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What’s Pulse-ible When It Comes To Extruded Products?

Alie Johnston1 | Rebecca Mollard1 | Julianne Curran2 | Peter J Jones1*

Health benefits of pulses
Pulses are the dry, edible seeds of podded plants in the legume family including chickpeas, dry beans, lentils, and yellow peas. Canadian pulse production represents about 35% of global pulse exports annually. In 2015, Canada exported 6.2 million tons of pulses valued at greater than $4.2 billion1. Pulses have a low carbon footprint, are a water-efficient source of protein, and improve soil health1,2. In addition to their contribution to sustainable agriculture, consuming 1⁄2 cup/day pulses can improve diet quality by increasing intakes of fibre, protein, folate, zinc, iron, and magnesium and reducing intakes of saturated fat and total fat4.

Pulses are a low fat, carbohydrate-rich plant food with high amounts of both soluble and insoluble fibre3, as well as resistant and slowly digestible starch and oligosaccharides3,4. Pulses also contain 2-3 times the amount of protein that is found in cereals and other plant crops like wheat, corn, quinoa and rice5. Based upon their nutritional composition, pulses have the potential to improve blood glucose and appetite control. Studies have shown that protein increases satiety to a greater extent than carbohydrate or fat6, while protein has minimal effects on blood glucose and only modestly if at all increases hepatic release and production of glucose7. Diets higher in protein reduce blood glucose postprandial and improve glucose control compared to diets lower in protein8. A variety of health benefits have been associated with consuming dietary fibre, including improved blood glucose and insulin sensitivity from the increased intake of soluble fibre, as well as enhanced weight loss due to fibre supplementation in obese individuals9. Similar to dietary fibre, demonstrated health effects of resistant and slowly digestible starches are improved blood glucose and insulin responses, as well as increased satiety and reduced energy intake10,11,12. The inherent nutritional compensation of pulses makes them very suitable to be considered for use as value adding ingredients.

A next step in pulse research
Whole pulses have been studied extensively for their beneficial effects on post-prandial glycemia and satiety in human trials. When consumed alone or within mixed meals, whole pulses have been shown to affect postprandial glycemic and satiety responses favorably13,14,15,16,17,18. A review of whole pulses has shown that pulses increase satiety by 31% when compared to a control19. However, whether pulse ingredients retain the health benefits of whole pulses when consumed in commercially available processed food products is unclear. To date, a limited amount of research has examining the impact of pulse flours and pulse fractions on blood glucose and satiety20,21,22,23,24,25.

The marketplace is flooded with processed foods that are convenient, offer little nutrition, are high in calories, and do not satiate. Overall, 55% of calories consumed by Canadians are in the form of ultra processed foods26; these foods lead the consumer to eat more and do not aid in “tiding them over” until their next meal. Ultra processed foods encompass frozen pasta, pizza, nuggets and sticks, burgers, chips, cookies, cereal, carbonated and sugary drinks, the bulk of snack products and more. These are made from ingredients that are obtained by refining and extracting whole foods26. They contain none or very little whole foods, are generally high glycemic, energy dense, and contain increased salt, fat, and sugar compared to meals prepared from unprocessed and minimally processed foods and ingredients26. The lack of readily available, nutritious, and satiable snacks and cereals offer few options to consumers striving to make nutritious choices to support their health26.

Despite the nutritional advantages and benefits for post-prandial glycemia and satiety, very few Canadians eat whole pulses25. Dry, unprepared pulses have lengthy cooking times and some require soaking. Canned pulse products are a convenient alternative, however, many Canadians are unfamiliar with how to use pulses in recipes and cooking. Thus, an opportunity exists to incorporate pulses into food products that are convenient and familiar to consumers. Commercially available snacks and cereals with pulse ingredients may also offer consumers added nutrition and satiety benefits25.

Pulse flour human research study findings

In recent years, research has started to emerge regarding the health effects of pulse ingredients. In a randomized cross-over trial, the effects of yellow pea flours on fasting insulin, insulin resistance, body composition, glucose, and other disease risk markers have been explored in individuals who were overweight and had high blood cholesterol levels. Researchers examined the effects of whole pea flour, fractionated pea flour containing hulls only, and white wheat flour in a muffin. Participants consumed two muffins each day. Fasting insulin levels were significantly reduced compared to the control by the whole pea flour treatment. Insulin resistance estimates were reduced by 25% in both treatment groups compared to the control. Women were found to have a 4.7% decrease in android:gynoid fat ratios for both treatments compared to control. A decrease in android fat may be beneficial because there is an association between android fat and cardiovascular risk factors24.

Research has also shown that the beneficial effects of whole beans on post-prandial glycemia were retained after pulses were ground to a powder. Experiments were done to examine effects of whole, pureed, and powdered pulses to whole wheat flour. In a first experiment, the treatments included whole navy bean, pureed navy bean, and navy bean powder. In a second experiment, treatments included whole lentil, pureed lentil, and lentil powder. In the third experiment treatments were whole chickpea, pureed chickpea, and chickpea powder. The treatments were served mixed into tomato sauce and a fixed pizza lunch was served after two hours. Seventeen normal weight men between the ages of 18-30 participated. Area under the curve (AUC) was calculated to describe the blood glucose response over time. In experiment 1, the difference in blood glucose net area under the curve (AUC) following consumption was significantly lower following the navy bean powder compared to the control, and was intermediate for the other two treatments. In experiment 2, mean blood glucose levels were significantly lower compared to the control for all lentil treatments following consumption. In addition, compared to the control, the blood glucose net AUC was lower for whole lentils and powdered. In experiment 3, blood glucose was significantly lower for powdered, pureed, and whole chickpeas compared to the control following consumption. The authors concluded that pureeing and commercial processing does not negate the acute glucose regulation benefits of consuming pulses, as there were overall no significant differences seen between the treatments due to processing25.

