AN ABSTRACT OF THE THESIS OF JAMES FRANKLIN AMOS for the DOCTOR OF PHILOSOPHY (Name) (Degree) m FOOD SCIENCE presented on Uuiin \3,ff7i (Major) -$Date) Title: THE INFLUENCE OF MOLD CONTAMINATION, PROCESS- ING AND MATURITY ON THE VOLATILES OF THE STRAWBERRY, FRAGARIA ANANASSA DUCH. Abstract approved: Yt - ' M_ Dr. R. E. Wrolstad The effects of mold level (Botrytis cinerea), processing method (fresh, individually quick frozen (IQF), frozen sugared sliced (FSS), freeze dried (FD), canned, and preserves), and maturity (underripe, normal, and overripe) and strawberry volatiles were analyzed by gas liquid chromatography (GLC) using on-column entrainment of head- space volatiles in aqueous extracts. Computerized analyses were used to calculate peak areas and to perform analyses of variance comparing the area of each peak for different samples. Peaks vary- ing significantly (P < 0.05) with processing method, maturity, and mold count were collected on Porapak Q columns, transferred to GLC columns, and identified by coupled GLC-mass spectrometry and by GLC retention times. All volatiles whose peak areas changed significantly with mold level (P < 0.05) decreased as mold level increased. These volatiles were as follows: n-propionic acid, n-butyric acid, acetaldehyde, isobutyraldehyde, methyl acetate, 1, 1-diethoxymethane, 1,1- diethoxyethane, acetophenone, propiophenone, 1-phenyl-1, 2- propanedione, diethyltoluene, and one unknown. Neither ethanol nor diacetyl changed significantly with mold level. Volatiles increasing significantly on processing were found in canned fruit and preserves. These were dimethyl sulfide, benzalde- hyde, furfural, and 1-propanethiol. In canned fruit and preserves 5-(hydroxymethyl)-2-furfural was newly formed. Many compounds (acetals, acids, alcohols, aldehydes, esters, ketones, and hydro- carbons) decreased significantly in level on processing; all were identified. Numbers of compounds decreasing significantly with each process were as follows: IQF, five lower-boiling compounds; FSS, two lower-boiling compounds; FD, 37 compounds; canned, eight compounds; and preserves, 29 compounds. In general most compounds varying significantly (P < 0. 05) with maturity increased. No new compounds were formed on ripening, and no compounds completely disappeared with ripening. The compounds varying significantly with maturity were esters (methyl acetate; ethyl formate, acetate, propionate, and butyrate; n- pentyl _n-hexanoate; P - phenylethyl acetate; cis-3-hexen- 1-yl hexanoate; and benzylacetate), aldehydes (acetaldehyde, isobutyraldehyde, benzaldehyde, and ethyl- benzaldehyde), acetals (1, 1-dimethoxymethane, 1, 1-diethoxymethane, 1, 1-diethoxyethane, and 1, 1-diethoxyoctane), acids (propionic, _n.- butyric, and isobutyric), aromatic ketones (acetophenone, propio- phenone, propylphenyl ketone, and 3-phenylpropan-2-one), ethanol, and one unknown. These results would not seem to encourage use of this technique for monitoring mold levels in strawberries. The Influence of Mold Contamination, Processing and Maturity on the Volatiles of the Strawberry, Fragaria ananassa Duch. by James Franklin Amos A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 1972 APPROVED: Assistant Professor of Food Science and Technology in charge of major f T^ PV Head of Department of Food Science and Technology Dean of Graduate School Date thesis is presented lUsHI Typed by Mary Jo Stratton for James Franklin Amos ACKNOWLEDGEMENT I would like to express my sincere appreciation for the encourage- ment and guidance given me by Dr. R. E. Wrolstad in this investiga- tion and in the rest of my doctoral program. Thanks are also due to the other members of my program committee, Dr. R. F. Cain, Dr. W. D. Loomis, Dr. A. W. Anderson, and Dr. K. E. Rowe, for their willing assistance. The cooperation and helpful suggestions of the faculty and graduate students of the Department of Food Science and Technology are gratefully acknowledged. Special thanks are due Dr. L. M. Libbey for his help in obtaining mass spectra and Dr. M. E. Morgan for his help with the technique for Porapak collection of volatiles. Thanks are also expressed to Dr. P. H. Krumperman, Dr. R. A. Scanlan, and Dr. M. W. Montgomery. The assistance of the personnel of the Computer Center, particularly Dr. L. C. Hunter's providing of the grant for computer time, is very much appreciated. The advice of Dr. A. D. Campbell, Food and Drug Administra- tion, was extremely helpful in planning the study. I would like to express my appreciation to the U. S. Public Health Service and the General Foods Corporation for their support of the work. TABLE OF CONTENTS Page INTRODUCTION 1 REVIEW OF LITERATURE 3 Strawberry Volatiles 3 Identification of Volatiles 