Effects of different extraction methods on the chemical composition, antioxidant activity and flavor of bayberry ( <i>Myrica rubra</i> Sieb. et Zucc.) kernel oil

Bayberry (Myrica rubra Sieb. et Zucc.) kernel is a by-products of bayberry processing and are rich in oil. This study investigates the effects of different processing methods on bayberry kernel oil (BKO) yield, including cold pressing (CP), direct solvent (n-hexane) extraction, ultrasound-assisted n-hexane extraction (UAE), steam explosion pretreatment to assist n-hexane extraction, aqueous enzyme extraction, and supercritical fluid extraction (SFE). The acid value, peroxide value, fatty acid composition, bioactive components content, and the antioxidant activity of the extracted BKO with six methods were compared. The results showed that the oil yield of bayberry kernel extracted by different methods was between 30.95% and 49.49%, and the oil yield of UAE was the highest. BKO samples extracted by different methods had lower acid value (0.39-0.59 mg KOH/g) and peroxide value (3.97-5.84 meq O₂/kg), and were rich in unsaturated fatty acids (>85%), mainly including oleic (46.9%-47.9%) and linoleics (37.0%-39.5%). Meanwhile, BKO contained phytosterols (384.67-597.14 mg/100 g) and tocopherols (632.09-1227.62 µg/100 g), which was positively correlated with antioxidant activity. The volatile organic compounds (VOCs) of BKO varied on extraction methods. BKO extracted by CP and SFE showed more VOCs (25 in CP-BKO, 26 in SFE-BKO). The representative VOCs in BKO are alcohols and esters. The results provide references for further processing of BKO.