The Pennsylvania State University The Graduate School Department of Food Science RETENTION OF FLAVOR COMPOUNDS BY DISPERSED HIGH‐AMYLOSE MAIZE STARCH (HAMS) IN AN AQEUOUS MODEL SYSTEM A Thesis in Food Science by Lihe Yeo © 2009 Lihe Yeo Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science December 2009 The thesis of Lihe Yeo was reviewed and approved* by the following: Donald B. Thompson Professor of Food Science Thesis Co-Advisor Devin G. Peterson Associate Professor of Food Science Thesis Co-Advisor Joshua D. Lambert Assistant Professor of Food Science John D. Floros Professor of Food Science Head of the Department of Food Science *Signatures are on file in the Graduate School. ii Abstract Flavor is one of the most important attributes considered when determining the acceptability and popularity of food products. The main objective of this study was to examine how hydrophobicity and solubility of flavor compounds relate to retention of these flavor compounds by dispersed native HAMS in an aqueous model system, for both single‐flavor and binary‐flavor systems. The effects of time and native lipids on flavor retention by dispersed HAMS and on precipitated starch yield were also examined. Ten cyclic compounds with similar molecular weights, but varying in water solubility and hydrophobicity, were studied. HAMS (Hylon VII) (0.7% w/w, db) was dispersed at 160oC for 10 minutes in a high pressure vessel. After cooling to 80oC, each flavor compound was added at a concentration 20% below its pre‐ determined solubility. The starch‐flavor mixtures were cooled and held for one day, one week, or one month at room temperature. Flavor compounds in the headspace were subsequently analyzed by static headspace GC. Flavor retention (%) by aqueous starch was calculated relative to water alone. Flavor retention for menthol (58%), menthone (57%) and thymol (29%) was significantly higher than for the other seven compounds (<5%). A plausible explanation for this behavior is that a combination of sufficient hydrophobicity and sufficient solubility, leading to sufficient concentration, is necessary to generate high flavor retention. In binary‐flavor systems, when limonene was added with menthone or thymol, an approximately 40‐70% increase in limonene retention was observed. The enhanced retention of limonene in the presence of either menthone or thymol might simply be due to the presence of pre‐formed single helices that are able to accommodate a limonene molecule when these molecules are otherwise in insufficient concentration to generate stable single helices. No difference in flavor retention was observed for native and lipid‐free starch dispersions. By X‐ray diffractometry of the dried precipitates at one week, B patterns were obtained for the flavor compounds (limonene, iii cymene, anethole, carvone) with low flavor retention (%) and low amount of flavor bound. V patterns were observed for menthol, menthone, thymol, pulegone and terpinen‐4‐ol. Since the flavor compounds were added into the starch dispersions in varied concentrations, a V pattern precipitate would also be obtained if the amount of flavor bound was high, despite low flavor retention (%). The generation of V pattern would depend on whether the single helices would associate to form a precipitate and the packing of the helices. Single helical starch‐flavor complexes reduced the formation of starch double helices over time. Overall, this work suggests an improved basis for understanding the association of flavor compounds with starch, and the results may be applicable to starch‐containing foods. iv Table of Contents List of Figures ……………………..……………………………………………………………………….…………………. vii List of Tables ……………………………………..……………………………………………………………….………….. viii Acknowledgements ………………………………..…………………………………………………………….……….. ix Chapter 1 Review of The Literature 1 The big picture‐ Why flavor and starch? ………………….……………………………..………...……….. 1 2 Flavor …………………………………………………………………………………………………….….…….….……… 1 2.1 Flavor properties………………………..………………………..…………………….………..… 1 2.2 Flavor retention and release ……..…………………………………...………….…..…..… 3 3 Starch ………………………………..……………………….…………………………………………..…….…..…….… 3 3.1 Structure and composition ...……………………………..……………..…………..…….. 3 3.2 Phase transition ………….……………………………….…………….………………….…….…. 5 4 Starch‐flavor Interaction..………………………………….…………………………………..………...…….…. 6 4.1 Types of starch‐flavor interaction..………………………….….….…..……..………….. 6 4.1.1 Starch‐flavor Inclusion complexes 4.1.1.1 Structural characteristics 4.1.1.2 Formation for inclusion complex 4.1.1.3 Factors that influence inclusion complexation 4.1.2 Other types of starch flavor interaction 4.2 Methods to investigate starch‐flavor interaction…………………………….…….