Lipid Accumulation of Macadamia Nuts during Kernel Development

Abstract

Macadamia nuts at four different stages of development, namely 3, 5, 7 and 9 months after flowering were examined for their physical and physiological characteristics. There were no significant differences among shell sizes and nut-in-shell weight at different growth stages. However, moisture contents were remarkably different among different development stages. Kernel of 3 month stage contained remarkably high amount of moisture and low total lipids (P<0.05). A remarkable decrease in moisture observed from 5 months after flowering, while total lipids significantly increased. The major lipid classes were found to be triacylglycerols for neutral lipids, and phosphatidylcholine and phosphatidylethanolamine for polar lipids at all development stages. The composition of polar lipids changed remarkably during kernel development, especially after 3 months. Fatty acid composition of total lipids at 3 months stages showed significantly higher amounts of myristic, palmitic and linoleic acid (P<0.05), while contents of stearic and oleic acid increased as the nuts grew further. A ratio of unsaturated to saturated fatty acid contents changed from 4.3 to 6.6 with kernel development and this was mainly due to an increase in oleic acid.