions and the high concentration of soluble solids during the prolonged drying [ 67 ]. The lowest pH was achieved by freeze-drying (3.98) and combined microwave–hot-air drying with ultrasonic pretreatment (4.03).…”

Various Natural Dyes from Different Sources

“…This process usually produces natural colours in dry powder form ready-to-use. [50] Drying under a vacuum Dye molecules should be sufficiently stable for heating, since dry powder is subjected to dry heat from warm air to follow this drying procedure. Many fine dye particles, too minute to be placed on the bottoms of the chamber, are also moved by heated air and lost, leading to less regeneration [49].…”

“…In this technique, the natural colour extract is congealed, and water is sublimated by lowering the pressure from the frozen extract. Equipment is expensive and operation costs are higher, but heat sensitive dyes may also be turned into dry powders when the procedure is carried out at low freezing temperatures [50]. Any of these procedures can be utilized to produce natural colour powder based on the quality and prices of colour extracting.…”

“…Any of these procedures can be utilized to produce natural colour powder based on the quality and prices of colour extracting. Highly pure dye extracts are now available in several countries, particularly the United States, although these are very expensive and are utilized for their unique characteristics largely by hobby groups [9,50].…”

Ultrasoni̇k Ve Elektri̇ksel Ön İşlemleri̇n Ki̇vi̇ Di̇li̇mleri̇ni̇n Kuruma Ve Kali̇te Özelli̇kleri̇ne Etki̇si̇

“…Drying is one of the oldest method of food preservation and the most common technique used in the food industry. Conventional air-drying allows longer shelf life and smaller space for storage (Nowacka et al, 2012;Demiray et al, 2017;Bozkir et al, 2021). However, there is a large loss of thermal energy and a lengthy drying time throughout the falling rate period in convective drying (Wang and Xi, 2005).…”