Factors Influencing Storage Quality of Hazelnut Varieties
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AN ABSTRACT OF THE THESIS Kais S. Ebrahem for the degree of Doctor of philosophy in Horticulture presented on October 16. 1992 Title: FACTORS INFLUENCING STORAGE QUALITY OF HAZELNUT VARIETIES Abstract approved: . ^. Dr. Daryl G.\. RichaRichardson, Professor of Horticulture This thesis research is a series of five studies dealing with various aspects of hazelnut quality: 1. Identification of kernel mold and its incidence among hazelnut varieties. 2. Seasonal development and composition of kernels. 3. Hazelnut oil composition (fatty acids and tocopherols) of seventeen varieties. 4. Hazelnut oil composition compared to 14 other nuts and oilseeds. 5. Storage and roasting effects on lipid oxidation. Barcelona, Daviana, and Ennis varieties of hazelnuts used to study white mold showed that mold incidence was highest in 1986, and much less in 1987 and 1988. Ramularia spp was the only fungus that was identified in all samples with kernel mold and was usually found at high percentages. Temperatures for drying, storage, and numbers of nuts per cluster had no significant effect on percent mold. The second part of this study measured fatty acid and vitamin E concentrations during the growing season. Samples were collected from seven varieties (Barcelona, Daviana, Ennis, Tonda Romana, Tonda Gentile della Langhe, Tombul, and Tombul Ghiaghli). Kernel oil and vitamin E (tocopherol) concentrations increased with time, while moisture decreased. Oleic acid was the major fatty acid (ca.75%) found in hazelnuts, followed by linoleic(ca.20%). Linolenic was high at the beginning of the season but then decreased to about 1% at harvest. Alpha-tocopherol was the major form of vitamin E found, composing almost 95% of total tocopherols. Hazelnuts are a rich source of vitamin E, with about 350 ng/g oil. Fourteen types of nuts, oil seeds, and seventeen varieties of hazelnuts were compared for oil content, fatty acid, and tocopherol composition. Macadamia nuts were the highest in oil content (77%) and chestnuts were the lowest (3%). Oil concentrations in oil seeds ranged from 5% in corn to 50% in sesame seeds. Oil concentration also varied among hazelnut cultivars. Hall's Giant had low concentrations (58%) of oil and Tombul had high concentrations (66%) of oil. Gamma-tocopherol was the dominant form in pistachios, English walnuts, black walnuts, pinenuts, and Brazil nuts. All four tocopherols were found in oil seeds and tocotrienols were found in some. Hazelnut varieties were stable during storage for up to two years with only slight loss in vitamin E. FACTORS INFLUENCING STORAGE QUALITY OF HAZELNUT VARIETIES by Kais S. Ebrahem A THESIS submitted to Oregon State University in partial fulfillment of the requirement for the degree of Doctor of Philosophy Completed October 16, 1992 Commencement June 1993 APPROVED: j" "*-' * *■-**■* Professor (of Horticulture in charge of major IMI ***—t i Head of Horticulture Department ""XT Dean of Graduare\pe\ Schoo]School Date of thesis presentation October 16. 1992 Typed by Amy Ellingson for Kais S. Ebrahem And in the Earth are neighbouring tracts, vineyards and ploughed lands, and date-palms, like and unlike,2 which are watered with one water. And We have made some of them to excel others in frait. Lo! herein verily are portents for people who have sense. IN THE NAME OF ALLAH, THE MOST BENEFICENT, THE MOST MERCIFUL. DEDICATION This thesis is dedicated to three special persons. The first person,to whom I am indebted for my education, is my father who died on March 16, 1990. I lost a wonderful father. Father, you are not around us but you will always live in my heart; while I have missed you, I have tried hard to achieve the goals that I Would told you about. (MAY GOD BLESS YOD FOR ALL THINGS YOU DID FOR THE THREE OF US). The second person is my lovely and devoted mother, who very early in my childhood, taught me that a little extra effort at the right time can prove profitable in the long run. Words are not inadequate to express my love and respect for her. I will never forget what you did for me during my study in high school, university, and how much it is difficult on you being far away from you (I LOVE YOU SO MUCH/ YOU ARE A WONDERFUL MOTHER). The third person is my wonderful wife, without of her help I could not get my degree. Khalida is so wonderful, patience, understanding, continued encouragement, and endless support, help me gain our objective during the past years. Without her optimism and faith in me, I would have never come this far. She has withstood the tensions, and miscellaneous stresses of her eccentric husband's graduate days with unfailing love. Thank you for all what you did to make our life easy during those difficult times. (I AM ALWAYS PROUD OF YOU, AND I LOVE YOU). In the name of Allah, most Gracious, most Merciful. ACKNOWLEDGEMENTS As any graduate student is sure to find out, a thesis would never be