Spatial and compositional variations in fruit characteristics of papaya (Carica papaya cv. Tainung No. 2) during ripening

Papaya fruit (Carica papaya) has different degrees of ripening within a fruit, affecting its commercial market value. The fruit characteristics of Tainung No. 2 papaya was investigated at the stem-end, middle, and calyx-end parts at three ripening stages and categorized based on fruit skin coloration: unripe at ca. 16 weeks after anthesis (WAA), half-ripe at ca. 18 WAA, and full-ripe at ca. 20 WAA. The fruits maintained an elliptical shape during ripening with 2.36 of the ratios of the length to the width. The peel and pulp color changed from green to white to yellow during ripening, regardless of the fruit three parts. In the pulp, soluble solid content increased to about 320% and firmness decreased to about 99% during ripening but did not differ among fruit three parts. Individual nutrient contents, including primary and secondary metabolites, and minerals, changed dynamically between the ripening stages and fruit parts. Total carbohydrates and proteins, N, and K, were more accumulated at the stem-end during ripening, meanwhile fructose, glucose, Mg, and Mn were at the calyx-end. In the principal component analysis, ripening stages and fruit parts were distinctly determined by the first and second principal components, respectively. These results provide fundamental information for improving ripening during papaya cultivation.