Total Phenolic Concentration and Browning Susceptibility in a Collection of Different Varietal Types and Hybrids of Eggplant: Implications for Breeding for Higher Nutritional Quality and Reduced Browning

Abstract

Phenolic compounds have numerous beneficial effects on human health. In consequence, the development of new varieties with higher content of phenolics is of interest for the improvement of the nutritional quality of eggplant (Solanum melongena L.). However, the oxidation of eggplant phenolics causes browning of the cut surfaces of the fruit and reduces its apparent quality. The authors investigated the relationship among, as well as the variation and heritability of, the content of phenolics, ascorbic acid, and soluble solids; pH; and the degree of browning and color difference of the cut surface of the fruit flesh in a collection of 69 eggplant varieties. These included landraces from different origins, commercial varieties, experimental hybrids, and four accessions of the related S. aethiopicum L. and S. macrocarpon L. species. Analyses of variance revealed significant differences among the materials studied for all traits considered. The concentration of phenolics in S. melongena spanned a threefold range, although the highest (1122 mg·kg−1) and lowest (134 mg·kg−1) concentrations of phenolics were found in S. macrocarpon and S. aethiopicum respectively. Concentrations of ascorbic acid were very low, a mean 27 times lower than those of phenolics, and soluble solids content ranged from 3.60% to 6.60% with a pH that ranged from 5.01 to 5.93. Commercial varieties had, as a mean, a 20% lower concentration of phenolics than landraces, as well as a lower degree of browning and color difference. Positive correlations existed between phenolic concentration and degree of browning (r = 0.388) and color difference (0.477), although only 15.1% and 22.8% of the total variation in degree of browning and color difference, respectively, could be attributed to variation in phenolics. Ascorbic acid, soluble solids content, and pH were not correlated to either degree of browning or color difference. The heritability was moderate for phenolic concentration (0.50) and high for degree of browning (0.71) and color difference (0.82). The information obtained indicates that there are opportunities for the development of new varieties with a high concentration of phenolics and low or moderate browning.