Pulse fraction human research study findings

Research has also shown pulse fractions retain the beneficial effects of whole beans on post-prandial glycemia. A study was conducted investigating the effects of yellow pea protein and fibre on glycemic response, food intake, and subjective appetite in healthy men. Treatments were tomato soup as control, and tomato soup with 10 g or 20 g of fibre or protein. In experiment 1, participants received an ab libitum pizza meal at 30 min, and in experiment 2 at 120 min. In experiment 1, blood glucose was significantly lower over the entire treatment period for both protein treatments compared to the control. Blood glucose was overall significantly lower with protein 20 g treatment compared to control and fibre 10 g treatment. In experiment 2, pre and post-meal blood glucose was not significantly affected by treatment. This study demonstrates that pea protein is rapidly digested similar to whey protein, which the authors felt attributed to the lack of an effect in experiment 2. The authors suggested that the null results from the fibre treatments though surprising may be because the fibre was taken from the hull only and not from the entire pea. The hull was mainly insoluble fibre, while fibre extracted from the entire pea contained both soluble and insoluble fibre.

Another study investigating the effects of pea fractions on food intake, appetite and blood glucose found that pulse fractions exerted beneficial effects on blood glucose levels. Following a randomized controlled cross-over design, participants consumed five treatments: yellow peas, pea hull fibre and pea protein, pea hull fibre, pea protein, and the control. Treatments were served with with tomato sauce and noodles. Similar to whole yellow peas, the combined pea protein and fibre treatment lowered the glycemic response compared to the control, however, this action was not seen in response to fibre or protein alone23. This study indicates that when consumed in combination pea fibre and protein retain the effects of whole peas, but these benefits were not retained when consumed alone. Further investigation is required to determine the optimal quantity of fractions that should be incorporated into foods to maximize the health benefits received from consuming pulses.

Pulse flours and fractions in extruded snacks and cereals

Pulse flours and their fractions show health benefits, however, the optimal dose and combination of pulse flours and fractions that should be incorporated into commercially relevant products is unknown. In addition, the effects of pulse ingredients incorporated into extruded snacks and cereals have not been examined. There is a need to test the impact of pulse flour and fraction ingredients within food matrices of interest to increase the commercialization of pulse food products and to substantiate health claims for these products27. The Canadian pulse industry would greatly benefit from approved pulse specific health claims because they would encourage increased use of pulse ingredients in food products as seen with other food/food constituents that have established health claims.

Our research will test acute effects of different extruded products containing pulse ingredients on post-prandial blood glucose, appetite, insulin, and food intake. This research is funded by Saskatchewan Pulse Growers and Alberta Pulse Growers, and will assess whether pulse ingredients retain their beneficial benefits when incorporated into extruded snacks and cereals.

Extruded pulses human clinical trials in progress

Ongoing research at the Richardson Centre for Functional Foods and Nutraceuticals is assessing effects of extruded pulse snacks and cereals on post-prandial glycemia, satiety, and food intake through two acute double blinded clinical trials. The first study is examining six extruded snacks: 1) corn flour control, 2) whole yellow pea flour, 3) split yellow pea flour, 4) lentil flour, 5) chickpea flour, and 6) pinto bean flour. The flours are replacing corn flour at a rate of 40%, while the control is 100% corn flour. The second study will examine six extruded cereals with fractions of varying percentages replacing oats: 1) 100% oat control, 2) 40% pea protein, 3) 50% pea starch, 4) 18% pea fibre plus 40% pea protein, 5) 40% pea protein plus 50% pea starch, and 6) 16% pea fibre, 45% pea starch plus 36% pea protein. The snacks were given as a 50 g portion and the cereals as a 35 g portion based on Health Canada’s reference serving sizes for extruded snacks and cereals. Participants will be given one pulse treatment or control once per week in a randomized order until all six sessions are completed.

We hypothesize that food products containing pulse ingredients and fractions will lead to lower blood glucose, insulin, appetite, and food intake responses compared to non-pulse products, and this effect will be greater when the pulse components are consumed in combination (e.g. protein vs. fibre vs. protein plus fibre) rather than in isolation. Our research is currently underway. If our hypothesis is correct and extruded pulse products retain the positive health effects of whole pulses, this will support the use of pulse ingredients as value added ingredients in processed food designed to improve the post-prandial blood glucose and appetite response. Through this, healthier snacks and cereals with proven health benefits will be available to consumers. The average consumer would have access to pulses in a readily available form at the supermarket that still provides the positive health effects attributed to whole pulses.

Conclusion

Understanding “what’s pulse-ible when it comes to extrusion” has only begun. Previous research has shown that the blood glucose lowering effects of pulses are retained after being ground to a powder25, and that the blood glucose lowering effects of pea protein are seen when a second meal is served 30 minutes after the treatment22. It has also been shown that pea fibre and protein lowers blood glucose, but that fibre or protein fractions alone do not23. Our current research will determine the effects of extruded pulse flours and fractions in snacks and cereals on blood sugar, food intake, and appetite. With their nutritional profile, blood sugar lowering effects, and sustainability benefits, pulses are a crop full of pulse-ibilities.

 

References
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1Richardson Centre for Functional Foods and Nutraceuticals (RCFFN), Department of Human Nutritional Sciences, University of Manitoba, Winnipeg, MB
2Pulse Canada

(*Corresponding author email: peter.jones@umanitoba.ca)

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