The legume family, Fabaceae (or Leguminosae), includes the oilseeds (peanuts and soybeans) and the dried “grain pulses” (lentils, peas, chickpeas, beans). The word “pulse” is derived from the Latin words puls, or pultis, meaning thick soup. Pulses are an incredibly nutrient-dense whole food and considered an excellent source of folate and thiamine at 20% or more of the recommended daily intake (RDI) per serving; a good source of pyridoxine (10-19% RDI/serving); and a source of riboflavin and niacin (≥ 5% RDI/serving). They contain a number of important minerals, including potassium, calcium, magnesium, copper, iron, selenium and zinc.

Pulses are an excellent source of dietary fiber (approximately 13% dry weight) of which 30-40% is soluble, and they are a high-quality protein source at about 20-25% dry weight.

Studies in animals and humans consistently demonstrate favorable effects of pulses on plasma lipid concentrations. The overall low lipid content of pulses is particularly important in light of dietary recommendations to lower fat to reduce risk for chronic disease. A recent meta-analysis of 10 trials including 268 participants reported reductions in total and low-density lipoprotein cholesterol of 11.8mg/dL (-16.1 to -7.5) and 8.0mg/dL (-11.4 to -4.6), respectively, which are similar to the hypocholesterolemic effects of oats or phytosterols. The range of beneficial nutrients in pulses includes soluble fiber, vegetable protein, folate and oligosaccharides, as well as phytochemicals—such as isoflavones and saponins—all of which could contribute to lowering cholesterol levels.

Pulses have a low glycemic index (GI): lentils and kidney beans at 27; chickpeas at 33; and split peas at 48. Forty-one trials with 1,674 participants have demonstrated that pulses alone, or as part of low-GI or high-fiber diets, improved long-term blood glucose control and lowered fasting glucose levels. In subjects consuming muffins made with either whole pea flour or pea fiber, fasting insulin levels were 15% lower than with participants consuming control muffins made with wheat flour.

McCrory et al. conducted a meta-analysis which indicated observational studies consistently show an inverse relationship between pulse consumption and BMI or risk for obesity. However, many do not control for potentially confounding dietary and other lifestyle factors. Randomized, controlled trials also support a beneficial effect of pulses on weight loss when pulse consumption is coupled with energy restriction. The investigators suggested that further studies, particularly of a longer term (≥1 year), be conducted to investigate the optimal amount of pulses to consume for weight management.

Accompanying the strong science is the continuing interest of food companies in using pulses. For example, there were nearly 160 product launches containing pea protein in 2009, in comparison to fewer than 10 products in 2000, according to figures derived by the research organization Mintel Group. The range of products that currently are using pulses and those being developed is impressive and supports the versatility of these ingredients for the food manufacturer. The current and future market/consumer trends, coupled with increased innovation in the use of pulses in food products (and positive health benefits resulting from clinical research), mean releases of new pulse products and ingredients will continue to rise.

Pea Fractions

Although not as well-established as soy protein, pea protein isolate is a relatively new, highly digestible (90-95%) powder available to the industry at competitive prices. Pea protein is less allergenic than soy and has not been linked with negative hormonal effects. Both these factors, as well as others, have resulted in a sudden surge in use and interest by manufacturers. Pea protein is often combined with other plant-based proteins (e.g., rice and corn) to achieve a more balanced amino acid profile. Unlike whey, when high concentrations of powder are mixed with small amounts of water, the pea protein can be formed into semi-solid mixtures. Pea protein isolates are thus used in a number of different applications, including as an alternative to dairy protein isolates in sports nutrition and weight management products; to bind fat and water in meat and fish; in processed foods; and for protein enrichment of baked goods, cereals and snacks.

Several pea protein ingredients, isolates as well as concentrates, are now available from a number of suppliers. Most of these ingredients are highly soluble, transparent and heat-stable in low-pH solutions. In addition, these products generally have a light, fluffy texture and a slightly sweet taste. Years of developmental research have yielded ingredients with “clean” flavor characteristics well-suited for use in low-pH beverages.

Pea fiber is derived from specially cleaned and processed pea hulls. Most products are above 90% fiber, low in fat with no taste or aroma, and offer the ability to increase soluble and insoluble fiber in food products without effecting texture or taste. Research has shown the addition of pea fiber in certain formulations can improve batter viscosity as well as substitute for various gums and thickening agents, providing cost reductions with the health benefits of pulses. Using pea fiber can boost the dietary fiber content of wheat-based products. Tortillas formulated with 35% pea fiber contained approximately 8g of fiber and are lighter in color than whole-wheat flour, with a mild flavor profile. These studies also demonstrated that spaghetti formulated with pea fiber at levels that provided 4g of dietary fiber per serving showed acceptable flavor intensity, texture and overall quality.

