Proximal composition and in vitro digestibility of starch in lima bean (Phaseolus lunatus) varieties

BACKGROUND: Beans are rich and inexpensive sources of proteins and carbohydrates around the world, but particularly in developing countries. However, many legume varieties are still underutilized. In this study, physical characteristics of the seeds of three Phaseolus lunatus cultivars were characterized. Also, the chemical composition and starch digestibility in the cooked beans were assessed. RESULTS: 'Comba floja' variety exhibited the highest thousand-kernel weight whereas the lowest was found in 'comba violenta'. This agrees with seed dimensions: 'comba floja' had the Longest seeds (16.36 mm) and 'comba violenta' the shortest ones (13.98 mm). All samples exhibited high protein content, but levels in 'comba blanca' variety (216 g kg^-1) were lower than the in other two cultivars. Total starch (370-380 g kg ^-1) and potentially available starch content (330-340 g kg ^-1) were similar in the three varieties. Resistant starch level in the cooked seeds ranged between 38 and 45 g kg^-1. Low enzymatic hydrolysis indices (HI) were recorded (30.2-35%), indicating a low digestion rate for Phaseolus lunatus starch. HI-based predicted glycemic indices ranged between 34% and 39%, which suggests a 'slow carbohydrate' feature for this legume. CONCLUSION: Phaseolus lunatus beans appear to be a good source of protein and slow-release carbohydrates with potential benefits for human health.