Analysis of the Oil Accumulation Process in Macadamia Nuts
Macadamia nuts take about 215 days from fruit set to maturity. When the fruit matures 30 weeks after the flowering period, the kernel oil content of the nut is 75%-79%. As the fruit develops, the kernel oil content continuously increases, while the total nitrogen (crude protein content) continuously decreases; the total sugar content increases continuously before 111 days after flowering, and gradually declines after 111 days. According to the South Subtropical
Macadamia nuts take about 215 days from fruit set to maturity. When the fruit matures 30 weeks after the flowering period, the kernel oil content of the nut is 75%-79%. As the fruit develops, the kernel oil content continuously increases, while the total nitrogen (crude protein content) continuously decreases; the total sugar content increases continuously before 111 days after flowering, and gradually declines after 111 days. According to the South SubtropicalCrops Research Institute, using developing fruits from bearing trees over seven years old of the four cultivars H2, 246, 660 and 508 as materials, the results of 4 years of measurement showed that: regarding the changes in crude fat content during fruit development, starting from 90 days after flowering, as the fruit age increased, the kernel oil content, whether expressed as a fresh weight percentage or a dry weight percentage, showed a trend of gradual increase, among which the period before 120 days after flowering was the most rapid period of oil accumulation. The rate of oil accumulation differed slightly among the cultivars; the oil accumulation of 660 and 246 was faster in the early stage, reaching 54.94% and 43.30% respectively at 120 days after flowering, while H2 and 508 reached only 32.59% and 36.1% respectively. By 150 days after flowering, all cultivars could reach above 60%, and when the fruit was fully mature, the oil content was above 72% in all cases. The change pattern of crude protein content (total nitrogen) during fruit development was as follows: after 90 days after flowering, as the fruit age increased, the crude protein content, if expressed as a percentage of fresh fruit, showed a trend of slow increase, while if expressed as a dry weight percentage, it showed a trend of gradual slowing; from 90 to 120 days after flowering, the percentage of protein in dry weight dropped from about 30% to about 10%, which was the rapid decline period. The specific contents differed slightly among the cultivars, but the declining trend was the same, and the final crude protein content in mature fruit was about 8%. The change in sugar content during fruit development was as follows: from 90 to 110 days after flowering, the reducing sugar, sucrose and total sugar in the kernel all showed an increasing trend; after 110 days, the reducing sugar and sucrose contents both declined rapidly, and by 150 days after flowering, no reducing sugar content could be detected. The sucrose content also dropped to about 8% (calculated as a dry weight percentage). Regarding the changes in moisture (or dry weight rate) during fruit development, after 90 days after flowering, the kernel moisture content was about 92%, and the dry weight rate was 6%-8%; as the fruit developed, the moisture in the kernel gradually decreased and the dry weight rate continuously increased, among which the 660 cultivar increased more slowly in dry weight rate in the early stage, reaching a dry weight rate of 38.70% at 120 days after flowering; when the fruit was mature, the kernel dry weight rate of all cultivars stabilized at about 70%.