PROBIOTIC VIABILITY AND STORAGE STABILITY OF YOGHURT ENRICHED WITH BAOBAB PULP (Adansonia digitata) ANGELA ALUKO MASTER OF SCIENCE (Food Science and Nutrition) JOMO KENYATTA UNIVERSITY OF AGRICULTURE AND TECHNOLOGY 2017 Probiotic Viability and Storage Stability of Yoghurt Enriched with Baobab Pulp (Adansonia digitata) Angela Aluko A Thesis submitted in partial fulfilment for the Degree of Master of Science in Food Science and Nutrition in the Jomo Kenyatta University of Agriculture and Technology 2017 DECLARATION This is my original work and has not been presented for a degree in any other University. Signature………………………………….. Date……………………………….. Angela Aluko This thesis has been submitted for examination with our approval as University supervisors. Signature……………………………….. Date……………………………………... Prof. Willis Owino, PhD JKUAT, Kenya Signature……………………………….. Date……………………………………... Dr. John Kinyuru, PhD JKUAT, Kenya Signature…………………… Date: …… ………………………………. Dr. Lucy Mlipano Chove, PhD SUA, Tanzania ii DEDICATION This work is dedicated to my parents, my late beloved father, Mr. Ezra Andy Aluko, and my mother, Esther Mwaikambo who made the foundation of my education. iii ACKNOWLEDGEMENT I humbly thank God, my Heavenly Father who made me for his own glory, for granting me life, strength and the entire blessing. My sincere appreciation would be incomplete without mentioning my sponsor, the Innovative Agricultural Research Initiative (iAGRI) under feed the Future program and Regional Universities Forum for Capacity Building in Agriculture (RUFORUM) for scholarship. I am deeply grateful to my supervisors: Prof. Willis Owino (Department of Food science and Technology, Jomo Kenyatta University of Agriculture and Technology, JKUAT) Dr. John Kinyuru (Department of Food science and Technology, Jomo Kenyatta University of Agriculture and Technology, JKUAT) and Dr. Lucy Mlipano Chove (Department of Food Technology, Nutrition and Consumer Sciences, Sokoine University of Agriculture) for their tireless, consistent guidance, scientific support and encouragement throughout my study, particularly during thesis development and writing of this work. Deserving no less gratitude are the technicians of the Department Food Science and Technology, Jomo Kenyatta University of Agriculture and Technology; P.N. Karanja, D. Abuja, J. Oruka, D. Volta, J. Wambungu, C. Muigai for their technical help during the laboratory analyses, without forgetting Mr. M. Okoth, Dr. P. Kahenya, M. Mwenda, J. Gachambi and M. Wairimu for their assistance in Dairy workshop and my friends Grace 8Ayite Banja and Mercy Mmari. Am thankful to my parents, siblings (Imelda and Nancy) and my aunt Aida with bottomless gratitude for their prayers, love, support and their believe in me. Thanks for being patient. Many thanks to my friends for their encouraging words and endless prayers during my research work. My appreciation also goes to my employer, Mbeya University of Science and Technology, for the permission to study. I also highly acknowledge the Regional Universities Forum (RUFORUM) for all logistical support on scholarship administrative issues throughout the program. iv Finally, heartfelt thanks to all who participated in the sensory evaluation experiments and to the members of Food Science and Technology Department at JKUAT in creating the best, stimulating and scholarly working environment for data collection, analysis, draft and final writing of this work. v TABLE OF CONTENTS DECLARATION ............................................................................................................................ ii DEDICATION ................................................................................................................................ iii ACKNOWLEDGEMENT ......................................................................................................... iv TABLE OF CONTENTS ........................................................................................................... vi LIST OF TABLES ....................................................................................................................... xii LIST OF FIGURES.................................................................................................................... xiii ACRONYMS AND ABBREVIATIONS ............................................................................ xiv ABSTRACT .................................................................................................................................... xv CHAPTER ONE ............................................................................................................................. 1 INTRODUCTION ......................................................................................................................... 1 1.1. Background of the Study ................................................................................... 1 1.2. Problem Statement and Justification.................................................................. 4 1.2.1. Problem Statement ...................................................................................... 4 1.2.2. Justification ................................................................................................. 5 1.3. Objectives .......................................................................................................... 6 1.3.1. Main Objective ............................................................................................ 6 1.3.2. Specific Objectives ...................................................................................... 6 1.3.3. Hypotheses .................................................................................................. 7 1.3.4. Expected outcomes ...................................................................................... 7 CHAPTER TWO ........................................................................................................................... 8 LITERATURE REVIEW ........................................................................................................... 8 2.1. Introduction ................................................................................................... 8 vi 2.2. Botanical description, habitat and distribution of baobab in Africa .............. 8 2.3. Traditional and modern uses of baobab....................................................... 10 2.4. Phytochemistry of baobab ........................................................................... 12 2.5. Biological activity ............................................................................................ 13 2.5.1. Antibacterial activity ................................................................................. 13 2.5.2. Anti-inflammatory activity, Phenolic, flavonoid content and anti-oxidant activity ................................................................................................................. 14 2.5.3. Anti-insecticidal activity and repellency ................................................... 