Pea and other pulse flours are most often used in gluten-free baking. Removing gluten from such applications presents significant formulation challenges. Yellow pea flour is an ideal flour substitute that can bind moisture to enhance texture while also providing enhanced fiber and protein to the finished product. Studies demonstrate that, for whole yellow pea flour, a level of 20% blended with durum semolina is recommended for spaghetti. Pulse flours can also be puffed to make aerated snack foods using 100% pulse ingredients. The same investigators have reported that in commercial-scale muffin preparations, navy bean and yellow pea flours significantly improved nutritional properties and yielded muffins that were acceptable in sensory and quality characteristics.

Native pea starch offers a clean-label alternative to modified starches. Generally high in amylose content (35%), these ingredients provide better thickening, gelling and film-forming properties than most other native starches. And, as with modified starches, pea starch exhibits stability under high temperature, acid and shear. Hot viscosity of pea starch remains low and stable, reaching high values only after cooling. Rapid increase of viscosity during cooling produces a strong, firm and sliceable gel, which is an advantage in cheese and meat applications. Pea starch also forms a gel at a much lower usage level than other starches (approximately 4% vs. 10-20%).

Applications for pea starch include: water binding in meat and fish products; water binding and gel formation in baking and dairy products; and crispiness and volume improvement in extruded snacks. The inclusion of pea starch and pea fiber at a level of 4% improved the texture and water retention of sausages formulated with a reduced fat content.

Noodles, pasta and bread containing 30% pulse starches can be formulated to supply 2g of resistant starch. Further, dough and crackers containing pea starch as the base ingredient exhibit good physical properties and acceptable dough quality without requiring additional moisture. Pea starch can also be used to improve soy protein-stabilized food emulsions, such as tofu.

Chickpea and Lentil Flour

Commercial-scale processing of pasta containing chickpea flour at a 30% inclusion results in a product of good sensory properties.  In spaghetti, increasing levels of chickpea flour blended with durum semolina can increase the protein content and reduce gluten levels.

Corn and lentil mixtures processed at low temperature and higher values of feed moisture content and feed rate were reported to yield snacks that were rigid, whereas using low feed rates and moisture contents resulted in a softer, crispier snack. In this research, extrusion conditions and raw material characteristics, such as moisture content and lentil-to-corn ratios (10–50% legume/corn), were important determinants when developing snacks with acceptable sensory characteristics.

When formulating with pulse flours, experts at Pulse Canada (www.pulsecanada.com) suggest using ingredients that are either complementary to, or can overcome, the color of the flour, while adjusting the quantity of wet ingredients to compensate for the greater water absorption associated with pulse flours. Using additives such as xanthan gum to compensate for gluten deficiency will improve texture and shelflife.

Modified bean starch has been developed that can improve the textual acceptability of fresh gluten-free bread, in addition to reducing crumb hardness and enhancing elasticity. As noted, removing gluten from baked products poses technological challenges, because the protein possesses unique properties vital for both the retention of gas during fermentation and the preservation of moisture levels in the dough. Many gluten-free types of bread are based mainly on starch and often suffer from poor crumb and crust characteristics, as well as poor mouthfeel and flavor.

Market Potential

The market potential for using pulse-based fractions in gluten- and wheat-free products is impressive. Gluten is a general name given to the storage proteins (prolamins) present in wheat, rye, barley and oats. Celiac disease occurs when consuming gluten proteins triggers an autoimmune response that damages the lining of the intestines. Approximately one in 133 (or more than 2.5 million) people in the U.S. are believed to suffer from celiac disease.

Packaged Facts reported that, since 2005, there has been an average annual growth rate of 29% in gluten-free foods and beverages in the U.S. In 2008, the market was worth $1.56 billion. The market in 2012 could be worth as much as $2.6 billion. Between January 2008-June 2009, Mintel’s Global New Products Database found “gluten-free” to be the 10th most popular claim for new product launches throughout Europe, followed by the U.S. In this period, 3,398 gluten-free products were launched globally.

Foods manufactured with natural ingredients and free of chemical-sounding names are another major driver for the food industry and another area where pulses can play an important role. Pulse fractions can provide more natural ways of delivering the same functionality in many food products as synthetic additives. Additionally, good products, including pulse ingredients, can utilize health-related claims such as “vegetarian,” “low/no/reduced fat,” “organic,” “all natural” and “low/no/reduced allergen.”

Clinical evidence continues to grow and support the dietary value of pulses and the benefits of adding them to many foods and beverages. A number of studies have been undertaken to examine the suitability of pulse flours and fractions in a variety of applications. The key to using pulse ingredients in specific product applications lies in matching the unique functional properties, color and flavor attributes of the ingredient with the end-product being formulated. pf