Publisher Summary

The experimental study of food is concerned with why foods are handled, processed, and prepared as they are; how and why variations in ingredients or treatments influence the quality of food; and how this knowledge can be used to improve the quality of food products. This chapter presents a scientific approach to the experimental study of food. The scientific approach includes three basic steps: (1) defining the problem and arriving at the hypothesis, (2) testing the hypothesis in a carefully designed and controlled experiment, and (3) accepting or rejecting the hypothesis in a report of the results. The chapter discusses the procedures used to control the experimental conditions. Formulas (recipes) for products may be presented in several different forms. The uniformity of each ingredient must be controlled in a food experiment. Temperature control and measurement also are important in an experiment. The quantity of each ingredient is controlled through measuring and/or weighing. Variations in the techniques used to prepare samples for experimental work are more difficult to control than variations in the quality and amount of food used, especially for batters and doughs. Objective and sensory evaluation may be used to determine the effects of treatments on the quality of products. The principles of sensory evaluation of food should be used in conducting sensory tests. The necessary parts of an experiment report are objectives or purpose, methods, results (data), discussion of results, conclusions, and reference list. Before drawing conclusions, it is necessary to interpret the data. After the data are interpreted, conclusions can be drawn.

I. INTRODUCTION

A scientific approach to the experimental study of food is presented in this book. The experimental study of food is concerned with why foods are handled, processed, and prepared as they are, how and why variations in ingredients or treatments influence the quality of food, and how this knowledge can be used to improve the quality of food products. The scientific approach includes three basic steps: defining the problem and arriving at the hypothesis; testing the hypothesis in a carefully designed and controlled experiment; and accepting or rejecting the hypothesis in a report of the results. The scientific study of food is an exciting field of investigation. Adequate answers to some food-related problems have been found, often by applying sciences, such as chemistry, physics, biology, and microbiology, that are basic to the study of foods. Answers to other problems are only partial or not yet known. Incomplete answers and the unknown offer challenges to the food scientist. Students can find challenging questions to study in an experimental foods class.

This book is divided into two parts. Part I explores methods used in food science and should serve as a reference for laboratory work and for understanding the basic food science principles discussed in Part II. Understanding of the methods described in Chapters 3 and 4 will facilitate an understanding of the literature in food science. Part I can serve as a guide to the student who is starting an independent problem in experimental foods, who wants to expand the suggested exercises outlined at the ends of the chapters, or who wants to develop experiments using the formulas in the Appendix as a guide.

This textbook contributes to several sections of a research report. Part II is essentially a review of literature, both recent and older. The most current literature must always be reviewed, because information in food science changes rapidly; older literature provides the foundation for our understanding of food and its functional properties. Suggestions for reviewing the literature are included in Chapter 2. Appendix A contains experimental formulas. The procedures in Appendix A, although written as instructions, provide information for writing procedures for a report.

The other essential parts of the research report—the data, the discussion of the results, the conclusions, and the reference list—should be incorporated into the student’s notebook or laboratory report. The reference list should give credit to the sources of information used in preparation of the report. Those sources should be cited in the text. For reference lists in this text and citations within the text, the Institute of Food Technologists’ (IFT) style with some modification has been used. Details of this style are found in the style guide published by the IFT (1988). The style has been modified for this book to provide chapter numbers and inclusive page numbers. This will facilitate the process of obtaining copies of papers via interlibrary loan if not available to the reader. In addition, states are spelled out to facilitate information retrieval by international readers. For class reports, either this style or one of the styles used in other professional journals may be selected. It is important, however, that the same style be used throughout a report.

Suggested exercises at the end of each chapter include suggested experimental variations in treatment or ingredients. Basic formulas and procedures for some basic products are given in the Appendix. For other suggested exercises literature references may be given for formulas and procedure. The product from the basic formula serves as a control, in other words, a basis for comparison of the experimental products. Variations not described in the suggested exercise may better serve the needs and interests of a class. For example, related problems of current concern and interest may serve as a basis for class or individual projects—interesting projects may be suggested by class members. It is assumed that students using this book have some background in food science and thus can be involved in planning the details of experiments based on the suggested exercises.

Carefully controlled experiments with appropriate replication are necessary if the results are to be meaningful and, in the case of more extensive research studies, worthy of publication. Experiments should be controlled experiments. In other words, in a simple controlled experiment one factor (independent variable) is varied while all other conditions that might affect the results are controlled as much as possible. The effects of variation of that factor on selected quality attributes of the products (dependent variables) are measured. In a study of the effect of level of oat bran on the volume of muffins, level of oat bran is the independent variable and volume of the muffins is the dependent variable.

If more than one factor is altered (there is more than one independent variable), it is difficult without more than simple statistical analysis to determine the cause of any changes that might be observed in the quality of the products. More than one factor may be varied in a more complex experiment, which is called a factorial experiment. For example, to study the effects of both sugar and salt level on the quality of yeast bread a study could be designed to look at all possible combinations of sugar and salt levels. If three sugar levels and three salt levels are of interest, nine combinations would be studied. Statistical analysis of the data would make it possible to determine the effect of sugar level alone, the effect of salt level alone, and the effects of the various combinations. It is beyond the scope of this book to give a detailed description of the principles of experimental design and statistical analysis that must be applied in studies of this type. A general overview of experimental design is presented by Joglekar and May (1987). For the advanced student, several books on experimental design and/or statistical analysis might be consulted (Bender et al., 1982; Gacula and Singh, 1984; O’Mahony, 1986).

Temperature and humidity in the laboratory are difficult to control but may influence the results of an experiment. Faulty measurements, misinterpretation of the instructions, and variation in individual techniques are other possible unexplained variables that should be considered. A record of any unplanned variables should be made in the laboratory notebook so that they may be considered when the results are evaluated and discussed. An unplanned variable, if its presence is known, may be most helpful in explaining the results of an experiment. Research workers have sometimes changed the direction of work because of accidental occurrence of a condition that gave a clue to the solution of a problem. The procedures used to control the experimental conditions are discussed in this chapter. These procedures...