Riddet Institute, Massey University, Palmerston North, New Zealand
Navy Beans are widely grown and consumed in various parts of the world and are a good source of vegetable proteins (20-38%), carbohydrates (50-60%) and fibre. The glycemic index of beans is generally low (~30) so they are regarded as a preferred source of energy. After eating the beans, the postprandial glucose response is moderate therefore immediate and chronic problems of hypoglycaemia can be avoided. Our team of researchers through experiments with navy beans observed that the thick and mechanically resistant nature of the intact bean microstructure prevents complete swelling of starch granules during cooking (gelatinization) and restricts their interaction with human digestive enzymes. The major objective of this work was to study the extent and rate of digestibility of starch in cooked and cooked-stored navy beans in a system simulating the human digestive system (in vitro). Sophisticated techniques such as scanning electron microscopy and comparative particle size analysis were used as tools to observe changes occurred to the microstructure of navy beans during simulated in vitro digestion.