Rice Bran Wax Oleogel Water Holding Capacity and Its Effects on the Physical Properties of the Network THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Erica Danielle Cramer Graduate Program in Food Science and Technology The Ohio State University 2016 Master's Examination Committee: Professor Farnaz Maleky, Advisor Professor Dennis Heldman, Advisor Professor Yael Vodovotz Copyrighted by Erica Cramer 2016 Abstract Over the past few years there has been much concern about the health effects of consuming saturated and trans fats. Therefore, the FDA revoked the GRAS status of partially hydrogenated oils in order to reduce trans fats in foods. The concern in the food industry is that it is not easy to replicate the structural attributes of foods provided by saturated and trans fats. Recently, studies introduced food-safe organogelators such as rice bran wax (RBW) to structure oil to mimic the behavior of solid fat. RBW oleogels have been tested as a saturated fat replacement in foods like ice cream and cheese. However, the current research is focused on structuring pure lipid systems, and not much is known about structuring a mixture of oil and water. It would also be of interest to replace liquid oil with water and reduce some foods calories. Therefore, the objective of this project was to determine the water holding capacity of RBW oleogels, and to see how water and an emulsifier would affect the properties of the gel. Oleogel samples were made with RBW (10% w/w), glycerol monooleate (0 or 1.67%), and water (0, 5, 10 or 20 % w/w). Soybean oil made up the rest of the mixtures. Samples were prepared and stored at 5°C. Their water content, rheological properties and thermal behavior were tested over 27 days. They maintained their moisture content over the 27-day storage period. The storage and loss modulus, maximum force, and melting point of the gels remained consistent over the 27-day storage period. However, variations were seen between gels with different water contents. The addition of the emulsifier reduced these ii variabilities. Microscope images showed that the wax had a needlelike structure and that the gels with higher water content had a higher frequency of larger water droplets. RBW oleogels can structure water and oil while maintaining the functional properties of a solid fat. These could be used to make foods with the same structural properties but reduced fat and calorie content. iii Acknowledgments I would like to thank the Center for Advanced Processing and Packaging Studies and the Ohio Agricultural Research and Development Center for their financial support on this project. I would like to thank Tanya Whitmar for her help with NMR, Steve Moeller for his help with TPA, and Norman St-Pierre for his help with statistics. I would like to thank Dr. Yael Vodovotz, Dr. Dennis Heldman, and Dr. Farnaz Maleky for their recommendations and their encouragement through this research project. Finally, I would like to thank Susan Cramer, Bryan Willett, and Nora Driscoll for all the amazing back-up support you provided me through my master’s program. iv Vita June 2010 .......................................................A. C. Reynolds High School December 2013 ..............................................B.S. Food Science and Nutrition, The Ohio State University August 2014 to present ..................................Graduate Research Associate, Department of Food Science and Technology, The Ohio State University Fields of Study Major Field: Food Science and Technology v Table of Contents Abstract ............................................................................................................................... ii Acknowledgments.............................................................................................................. iv Vita ...................................................................................................................................... v Fields of Study .................................................................................................................... v Table of Contents ............................................................................................................... vi List of Tables ................................................................................................................... viii List of Figures .................................................................................................................... ix Chapter 1: Introduction ...................................................................................................... 1 Chapter 2: Literature Review .............................................................................................. 4 2. 1: Health impacts of fatty acids ................................................................................... 4 2.2: Methods for replacing trans and saturated fats in foods .......................................... 7 2.3: Oleogels.................................................................................................................. 11 2.4: Recent advances of oleogels in foods .................................................................... 18 2.5: Emulsions ............................................................................................................... 23 2.6: Measuring the properties of an emulsion ............................................................... 27 vi Chapter 3: Materials and Methods ................................................................................... 34 3.1: Materials ................................................................................................................. 34 3.2: Oleogel production ................................................................................................. 34 3.3: Moisture content..................................................................................................... 36 3.4: Nuclear magnetic resonance .................................................................................. 36 3.5: Melting properties .................................................................................................. 37 3.6: Solid fat content ..................................................................................................... 37 3.7: Rheology ................................................................................................................ 38 3.8: Texture profile analysis .......................................................................................... 38 3.9: Microstructure ........................................................................................................ 38 3.10: Statistical analysis ................................................................................................ 39 Chapter 4: Results and Discussion ................................................................................... 41 4.1: Preliminary Study: Properties of oleogels made with 2% and 5% wax ................. 41 4.2: Moisture content of gels made with 10% RBW..................................................... 45 4.3: Microstructure properties ....................................................................................... 51 4.4: Physical properties ................................................................................................. 66 Chapter 5: Conclusions .................................................................................................... 85 References ......................................................................................................................... 86 Appendix A: Data for low wax oleogel measurements .................................................... 94 vii List of Tables Table 1. Moisture content measured for samples after 1 day in storage. Samples A-D do not contain emulsifier, samples E-G do. ........................................................................... 48 Table 2. Solid fat content of gels without and with emulsifier, measured at 5°C. ........... 52 Table 3. Enthalpy of gels made with increasing water content. ....................................... 57 Table 4. G” in KPa of samples, comparing effects of water content and storage time, without and with emulsifier. Letters compare the effect of water content, while numerals compare storage time. ....................................................................................................... 80 Table 5. Tan delta of samples, comparing effects of water content and storage time, without and with emulsifier. Letters compare the effect of water content, while numerals compare storage time. ....................................................................................................... 80 Table 6. G* in KPa of samples, comparing effects of water content and storage time, without and with emulsifier. Letters compare the effect of water content, while numerals compare storage time. ....................................................................................................... 81 viii List of Figures Figure 1. Shape of a saturated and an unsaturated fatty acid. The unsaturated acid is bent, which contributes to its lower melting point and differing textural properties. .................. 6 Figure 2. A cryo-TEM micrograph of tubules formed by β-sitosterol and γ-oryzanol in a corn oil emulsion. Source: (Duffy and others). ...............................................................