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Effect of Enzymes on Strawberry Volatiles During Storage, at Different Ripeness

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Effect of Enzymes on Strawberry Volatiles During Storage, at Different Ripeness Effect of Enzymes on Strawberry Volatiles During Storage, at Different Ripeness Level, in Different Cultivars and During Eating Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Gulsah Ozcan Graduate Program in Food Science and Technology The Ohio State University 2010 Thesis Committee: Sheryl Ann Barringer, Adviser W. James Harper John Litchfield 1 Copyright by Gülşah Özcan 2010 ii ABSTRACT Strawberry samples with enzyme activity and without enzyme activity (stannous chloride added) were measured for real time formation of lipoxygenase (LOX) derived aroma compounds after 5 min pureeing using selected ion flow tube mass spectrometry (SIFT-MS). The concentration of (Z)-3-hexenal and (E)-2-hexenal increased immediately after blending and gradually decreased over time while hexanal concentration increased for at least 5 min in ground strawberries. The formation of hexanal was slower than the formation of (Z)-3-hexenal and (E)-2-hexenal in the headspace of pureed strawberries. The concentration of LOX aldehydes and esters significantly increased during refrigerated storage. Damaging strawberries increased the concentration of LOX aldehydes but did not significantly affect the concentration of esters. The concentrations of many of the esters were strongly correlated to their corresponded acids and/or aldehydes. The concentration of LOX generated aldehydes decreased during ripening, while fruity esters increased. Different varieties had different aroma profiles and esters were the greatest percentage of the volatiles. The aroma release of some of the LOX derived aldehydes in the mouthspace in whole strawberries compared to chopped strawberries showed that these volatiles are formed in the mouth during chewing. The persistence of LOX derived compounds was higher than esters after swallowing. The MSas/MSbs persistence ratio of esters decreased as the chain length of the acid part of the ester compounds increased in whole strawberries. ii PRACTICAL APPLICATIONS The results of the storage study showed that the concentrations of fruity and fresh volatiles increased during ripening and storage. These results can be used to determine the best edible time of strawberries during storage based on their fruity and fresh flavor. More ripened strawberries are rich in fruity flavor which can show the best maturity to pick strawberries and market them. Maximizing the fruity flavor of strawberries in a product requires selecting the highest ester concentrated fruit variation, waiting until fruits ripen to harvest, trying to keep them from any damage to avoid off flavor formation during storage and storing them in a fresh condition until their consumption. The 4-41% of strawberry volatiles persist in the mouth after swallowing and the persistence of LOX derived compound was higher than esters. This knowledge can be used in flavor industry to improve the formula of natural strawberry flavor by considering human perception during eating. iii DEDICATION To my parents Nadire and Ömer iv ACKNOWLEDGEMENT I would like to thank my adviser Dr. Sheryl A. Barringer for her generous guidance and support throughout my graduate study. She thought me how to solve problems and questions. Without her I couldn‟t get my current point of view in food science. I also want to thank Dr. W. James Harper and Dr. John Litchfield being part of my graduate committee and their priceless works in food science. I want to thank all my lab mates, especially Carolina, Yi-Hsuan, Yang, Fah and Offy for the greatest times we had. I would also like to thank my greatest friends Murat, Alex, Huseyin, Peren, Goksel, Onur, Derya and Cagla for their friendship and support. I‟m grateful to the Republic of Turkey Ministry of Education for giving me the opportunity to complete my M.S. study at the Ohio State University. I would like to acknowledge Julia Barton for picking strawberries from OSU farms for my study. Very special thanks to my parents Nadire and Omer, my brother and his lovely family for their endless love and support. Finally, I want to thank to my love Sercan for all of his patience and love. v VITA October 16, 1984……………………Born – Istanbul, Turkey 2002 -2006…………………..………B.S. Food Engineering, Trakya University 2006 -2007…………..………………Invoicing Supervisor, MIGROS TURK T.A.S. 2008 to present………………….......Master Student, Department of Food Science and Technology, The Ohio State University FIELDS OF STUDY Major Field: Food Science vi TABLE OF CONTENTS ABSTRACT ..................................................................................................................................... ii ACKNOWLEDGEMENT ............................................................................................................... v VITA ............................................................................................................................................... vi LIST OF TABLES ........................................................................................................................... x LIST OF FIGURES .......................................................................... Error! Bookmark not defined. CHAPTER 1 .................................................................................................................................... 1 INTRODUCTION ........................................................................................................................... 1 CHAPTER 2 .................................................................................................................................... 4 REVIEW OF LITERATURE .......................................................................................................... 4 2.1 Strawberry Aroma .................................................................................................................. 4 2.1.1 Odor Characteristics of Some Strawberry Volatiles ....................................................... 6 2.2 Breath ..................................................................................................................................... 7 2.2.1 Flavor perception ............................................................................................................ 7 2.2.2 Persistence....................................................................................................................... 9 2.2.3 Headspace, Nosespace and Mouthspace ....................................................................... 10 2.2.4 Other Foods ................................................................................................................... 12 2.3 Enzymatic formation ............................................................................................................ 14 2.3.1 Lipoxygenase generated aroma ..................................................................................... 14 2.3.2 Esters ............................................................................................................................. 17 2.4 Heat ...................................................................................................................................... 20 2.4.1 Volatility and Partition Coefficient ............................................................................... 21 2.5 High Pressure ....................................................................................................................... 21 vii 2.6 Storage and Different Varieties ........................................................................................... 22 2.7 Ripening ............................................................................................................................... 23 2.8 Other Processes .................................................................................................................... 24 2.9 Analytical methods for analyzing flavor compounds .......................................................... 25 2.9.1 Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) ............................................. 25 CHAPTER 3 .................................................................................................................................. 27 MATERIALS AND METHODS ................................................................................................... 27 3.1. Raw Material ....................................................................................................................... 27 3.2 Headspace: with and without enzyme inhibition ................................................................. 27 3.3 Refrigerated Storage ............................................................................................................ 28 3.4 Unripe and ripe fruit............................................................................................................. 28 3.5 Different Varieties ............................................................................................................... 29 3.6 Headspace measurements for whole and chopped strawberries .......................................... 30 3.7 Mouthspace and Nosespace ................................................................................................. 30 3.8 Method Information ............................................................................................................. 31 3.9 Statistical Analysis ..............................................................................................................
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