AN ABSTRACT OF THE THESIS OF Carolyn Gene Brown for the degree of Master of Science in Foods and Nutrition presented on May 25, 1979 Title: PHYSICAL AND SENSORY CHARACTERISTICS OF A WHEAT FLOUR AND MODIFIED WAXY MAIZE STARCH SYSTEM IN A COMMERCIALLY PREPARED CREAM OF CHEESE WITH BACON FROZEN SOUP CONCENTRATE DURING PROCESSING AND AFTER STORAGE Abstract approved: ^_ W- Zoe Ann Holmes The effect of thermal stress, as evidenced by changes in physical and sensory characteristics, on wheat flour and waxy maize starch combined in a commercially prepared Cream of Cheese with Bacon Frozen Soup Concentrate, was tested objectively and evaluated by a consumer panel. Samples for light photomicrographs, scanning electron micrographs, Brookfield viscosi- ties and temperature measurements were collected. Sensory evaluation of four soup characteristics included overall acceptability, texture accept- ability, consistency and syneresis. Soup was sampled at two places during processing, after reheating the refrigerated stored product and reheating after eight weeks of frozen storage. Results from light microscopy indicated increases in granule size and more deformation of starch granules with processing and storage times as compared with the raw starch. Granule outlines were evident in the fresh, frozen and reheated product. Scanning electron microscopy pictures revealed less granule integrity at the time the starch was incorporated into the soup. The cooked soup appeared as a more homogeneous mass. With frozen storage, the mass became even more homogeneous. The viscosity of the soup was significantly different (p < 0.05) between step 5 of processing versus when ready for service, and between the soup immediately ready for service versus 25 minutes later. Regres- sion analysis indicated that the viscosity measurements taken when ready for service and 25 minutes later were best indicative of the final viscosity of the soup (F = 120.6, significant at p < 0.05) . A high correlation (r = -0.76), was found between final viscosity when ready for service and temperature taken at time of that test. Sensory evaluation of overall acceptability, texture acceptability, consistency and syneresis indicated that test session and scores were highly correlated during the first four weeks, but not during the second four weeks. Analysis of variance indicated a significant difference in overall acceptability scores between fresh and frozen (p < 0.05). No significant difference in scores was observed due to the soup being served for dinner or lunch. PHYSICAL AND SENSORY CHARACTERISTICS OF A WHEAT FLOUR AND MODIFIED WAXY MAIZE STARCH SYSTEM IN A COMMERCIALLY PREPARED CREAM OF CHEESE WITH BACON FROZEN SOUP CONCENTRATE DURING PROCESSING AND AFTER STORAGE by CAROLYN GENE BROWN A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Completed May 25, 1979 Commencement June 1980 APPROVED: il *—» t r AssoeYate Professor of Foods and Nutrition ^ in charge of major Head of DepartmentDeroarrment of Foods and Nutrition Dean of Graduate School Date thesis is presented May 25, 1979 Typed by Rebecca Rakish for Carolyn Gene Brown ACKNOWLEDGMENTS I would like to first thank my major professor. Dr. Holmes, for her support, guidance, and patience throughout this project. I would also like to thank Chef Francisco for allowing us to take samples along their production line and providing lab space and samples. The scanning electron microscopy work done by Al Soeldner was greatly appreciated. Dr. Phinney's advice on light microscopy techniques was very helpful. The technical assistance provided by Becky Tice and Jane Anderson was greatly appreciated. The members of the Coed Cottage Cooperative deserve a special thank you for their cooperation during the taste panels. I want to thank two friends very much for their help with the statistics and computer analysis, Ruth Phinney and Jim Keniston. A special thanks to Carrie Ganong for her support and friendship and to my parents for all their support and help. This research was supported in part by an Agricultural Experiment Station grant (Project 296). TABLE OF CONTENTS Page INTRODUCTION 1 REVIEW OF LITERATURE 5 Starch structure and origins 5 Native starch 5 Chemically modified starch 6 Gelatinization and retrogradation 7 Gelatinization 8 Retrogradation 9 Starch/Ingredient interactions 10 Microscopy 11 Light microscopy 11 Electron microscopy 14 Transmission electron microscopy 15 Scanning electron microscopy 15 Viscosity 18 Apparent viscosity 19 Intrinsic viscosity 21 Thermal transfer of heat 22 Sensory evaluation 23 METHODOLOGY 28 Research design 28 Soup preparation procedures at Chef Francisco and Coed Cottage Cooperative 31 Sampling times at Chef Francisco and Coed Cottage Cooperative 34 Test