Fruit quality analysis and comprehensive evaluation of 27 avocado varieties

【Objective】The flesh of the avocado is fine in texture and rich in unsaturated fatty acids, flavonoids, phenols and other nutrients, which have health care functions such as preventing arteriosclerosis, stroke and diabetes. Principal component analysis, membership function analysis and clustering analysis were used to comprehensively evaluate the quality traits of 27 avocado varieties preserved in the avocado germplasm resource nursery of Guangxi South Subtropical Agricultural Science Research Institute, to establish a fruit evaluation system, and to determine the difference in fruit quality among the different avocado varieties.【Methods】A comparative analysis of fruit quality indexes, such as thedry matter content, soluble solid content, bioactive substance content and fatty acid composition, were carried out among 27 avocado varieties. Principal component analysis, membership function analysis, and clustering analysis were used to evaluate the fruit quality of different avocado varieties comprehensively.【Results】Significant differences were observed in 13 fruit quality indexes among 27 avocado varieties, with coefficients of variation ranging from 3.73% to 160.07%. Hass was rich in the contents of dry matter, total fatty acid, saturated fatty acid and polyunsaturated fatty acid. The highest soluble solids content, total phenolic content and total flavonoid content were found in Guilong No. 4, Lisa and Guilong No. 3, respectively. Lamb Hass had the highest contents of unsaturated fatty acid and monounsaturated fatty acid, while the DPPH free radical scavenging capacity of Tenglong and ABTS free radical scavenging capacity of Guiyan No. 3 were the highest compare to other varieties. All samples were clustered based on 13 fruit quality traits, and the 27 avocado varieties were divided into 5 categories. The cluster 1 included Hass, Fuerte and Lamb Hass. The cluster 2 included Guikenda No. 2, Guilong No. 15 and Guiyan No. 3. The cluster 3 included Lisa, Guiyan No. 4, Bernecker, Guilong No. 8, Guilong No. 12, Booth 8, Guilong No. 4, Nanya D and Choquette. The cluster 4 included Guilong No. 3, Guiyan No. 8, Reed, Qiuhong and Tenglong. The cluster 5 included Loretta, Nanya A, Guilong No. 1, Miguel, Guiyan No. 10, Wilson seedless and Zijin. The 13 quality indexes of avocado fruits were simplified and extracted, and the components with eigenvalues greater than 1 were extracted, and a total of four principal components were extracted, with a cumulative contribution rate of 80.553%, and the contribution rate of the 1st principal component amounted to 46.619%, and the content of total fatty acids, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids and unsaturated fatty acids positively affected the 1st principal component, which mainly reflected the nutritive qualities of the fruits. The contribution of the 2nd principal component was 12.825%, which was mainly represented by soluble solids content and M/S value. The contribution of the 3rd principal component was 11.259%. The main representatives were DPPH free radical scavenging capacity and P/S value. The contribution of the 4th principal component was 9.850%, which showed a significant positive correlation with total flavonoid content and ABTS free radical scavenging capacity. Through comprehensive analysis of 27 avocado varieties, a comprehensive evaluation system for avocado quality was established. The results showed that Lamb Hass, Hass and Fuerte scored the highest in the comprehensive quality evaluation of avocados. The contents of fatty acids and dry matter were the highest in Lamb Hass, Hass and Fuerte, and other quality indexes were also better, indicating that the overall quality of the fruit was better than other varieties. The content of saturated fatty acid, M/S value, DPPH free radical scavenging capacity and total flavonoid content were the core indexes for evaluating the quality of avocado fruits.【Conclusion】Comprehensive evaluation of 13 fruit quality indicators (dry matter content, soluble solids content, total phenolic content, total flavonoid content, DPPH free radical scavenging capacity, ABTS free radical scavenging capacity, total fatty acid content, saturated fatty acid content, monounsaturated fatty acid content, polyunsaturated fatty acid content, unsaturated fatty acid content, M/S value, and P/S value) was conducted using principal component analysis, membership function analysis, and cluster analysis. Three varieties including Hass, Fuerte and Lamb Hass were selected as the top 3 excellent avocado varieties. In conclusion, through the comprehensive analysis of the core quality indicators of 27 avocado varieties, an evaluation system for avocado resources was established, which provided scientific basis and data support for the quality evaluation and product development of avocados, with certain theoretical and practical significance. This can provide a reference basis for screening the excellent avocado varieties, and their development and utilization.