Analysis of texture quality of the fruits in litchi based on the texture profile analysis (TPA)

Abstract:【Objective】Litchi (Litchi chinensis Sonn.) is a subtropical evergreen fruit tree of the Sapindaceae family. It was firstly planted in Southern China and Northern Vietnam, and now is grown in more than 20 countries of the world, mainly distributed in Southeast Asia, especially in China, Vietnam, Indonesia, Thailand, and the Philippines. It has become one of the most popular fruits because of its delicious taste, attractive color, high nutrition and food therapy value. However, the fruits of litchi have a short shelf life, and are difficult to transport and store for a long time. Therefore, it is urgent to select new variety with long shelf life. The texture quality is important for shelf life and storage ability. Texture analyzer has been widely used in the study of texture characteristics of various fruits and vegetables. However, there have been few reports on the texture study of litchi. This paper dealt with the quick and objective evaluation of different litchi varieties, and the groups of litchi fruits distinguished by the texture quality.【Methods】Texture profile analysis (TPA) was used to test the texture quality of 120 varieties of litchi in 2020 and 196 varieties in 2021, respectively. The fruits were collected from the National Germplasm -Guangzhou Litchi Nursery. The probe of TMS-75 mm was used, its height above the surface of sample was 18 mm, the range of force sensing element was 250 N, the deformation was 50%, the test speed was 30 mm · min^-1, the initial fracture was 0.2 N. All samples were in a same size and were peeled.【Results】According to the TPA results, the texture parameters of litchi fruits mainly included the hardness, adhesive force, adhesiveness, cohesiveness, springiness, gumminess and chewiness. The correlation analysis was performed with each texture indicator. The results showed that hardness was significantly and positively correlated with the gumminess, chewiness, and springiness and significantly and negatively correlated with cohesiveness (p＜0.01); the adhesive force was significantly and negatively correlated with the adhesiveness, also positively correlated with the springiness (p＜ 0.01); the springiness was significantly and positively correlated with the chewiness, gumminess, adhesive force, and hardness (p＜0.01); the gumminess was significantly and positively correlated with the hardness, cohesiveness, springiness and chewiness (p＜0.01); the chewiness was significantly and positively correlated with the hardness, cohesiveness, springiness and gumminess (p＜0.01). Then the principal component analysis was performed. The indicators could be divided into three main components, the accumulative variance contribution of first three principal components was 90.535%, which could basically reflect most information of the texture quality of litchi fruits and would have high representa-tiveness of texture quality information. According to the representative texture parameters, 196 varieties in 2021, were divided into three main groups through clustering analysis, namely the palatability group, adhesiveness group and cohesiveness group.【Conclusion】Based on litchi texture parameters, we performed correlation analysis and the principal component analysis. 196 litchi varieties could be divided into three main groups, namely the palatability group, adhesiveness group and cohesiveness group. The hardness, springiness, gumminess and chewiness of the palatability group were higher than those of the other groups; the adhesiveness of the adhesiveness group was lower, and the adhesive force was higher, and the two texture parameters were negatively correlated; compared with the other two groups, the hardness of the cohesiveness group was lower, and the cohesiveness was higher, and the two texture parameters were negatively correlated.