Ways to help you love your legumes

13 May 2024 - Legumes are a great source of plant-based protein and are packed with nutrients. But the preparation required, taste, or texture puts people off eating them. 

A team of Riddet Institute-affiliated scientists, led by Professor Indrawati Oey and Dr Kevin Sutton, believe incorporating legumes into other common foods could be key to overcoming this. Publishing in the journal Trends in Food Science & Technology in May, they reviewed available studies looking at different food processing techniques, and the use of emerging technologies, to prepare different kinds of beans. The consumer response to the resulting legume-enriched foods was also reviewed.

The researchers lead the Riddet Institute’s project 2.1, under the umbrella of the sustainable future proteins theme. The project bridges plant protein, food processing, digestion, and consumer impact on satiety.

Western diets are often low in protein and fibre and high in less-desirable refined carbohydrates that can trigger blood sugar surges and contribute to metabolic diseases. Legumes could be part of the answer. Packed with essential amino acids, legumes are a useful ingredient to incorporate with other plants, such as cereals, to attain a complete amino acid profile and slow the gyclemic response after eating.

But the authors noted that despite these benefits, consumption was low. On their own, legumes can be difficult to prepare, are less palatable than other options, and may cause digestive problems. In addition, not all the protein in legumes can be absorbed and they are hard to chew if they are uncooked. 

There has been considerable research into ways to improve the protein digestibility of legumes or manipulate their taste and texture. Conventional processing has included initial preparation such as soaking, dehulling, germination and fermentation, which removes the antinutrients and makes the proteins more digestible. Cooking with heat, with or without water, is still needed to make them more chewable, and further aids protein digestibility, but in some varieties this can reduce overall protein.

New processing techniques now emerging as alternatives to conventional cooking include high hydrostatic pressure (or high-pressure processing), radiation, ultrasound, and pulsed electric fields technologies.

For use as a food ingredient, processing techniques such as milling into legume flours was common.  But the reviewed studies showed that limiting legume flour substitution to 10-15% was preferred to maintain the structural integrity and texture of breads, and create baked goods that were acceptable to consumers. Sprouted (pre-germinated) legume flours and fermentation techniques could deliver better performance, enabling up to 30% substitution with acceptable final texture and firmness of baked goods, depending on the bean. Flavour was another key consideration and different techniques had different implications for taste.

The authors concluded there were opportunities for improving the use of legume proteins in the diet. This was particularly the case when legumes were incorporated with other ingredients to enhance the nutritional values of commonly consumed foods. Future research was needed to investigate the potentially highly beneficial metabolic effects of these novel foods, such as the insulinemic response for patients with type 2 diabetes.

The complete study can be found at: https://doi.org/10.1016/j.tifs.2024.104466