Technical Talk: Taking The Pulse Of Pulses

Pulses are the edible seeds of crops mainly from the legume family, such as beans, peas, lentils and chickpeas. These seeds are normally found in pods.

Pulses are the edible seeds of crops mainly from the legume family, such as beans, peas, lentils and chickpeas. These seeds are normally found in pods.

However, not all of the crops producing seeds in a pod are classified as pulses. Those that contain a substantial amount of oil that can be commercially extracted are categorized as oilseeds. Some examples of these are soybeans and rapeseed or canola.

The legume family represents a vast number of varieties found throughout the world. Within the groups of beans, peas, lentils and chickpeas, many varieties are grown as food. Within the bean group, many varieties – such as black, navy, cranberry, pinto, dark red kidney and light red kidney – are known. Many common names of these pulses can be found within the different geographical regions of the world.

The legume family of crops represents a substantial portion of farming efforts in Canada. The majority of these crops are dried or processed whole. Dried legumes are used in canning and other food preparations and a major portion is exported to other countries for further processing.

Many researchers have investigated the nutritional aspects of pulses. They are known to contain a wealth of nutrients, making them an excellent source of healthful food for the human diet.  They contain substantial amounts of good quality protein and complex carbohydrates, including soluble and insoluble fibre, and are low in fat content. They are a good source of vitamins and minerals such as B complex vitamins, calcium, potassium, iron, phosphorus and zinc. Legumes also offer many other health benefits beyond regular nutrition. They contain components such as antioxidants that may reduce the risk of certain diseases and promote overall human health.

Consumers now are focusing on foods that provide additional health benefits other than basic nutrition. These foods are collectively called functional foods, and legumes certainly satisfy this definition.

Numerous investigations have identified a number of phytochemicals in pulses that can act as antioxidants or have other positive effects in preventing the onset of chronic diseases. For example, studies have shown that baked bean consumption reduces serum cholesterol in hyper-
cholesterolemic adults; pinto beans have been identified as reducing the biomarkers for heart disease risk; phytochemicals of black bean coats have been identified to act against cancer cell proliferation; diet supplementation with chickpeas was shown to result in a small but significant reduction of total and low-density lipoprotein cholesterols in adult women and men; intake of legumes such as dried beans, split peas and lentils was found to be associated with a significant reduction in colorectal cancer (81 per cent) possibly due to their dietary fibre and other phytochemical content that may play a role in reducing adenoma formation.

Beans also contain a chemical compound that acts as an amylase inhibitor. This “starch blocker” sends undigested starch directly to the colon, where it is fermented like resistant starches and acts as a prebiotic. Phase 2 starch neutralizer (also known as Phaseolamin 2250 and Phase2) is a commercially isolated ingredient from white kidney beans that has been clinically studied to reduce the absorption of calories from starch by inhibiting the digestive enzyme alpha-amylase. There is potential for Phase2 white bean extract to be a novel ingredient in products that will reduce the glycemic index (GI) without modifying the ingredient profile.

Legumes certainly have a low glycemic value, making them ideal for people with a risk of diabetes. For example, compared to white bread with a GI value of 100, the approximate GI values for chickpeas are 40, lentils 42 and split peas 45, while beans can vary from 40 to 55. Legumes are also known to promote satiety. There is a great potential in this area for consumers concerned about weight control and reduction of the risk of other chronic diseases associated with obesity.

Information about these health benefits is gradually finding its way to consumers and for this reason the consumption of foods containing legumes around the world and in North America is on the rise.

But the use of pulses as ingredients in North America and Europe has been greatly underdeveloped. Pulses in general tend to be consumed whole. A limited supply of ingredients derived from these pulses is used in food products. However, their potential for the development of healthful ingredients – especially weight control, lower GI and prebiotic markets is great. Bean, pea and other flours are available in the market and are finding their way into gluten-free and other food products.

Some dietary fibre ingredients from pulses have also been developed and marketed, but the potential for greater utilization for production of both soluble and insoluble dietary fibre is great. In addition, protein and starch ingredients with specific functional properties have been developed.
Suppliers of ingredients from pulses include Grain Process Enterprises of Scarborough, Ont.; Bob’s Red Mill products of Milwaukie, Ore.; Heartland Ingredients of Ubly, Mich.; and other small operations. The most successful producer of these ingredients is Best Cooking Pulses in Manitoba, which produces pea fibre and pea flour. Its main product is the pea hull fibre, which is being used in many food products, while the company’s Best Pea Fibre is a dietary fibre ingredient approved by Health Canada.

Best Cooking Pulses’ pea flour is produced by grinding green or yellow peas and is primarily exported to the United States for use in bakery products. Roquette, a French ingredient manufacturer, supplies a pea protein under the brand name Nutralys, which is highly purified and extracted without chemical solvents. Pea protein is an excellent emulsifier and thus improves texture and ensures better cooking results. It is a concentrated source of protein with a well-balanced amino-acid profile, and is easily digestible due to the elimination of anti-nutritional factors during the manufacturing process. As it has a neutral taste and is in a granular form, it can be easily incorporated into many types of products without forming dust, foam or lumps.

Current research is being carried out on better processing techniques for lentils and other legumes, development of specialty ingredients such as flour mixtures that will reduce the fat absorption of fried foods, de-flavouring of bean flours as well as fractionation and separation of starches and proteins.

One of the results of recent research efforts is the development of composite flours that contain wheat and legume flours. The University of Manitoba food science department is actively involved in this area and students in this department have developed prototypes of extruded snacks that contain both wheat and bean flour. Extruded snacks represent a good opportunity for utilization of these flours and researchers at the U.S. Agricultural Research Service developed a process to make a crunchy snack from lentils and other legumes.

Flours from pre-cooked and raw navy, pinto, black, cranberry, light red, dark red, romano and great northern beans are also being explored. These flours could be used to improve the nutritional value of products such as muffins, tortillas and gluten-free breading and batters. They could also be used as thickening agents for soups.

The Canadian International Grains Institute has developed muffin recipes using pea flours and pea fibre. Pea fibre has proved to be more advantageous than pea flour by significantly increasing fibre content in the muffins. Pea flours tend to have a stronger flavour, so product formulations would need to be adjusted to compensate.

One of the most recent advances in the application of ingredients from legumes in foods deals with the development of gluten-free food products – especially baked goods. For the gluten-free baked goods industry, alternatives to wheat flour are difficult to find. Rice flour is extensively being used, but legume flour is becoming popular and its application is becoming more extensive.

Research in the technology of application of certain enzymes to legume flour in order to improve its performance in gluten-free baked goods has been initiated recently. In particular, the enzyme transglutaminase is being investigated because of its ability to link certain amino acids within a protein matrix or from different proteins, thus forming complexes that can perhaps mimic the action of gluten in baking systems. This enzyme can link together the amino acids glutamine and lysine, both of which are present in legumes.

Ingredients from pulses represent a great opportunity for the baking industry. They are much more nutrient dense, possess more health-promoting characteristics than wheat flour and have no known allergenic properties. Unlike several other crops they are also not yet subject to pressure from biofuels and bioproducts and they may present a cheaper alternative as a source of healthful food ingredients in the near future.

Funding for this report was provided in part by Agriculture and Agri-Food Canada through the Agricultural Adaptation Council’s CanAdvance Program. For more information, or fee-for-service help with product or process development needs, please contact the GFTC by phone at 519-821-1246, by fax at 519-836-1281, or by e-mail at gftc@gftc.ca.

Dr. John Michaelides is director of research and technology at the Guelph Food Technology Centre, www.gftc.ca.