Chemical characterisation and oxidative stability of cold-pressed Macadamia integrifolia oil from Brazilian cultivars

Abstract Macadamia oil (as with other vegetable oils) can be obtained via solvent extraction, aqueous extraction or by cold pressing. The latter technique avoids the use of solvents and high temperatures which maintains the physical and chemical properties of the extracted oil. In this study, four different varieties of Macadamia integrifolia were grown at two separate farms in the southeastern region of Brazil. Harvested nuts were processed, dried and then cold-pressed (resulting in a ~ 33% yield). Analysis highlighted significant differences across the four varieties. The fatty acid composition demonstrated a predominance of oleic and palmitoleic acids, and the triacylglycerol composition showed mostly unsaturated triacylglycerides. Despite having highly similar overall unsaturation, substantial differences in oxidative stability were observed, with induction times ranging from 11.87 to 22.73 h with the São Miguel Farm oils (412-B and 920) exhibiting greater stability than the Santa Helena Farm oils (344 and 816). This nearly two-fold variation cannot be explained by iodine values (73.8–74.4 g I₂/100 g), total monounsaturated fatty acids (approximately 80%) or polyunsaturated fatty acids (1.55–2.12%). Notably, variety 412-B combined the highest palmitoleic acid content (21.47%) with the longest induction time (22.73 h) and lowest acidity (0.448 mg KOH/g), demonstrating that within the narrow, highly monounsaturated compositional range of these Brazilian macadamia oils, overall unsaturation levels are a poor predictor of oxidative stability.