Pulse Industry

Project Abstract: Developing pulse-based functional food ingredients and foods

The key challenge to food researchers and the food industry is the production of consumer friendly foods which contain enough resistant starch (RS) and/or slowly digestible starch (SDS) to result in a significant improvement in human health, and how to evaluate or predict the nutritional properties using an effective model.

The physicochemical characterization of starch will play an important role in providing information on the properties of pulse starch-based foodstuffs, and facilitate an understanding of the key structural determinants of starch and its modification and applications in functional food products. Extensive research on cereal, potato, sweet potato and cassava starches has made them readily available for use in food and non-food applications. Research is needed in this collaborative project to understand how enhanced slowly digestible and/or resistant starch is formed through pulse variety selection and effective processing to manipulate starch structure, and what the microstructure and the functionalities are for slowly digestible and resistant starch.

For the year 2016, we continued our research work on Canadian grown pulses with a focus on wrinkled pea and smooth pea. Pulse flour and starch were isolated from selected wrinkled pea and smooth pea varieties from different growing locations. Physicochemical properties of flour and starch including chemical composition, amylose leaching, morphology, particle size, gelatinization, retrogradation, pasting, chain length and its distribution and crystalline structure as well as digestibility were characterized using various analytical techniques.

There appeared to be a difference in chemical composition between the smooth and wrinkled peas and there were differences between similar peas grown in different locations. For the digestibility in vitro, rapidly digestible starch content was found to be moderately low in smooth pea starch but high in wrinkled pea starch although wrinkled pea starch contained much higher amylose content than smooth pea starch. Wrinkled pea starch seemed to have a longer average chain length than smooth pea starch. Slowly digestible starch and resistant starch contents were high in smooth pea starch but low in wrinkled pea starch. Smooth pea starch seems to be more resistant to digestion when compared to wrinkled pea starch. This finding is interesting as it is contradictory to other high amylose starches. Further research is needed on the mechanism of enzyme digestion for pea starch.

In this project, we also developed pulse-based breads using different pea, lentil and chickpea as major ingredients. Those breads are low GI foods as tested at GI lab at University of Toronto. We also made great efforts to enhance slowly digestible starch and resistant starch content in the breads by using various technologies including adjusting bread formula, roasting, and alginate encapsulation.

Pea bread containing up to 37.5% encapsulated roasted pea starch not only displayed a decrease in RDS by 25.78% and an increase in SDS and RS by 8.55% and 17.23%, but also provided a better mouthfeel and texture to the bread. As a result of this research, pulse-based breads are low GI foods that will benefit consumers with chronic diseases such as diabetes, cardiovascular disease and obesity.

We continue modifying pulse starch using chemical and physical means to enhance its enzyme resistance. We have developed extrusion technology to produce cross-linked pulse starch for food applications with a retained granular structure.

Our innovation and information items from this research include: (1) Developed novel large-scale extrusion and lipid complexing technology to modify the functional properties of pulse starch for food and non-food applications; (2) Developing novel large-scale extrusion technology for citric acid modification of pulse starch for food and non-food applications; (3) Developed technologies of roasting (air-oven and microwave) and alginate encapsulation to produce novel food ingredients for enhancing slowly digestible and resistant starch content in pulse flour/starch. Pea flour treated either by oven-roasting or by microwave-roasting effectively retained its slow digestibility similar to the native form. When oven-roasting was applied to pea starch, 25% increase in SDS was achieved compared to the fully cooked counterpart.

For the year 2016-2017, three research manuscripts were published associated with this project: one research paper on pea flour modification, one research paper on Bioaccessibility in vitro antioxidant and anti-inflammatory activities of phenolics in cooked green lentil, and one research paper on the molecular structure and functional properties of starch from different peas. We also submitted one research manuscript on cross-linked pulse starch using extrusion. New knowledge was generated from this research and was transferred to the public through peer-reviewed scientific journals. We presented an invited lecture at Pulse Workshop, on Pulse Starch: Structure and Modification, in Saskatoon, SK, in September 2016. We also presented our pulse flour research at 18th World Congress of Food Science & Technology in Dublin, Ireland. In addition, a media article featuring our research on nutritional value of pulse ingredients was released on the AAFC website in November 2016.

 

Project lead: Dr. Qiang Liu (519) 780-8030 qiang.liu@agr.gc.ca

 

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