completed without guidance, lab assistance, farm assistance, and peer support. I was very lucky to have plenty of "all of the above" so that my years at OSU were not only profitable but immensely enjoyable. I would like to take this opportunity to thank many people who kindly helped me throughout my doctoral program and thesis. First I want to thanks my major professor Dr. Daryl G. Richardson for his inspiring guidance, encouragement, support, patience, friendship, concern through the course of this study, and for teaching me the way of experimental science. My gratitude is expressed to Dr. Richard M. Tetly, who helped me to develop some of the techniques I used during this investigation. My sincere thanks to my committee members, Dr. Shawn Mehlenbacher, Dr. Jack Stang, Dr. Daniel Selivonchick, and to my graduate representative, Dr. Larry Moore. Special thanks go to a very special friend, Amy Ellingson, for her friendship, assistance whenever needed, encouragement, support during past years, gentleness, and for the excellent typing of this manuscript. I am grateful to ( University of Baghdad) for financially supporting my studies until end of 1989, and Oregon State University for providing me with excellent education. I sincerely appreciate the plentiful assistance I had from Head Department Dr. Conard J. Weiser, and International Education Office for all the help they provided for me during the war times. I am also grateful to all the fellow friends, especially Abdel Azim Y. Gadir for helping with statistical analysis. My thanks and appreciation also to Drs. Porter Lombard, and Anita Azerenko. Last, but not at all the least, I would like to express my deepest gratitude and love to my two brothers "Ebrahem, and Hameed" for their encouragement, friendship and love. Table of Contents Page Chapter 1. Introduction 1 Chapter 2. Review of literature 7 Chapter 3. Occurrence and identification of white mold on hazelnut kernels. Abstract 91 Introduction 92 Materials and methods 96 Results 100 Discussion 105 Literature cited 109 Chapter 4. Changes in oil content, fatty acid, and vitamin E composition in developing hazelnut kernels. Abstract 127 Introduction 129 Materials and methods 132 Results 140 Discussion 148 Literature cited 155 Chapter 5. Oil content, fatty acid composition, and vitamin E concentration of seventeen varieties of hazelnuts, compared to other nuts and oil seeds. Storage studies of hazelnut oil composition. Abstract 187 Introduction 189 Materials and methods 195 Results 200 Discussion 212 Literature cited 221 Chapter 6. Effects of storage temperature, kernel intactness, and roasting temperature on vitamin E, fatty acids, and peroxide value of hazelnuts. Abstract 261 Introduction 262 Materials and methods 265 Results 267 Discussion 273 Literature cited 283 Chapter 7. Conclusions 323 Chapter 8. Bibliography 327 Appendices 368 LIST OF FIGURES Figure Page Chapter 2 2.1 Comparison of oleate autoxidation and 34 photo-oxidation. 2.2 Mechanisms of oleate, linoleate, and 35 linolenate autoxidation. 2.3 Typical autoxidation of a polyunsaturated 38 lipid as a function of time showing the various stages in the reaction. 2.4 The structure of tocopherol. 56 2.5 The structure of tocotrienol. 56 2.6 Probable course of the biosynthesis of 78 tocopherols and tocotrienols. 2.7 Methylation and hydrogenation of 79 tocopherol and tocotrienol. Chapter 3 3.1 "Barcelona" kernel seasonal mold incidence 121 for 1986, 1987, and 1988. 3.2 "Daviana" kernel seasonal mold incidence 122 for 1986, 1987, and 1988. 3.3 "Ennis" kernel seasonal mold incidence for 123 1986, 1987, and 1988. 3.4 Percent of mold during the growing season 124 for Barcelona, Daviana, and Ennis, 1986. 3.5 Percent of mold during the growing season 125 for Barcelona, Daviana, and Ennis, 1987. 3.6 Percent of mold during the growing season 126 for Barcelona, Daviana, and Ennis, 1988. Chapter 4 4.1 Growth of the whole nut and kernel of 162 seven hazelnut varieties, 1987 and 1988. (Barcelona, Ennis, Daviana, Tonda Romana, Tonda Gentile delle Langhe, Tombul, and Tombul Ghiaghli) 4.2 Growth of the whole nut of seven hazelnut 163 varieties, 1987 and 1988. (Barcelona, Ennis, Daviana, Tonda Roinana, Tonda Gentile delle Langhe, Tombul, and Tombul Ghiaghli) 4.3 Growth of the kernel of seven hazelnut 164 varieties, 1987 and 1988. (Barcelona, Ennis, Daviana, Tonda Roinana, Tonda Gentile delle Langhe, Tombul, and Tombul Ghiaghli) 4.4 Moisture content of seven hazelnut 165 varieties. (Barcelona, Ennis, Daviana, Tonda Romana, Tonda Gentile delle Langhe, Tombul, and Tombul Ghiaghli) 4.5 Changes in % oil, moisture, and residue in 166 seven varieties of hazelnut kernels, 1988. (Barcelona, Ennis, Daviana, Tonda Romana, Tonda Gentile delle Langhe, Tombul, and Tombul Ghiaghli) 4.6 Length to width ratio of seven hazelnut 167 varieties, 1987 and 1988. (Barcelona, Ennis, Daviana, Tonda Romana, Tonda Gentile delle Langhe, Tombul, and Tombul Ghiaghli) 4.7 Fatty acid development of seven hazelnut 168 varieties, 1987.