Evaluation of nutritional quality in different varieties of green and purple leaf lettuces

To determine the quality difference in different varieties of leaf lettuces, we investigated the characteristics of 74 varieties of leaf lettuces (55 green and 19 purple varieties). Both domestic and foreign varieties of lettuce were included in this study. We determined six nutritional indicators of these varieties: such as total soluble sugar, starch, cellulose, proteins, and vitamin C. The grey correlation analysis was used to analyze the 74 varieties of leaf lettuces. Thus, the merits of these traits were compared. The results indicate that the purple leaf lettuce P-S23 had grey comprehensive evaluation value of about 0.8, which was the highest among all varieties. For green leaf lettuces G-S68 and G-S10, grey comprehensive evaluation values were less than 0.5. This indicates that nutritional quality and nutritional value of the purple leaf varieties were higher than that of the green leaf varieties. Furthermore, the quality of green varieties of G-S68 and G-S10 were of poor quality, whereas the purple variety P-S23 was most suitable for commercial production.