ENZYMATIC SYNTHESIS AND APPLICATION OF STRUCTURED LIPIDS FOR INFANT FORMULA by LONG ZOU (Under the Direction of Casimir C. Akoh) ABSTRACT A human milk fat (HMF) analogue synthesis from tripalmitin, stearidonic acid (SDA) soybean oil, and docosahexaenoic acid (DHA) was scaled up by interesterification catalyzed by Novozym 435 and acidolysis by Lipozyme TL IM, and then purified by short-path distillation (SPD). This structured lipid (SL) contained 5.4 mol% DHA and 8.0 mol% SDA, with 57.0 mol% palmitic acid esterified at sn-2 position. Although tocopheryl and tocotrienyl fatty acid esters were formed during interesterification and acidolysis, >50% of vitamin E isomers were lost into distillates (wastes) during SPD, which contributed mostly to the rapid oxidative deterioration of SLs in the recent and past studies. Response surface methodology was applied to investigate the effects of lecithin, monoacylglycerol, locust bean gum (LBG), and carrageenan on the physical and oxidative properties of SL-based infant formula (IF) emulsion. Particle size, optical stability, viscosity, relative content of DHA and SDA, and total oxidation value were assessed during 28-day storage. In addition, the effect of permitted antioxidants (added at 0.005 and 0.02% of oil, respectively), including α-tocopherol, β-carotene, ascorbyl palmitate, ascorbic acid, citric acid, and their combinations, on the lipid oxidation was evaluated under an accelerated storage. The peroxide value, anisidine value, and hexanal concentration of emulsion samples were measured. It was found that the optimal conditions to achieve the highest physical and oxidative stability of SL-based IF emulsion were 0.2 g/100 mL lecithin, 0.4 g/100 mL monoacylglycerol, 0.045 g/100 mL LBG, 0.015 g/100 mL carrageenan, and 0.005% ascorbyl palmitate. On the basis of measurement of peroxide and anisidine values over a 28-day period, annatto TRF was found to be a more effective antioxidant than palm TRF and α-tocopherol in inhibiting lipid oxidation in menhaden fish oil and SL-based IF emulsion at 0.02% and 0.05%. Addition of α-tocopherol (0-75%) did not interfere with the antioxidant activity of tocopherol-free annatto TRF in the foods tested. Overall, this study has important implications for the successful incorporation of SL into IF products for better infant nutrition and health. INDEX WORDS: Structured lipid, Lipase, Infant formula, Tocopherol, Tocotrienol, Antioxidant, Lipid oxidation, Oil-in-water emulsion, Annatto, Stearidonic acid soybean oil, Human milk fat ENZYMATIC SYNTHESIS AND APPLICATION OF STRUCTURED LIPIDS FOR INFANT FORMULA by LONG ZOU B.S., Jimei University, China, 2005 M.S., Ocean University of China, China, 2008 A Dissertation Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY ATHENS, GEORGIA 2014 © 2014 Long Zou All Rights Reserved ENZYMATIC SYNTHESIS AND APPLICATION OF STRUCTURED LIPIDS FOR INFANT FORMULA by LONG ZOU Major Professor: Casimir C. Akoh Committee: Rakesh K. Singh William L. Kerr Ronald B. Pegg Electronic Version Approved: Julie Coffield Interim Dean of the Graduate School The University of Georgia August 2014 DEDICATION To my dear wife, my parents, and my sister iv ACKNOWLEDGEMENTS First of all I would like to especially thank my advisor, Dr. Casimir C. Akoh, for his valuable advice and guidance on my academics, career, and personal matters throughout the Ph.D. study. It has been my greatest pleasure to be his student under his enthusiasm and expertise. I also express my deep appreciation to Drs. Yao-Wen Huang, William L. Kerr, Rakesh K. Singh, Alex Kojo Anderson, and Ronald B. Pegg for serving on my advisory committee, and to Dr. Mark Harrison, Ms. Karen Simmons, and Ms. Lisa Cash for their support and advice during my study. Also, I deeply appreciate my former M.S. advisor, Dr. Hong Lin for his constant encouragement, support, and advice to lead my step forward. I am grateful for the funding support from USDA National Institute of Food and Agriculture for their grant to Dr. Akoh and also the two-year assistantship from the Graduate School, The University of Georgia. I would like to thank all my lab members for their kind support towards the completion of my research. Special thanks to Ms. Victoria Wentzel, Garima Pande, Supakana Nagachinta, Leslie Kleiner, and Ebenezer Ifeduba. I owe my sincere thanks to all the faculty and staff of the Department of Food Science & Technology for helping me out through the study. Lastly, I would like to thank my parents and family for their endless love and encouragement. