Classification of Phenotypic Traits, Identification of Volatile Compounds and Characteristic Aroma Analysis of Canarium album Fruit

Abstract

The phenotypic characteristics (including single fruit mass, longitudinal diameter, transverse diameter, and fruit shape index) of 59 varieties of Chinese olive fruit were assessed and categorized based on probability. 15 Chinese olive varieties with varying fruit shape indexes and genetic backgrounds were selected for analysis of volatile compounds using headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). The results indicated a wide range of variation in four phenotypic traits, with coefficients of variation (CV) between 10.70% and 26.67%. The Kolmogorov-Smirnov (K-S) test showed that the data of fruit shape index, longitudinal diameter, and transverse diameter followed a normal distribution, allowing for their categorization based on probability. A total of 886 volatile compounds were identified including 186 terpenoids, 157 heterocyclic compounds, 146 esters, 73 ketones, 64 hydrocarbons, 64 alcohols, 53 aldehydes, 51 aromatic hydrocarbons, 21 acids, 21 amines, 20 phenols, and 30 other compounds at concentration levels ranging from 1 881.70 to 6 727.40 μg/g of fresh mass. Terpenes were the dominant volatile compounds in Chinese olive fruit, accounting on average for 52.49% of the total volatile compounds. The most abundant terpene was α-pinene, with a relative content of 7.13% (309.66 μg/g of fresh mass). A total of 181 characteristic aroma components were identified using odor activity value (OAV) analysis, contributing to the overall aroma profile of Chinese olive fruit. Among these components, the heterocyclic compound 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone was the biggest contributor with the highest OAV of 2 468 148.28, being responsible for sweet aroma. Utilizing principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) analysis, 6 differential characteristic aroma components were identified among different varieties of Chinese olive fruit. Notably, α-farnesene had the highest variable importance in the projection (VIP) value with an OAV of 19.71, being responsible for floral and fruity aromas. These findings serve as a valuable reference for the quality grading of Chinese olive fruit, as well as for future investigations into its aroma formation mechanism and quality improvement.

Keywords

• canarium album l.; phenotypic traits; probability classification; volatile compounds; odor activity value; characteristic aroma components