Processing of food legumes: a boon to human nutrition

Abstract

Food legumes are widely consumed all over the world on account of their high nutritive value. These days legumes are greatly consumed on account of their therapeutic value in various lifestyle diseases such as diabetes and cancer. However, legumes contain several antinutritional factors in the raw seeds that need to be reduced by processing so as to enhance the digestibility and nutritive value. This review discusses the effect of common processing techniques viz ordinary cooking, pressure-cooking, microwave cooking, germination and soaking on the nutritional parameters and the antinutrients. A combination of the above techniques and also the effect of additives (such as citric acid, sodium bicarbonate used during processing) on the nutritional quality of the legumes has also been done. A comparison of the various techniques hence allows for the selection of the best processing technique that enhances the nutritional value with minimum loss of nutrients and maximum reduction in antinutrients. Extensive literature review demonstrates that in most cases such processing methods lead to considerable enhancement in the nutritional status of the prepared food legume. It is concluded that amongst all the processing techniques germination is the best one as it significantly enhances the nutritional value of legumes. For example, increase in content and bioavailability of minerals, vitamins, digestibility and decrease in antinutrients during germination is well established. Similarly, cooking treatments (ordinary cooking, pressure-cooking and microwave cooking) in addition to improving the digestibility lead to a considerable decrease in the antinutrients. Microwave cooking could be recommended for legume preparation, not only for improving nutritional quality (better retention rates of both B-vitamins and minerals, reduction in the level of antinutritional factors as well as increase in vitro protein digestibility), but also for reducing the cooking time. With respect to the whole soaking and cooking processes, the best conditions, which result in minimum vitamin loss, are 9 h soaking in 0.1% citric acid solution or in water and subsequent microwave cooking of the seeds. These conditions are found to be optimal for best retention of other nutrients as well.