Ultrasound-assisted aqueous enzymatic extraction of gardenia fruits (Gardenia jasminoides Ellis) oil: Optimization and quality evaluation

Aqueous enzymatic extraction (AEE) process is known as a safety and environmental- friendly method for oil extraction. In this work, ultrasonic pretreatment was used to accelerate aqueous enzymatic extraction (using both Cellic CTec3 and Alcalase 2.4 L) of gardenia fruit (Gardenia jasminoides Ellis) oil. The extraction conditions of two enzymes were optimized by the response surface method (RSM) respectively: Cellic CTec3: solid-liquid ratio 1:6 g/mL, incubation temperature 45 ℃, incubation time 120 min and enzyme concentrate 1.7%; Alcalase 2.4 L: solid-liquid ratio 1:6 g/mL, incubation temperature 51 ℃, incubation time 120 min and enzyme concentration 1.3%. The optimized oil extraction yield obtained by ultrasound-assisted aqueous enzymatic extraction (UAEE) was as high as 18.65%. Nutritional composition, apparent color and rheological properties of gardenia fruit powder before and after ultrasonic pretreatment were measured, illustrating that ultrasonic pretreatment reduced the protein content in the raw material and increase the fluidity of the powder. Scanning electron microscopy showed more pores and interspaces of the enzymatic residues of gardenia fruit powder with ultrasonic pretreatment than those without. The oil sample extracted by UAEE showed better quality and higher contents of tocopherol, squalene and polyunsaturated fatty acids (PUFAs), compared with oils extracted by solvent extraction (SE) and cold pressing extraction (CPE).