14 2.5.4. Antiviral activity ........................................................................................ 15 2.6. Nutrient composition of Baobab fruit pulp ................................................. 15 2.7. Probiotic Concepts ...................................................................................... 18 2.7.1. Definition ................................................................................................... 18 2.7.2. Probiotics and human health ..................................................................... 18 2.7.3. Application of probiotics in food .............................................................. 19 2.8. Yoghurt as a probiotic product .................................................................... 19 2.9. Functional food: defining the concept ......................................................... 20 2.9.1. Functional Food: European Consensus ..................................................... 21 2.9.2. Functional Foods and Health ..................................................................... 23 2.10. Yogurt as a Functional food ........................................................................ 24 CHAPTER THREE .................................................................................................................... 26 METHODOLOGY ...................................................................................................................... 26 3.1. Materials and Methods ................................................................................ 26 3.2. Materials .......................................................................................................... 27 3.2.1. Baobab fruits ................................................................................................. 27 vii 3.2.2. Description of the area where baobab samples collected .......................... 27 3.2.3. Milk ........................................................................................................... 29 Fresh cow milk for preparation of yoghurt was obtained from local suppliers in Juja, Kenya. ......................................................................................................... 29 3.2.4. Starter Cultures and Probiotics .................................................................. 29 3.3. Sample preparation .......................................................................................... 29 3.3.1. Preparation of Baobab pulp ....................................................................... 29 3.4. Analysis for determination of baobab quality and probiotic yoghurt .............. 34 3.4.1. Functional properties of Baobab pulp powder .......................................... 34 3.5. Proximate composition .................................................................................... 36 3.5.1. Determination of moisture content ............................................................ 36 3.5.2. Determination of ash ................................................................................. 37 3.5.3. Determination of Protein ........................................................................... 38 3.5.4. Fat Analysis by Soxhlet‟s method ............................................................. 39 3.5.5. Garber fat method for fat analysis on yoghurt........................................... 40 3.5.6. Fiber Determination .................................................................................. 40 3.5.7. Carbohydrate Content Determination .................................................. 41 3.6. Post Acidification and Titratable Acidity ........................................................ 41 3.7. Microbiological Analyses ............................................................................ 42 3.7.1. de Man, Rogosa and Sharpe Agar (MRS agar) ....................................... 42 3.7.2. Coliforms, Yeast and Molds Count ......................................................... 42 3.7.3. Enumeration of yeast/moulds, coliform and probiotic .............................. 43 3.8. Survival in Gastral Intestinal Tract (GIT) Test for Selected Probiotic bacteria .................................................................................................................... 44 viii 3.8.1. Preparations of artificial fluids ................................................................ 44 3.9. Nutrition composition determination .......................................................... 45 3.9.1. Sugars....................................................................................................... 45 3.9.2. Determination of β-carotene .................................................................... 46 3.9.3. Determination of vitamin C ..................................................................... 46 3.9.4. Determination of Calcium, Magnesium and Zinc ................................... 47 3.9.5. Fatty Acid Profile..................................................................................... 47 3.9.6. Total Soluble Solids ................................................................................. 48 3.9.7. Viscosity .................................................................................................. 48 3.10. Sensory evaluation ...................................................................................... 48 3.11. Data Analysis ................................................................................................. 49 CHAPTER FOUR ........................................................................................................................ 50 RESULTS AND DISCUSSION .............................................................................................. 50 4.1. Baobab pulp yield ............................................................................................ 50 4.2. Chemical Composition .................................................................................... 51 4.2.1.Moisture content ......................................................................................... 51 4.2.2. Fat content................................................................................................ 51 4.2.3. Ash content .............................................................................................. 52 4.2.4. Fiber content ............................................................................................ 52 4.2.5. Protein content ......................................................................................... 53 4.2.6. Total carbohydrates.................................................................................. 53 4.3. Ascorbic acid (vitamin C) content ............................................................... 53 4.4. Beta carotene ............................................................................................... 54 4.5. Minerals ....................................................................................................... 55 ix