Quality Analysis and Comprehensive Evaluation of the Fruit of Macadamia integrifolia Grown in Yunnan Province

In order to ascertain the quality characteristics of macadamia nut from different regions and varieties in Yunnan so as to establish their comprehensive evaluation model. Thirty-five samples of macadamia nuts from 3 major production areas in Yunnan were selected to determine indicators of fruit characteristics and quality indexes including the composition and content of physicochemical, nutritional and functional components and amino acids in kernels. The quality of macadamia nuts was comprehensively evaluated by correlation analysis (FCOR), principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). The results showed that there were significant differences in the fruit characteristics of 35 samples from different regions and varieties in Yunnan (P<0.05), and the single fruit weights of nut-in-husk, nut-in-shell and kernel were 13.85 g to 30.48 g, 5.92 g to 11.68 g, and 1.87 g to 3.75 g, respectively, the large fruit rates of nut-in-shell and kernel were 38.89% to 100.00% and 10.00% to 100.00%, respectively, and the rates of seed, kernel yield and defect kernel were 37.86% to 72.41%, 25.18% to 44.61%, and 1.67% to 17.00%, respectively. The large fruit rates of nut-in-shell and kernel of macadamia nut from Lincang producing areas in Yunnan were both highest, and the defect kernel rate of macadamia nut from Pu'er producing areas in Yunnan was highest, suggesting the necessity of strengthening orchard management. The results of variation analysis showed that 35 samples of macadamia nuts were rich in variation, the coefficient of variation ranging from 4.49% to 68.01%. The variation coefficient of contents of total phenol, polysaccharide, total sugar, kernel moisture and ash were all greater than 10%, which showed that there were significant differences between macadamia nuts samples. Seventeen kinds of amino acids were all detected in 35 samples of macadamia nuts, their medicinal amino acids accounted for 63.22% to 73.36% of the total amino acids with the largest proportions. Indicators used to evaluate the quality characteristics of macadamia nut were obtained by orthogonal partial least squares-discriminant analysis method, which were contents of crude fat, seed rate, leucine, the large fruit rate of nut-in-shell, polysaccharide, histidine, total sugar, the single fruit weights of nut-in-shell, alanine, valine, threonine, tyrosine, aspartic acid, and the single fruit weights of kernel. The comprehensive quality evaluation model of macadamia nuts was established by principal component analysis, which showed that the samples with the best comprehensive quality were respectively Pu'er 'HVA4', Baoshan 'Nanya No.3', Baoshan 'HAES246', Baoshan 'HVA16' and Pu'er 'Own Choice' in 35 samples of macadamia nuts. The results of this study can provide important reference for breeding of new varieties, variety screening of processed products and quality control of macadamia nuts.