Production of Kefir from Bovine and Oat Milk Mixture
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PRODUCTION OF KEFIR FROM BOVINE AND OAT MILK MIXTURE A Thesis Submitted to the Graduate School of Engineering and Sciences of İzmir Institute of Technology in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE in Food Engineering by Cihan KAHRAMAN August 2011 İZMİR We approve the thesis of Cihan KAHRAMAN ____________________________ Assoc. Prof. Dr. Figen KOREL Supervisor ____________________________ Prof. Dr. Özer KINIK Committee Member ____________________________ Assoc. Prof. Dr. Figen TOKATLI Committee Member 18 August 2011 ____________________________ ____________________________ Prof. Dr. Şebnem HARSA Prof. Dr. Sedat AKKURT Head of the Department of Dean of the Graduate School of Food Engineering Engineering and Sciences ACKNOWLEDGMENTS I would like to express my sincere gratitude to my thesis advisor Assoc. Prof. Dr. Figen KOREL for her endless supervision, guidance, encouragement, support optimism and giving me the chance to work on this study. I express my special thanks to Prof. Dr. Özer KINIK for his unending support, advices and friendship also for readily agreed to be my thesis committee member. I am grateful to Assoc. Prof. Dr. Figen TOKATLI for agreed to be my thesis committee member and also her interest, suggestions and spending her valuable time. I would like to thank my friends; Hande ORġAHĠN, Gökçen KÖMEN, Pınar KADĠROĞLU, Mehmet ReĢat ATILGAN and Levent Yurdaer AYDEMĠR for their help and support throughout the study. I would like to thank all the specialists of Izmir Institute of Technology, staff of Food Engineering Department, Specialists Burcu OKUKLU and Ġlknur ġEN. I would also like to thank staff of Biotechnology and Bioengineering Research and Application Center; Yekta Günay OĞUZ, Evrim BALCI and Özgür Yılmazer ÇAKMAK and staff of Environmental Research Centre Specialist Handan GAYGISIZ for helping me during this study. I am very thankful to Ege University Faculty of Agriculture staff; Dr. Nayil DĠNKÇĠ and Assoc. Prof. Dr. Harun KESENKAġ, for their help and advisory. I would like to give my precious thanks to panelists for their help, spending their time for this study. Lastly and most importantly, I would like to express my special thanks to my parents Hatice Nergiz and Kemal KAHRAMAN, and my sister Duygu KAHRAMAN to whom I dedicate this thesis for their never ending love, support and encouragements in my entire and future life. ABSTRACT PRODUCTION OF KEFIR FROM BOVINE AND OAT MILK MIXTURE During recent years non-dairy milk types such as cereal and grain milks have been an increased demand from consumers due to their functional properties. The cereal and grain milks do not contain cholesterol or lactose; therefore, these milk types are preferred by consumers who are vegetarians, have special diets or are lactose intolerant. In this study, different concentrations of oat milk (0, 15, 30, 45, and 60%), blueberry aroma(9, 12, 15, 18, and 21%), and kefir culture(1, 2, 3, 4, and 5%) were used for the optimization of the kefir production and samples were stored at 4ºC for 21 days. The response surface methodology was used for the optimization process. Sensory characteristics, the pH changes and microbial characteristics of the kefir samples were determined during storage and the concentrations of the oat milk, blueberry aroma and kefir culture for the best three kefir products were chosen based on the optimization results According to optimization results, three kefir samples which contained the highest level of oat milk with optimum organoleptic characteristics, optimum pH and optimum microbial counts were selected and produced. Based on the organoleptic results, kefir samples composed of 20% oat milk, 4% kefir culture and 10% aroma concentration, were produced. According to the pH results kefir samples within 15% oat milk, 4% kefir culture and 9% aroma concentration were produced. Based on the microbiological results kefir samples within 30% oat milk, 3% kefir culture and 15% aroma concentration were produced. The pH, titratable acidity, dry matter, fat, protein, phenol content, beta-glucan content, whey off, viscosity, volatile and organic acid profile of samples, color change, microbiological characteristics and sensory characteristics of these samples were investigated during 21 days of storage. iv ÖZET ĠNEK VE YULAF SÜTÜ KARIġIMINDAN KEFĠR ÜRETĠMĠ Son yıllarda hububat ve tahıl gibi hayvansal kaynaklı olmayan sütler, yüksek seviyedeki fonksiyonel özelliklerinden dolayı tüketiciler tarafından tercih edilmekte ve tüketimi artmaktadır. Ayrıca bu sütler kolesterol ve laktoz içermediklerinden dolayı diyet uygulayan kiĢiler, vejetaryenler, laktoz intoleransı olan kiĢiler tarafından süt tüketiminde tercih edilmektedir. Bu