Ultrasonic-assisted Extraction of Dietary Fiber from Defective Lemon Basil (Ocimum basilicum var. citriodorum) Seed

Abstract

Lemon basil (Ocimum basilicum var. citriodorum) is an herbaceous plant cultivated for seed consumption only in Sukhothai Province, Thailand. Unlike cultivating for fresh leave consumption, the production of lemon basil seed requires maturity and reproduction phases, the same as rice and wheat. After harvesting, the farmer separates unmatured red basil seeds (RBS) because of their diverse color. The RBS contains valuable compounds, such as dietary fiber, that could be extracted by an ultrasonic-assisted extraction (UAE). This work aims to extract DF with the highest brightness using Lab* color in liquid form as an indicator. The optimal condition was identified by the crossing point between the brightness (L*) and extraction yield. The proximate nutrient analysis showed that RBS has a higher fiber content than high-quality basil seed (HBS). For water swelling ability, HBS performed 4-fold higher than RBS. The complete extraction of dietary fiber was observed at 10 min for UAE at 200 W, a water-to-seed ratio of 30:1, and 100% amplitude, and it was preferably conducted at room temperature (30±2°C) without an external cooling system. The correlation between UAE extraction time and temperature at constant total power and amplitude was also explored. When the extraction temperature exceeded 80°C, the extracted mucilage was rotten within 24 h, even if stored at 4°C. Moreover, the extracted RBS contained Omega-3 oil that a screw-press machine or supercritical CO2 could extract in further study.