Effect of hydrocolloid type on rheological and sensory properties of pureed carrots By Madhu Sharma A Thesis Presented to The University of Guelph In partial fulfilment of requirements for the degree of Master of Science in Food Science Guelph, Ontario, Canada © Madhu Sharma, April, 2015 ABSTRACT Effect of hydrocolloid type on rheological and sensory properties of pureed carrots Madhu Sharma Advisor: University of Guelph, 2015 Dr. Lisa Duizer Hydrocolloids are added to pureed foods to give desired consistency based on visual judgement, due to the existing qualitative guidelines. The current study was undertaken to understand how different hydrocolloids affect texture and other sensory modalities of pureed carrots when viscosity is kept within a specific range. Eight hydrocolloids and one commercial sample were tested using small (rheology) and large deformation (rheology and TPA) instrumental measurements. Sensory analysis was also conducted. Hydrocolloids showed differences in gel strength (small deformation) and ease of deformation to make a swallow-able bolus (large deformation) and similarities in elastic behaviour. Trained panel sensory results indicated textural similarities among some hydrocolloids. Partial napping gave a product map and associated descriptors of each hydrocolloid for appearance, flavour and texture. Hydrocolloids with similarities in texture differed in appearance and flavour. This data can be used for understanding the impact of hydrocolloids on foods for individuals with dysphagia. ACKNOWLEDGEMENTS This thesis would not have been possible without the support and guidance of my advisor Dr. Lisa Duizer. It was only because of her trust and confidence in me which made all the stages of this research a great learning cum enjoyable experience. You made me love sensory and gave the much needed encouragement with ‘positive reinforcement’ at all times. It was only because of your constant guidance that now statistics seems so much more interesting. Thank you Lisa for editing and re-editing my work which gave the thesis such a great look. I owe my deepest gratitude to Dr. Milena Corredig, my advisory committee member, who has always been there to clarify all my doubts. Thank you Milena for guiding me to analyse all the rheology data and spending so much time in improving my thesis. I will always remember you for helping me anywhere and anytime, taking time off from your busy schedule and investing the same in me, be it just after your knee surgery or in-between conference meetings. I feel myself to be lucky to have Lisa and Milena as my advising gurus. I am indebted to Eleana Kristo, for always supporting me and making me comfortable in using rheometers and answering all my questions. Whenever I had the slightest doubt, I would just run to you and you were always there to help me, even during your maternity leave!!!!! I will never forget your caring and calm attitude and your smiling face even though I always had bag full of questions for you. I would like to thank CP Kelco, Ingredion Inc., GIC and Marsan Foods for supplying the hydrocolloids and commercial product for testing in this research. Thank you to my colleagues and friends who have helped me in every possible way from sensory setting to making me understand statistics. The huge amount of work involved in arranging everything for sensory evaluation became easy only because of my lab mates. Patti, Stefanie, Elizabeth, Thais and Nicholas, I will always remember the fun we had while working together in the kitchen and preparing so much purees. This whole process has been a smooth sailing with the blessings of my parents and in-laws. A big thanks to my husband and lovely kids for always being supportive, appreciative and being around whenever I needed them. I know that they have been eagerly waiting for this moment and are more excited about me achieving this milestone in my life. Thank you to my family friends who have always offered to help in making this whole thing a big hit. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................................ III LIST OF TABLES ...................................................................................................... VII LIST OF FIGURES ......................................................................................................IX LIST OF ABBREVIATIONS ......................................................................................XI 1. GENERAL INTRODUCTION ................................................................................ 1 2. LITERATURE REVIEW ........................................................................................ 4 2.1 DYSPHAGIA ......................................................................................................... 4 2.1.1 Physiological changes and dysphagia .............................................................. 6 2.1.2 Psychological effects of dysphagia .................................................................. 7 2.1.3 Treatment / Management of dysphagia ............................................................ 8 2.2 PUREED FOODS .................................................................................................... 9 2.2.1 Existing standards of pureed foods ................................................................ 11 2.3 TEXTURE ........................................................................................................... 15 2.3.1 Hydrocolloids as texturizing or structuring agents .............................................. 16 2.4 TECHNIQUES FOR MEASURING TEXTURAL PROPERTIES OF PUREED FOODS ......... 21 2.4.1 Structural properties using Rheological measures ......................................... 21 2.4.2 Breakdown properties using Rheology and Texture Profile Analysis ................ 27 2.4.3 Sensory properties of pureed foods ................................................................ 31 2.4.4 Correlation of Instrumental and Sensory evaluation ...................................... 34 3. TEXTURAL CHARACTERISATION OF PUREED FOODS WITH HYDROCOLLOIDS USING INSTRUMENTAL TECHNIQUES ......................... 37 3.1 INTRODUCTION........................................................................................................... 37 3.2 MATERIALS AND METHODS ....................................................................................... 40 3.2.1 Materials .............................................................................................................. 40 3.2.2 Sample Preparation .............................................................................................. 41 iv 3.2.3 Viscosity Measurement ....................................................................................... 41 3.2.4 Rheological Properties ......................................................................................... 42 3.2.5 Mechanical Properties ......................................................................................... 43 3.3 DATA ANALYSIS ........................................................................................................ 44 3.4 RESULTS AND DISCUSSION ......................................................................................... 44 3.4.1 Viscosity .............................................................................................................. 44 3.4.2 Small Deformation Tests ..................................................................................... 47 3.4.3 Texture Profile Analysis (TPA) ........................................................................... 60 3.4.4 Discussion ............................................................................................................ 62 3.5 CONCLUSIONS ............................................................................................................ 64 4. TEXTURAL CHARACTERISATION OF PUREED CARROTS WITH HYDROCOLLOIDS USING SENSORY TECHNIQUES OF NAPPING® AND DESCRIPTIVE ANALYSIS ........................................................................................ 65 4.1 INTRODUCTION........................................................................................................... 65 4.2 MATERIALS & METHOD ............................................................................................. 67 4.2.1 Samples ................................................................................................................ 67 4.2.2 Sensory Evaluation .............................................................................................. 68 4.2.3 Data Analysis ....................................................................................................... 72 4.3 RESULTS AND DISCUSSION ......................................................................................... 74 4.3.1 Effect of hydrocolloids on Appearance, Flavour and Texture of pureed carrots: 74 4.3.2 Effect of hydrocolloids on texture of pureed carrots: .......................................... 90 4.3.3 Comparison of trained panel and Napping® (texture) results ............................. 93 4.4 CORRELATIONS OF INSTRUMENTAL AND SENSORY MEASUREMENTS .......................... 94 4.5 CONCLUSION .............................................................................................................. 98 v 5. OVERALL CONCLUSIONS AND RECOMMENDATIONS ........................... 99 REFERENCES ...........................................................................................................