Effects of Different Drying Methods on Resveratrol Content of Mulberry Fruits Determined by High-Performance Liquid Chromatography Technique

Abstract

Mulberries are fruits rich in many essential compounds, one of which is resveratrol. This compound is highly sensitive to temperature; exposure to either excessively low or high temperatures can cause it to degrade. Therefore, the drying process of mulberries has an impact on the retention of resveratrol. The objective of this study was to determine the amount of resveratrol extracted from the fruit of the Mulberry cultivar Buriram 60, which was sampling from Phu Luang District, Loei Province. The samples were dried using five methods: hot air drying at 80°C, hot air drying at 104°C, sun drying, freeze drying, and drying by reducing relative humidity. These dried mulberry fruits were ground finely and sieved through 100 mesh to achieve uniform particle size. They were then extracted with a 60%v/v methanol solution, utilizing ultrasonic assistance for 40 minutes. The solids were removed, and the clear extract was filtered through a 0.45-micron membrane filter prior to the analysis of resveratrol content using high-performance liquid chromatography (HPLC) at a detection wavelength of 306 nanometers.
The quantitative analysis results indicated that different drying methods led to varying amounts of resveratrol. Exposure to the hot air oven caused significant degradation of resveratrol, resulting in its undetectability. Only the sun-drying method, freeze-drying method, and drying by reducing relative humidity still yielded detectable levels of resveratrol, with values of 10.73±0.61 mg/100g DW, 12.29±0.30 mg/100g DW, and 18.19±0.10 mg/100g DW, respectively. Therefore, this study concludes that the most suitable method for drying mulberry fruit while preserving the resveratrol content is the drying method that reduces relative humidity.