… 11 4.2.1 Precipitation method 4.2.2 Headspace method 4.3 The role of lipid in starch‐flavor interaction……………………………..….………… 15 4.4 Flavor retention by starch in a mixed‐flavor system …………………..….…..…. 16 4.5 Flavor retention by starch over time…………………..……………………..……….…… 17 5 Statement of the problem …………………………………………………..………………..………..….….…... 20 6 Goal…………………………………………………………………………….……………………………….…….….....… 21 7 Specific objectives……………..…………………………………………………………………….………….….…… 21 8 References …………..…………..…………………………………………………………………..…..……….….…… 22 Chapter 2 Materials and Methods 1 Materials …………………………………………..……………..………………………………………………......….. 26 1.1 Starches 1.2 Flavors 2 Methods ……………………….…………………………………………………………………………………..…….… 26 2.1 Preparation of lipid‐free starch………………………………………………………………. 26 2.2 Determination of lipid content ………………………………………………………………. 28 2.3 Octanol‐water partition coefficient analysis ……………………………………..…… 28 2.4 Determination of saturation point using headspace analysis …………………. 29 2.5 Starch‐flavor complex preparation ………………………………………………………… 29 2.6 Determination of flavor retention using headspace analysis………………..… 30 2.7 Determination of precipitation yield ……………………………………………………… 33 2.8 Wide angle X‐ray diffractometry……..……………………………………………………… 33 2.9 Statistical analysis ……………………………………………………………………………..….. 34 3 References ……………………………………………………………………………………………..………….………. 34 v Chapter 3 Retention of Flavor Compounds by Native Starch Dispersions 1 Single‐flavor starch system ………………………………………………………………………………..…...….. 35 1.1 Results …………………………………………………………………………………………..…….. 35 1.1.1 Solubility and hydrophobicity of flavor compounds…….….……..... 35 1.1.2 Flavor retention by native starch dispersion...……………………..….. 40 1.1.3 Flavor retention by native starch dispersion over time.…..…..….. 40 1.2Discussion …………………………………………..…………………………………………..…..….. 40 1.1.4 Measurement of hydrophobicity and solubility of flavor compounds on flavor retention by native starch dispersion…………………………………………………………………………….….. 40 1.2.2 The relationship of hydrophobicity of flavor compounds and Their flavor retention by native starch dispersion ……………………. 45 2 Binary‐flavor starch system …….…..………………………………………………………………………...……... 53 2.1 Results ….……………….………………………….………..……………………………….……...….. 53 2.1.1 Flavor retention by native starch dispersion ……………….…..…..….. 53 2.2 Discussion..….……………….……………………………………………………………………..……. 53 2.2.1 Possible explanations of flavor retention by native starch dispersion…………………………………..……………………………………..….…. 53 3 Conclusion …….………………………………………….……………………………………………………….…………... 57 4 References …...………………………………………….……………………………………………………….…………... 57 Chapter 4 Influence of Native Lipids on Flavor Retention and Precipitated Starch Yield 1 Effects of presence of native lipids on flavor retention…………………..…………………………….... 59 1.1 Results……………….………………………………….……………….…..……..…………..……….. 59 1.2 Discussion …………..….…………………………………………………..……..………….….…….. 59 2 Effects of presence of native lipids on precipitated starch yield over time without flavor addition…………………..………………………………………………………………………………………..….. 61 2.1 Results……………….………………………………….……………….…..……..…………..……….. 61 2.2 Discussion…………………………………………………………………………………………………. 62 3 Effects of flavor addition to native starch dispersion on precipitated starch yield over time…………..……………………………………………………………...…….……………..……..…….…….………… 62 3.1 Results…………………………………….………………………………………………………………... 62 3.2 Discussion ………………………………………………..…………………………………….…………. 68 4 Effects of flavor addition to lipid‐free starch dispersion on precipitated starch yield over time ……………………….………………………………………..…….……………..……..…………………..………… 70 4.1 Results………………………..……………….……………………………………………………………. 70 4.2 Discussion ………………………………………………..…………………………………….…….…… 70 5 Conclusion ….………………………………………….…………..…………………………………………………………. 72 6 References ….………………………………………….…………..…………………………………………………………. 73 Chapter 5 Suggested Future Works…..………………………..……………………….…..…………………..….. 74 Appendix Figures and Tables …………………………………………………….......................................... 76 vi List of Figures Figure 1.1 The effect of amylose concentration and chain length on phase behavior in aqueous amylose solution .………………………………………………………………………….…. 7 Figure 1.2 A schematic diagram of a common method for preparation of starch‐flavor complexes………………………………………………………………………………………………………. 12 Figure 2.1 Starch sample in a 20 mL headspace vial ……………………………………………………….. 31 Figure 2.2 The cooling profile for starch‐flavor mixture ………………………………………………..... 32 Figure 3.1 Determination of saturation concentration for A) limonene, B) thymol .………... 36 Figure 3.2 The relationship between hydrophobicity (log Pow) and saturation concentration ……….………………………………………………………………………………….……. 38 Figure 3.3 Flavor retention by native starch dispersion