Instrumental and Sensory Characteristics of a Baked Product Containing Barley Flour with Varying Amounts of Beta-Glucan and Sugar Substitute by Niti Lathia A Thesis submitted to the Graduate School-New Brunswick Rutgers, The State University of New Jersey in partial fulfillment of the requirements for the degree of Master of Science Graduate Program in Food Science written under the direction of Dr. Henryk Daun Dr. Paul Takhistov and approved by ________________________ ________________________ ________________________ New Brunswick, New Jersey October 2011 ABSTRACT OF THE THESIS Instrumental and Sensory Characteristics of Baked Product Containing Barley Flour with Varying Amounts of Beta-Glucan and Sugar Substitute By Niti Lathia Thesis Directors: Dr. Henryk Daun Dr. Paul Takhistov The objective of this study was to determine the influence of varying levels of beta-glucan in barley flour on selected properties of a model baked product. Another aim was to reduce sugar levels in the product by incorporating a natural sweetener stevia and to monitor its influence using instrumental and sensory analysis. Batter rheology was studied using a lubricated squeezing flow technique, pasting profiles of the barley flours were determined with a rheometer, viscoelastic properties were evaluated using dynamic oscillatory rheology to measure G’ and G”, and firmness of the baked products was monitored using a texture analyzer, for changes occurring due to varying β-glucan levels in barley flour and removal of sugar. L a* b* color values of barley flour and muffins were obtained using a colorimeter. A descriptive sensory panel was trained to observe changes in product attributes when stevia was used to replace sugar in the high beta- glucan product. Water absorption index was found to be significantly higher for high β-glucan barley flour. The color of both barley flours also had a significant difference in L* (lightness) and b* (yellowness) values. Similarly, muffin samples prepared without sugar, using stevia, were significantly lighter in surface color (higher L*), while the ii interior colors were darker (higher b*). Low beta-glucan dough showed a lower biaxial extensional viscosity compared to the high beta-glucan dough, which indicates that the level of beta-glucan present in the barley flour has an impact on the dough viscosity. The pasting profiles of the flours were also found to be significantly different, where the high beta-glucan barley flour resulted in a significantly higher peak viscosity but lower peak time compared to low β-glucan barley flour. Muffin firmness was found to be significantly higher when sugar was omitted from the formulation, but there was no significant difference in firmness among the two beta-glucan levels in the muffins. The sensory descriptive panel found significantly higher firmness, surface roughness, and bitterness attributes for the high β-glucan muffins prepared with stevia. Additional efforts will be needed to mask the undesirable attributes in the model baked product occurring due to the removal of sugar. iii Acknowledgement First and foremost, I would like to express my sincere gratitude towards both of my thesis advisors, Dr. Henryk Daun, who brought the project to my attention, and equally to Dr. Paul Takhistov whose lab I conducted my research in. Both professors have provided guidance, support, encouragement, and have had patience in explaining my numerous inquiries throughout the duration of my project research. Secondly, I would like to thank Dr. Kit Yam for being on my thesis defense committee, whose input and suggestions I value. In addition, a big thank you to my lab mates for their assistance with learning new instrumentation as well as providing a fun learning environment. Also, I appreciate the efforts of the undergraduate team of students that participated in the sensory portion of this research as panelists; your help and cooperation was greatly appreciated. Most importantly, I would like to thank my parents and family for providing the financial support for my graduate studies as well as love, encouragement, moral support, providing comfort during the challenging times, and accepting my absence while I worked towards completing my degree. I have relied on them for guidance and strength throughout my academic career. Thank you for your confidence and unwavering support. iv TABLE OF CONTENTS Page ABSTRACT OF THESIS ii-iii ACKNOWLEDGEMENTS iv TABLE OF CONTENTS v LIST OF ABBREVIATIONS vii LIST OF TABLES viii LIST OF ILLUSTRATIONS ix LITERATURE REVIEW – CHAPTER ONE 1.0 Introduction 1 1.1 Health Benefits of Barley 4 1.2 Chemical and Physical Characteristics of Barley 10 1.3 β-Glucans and Arabinoxylans 13 1.4 Properties and Molecular Interactions among Major Food Components 17 1.5 Beta-glucan extraction 17 1.6 Water absorption capacity and effect on end-products 19 1.7 Rheological Properties Influenced by barley flour beta-glucan content 21 1.8 Stevia as a Sweetening Agent in Consumer Products 22 1.9 Conclusions from Literature Review and Objectives for Research 24 MATERIALS AND METHODS – CHAPTER