Flavor quality analysis of five kiwifruit germplasm based on HS-SPME- GC-MS

Abstract：【Objective】Five accessions of kiwifruit were analyzed for their sugars and acids, composi-tion of aroma substances and sensory characteristics. Interspecific differences in these components wereidentified with an aim to provide reference for kiwifruit flavor evaluation and crop improvement.【Methods】The volatile aroma compounds in kiwifruit of different cultivars/strains were determined us-ing headspace solid phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), and fruit flavor was evaluated with sensory evaluation method.【Results】Soluble solid con- tent in the five kiwifruit cultivars/strains ranged from 13.53% to 19.23% at full commercial maturity. The highest was found in Ganhong-7, and the lowest in Mamao-13. Flesh firmness was in the range of 7.35-14.31 N, and the highest strain was Mamao-13, the lowest was Ganhong-7. Total soluble sugar content varied from 11.02% to 13.66% and was highest in Mamao-13, and lowest in Mamao-10. The ti- tratable acid content was 1.15% - 1.51% and highest in Changchu-2 and lowest in Ganmi-6. Sugar to acid ratio was in the range of 8.50-11.35 and highest in Mamao-13 and lowest in Changchu-2. A total of 6 categories and 57 aroma compounds were detected in the 5 cultivars/strains, including 3 aldehydes, 8 alcohols, 1 alkanes, 22 esters, 13 terpenes, and 10 other aroma species. The dominant aldehydes were 2- hexenal with a relative content was 28.26% ; the highest alcohols were 1- hexanol accounting for 12.77%; the highest esters were α-terpinolene, which was 54.10%; the highest content in terpenes was terpinolene, which accounted for 82.69%; p-xylene was the highest in other aroma species and account-ed for 0.40%. The number of aroma substances detected in the five cultivars/strains was 19 in Chang-chu-2, 30 in Ganmi-6, 18 in Ganhong-7, 21 in Mamao-10 and 26 in Mamao-13. There were some low aroma compounds such as benzedrone (0.14%), urea, 2-propenyl- (0.18%), propyl isobutyrate (0.21%) and p-methylphenyl isopropyl alcohol (0.05%). The main aroma substances differed among cultivars/ strains. The most abundant aroma substance in Changchu- 2 was ethyl butyrate, with a content of 55.97%, followed by 2-hexenal, which was 28.62%. The highest aroma substance in Ganmi-6 was α-ter- pinolene, with a content of 54.10%, followed by 1-hexanol, which was 12.77%. The highest aroma sub-stance in Ganhong-7 was ethyl butyrate, with a content of 48.59%, followed by methyl butyrate, which was 12.38%. The dominant aroma substance in Mamao-10 was terpinolene, with a content of 82.69%, followed by d-limonene, which was 4.58%. The highest aroma substance in Mamao-13 was ethyl butyr- ate, with a content of 43.78%, followed by d-limonene, which was 13.61%. 2-hexenal, 1-hexanol and p-xylene were detected in all the 5 cultivars/strains kiwifruit. Hexanal, ethyl butyrate and d- limonenewere detected in four cultivars/strains. Some chemical compounds appeared only in specific cultivars/strains. For example, cyclopentane was only found in Mamao-10, butyl isobutyrate in Changchu-2, sty-rene in Ganhong-7 and formamide in Mamao-13. It could be found that esters were the main aroma sub-stances in Changchu-2, Ganhong-7 and Mamao-13, while terpenes were the main aroma substances in Ganmi-6 and Mamao-10. Ethyl butyrate and methyl butyrate were the main fruity and sweet aroma. Both 2-hexenal and 1-hexanol showed obvious grass flavor. Terpinolene showed a strong lemon flavor; α-terpinene had a typically sweet citrus flavor; d-limonene had a sweet lemon flavor. In sensory evalua- tion, Mamao-13 had the highest firmness and acidity scores; Ganmi-6 had the highest aroma and over-ripe flavor; Changchu-2 had the highest water content and sweetness; and Ganhong-7 had the highest ki-wifruit flavor. The highest comprehensive score of sensory evaluation was 46.37 found in Ganmi-6, fol-lowed by Mamao-13 with 46.19. The cultivars/strains with the highest comprehensive score of sensory evaluation were Changchu-2.【Conclusion】The flavor quality of kiwifruit at soft ripening stage was evaluated based on sugar acid content, sugar acid ratio, aroma substances and sensory evaluation, and the differences in flavor and quality among different kiwifruit cultivars were clarified.