Addressing consumer needs: potential for developing wheat products with lower glycemic response

Transcription

1 Addressing consumer needs: potential for developing wheat products with lower glycemic response Dr. Nancy Ames & Dr. Sijo Joseph Agriculture and Agri-Food Canada Richardson Centre for Functional Foods and Nutraceuticals Winnipeg, MB November 24, 2016

2 How can we develop wheat products with lower glycemic response? Consumers: Breeding: Processing Methods Awareness of consumer needs Breeding - E.g. results from recent Manitoba Consumer Monitor (MCM) surveys show: Higher fibre, including resistant starch Composition 70% of Higher respondents protein Milling particle size Altered Processing starch composition purchase Sourdough wholegrains fermentation (higher amylose; slowly Freezing digestible starch) Consumers Bread Structure Starch bioaccessibility - Toast/bread was one of the foods most often consumed for breakfast by almost - 77% of respondents indicated that increasing fibre is a main reason for choosing to Collaboration with food industry partners E.g. Warburtons Interactions with health professionals and clinical researchers Provide consumers with substantiated benefits (health claims) - Only 11% of respondents considered health claims to be a trustworthy source of info when purchasing wholegrain products (MCM); shows more consumer education is needed surrounding health claims

3 Glycemic Response and Diabetes Glycemic Response: The elevation of blood glucose concentrations after consumption of a food and/or meal (ie. post-prandial) Glycemic Index (GI): A scale that ranks foods based on how much they raise blood glucose compared to glucose or white bread Type 2 Diabetes: The body no longer uses insulin properly and is unable to control blood sugar, leading to high levels of sugar (glucose) in the blood One in three Canadians are already living with diabetes or prediabetes, including an estimated 1.5 million with undiagnosed diabetes (Canadian Diabetes Association, 2016)

4 Consumer Perspective Wheat based food products have varying ranges of glycemic indices. Choosing low glycemic foods is especially important for those who live with diabetes. Access to low-gi wheat products is an important priority for consumer health and presents market opportunities for the wheat industry.

5 Starch Digestibility and Glycemic Response Rate of starch digestibility is related to glycemic response Rapidly digestible starch (RDS): broken down in 20 minutes Slowly digested starch (SDS): broken down in 100 minutes - Raw cereal starches naturally have high SDS - Offers the possibility of moderated glucose delivery to the body Resistant starch (RS): not digested in the small intestine but fermented in the large intestine Higher RS content for high amylose products Resistant starch Formed during processing (retrograded amylose) Not hydrolysed in the small intestine (undergoes colonic fermentation and forms bioactive SCFA) Lower glucose response

6 Opportunities for Wheat Breeders Breeding for lower glycemic wheats - Slowly digestible starch - Resistant starch (high amylose) - Starch/ protein matrix - Digestive enzyme inhibitors - E.g. AAFC potato breeders have successfully developed a low GI potato using traditional breeding methods and natural genetic diversity

7 Starch Synthesis Enzymes Starch consists of amylose and amylopectin; granule bound starch synthase I (GBSSI) is responsible for amylose synthesis and soluble starch synthase IIa (SSIIa) plays a major role in amylopectin synthesis. Combining wild type and null A,B and D genes for GBSSI and SSIIa allows production of genotypes with a range of starch characteristics. A recent study (Regina et al, 2015) showed suppression of both SBEIIa and SBEIIb resulted in wheat with up to 85% amylose and >35% RS.

8 Two dimensional array of homozygous genotypes developed from GBSSI and SSIIa wild-type mutant alleles. For each of the six genes, the homozygous wild type allele is indicated by + and the homozygous mutant allele -. Homoeologous genes are indicated as A1, B1 or D1 Nakamura et al, 2015.