3 Effect of Various Parameters on Volatile Composition 6 Microbially-Produced Volatiles 8 Use in Identification of Microorganisms 8 Use as a Food Quality Indicator 9 Mold-Produced Volatiles 10 Botrytis cinerea 12 Economic Significance 12 Growth Conditions 14 Products 17 Enzymes 17 Detection 19 EXPERIMENTAL 20 Strawberries 20 Source 20 Mold-Level Classifications 20 Maturity Classifications 21 Fruit for Processing 21 Processing Methods 22 Fresh 22 Individually Quick Frozen 22 Frozen Sugared Sliced 23 Freeze Dried 23 Canned 23 Preserves 24 Microbiological Materials and Methods 24 Mold Counts 24 American Type Culture Collection Culture 24 Mold Culture from Strawberries 25 Comparison of Mold Cultures 25 Analysis of Headspace Volatiles 26 On-Column Entrainment 2 6 Gas Liquid Chromatography 27 Page Quantitation of GLC Data 28 Statistical Procedures 29 Identification of Volatiles 2 9 Porapak Collection 29 Mass Spectrometry 33 GLC Retention Times 34 RESULTS AND DISCUSSION 35 Effect of Mold Level 36 Mold Counts 36 Comparison of Mold Cultures 36 Comparison of Volatiles 38 Effect of Processing Method 48 Effect of Freezing (IQF and FSS) 53 Effect of Freeze Drying 58 Effect of Canning 5 9 Effect of the Preserving Process 62 Effect of Maturity 63 Esters 70 Aldehydes 71 Acetals 72 Acids 73 Aromatic Ketones 73 Alcohols 1 74 Other Considerations 75 BIBLIOGRAPHY 77 APPENDICES 92 LIST OF FIGURES Figure Page 1 Headspace assembly for the entrainment of volatiles on the Porapak column. 31 2 Analysis of the headspace volatiles present in an aqueous extract of individually quick frozen (IQF) strawberries using a TRIS column, ('very moldy (VM) and normal good quality (NGQ) fruit). 39 3 Analysis of the headspace volatiles present in an aqueous extract of individually quick frozen (IQF) strawberries using a Carbowax column (very moldy (VM) and normal good quality (NGQ) fruit). 40 4 Analysis of the headspace volatiles present in an aqueous extract of normal good quality (NGQ) strawberries using a TRIS column (freeze dried and fresh fruit). 49 5 Analysis of the headspace volatiles present in an aqueous extract of normal good quality (NGQ) strawberries using a TRIS column (preserves and fresh fruit). 50 6 Analysis of the headspace volatiles present in an aqueous extract of normal good quality (NGQ) strawberries using a Carbowax column (freeze dried and fresh fruit). 51 7 Analysis of the headspace volatiles present in an aqueous extract of normal good quality (NGQ) strawberries using a Carbowax column (canned and fresh fruit). 52 8 Analysis of the headspace volatiles present in an aqueous extract of individually quick frozen (IQF) strawberries using a TRIS column (underripe (UR), normal good quality (NGQ) and overripe (OR) fruit). 64 Figure Page 9 Analysis of the headspace volatiles present in an aqueous extract o*. individually quick frozen (IQF) straw- berries using a Carbowax column 65 (underripe (UR), normal good quality (NGQ) and overripe (OR) fruit). LIST OF TABLES Table Page 1 Howard mold counts for strawberries of different subjective mold-level classifica- tions processed in different ways. 37 2 Normalized peak areas of TRIS volatiles and comparison of different mold levels. 41 3 Normalized peak areas of Carbowax volatiles and comparison of different mold levels. 41A 4 GLC-MS identification of volatiles important in mold-level differences. 42 5 Comparison of relative amounts of TRIS compounds decreasing on mold growth with relative amounts of the products to which they could have been altered. 46 6 Normalized peak areas of TRIS volatiles and comparison of processed with fresh fruit. 54 7 Normalized peak areas of Carbowax volatiles and comparison of processed with fresh fruit. 55 8 GLC-MS identities of TRIS volatiles differing in amount with processing method. 56 9 GLC-MS identities of Carbowax volatiles differing in amount with processing method. 57 10 Normalized peak areas of TRIS volatiles and comparison of different maturities. 66 11 Normalized peak areas of Carbowax volatiles and comparison of different maturities. 67 Table Page 12 GLC-MS identities of TRIS peaks varying with maturity. 68 13 GLC-MS identities of Carbowax peaks varying with maturity. 69 THE INFLUENCE OF MOLD CONTAMINATION, PROCESSING AND MATURITY ON THE VOLATILES OF THE STRAWBERRY, FRAGARIA ANANASSA DUCH. INTRODUCTION Molds have long been known to be responsible for economic loss and to cause infectious diseases; their presence in most foods is directly related to spoilage and decomposition (Wilson, 1966; Anony- mous, 1970). Administrative guidelines for mold levels in different food products have been established by the Food and Drug Administra- tion (Anonymous, 1970),, Mold levels in excess of these values are considered to