NEW CHALLENGES IN FOOD AND HUMAN NUTRITION AT AAFC Nutritional Benefits of Cereal  -Glucans Dr. Susan M. Tosh Research Scientist Guelph Food Research Centre PRES TETRAPARTITE 2008 Bordeaux, France

2 Food Research Map of Canada Summerland Lacombe Kentville Guelph Winnipeg Ottawa St-Hyacinthe Charlottetown 600 Researchers 19 Research Centres 20% on Food Research in 7 locations

3 Food and Nutrition Research in AAFC 20% of Research Branch Safety 40% Processing 30% Nutrition 30% Antioxidants Bioactive lipids Probiotics Polyphenolics Dietary fibre

4 Nutrition Research Areas - new challenges Antioxidants Bioactive lipids Probiotics Polyphenolics Dietary fibre Fruits & Grains Meat &Dairy Products Dairy Products Pulses & Oil Seeds Cereals & Pulses

5 Investigation of the Impact of Dietary Fibre from Cereals on Blood Glucose Levels in Humans Dietary fibre is found in the cell walls of cereal grains and other plant materials Insoluble fibres –Cellulose –Lignin Soluble fibres –Arabinoxylan –  -Glucan

6 Mixed linkage  -glucan  - Glucan in Oat Bran Micrographs by Dr. Shea Miller, AAFC Grain  -glucan content (%) Wheat0.5 – 1.0 Rye1.0 – 2.1 Oat groats3.9 – 6.8 Barley3.0 – 10.6 Corn0.1 Rice0.1 Oats and barley have the highest  -glucan contents of the cereal grains

7 Oat and Barley Foods Prolong Glucose Release into the Blood Stream Attenuate postprandial blood glucose levels Prevent spike and overshoot of glucose concentrations after a meal Many oat and barley foods are considered low glycemic index

8  -Glucan Identified as the Bioactive Component for Glucose Control (Wood, AAFC)

9 Human Subjects were given Drinks containing  -Glucan and Available Carbohydrate (Wood et al., 1994, AAFC) Their peak blood glucose was decreased as the viscosity of the drink increased Log [Concentration x Mw] Blood Glucose (mmol/L)

10 Efficacy of  -Glucan can be Different in Different Foods  -Glucan is not digested or absorbed –Activity is in the lumen of the gut –Thought to increase viscosity of intestinal contents Factors affecting development of viscosity –Aggregation causes loss of solubility –Enzymes cause depolymerization Food processing steps –Heating, freezing, shear, fermentation –Can affect bioactivity

11 Concentration and Molecular Weight are the Major Factors Influencing Viscosity of  -Glucan Solutions (Tosh et al., 2004)(Ren et al., 2003) Concentration Effect Molecular Weight Effect

12 Two Clinical Trials to Investigate Effects of Viscosity on Glycaemic Response Investigate effects of processing –Oat bran muffin compared to whole wheat muffins –Changes in solubility and molecular weight induced in some oat bran muffins 11 or 12 healthy human subjects –Age 20 – 50, BMI 20 – 36.2 Finger-prick capillary blood samples collected over 2 hours Blood glucose concentration measured (Clinical trials conducted by Thomas M. S. Wolever at University of Toronto)

13 Trial 1: Muffins with Modified  -glucan Solubility Oat bran muffins contained 8g or 12g  -glucan/serving (130g) Solubility reduced by freeze-thaw (FT) cycling –2 FT or 4 FT cycles – –Up to 54% reduction in solubility –Extracted at 37ºC under physiological conditions (Tosh, AAFC)

14 Freeze/Thaw Treatment Caused Aggregation and Reduced Solubility of  -Glucan in Muffins 8g  -glucan/serving No treatment Freeze/thaw treated

15 Reduced Solubility Resulted in Diminished Efficacy Fresh gave 45% reduction in peak blood glucose compared to control (Lan-Pidhainy et al. 2007, AAFC) 8g  -glucan/serving

16 Trial 2: Muffins with Modified  -Glucan Molecular Weight Added  -glucanase enzyme to muffin batter to cause depolymerization Molecular weights –2,210,000 to 120,000  -Glucan solubility also decreased Muffins containing 4g or 8g  -glucan/serving

17 Enzyme Treatment Caused Cell Wall Degradation and Aggregation of  -Glucan 4g  -glucan/serving No treatment  -Glucanase treated

18 Depolymerization Reduced  -glucan Bioactivity 2 Lowest MW’s not significantly different from whole wheat control Time (min) Blood Glucose (mmol/L) Control 120,000g/mol 390,000g/mol 620,000g/mol 2,210,000g/mol 8g  -glucan/serving (Tosh et al., 2008)

19 Glycaemic Response was Correlated with Viscosity of Extractable  -Glucan Extractable  -glucan –MW x concentration Pooled data from solubility and MW trials Correlation with peak blood glucose rise in clinical trial

20Summary Cereal  -glucans as part of a healthy diet can attenuate post-prandial serum glucose concentrations Distribution of  -glucan, solubility and molecular weight affect bioactivity These factors can be affected by processing and storage conditions This information can assist food manufactures in producing low glycaemic index foods

22 In Vitro Digestion  -Glucan extracted from muffins at 37ºC Measure extract viscosity, concentration and molecular weight (Beer et al., 1997) Crumbs pH 6.9, Amylase pH 2, Pepsin pH 6.9, Pancreatin Centrifuge Soluble Fibre