TWO 2.1 Ingredients Used in Baking Procedures and Analytical Measurements 26 2.2 Water Absorption Index of Low and High β-glucan Barley Flour 27 2.3 Microbakery Model Formulations for Barley Muffins 29 v 2.4 Rise and Moisture Loss of Muffins 32 2.5 Rheological properties of barley dough using lubricating squeezing flow technique 33 2.6 Pasting Properties of High β-glucan and low β-glucan barley flours 36 2.7 Dynamic Rheological Properties of Muffin Batter 39 2.8 Assessing Muffin Firmness Using a Texture Analyzer 40 2.9 Evaluation of Colors Using a Colorimeter 42 2.10 Nutritional Comparison of Muffins 44 2.11 Sensory Methodologies Used to Evaluate Muffin Products 45 RESULTS AND DISCUSSION – CHAPTER THREE 3.1 Water absorption values for barley flours 50 3.2 Increase in Muffin Heights After Baking 51 3.3 Muffin Moisture Loss After Baking 53 3.4 Rheological Properties of barley flour doughs and muffin batters 55 3.5 Pasting properties of barley flours 62 3.6 Color values for Barley Flour Varieties 64 3.7 Muffin Surface Color 66 3.8 Muffin Interior Color 71 3.9 Muffin Firmness 74 3.10 Nutrition Facts for Muffin Formulations 77 3.11 High β-glucan Muffin Sensory Quantitative Descriptive Analysis 79 3.13 Conclusions and Suggestions for Future Work 85 vi LIST OF ABBREVIATIONS United States Department of Agriculture (USDA) National School Lunch Program (NSLP) National Health and Nutrition Examination Survey (NHANES) Dietary Reference Intakes (DRI) Recommended Daily Allowances (RDA) Coronary Heart Disease (CHD) Low density lipoprotein (LDL) Food and Drug Administration (FDA) Code of Federal Regulations (CFR) Apparent Biaxial Extensional Viscosity (ABEV) The International Commission on Illumination (CIE) Rapid Visco Analyzer (RVA) Quantitative Descriptive Analysis (QDA) vii LIST OF TABLES Table 1: Nutritional Composition of Sustagrain Barley Table 2: Average Nutrient Comparison for Hulless Barley, Oats, and barley variety Prowashonupana (Prowash) Barley Table 3: Formulations for Muffin Batters Used to Prepare a Model Baked Product Table 4: Reference standards for selected attributes used in Spectrum Descriptive Analysis panel Table 5. Descriptors used to evaluate muffin samples in the QDA panel Table 6: Water Absorption indices of high and low β-glucan barley flour Table 7: Percentage Increase in Muffin Height (Rise) After Baking Table 8: Percentage Decrease in Muffin Weight (Moisture Loss) After Baking Table 9: Pasting profile for low and high β-glucan barley flours Table 10: Consistency index and flow behavior index for muffin batter with varying amounts of beta-glucan and sugar Table 11: Average L a*b* Values for low β-glucan and high β-glucan Barley Flour Varieties Table 12: Average L, a*, b* color values for surface color of muffins prepared with low or high β-glucan barley flour with 100% sugar Table 13: Average L, a*, b* color values for surface color of muffins prepared with low or high β-glucan barley flour with 0% sugar Table 14: The average L, a*, b* color values for interior color of muffins prepared with low or high β-glucan barley flour with 100% sugar Table 15: The average L, a*, b* color values for interior color of muffins prepared with low or high β-glucan barley flour with 0% sugar Table 16: Average maximum peak force to compress muffins as a measure of firmness Table 17: Nutrition Facts for Muffin Formulations Table 18: The mean values of each attribute measured by the QDA panel for muffins prepared with Sustagrain flour with 100% sugar and 0% sugar, sweetened with stevia viii LIST OF ILLUSTRATIONS Figure 1: Molecular Structure of β-(1 3)- and β-(1 4)-glucan Figure 2: Structural elements present in arabinoxylans Figure 3: Extraction and purification of β-glucans from barley and oats Figure 4: Structural Components of Stevioside, Rebaudioside A, and Steviol Figure 5: Nutrition Label for Bob’s Red Mill Ground Flaxseed Meal and Bob’s Red Mill barley flour Figure 6: Example of water separated from barley flour after centrifugation Figure 7: Apparatus and set-up of TA.XT2 Texture Analyzer for Lubricated Squeezing Flow Technique Analysis of Doughs Prepared Using Barley Flours Figure 8: Typical RVA pasting profile of a normal maize starch for viscosity and temperature as a function of time Figure 9: Water absorption indices of high and low β-glucan barley flour Figure 10: Percentage Increase in Muffin Height (Rise) After Baking Figure 11: Percentage Decrease in Muffin Weight (Moisture Loss) After Baking Figure 12: Biaxial Extensional Viscosity as a Function of Biaxial Strain Rate for Sustagrain Dough and Bob’s Red Mill Barley Flour Dough Figure 13: Pasting profile for low and high β-glucan barley flours Figure 14: Strain vs. shear rate relationship of muffin batter with varying levels of beta- glucan and sugar Figure 15: Effect of % Strain on G’ of muffin batters containing varying amounts of beta- glucan Figure 16: Effect of % Strain on G” of muffin batters containing varying amounts of beta-glucan Figure 17: Average L a*b* Values for low β-glucan and high β-glucan Barley Flour Varieties Figure 18: Visual Difference in Flour Color.