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ............................................................................................. v LIST OF TABLES ........................................................................................................vii LIST OF FIGURES ........................................................................................................ ix CHAPTER 1 INTRODUCTION.......................................................................................... 1 2 LITERATURE REVIEW ............................................................................... 7 3 IDENTIFICATION OF TOCOPHEROLS, TOCOTRIENOLS, AND THEIR FATTY ACID ESTERS IN RESIDUES AND DISTILLATES OF STRUCTURED LIPIDS PURIFIED BY SHORT-PATH DISTILLATION .. 67 4 CHARACTERIZATION AND OPTIMIZATION OF PHYSICAL AND OXIDATIVE STABILITY OF STRUCTURED LIPID-BASED INFANT FORMULA EMULSION: EFFECTS OF EMULSIFIERS AND BIOPOLYMER THICKENERS ................................................................... 98 5 OXIDATIVE STABILITY OF STRUCTURED LIPID-BASED INFANT FORMULA EMULSION: EFFECT OF ANTIOXIDANTS ....................... 129 6 ANTIOXIDANT ACTIVITIES OF ANNATTO AND PALM TOCOTRIENOL-RICH FRACTIONS IN FISH OIL AND STRUCTURED LIPID-BASED INFANT FORMULA EMULSION ................................... 161 7 CONCLUSIONS ........................................................................................ 185 vi LIST OF TABLES Page Table 2.1: Dietary reference intakes: recommended dietary allowances and adequate intakes for infants from birth to 1 year................................................................ 58 Table 2.2: Composition of mature human milk .............................................................. 59 Table 2.3: Major fatty acid composition of mature human milk ..................................... 60 Table 2.4: Representative studies on lipase-catalyzed synthesis of human milk fat analogues ........................................................................................................... 61 Table 2.5: Compositional regulations of infant formula ................................................. 63 Table 2.6: Additives permitted in infant formula products ............................................. 65 Table 3.1: Total fatty acid profiles (mole percent) and molecular weight of substrates and scaled-up SLs at optimal conditions ................................................................... 91 Table 3.2: Tocopherol and tocotrienol concentration and free fatty acid percentage of substrates and scaled-up SLs .............................................................................. 92 Table 3.3: Tocopheryl and tocotrienyl esters identified by GC-MS in distillates after short-path distillation ......................................................................................... 93 Table 4.1: Composition of the micronutrient premix fortified in ready-to-feed structured lipid-based infant formula ................................................................................ 122 Table 4.2: Composition of structured lipid-based infant formula emulsion ................... 123 Table 4.3: D-optimal design: independent (Xi) and response variables (Yi). ................. 124 vii Table 4.4: ANOVA for the effects of independent variables on the dependent variables, and corresponding coefficients of the regression models .................................. 125 Table 4.5: Correlation coefficients (R) among methods for assessing the physical and oxidative stability of infant formula emulsion .................................................. 126 Table 4.6: Expected and observed values for the model verification using a Chi-squared test ............................................................................................................ 127 Table 5.1: Volatile oxidation compounds of structured-lipid based infant formula identified by dynamic headspace GC-MS ......................................................... 154 Table 5.2: Fatty acid profiles (mole percent) of extracted fat from infant formulas ....... 155 Table 6.1: Summaries of research on the antioxidant activity of tocotrienols in model systems, fats, and oils ....................................................................................... 179 viii LIST OF FIGURES Page Figure 3.1: MALDI-TOF mass spectra of α-tocopherol, α-tocopheryl oleate and α- tocopheryl linoleate from vitamin E linoleate mixture in positive ion mode. ....... 94 Figure 3.2: Total ion chromatograms of tocopheryl and tocotrienyl esters identified in the (A) WNSL and (B) WLDHA in the SIM mode. ................................................. 95 Figure 3.3: Representative structures and EI full scan mass spectra of tocopheryl and tocotrienyl esters: (A) α-tocopheryl oleate from vitamin E linoleate mixture, (B) β(or γ)-tocopheryl palmitate from WNSL, and (C) α-tocotrienyl palmitate from WLDHA. ..........................................................................................................