Effect of maturity and processing on total, insoluble and soluble dietary fiber contents of Indian green leafy vegetables.

Vegetables are very important in the diet and provide minerals, vitamins, antioxidants and fiber. A beneficial role of dietary fiber in human nutrition is known but the data on the effect of maturity and processing of Indian vegetables on dietary fiber and its fractions are not available. Hence, the present study was undertaken to generate data on total (TDF), insoluble (IDF) and soluble (SDF) dietary fiber contents of green leafy vegetables (GLV) and to assess the effect of leaf maturity and cooking on these parameters. Sixteen GLV (namely, agathi, alternanthera, amaranth, basella, cabbage, colocasia, coriander, curry leaves, drumstick, fenugreek, hibiscus, mint, portulaca, rumex, spinach and tender tamarind leaves) were analysed for TDF, IDF and SDF by the enzymatic and gravimetric method of the Association of Official Analytical Chemists. Among the GLV analysed, the TDF and IDF contents were the lowest (2.5 g% and 1.6 g%) in basella and were the highest (16.3 g% and 13.4 g%) in curry leaves. The SDF content ranged from 0.7 g% in spinach to 2.9 g% in curry leaves. The SDF as a percentage of the TDF ranged from 11.3% in tender tamarind leaves to 36.0% in basella, but the majority of GLV had around 25% of the TDF as SDF. Significant (P < 0.01) variation was observed between inter-species and intra-species in TDF, IDF and SDF contents of all the GLV. As the leaf matured from tender to mature and to coarse stage, the TDF and IDF contents of amaranth, basella, hibiscus, rumex and spinach increased significantly (P < 0.05), The SDF content significantly (P < 0.05) increased from tender to mature stage in all five GLV, but there was no further increase from mature to coarse stage except in rumex, where a significant (P < 0.01) increase (25%) was observed. Processing/cooking of GLV had no significant effect on their TDF, IDF and SDF contents.