methods 34 Time-temperature data 34 Viscosity determinations 34 Light miscroscopy 35 Scanning electron miscroscopy 36 Freeze-drying 36 Mounting and microscopy 36 Sensory evaluation 37 Data analysis 39 RESULTS AND DISCUSSION 41 Microscopy 41 Objective evaluation of the data 51 Sensory evaluation of the data 55 SUMMARY, CONCLUSIONS, AND FUTURE DIRECTIONS 60 BIBLIOGRAPHY 62 APPENDICES Page Appendix I. Itemized meal menus at Coed Cottage Cooperative 70 Appendix II. Personal communication from Susan Waring, Senior 73 Home Economist with the National Starch and Chemical Corpora- tion describing physical characteristics of Purity W starch Appendix III. Additional light and SEM photomicrographs 75 Appendix IV. Individual data from objective tests and corre- 79 lations LIST OF FIGURES Figure Page 1 Scorecard for sensory evaluation 38 2 Comparison of Purity W and System Flour, raw state 42 using light microscopy and SEM, representative pictures 3 Effect of processing on the starch system of the soup, 44 light microscopy and SEM, representative pictures Effect of one day refrigeration and reheating on the 48 starch system of the soup, light microscopy and SEM, representative pictures Effect of eight weeks frozen storage and reheating on 50 the starch system of the soup, light microscopy and SEM, representative pictures Higher magnifications of Purity W Starch and the System 75 Flour, representative SEM pictures Higher magnifications of representative SEM pictures 76 from step 2 and step 5 of processing showing association with protein strands and the formation of more of a homogeneous mass. Higher magnifications of representative SEM pictures 77 from the fresh reheated soup and after eight weeks of frozen storage Effect of 25 minutes of cooling on the starch system of 78 the cheese soup, light microscopy and SEM, representa- tive pictures LIST OF TABLES Table Page 1 Sampling procedure for objective and sensory testing of 29 Cream of Cheese with Bacon Frozen Soup Concentrate 2 Ingredients and preparation of Cream of Cheese with 32 Bacon Frozen Soup Concentrate at Chef Francisco and Coed Cottage Cooperative 3 Viscosity and temperature means and standard devia- 52 tions (St. Dev.) during processing, reheating, and 25 minutes later for Cream of Cheese with Bacon Frozen Soup Concentrate 4 Session means, overall means, and standard deviations 56 (St. Dev.) of sensory scores by test session involving Cream of Cheese with Bacon Frozen Soup Concentrate 5 F values for sensory data for Cream of Cheese with 58 Bacon Frozen Soup Concentrate: 2-way interaction; lunch versus dinner, and fresh versus frozen; and 1-way; fresh versus frozen 6 Spindle sizes, speeds, readings, and conversion 79 factors used to convert Brookfield viscosity readings of Cheese Soup to centipoises (cps) 7 Raw Brookfield viscosity, temperature, length of 82 reheating, and storage data for the fresh, fresh refrigerated, and eight week frozen Cream of Cheese with Bacon Frozen Soup Concentrate 8 Correlations between objective data variables and 85 sensory characteristics for Cream of Cheese with Bacon Frozen Soup Concentrate 9 Correlations between tasting sessions and sensory 86 score for Cream of Cheese with Bacon Frozen Soup Concentrate. Testing for a time trend in the data PHYSICAL AND SENSORY CHARACTERISTICS OF A WHEAT FLOUR AND MODIFIED WAXY MAIZE STARCH SYSTEM IN A COMMERCIALLY PREPARED CREAM OF CHEESE WITH BACON FROZEN SOUP CONCENTRATE DURING PROCESSING AND AFTER STORAGE INTRODUCTION The frozen food industry is one food industry enjoying expansion and increasing sales. By 1980, it is projected that the total frozen food poundage will reach 22 billion pounds, making an annual increase of four percent (Martin, 1976). Of this total frozen food poundage, prepared foods are expected to grow at an annual rate of 5.5% through 1980 and comprise one-quarter of the total poundage of frozen foods. Many starch containing items are included in these prepared and precooked foods. The availability of prepared and precooked frozen foods has brought about changes in the food service industry both in the institutional and restaurant areas. These changes are reflected in the increased use of frozen convenience entrees in the late 1960's and early 1970's (Staff, 1976a). Tinsley (1978) has reported that approximately 66% of the commercial operators and 78.9% of the noncommercial operators serve frozen entrees either regularly or occasionally. This is an increase of 17% and 27% in .the commercial and noncommercial sector, respectively, since 1976. According to the 1976 Food Buying Trends (Staff, 1976b), 94% of the new entrees introduced during that year were frozen and 27% of the new soups were frozen. Most of this increase was due to an increased