Optimization of supercritical CO2 extraction process for oleoresin from rotten onion waste

Supercritical fluid extraction technique (SFE) was utilized to obtain the superior quality of onion oleoresin from the dried rotten onion. The effects of temperature (50, 60, 70, 80 and 90 degrees C), pressure (150, 225, 300, 375 and 450 bar), dynamic time (30, 60, 90, 120 and 150 min) and particle size (0.4, 0.6, 0.8, 1.0 and 1.2 mm) were evaluated with respect to oleoresin yield, sulphur content and pyruvate content in oleoresin. The optimization of supercritical fluid extraction was carried out by using a central composite rotatable design (CCRD). From the responses, optimized condition for SFE of onion oleoresin was found as 80 degrees C temperature, 400 bar pressure, 0.53 mm particle size and 60 min dynamic time. Oleoresin extracted at optimized SFE condition had a yield of 1.012% oleoresin, 31 g sulphur content per kg of oleoresin and 10.41 mu mole pyruvate per g fresh weight of onion. It was observed that SFE provided shorter extraction time, comparatively similar oleoresin yield and a higher percentage of sulphur content which represents the useful sulphur containing compounds in onion. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.