Submitted to: Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/21/2010
Publication Date: 8/1/2010
Citation: Wall, M.M. 2010. Functional lipid characteristics, oxidative stability, and antioxidant activity of macadamia nut (Macadamia integrifolia) cultivars. Food Chemistry. 121:1103-1108. Interpretive Summary: Phytochemical compounds (tocopherols, tocotrienols, and squalene) were measured in different macadamia cultivars to establish whether these compounds enhance the oxidative stability of roasted kernels. The presence of phytochemicals in macadamia nuts may protect the kernels from oxidation reactions during storage and marketing, thereby extending shelf-life. In addition, these compounds may contribute to human health. Macadamia nuts were a significant source of dietary tocotrienols and squalene, and two cultivars were identified with superior oxidative stability, suggesting that the kernel quality of these cultivars is more stable during storage.
Technical Abstract: Off-flavor development (oxidation and rancidity) during storage reduces macadamia nut quality. The presence of phytochemicals in macadamia nuts may protect the kernels from oxidation reactions during storage and marketing, thereby extending shelf-life. Also, these antioxidant compounds may contribute to human health. Research was conducted to identify and quantify the major phytochemical compounds in different macadamia cultivars, and to establish whether these compounds enhance the oxidative stability of macadamia nuts. Seven cultivars of macadamia nuts were harvested from four locations on Hawaii island during two seasons and analyzed for total oil content, antioxidant activity, oxidative stability, and phytochemical concentrations. A positive correlation was found between the oxidative stability and total lipid-soluble antioxidant activity of macadamia oils. Tocopherols were not detected in most macadamia nut samples, but the kernels contained significant amounts of tocotrienols (T3s) and squalene for all cultivars tested. Total T3 content was highest for cultivar HAES 294 (91.59 µg/g oil) and lowest for HAES 246 (46.56 µg/g oil) in the first season. T3 levels were lower in the second year, suggesting considerable environmental effects on T3 accumulation during kernel development. Mean squalene concentrations ranged from 72 to 171 µg/g oil, and generally were consistent over the two harvest seasons. Macadamia nuts appear to be a significant source of dietary tocotrienols and squalene. No statistical correlations were found between oxidative stability and phytochemical concentrations. However, cultivars HAES 294 and HAES 835 had superior oxidative stability for both years, and HAES 294 had high T3 concentrations, suggesting that these cultivars may maintain kernel quality during long-term storage or marketing.