A Comprehensive Evaluation of Tomato Fruit Quality and Identification of Volatile Compounds

Abstract

Tomatoes (Lycopersicon esculentum) are the most valuable vegetable crop in the world. This study identified the morphological characteristics, vitamin content, etc., from 15 tomato varieties in total, that included five each from the three experimental types, during the commercial ripening period. The results showed that the hardness with peel and the moisture content of tasty tomatoes were 157.81% and 54.50%, and 3.16% and 1.90% lower than those of regular tomatoes and cherry tomatoes, respectively, while the soluble solids were 60.25% and 20.79% higher than those of the latter two types. In addition, the contents of vitamin C, lycopene, fructose, glucose, and total organic acids of tasty tomatoes were higher than those of regular tomatoes and cherry tomatoes. A total of 110 volatile compounds were detected in the 15 tomato varieties. The average volatile compound content of tasty tomatoes was 57.94% higher than that of regular tomatoes and 15.24% higher than that of cherry tomatoes. Twenty of the 34 characteristic tomato aroma components were identified in tasty tomatoes, with fruity and green being the main odor types. Ten characteristic aroma components in regular tomatoes were similar to those of tasty tomatoes; ten types of cherry tomatoes had floral and woody aromas as the main odor types. The flavor sensory score was significantly positively correlated with the content of soluble solids, fructose, glucose, citric acid, fumaric acid, and β-ionone (p < 0.01), and significantly negatively correlated with water content and firmness without peel. Regular, tasty, and cherry tomatoes were separated using principal component analysis, and the quality of tasty tomatoes was found to be better than cherry tomatoes, followed by regular tomatoes. These results provide valuable information for a comprehensive evaluation of fruit quality among tomato varieties to develop consumer guidelines.

Keywords: flavor; quality evaluation; tomato; volatile compounds.

Figure 1

Tomato fruit varieties used in this study: P₁, Huachen 70; P₂, Yinfeng 79; P₃, Puluowangsi; P₄, Hunshuo 188; P₅, Dongfeng 199; T₁, Zhengfan P190; T₂, Zhengfan P210; T₃, Youyou 2045; T₄, Gaotang 100; T₅, Yuanwei No.1; Y₁, Pink Baby; Y₂, Bay Butter; Y₃, Red Bean; Y₄, Hongmei 1850; Y₅, Juan-zhulian.

Figure 2

The a* values (A), b* values (B), and color indexes (C) of the tomatoes. Data represent the mean ± SE. Different lowercase letters indicate statistical significance by Duncan’s multiple range test (p < 0.05). P, regular tomatoes; T, tasty tomatoes; Y, cherry tomatoes.

Figure 3

The soluble solids (A), vitamin C (B), and lycopene (C) contents in tomato fruits. Data represent the mean ± SE. Different lowercase letters indicate statistical significance by Duncan’s multiple range test (p < 0.05). P, regular tomatoes; T, tasty tomatoes; Y, cherry tomatoes.

Figure 4

The contents of fructose (A), glucose (B), and organic acids (C) in tomato fruits. Data in (A,B) represent the mean ± SE. Different lowercase letters indicate statistical significance by Duncan’s multiple range test (p < 0.05). The colored areas in (C) correspond to the content of acids from high (red) to low (blue). The data were log2 transformed and standardized. Euclidean distance and average linkage were used to construct the clustering of acids and varieties. P, regular tomatoes; T, tasty tomatoes; Y, cherry tomatoes.

Figure 5

The types (A) and contents (B) of volatile compounds in tomato fruits. P, regular tomatoes; T, tasty tomatoes; Y, cherry tomatoes.

Figure 6

The aroma shape of the three types of tomato based on the characteristic aroma components with the odor activity values (OAVs). P, regular tomatoes; T, tasty tomatoes; Y, cherry tomatoes.

Figure 7

The heat map of Pearson’s correlation analysis. Values are Pearson’s correlation coefficients. * and ** denote correlation coefficients that are significant at the p < 0.05 and p < 0.01 levels, respectively.

Figure 8

Principal component analysis (PCA) of tomato samples with a different score plot and loading plot. Circles in (A) are 95% confidence ellipses. The arrow in (B) indicates the loadings. P, regular tomatoes; T, tasty tomatoes; Y, cherry tomatoes.