Optimization of hydration method for efficiently separating high‐quality oils from macadamia seed kernels

Abstract

Green processing techniques are in high demand among food processors, especially for oil recovery. This paper illustrates that solid hydration processing was efficient in green extraction of macadamia oil. Optimization illustrated that microwave-heating macadamia kernels for 1 min at 320 W power, grinding the kernels to pass through a sieve with 200–250 meshes, adding 1.20–1.29 ml water to 10.00 g ground kernel, and agitating for 30–60 min at room temperature provided high-quality oil recovery. The hydration method recovered ca. 94.83% or ca. 97.83% oil depending upon oil collection methods used, similar to solvent extraction and better than hot pressing. The edible oil contained lower undesirable compounds (e.g., acid or peroxide value) or higher fat-soluble bioactivators (e.g., vitamin E/A/D, squalene, phytosterols, and antioxidants), and defatted meal avoiding water-soluble bioactivator (e.g., B vitamins) losses as compared with solvent extraction and hot pressing. No waste water was discharged during oil extraction. Novelty impact statement Macadamia kernels had different chemical compositions and characteristics of structure as compared with other oilseed kernels so that the optimal parameters of hydration method for recovering oils from them were significantly different. Hydration method as a green technology extracted more than 97% macadamia oils rich in fat-soluble bioactive compounds and high-quality defatted meal rich in water-soluble bioactive compounds with no waste water discharged during oil extraction. Hydration method is believed to be environmentally friendly and economically efficient and have greatly positive impact on society.