çalıĢmada, farklı miktarda yabanmersini aroması (9-12-15-18 ve %21), kefir kültürü (1-2-3-4 ve %5) ve yulaf sütü (0-15-30-45 ve %50) içeren kefir ürünlerinin optimizasyonu yapılmıĢ ve 4 C de 21 gün boyunca depolanmıstır. Optimizasyonda yüzey tepki yöntemi kullanılıp, örneklerin mikrobiyolojik, pH ve duyusal karakteristikleri incelenmiĢtir. Optimizasyon sonucunda ideal seviyede mikrobiyolojik, pH ve duyusal özellik gösteren kefir örneklerinden en fazla yulaf sütü içeriğine sahip olan üç örnek tekrar üretilip, bu örneklerde fiziksel, kimyasal mikrobiyolojik, duyusal ve aroma özellikleri depolama süresi boyunca analiz edilmiĢtir. Optimizasyon sonuçlarına göre en ideal duyusal özelliklere sahip olan %20 yulaf sütü, %4 kefir kültürü ve %10 aroma konsantrasyonundaki ürün üretilmiĢtir. pH sonuçlarına göre %15 yulaf sütü, %4 kültür ve %9 aroma konsantrasyonuna sahip olan ürün üretilmiĢtir. Mikrobiyolojik analizlere göre %30 yulaf sütü, %3 kültür ve %15 aroma içeren ürün ideal ürün olarak üretilmiĢtir. Optimizasyon sonrası üretilen örneklerin pH, titreedilebilir asitlik, kuru madde, yağ, protein, fenol, beta-glukan, su salma, viskozite, uçucu ve organik asit bileĢenleri, renk değiĢimi, mikrobiyal özellikleri ve duyusal karakteristikleri depolanma süresi boyunca incelenmiĢtir. v TABLE OF CONTENTS LIST OF FIGURES ......................................................................................................... ix LIST OF TABLES .......................................................................................................... xii CHAPTER 1. INTRODUCTION ..................................................................................... 1 CHAPTER 2. LITERATURE REVIEW .......................................................................... 3 2.1. Milk ........................................................................................................ 3 2.2. Oat Milk ................................................................................................. 4 2.3. Fermented Dairy Products ..................................................................... 6 2.4. Kefir ....................................................................................................... 8 2.4.1. Historical Background ..................................................................... 8 2.4.2. Kefir Grains ...................................................................................... 9 2.4.2.1. Chemical composition and Appearance ........................................ 9 2.4.3. Kefir Production ............................................................................. 13 2.4.4. Chemical and Physical Characteristics of Kefir ............................. 16 2.4.5. Sensory Profile of Kefir ................................................................. 17 2.4.6. Beneficial Effects of Kefir ............................................................. 18 2.5. Blueberry .............................................................................................. 19 CHAPTER 3. MATERIALS AND METHODS ............................................................ 21 3.1. Materials .............................................................................................. 21 3.1.1. Chemicals and Media ..................................................................... 21 3.1.2. Reagents and Solutions .................................................................. 21 3.1.3. Samples .......................................................................................... 21 3.2. Methods ................................................................................................ 23 3.2.1. Kefir Production ............................................................................. 23 3.2.1.1. Preparation of Kefir Culture ..................................................... 23 3.2.1.2. Preparation of Oat Milk ............................................................ 23 3.2.1.3. Preparation of Aroma ............................................................... 23 3.2.1.4. Kefir Production and Sampling ................................................ 24 vi 3.2.3. Chemical and Physical Analysis .................................................... 26 3.2.3.1. pH and Titratable Acidity ......................................................... 26 3.2.3.2. Total Dry Matter Content ......................................................... 26 3.2.3.3. Total Protein Content ............................................................... 27 3.2.3.4. Total Fat Content ...................................................................... 27 3.2.3.5. Determination of Whey off ...................................................... 27 3.2.3.6. Rheological Analysis ................................................................ 27 3.2.3.7. Color Analysis