In order to determine the maturation period of lotus seeds suitable for fresh consumption and to evaluate their quality, the physicochemical and sensory quality of lotus seeds at the milky, waxy, complete and dead ripeness stages were evaluated. The relationship between physicochemical and sensory quality was determined through principal component analysis (PCA), correlation analysis and regression analysis, and the quality characteristics of fresh lotus seeds were quantified. The results showed that the hardness, fullness, starch content, reducing sugar content and soluble protein content of lotus seeds increased gradually with maturity, while the water content decreased; the brittleness, chewability and viscosity increased firstly and then decreased, while the opposite trend was recorded for the contents of soluble solids and soluble sugar. The taste of lotus seeds at the milky ripeness stage was the most popular, whereas the appearance and color of lotus seeds at the waxy ripeness stage were the most satisfactory, and the overall acceptance was the highest. Lotus seeds suitable for fresh consumption were characterized by yellowish-green and shiny peels, high moisture content, low contents of reducing sugar and soluble protein, and low hardness. A model for the prediction of overall acceptance (Y) as a function of hardness (X) was determined as follows: $\hat{Y}$= 9.766 - 0.537X, which simplifies the process of determining the suitability of lotus seeds for fresh eating.

This study was performed to explore the differences in the composition of astringent substances in different tissues of fresh lotus seeds and the expression of key enzyme genes involved in the synthesis of astringent compounds. The contents of soluble tannins, insoluble tannins and proanthocyanidins in lotus seed coat, lotus seed pulp without coat and lotus seed plumule were determined. Meanwhile, the activity and gene expression of key enzymes in the tannin synthesis pathway were detected. Sensory evaluation and electronic tongue analysis were performed on lotus seed samples. The data obtained was analyzed by orthogonal partial least squares discriminant analysis (OPLS-DA) and correlation analysis. Results showed that the major substance contributing to the astringency of lotus seeds was soluble tannins. Tannins had a positive effect on its excellent flavor at the waxy ripeness stage. Anthocyanin reductase was a key enzyme affecting the astringency intensity of lotus seeds. SnANR9 played a role in regulating the astringency of different tissues of lotus seeds.