2002 Volume 8 Issue 1 Pages 32-35
Moisture content, total lipid content, lipid classes, fatty acid composition and sugar composition were used to express quality characteristics of macadamia nuts. These parameters of the dry nuts were determined during a peak harvest season in 1999, and the quality parameters were compared with those of nuts rejected by a nut processor. Moisture content of rejected nuts showed significantly higher value than that of acceptable nuts (p<0.05). There is a significant difference between acceptable and rejected nuts in total lipid content (p<0.05), and the total lipid content of acceptable nuts gradually increased towards the end of the peak harvest season. The rejected nuts exhibited total lipid contents of 60% and moisture content of 1.96% wet basis (w.b.), while the acceptable ones showed total lipid content of more than 63% and moisture content less than 1.42% w.b. The sugar composition of the rejected nuts was also remarkably different from the acceptable nuts, and the former had higher sucrose content than the later. Fructose and glucose contents showed a similar tendency but with smaller magnitude. These results clearly indicate that the rejected nuts are poor in quality, which may lead to shorter shelf life, harder texture and bitter taste. Lipid classes were also identified and the major neutral lipid was triacylglycerols, which accounted for more than 73%. The lowest content of triacylglycerols was observed in the rejected nuts and no remarkable differences were noted from other lipid classes. Fatty acid composition determined in the present paper agreed with published data and showed the major acid to be oleic acid (> 55%), followed by palmitoleic acid (> 28%). The rejected nuts contained more saturated fatty acids: palmitic, stearic and arachidic acids, and a remarkably low content of palmitoleic acid (p<0.05). The ratio of unsaturated to saturated fatty acids for the acceptable nuts was higher than that in the rejected nuts.