9 Starch Protein Matrix Gluten proteins may form matrices with starch, offering protection from gelatinization and digestive enzymes ( starch digestibility ) Jenkins et al. (1987) and Hallstrom (2011) showed that natural starch-protein interactions played an important role in reducing rate of starch digestion and subsequent glycemic response Excessive kneading/mixing can lead to poor matrix structure (disulfide bond breakage and glutenin particles dissociated into smaller fragments) ( starch digestibility) Breeding for stronger protein may lower glycemic response

10 Processing Effects on Glycemic Response Shorter proof time resulted in decreased bread loaf volume and significant reduction in glycemic response (Burton & Lightowler, 2006) Steam bread process showed trend towards lower IAUC, GI and max peak rise in glucose compared to baked bread, regardless of ingredients (Lau et al., 2015) Sourdough bread showed significantly lower post-prandial glucose and insulin responses compared to a standard white wheat bread control (Lappi et al., 2010) Products with low porosity but with similar composition to bread resulted in lower peak glucose and insulin response (Eelderink et al., 2015) Source: Eelderink et al., Food Funct., 2015, 6, p Control Bread Flat Bread Pasta

11 Processing Effects on Glycemic Response Freezing and toasting of bread resulted in lower glycemic response compared to fresh bread (Burton & Lightowler, 2007) Incorporation of intact kernels into bread elicited changes in insulin response and GLP-1 hormones (Eelderink et al., 2016) Coarse particle size (2 mm) wheat porridge resulted in significantly lower blood glucose, insulin and other metabolic outcomes compared to smooth porridge (<0.2 mm). These results were consistent with in vitro starch digestibility rates. (Edwards et al., 2015) Source: Edwards et al., Am J Clin Nutr 102;

12 Combining Breeding and Processing Strategies Using a wheat genotype with high amylose combined with a baking process to promote amylose retrogradation significantly increased RS (Hallstrom et al., 2011). Pumpernickel baking (slow temp increase and acid) alone also resulted in increased SDS. Resistant Starch (g/portion) Glycemic Index White Wheat Bread (Ref) Whole Grain Wheat Bread Elevated Amylose Content Elevated Amylose with Lactic Acid Hallstrom et al., 2011 Food & Nutrition Research 55:7074

13 Slowly Digestible Starch Opportunities for Breeding and Processing Chemical structure leading to SDS formation (E.g. physical modification of starch using heat-moisture treatments) Food factors that decrease digestion rate (E.g. breed for natural α- amylase and α-glucodisase inhibitors (phenolics); delay gastric emptying with organic acids (sourdough fermentation) Processing techniques that form food matrix structures that decrease enzyme accessibility (E.g. dense protein matrix of pasta)

14 Rapid screening tools to effectively evaluate the physiological outcomes How do we effectively translate the research? How do we evaluate whether these products really exhibit significant physiological effects in human? Research exists on how to develop low glycemic wheat products through breeding/processing strategies

15 New Predictive Tools: In vitro models of digestion There are various factors relevant to glycemic response (E.g. bioavailability of starch, processing, storage time, botanical origin and genotype) which can be measured using in vitro methods. We have developed a static in vitro starch digestibility assay to predict glucose response Dynamic stomach model (TIM 2- TNO) to assess the glycemic response to cereal food products and formulations New AAFC Collaborative Project: Developing a platform comprising novel experimental tools for improving the health benefits of wheat

16 Summary - Breeding Opportunities exist for breeding wheat with increased amylose content and slowly digested starch. New methodologies such as in vitro digestion assays and model stomach systems offer new opportunities for rapid screening of bioactive components and predicating physiological outcomes of wheat consumption

17 Summary - Processing Several studies show how processing impacts food macrostructure, particle size, degree of starch gelatinization and resistant starch content, which in turn affects starch digestibility (amount of slowly digestible starch) and glycemic response. Overall, processing steps that limit starch accessibility to enzymes are beneficial (Fardet et al., 2006). E.g. a more compact structure, due to reduced porosity and/or air cell diameter Milling can cause physical damage to starch granules : - particle size is an important predictor of starch bioaccessibility (fractured particles = increase access to enzymes)

18 THANK YOU 18