Strategies for the Removal of Raffinose Family Oligosaccharides from Navy Bean Flour a Thesis Presented in Partial Fulfilment of the Requirements for the Degree Of
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Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author. Strategies for the Removal of Raffinose Family Oligosaccharides from Navy Bean Flour A thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Bioprocess Engineering at Massey University, Palmerston North, New Zealand Jarod Christopher Brain 2013 Abstract Navy beans are legumes with highly nutritious qualities. However they are underutilised in the processed food industry due to the undesirable bloating, abdominal discomfort and excessive flatulence associated with ingestion of the raffinose family oligosaccharides (RFOs) present in them. If a suitable technology were available to sufficiently reduce the concentration of RFOs then navy bean flour could find application in many food production processes. The traditional method for decreasing RFO content in navy beans and other similar legumes has been through soaking in large quantities of water, thereby leaching the RFOs from the bean. However this is a slow process and results in the depletion of all water soluble solids (up to 25% of the dry weight of the bean). The leaching process can be sped up dramatically through the decrease in particle size achieved by milling the beans into navy bean flour prior to the addition of water. However this process makes dewatering of the flour difficult. Rates of moisture uptake and RFO leaching were characterised for navy bean flour and de- hulled navy bean cotyledons demonstrating that RFO leaching is slower but of a similar magnitude as moisture uptake and that these rates are dramatically increased with decrease in particle size. The addition of α-galactosidase to the leaching water enables the rapid removal of RFOs from navy bean flour without the need to separate the flour from the leaching water because the RFOs leached out of the flour are hydrolysed into simple sugars. Galactose is a product of the hydrolysis of RFOs and its presence at high concentrations can result in the inhibition of α-galactosidase. However at the concentrations likely to be experienced during RFO reduction in bean flour the inhibition effect is minimal. Rates of hydrolysis were studied for raffinose and stachyose hydrolysis by α-galactosidase in the concentration range expected during processing of navy bean flour. i Enzymatic processing using very small amounts of moisture addition was investigated demonstrating partial RFO removal at moisture contents as low as 28% (wet basis). Reduction in RFO content to a level at which the flatus response is negligible can be achieved at moisture contents as low as 38% (wet basis) which significantly minimises the drying required to produce a dry navy bean ingredient or could allow direct application in an extrusion process. The application of α-galactosidase at low moisture content is a novel process for the depletion of RFOs in navy bean flour. The mechanism for this process is explained by preliminary modelling of moisture and RFO diffusion which demonstrates how partial RFO removal is possible. From these mechanisms a series of commercially practical methods for RFO depletion of navy bean flour were explored for several targeted product applications. This process also has potential applications for low moisture enzyme processing in a range of food and other biological systems. The simple processes developed in this work open up the commercial use of navy bean flour for the food industry to develop products that take advantage of its functional and nutritional properties without the negative nutritional problems usually associated with this material. ii Acknowledgements A PhD is very much like a marathon, it requires a large amount of effort, perseverance and in the end a dogged determination to see it through. I could not have made it through without the help of a number of people. Firstly, thanks go to my primary supervisor Professor John Bronlund. My academic path has been much influenced by John; he supervised my 4 th year research project in my undergraduate days; he took me on as a research assistant while I was writing up my master’s thesis; and he suggested this project to me when I decided to do a PhD. John, your support, advice and guidance throughout this project has been crucial to its success and your patience and understanding during the times of slow progress has been much appreciated. In particular you’re willingness to sacrifice evenings and weekends to this project during the weeks immediately preceding submission of this thesis was beyond the call of duty, and for this you have my profound gratitude. Thanks also go to the other university supervisors I have had over the course of this project, Inge Merts, Charles Brennan and Brian Wilkinson have all made their knowledge and advice available to me. The time and effort that they contributed to this project is much appreciated. To my industry supervisors Sam Bounds and Willem Van De Ven, my thanks go to you for providing the project in the first place as well as the provision of samples, equipment and much sage advice. The industry perspective I gained in my visits to Heinz Watties has stood me in good stead throughout the project and in my burgeoning career in food engineering research. My appreciation also goes to Heinz Watties Ltd who together with the Foundation for Research Science and Technology provided funding for the project. Without financial support of this kind it is hard to see how any projects of this nature could be undertaken and so I applaud your efforts in this area. Thanks also go to my managers at Fonterra, David Pearce and Vijay Ganugapati for their patience and understanding during the final stages of writing this thesis, this made what was a very stressful period that little bit easier and I am grateful for that. The commitments involved in the undertaking of this task cannot be made in isolation from the rest of one’s life, and in order to dedicate the time and energy required to complete this thesis I have been fortunate to receive vital support and encouragement from many people. iii Thanks to my family and friends for your support, encouragement and understanding. To my parents and in-laws, thank you for the frequent but gentle prodding that helped keep me focussed on this task. Finally and most importantly to my wife Derryn, your love, patience and unconditional support as well as your willingness to let me sacrifice our time together to get this project done has been nothing short of amazing. Thank you so much, I love you and I literally could not have done this without you. iv Table of Contents Strategies for the Removal of Raffinose Family Oligosaccharides from Navy Bean Flour ................. i Abstract .................................................................................................................................................... i Acknowledgements ................................................................................................................................ iii Table of Contents ................................................................................................................................... iii List of Figures ......................................................................................................................................... vi List of Tables .......................................................................................................................................... ix Nomenclature ......................................................................................................................................... x Chapter 1 ................................................................................................................................................. 1 Introduction ............................................................................................................................................ 1 Chapter 2 ................................................................................................................................................. 5 Literature Review .................................................................................................................................... 5 2.1 The Navy Bean ( Phaseolus vulgaris ) ........................................................................................ 5 2.2 Microstructure of Navy Bean Seeds ........................................................................................ 7 2.3 Nutritional Benefits of Legume Seeds ..................................................................................... 8 2.4 Anti Nutritional Factors in Common Beans ........................................................................... 13 2.5 Raffinose Family Oligosaccharides (RFOs) and Their Role in Causing Flatulence ................. 16 2.6 Methods for RFO Reduction and/or removal from Legumes ................................................ 19 2.6.1 Soaking and Boiling ................................................................................................................ 19 2.6.2 Hydrolysis using α-galactosidase ........................................................................................... 21 2.6.3 Autolysis using Endogenous α-galactosidase ........................................................................ 23