J. E. Hardcastle Texas Woman's University Denton, 76204
A One Semester Food Chemistry Laboratory Program
In teaching a food chemistry course I could find no suitable laboratory manual directed toward food chemistry and technology. Thus, I prepared the program presented i n this report. Though this program is not perfect and will undergo change and improvement with further use, I found it t o be suitable for our needs, a n d I believe it was well received by the students. I present this program in hope t h a t others teaching such a course will find some useful ideas. Essentially all t h e students who take this course here a t Texas Woman's Universitv are maiorine in Foods a n d Nutrition, Dietetics, and ~ o i ~d e e h n h o d T. h e prerequisites for the course are a year of chemical principles and one semester of organic cbemistry. The students usually have not taken any course in analytical chemistni. Thus, one of the purposes~oft h e l a b o r a t o j program is t o teach the student some laboratory techniques used in quantitative chemical analvsis. B u t the main . Durnose is t o teach the student some practical knowledge of food composition and analvsis t h a t will be useful i n their future careers. T; accomplish these purposes common food stuffs were quantitatively analyzed by standard techniques used in the food industry. Also, t o make this a relevant and useful laboratory program, a n animal nutrition study was integrated with the chemical analysis of the diets fed t o the animals.
Table 1. Weights of Hamsters in Nutrition Study
Weigh- Cage 1.2 Cage 3 . 4 ing Rodent Rodent Cage 5 , 6 Cage 7,8 Cage 9.10 Date Chow Chow Cereal I Cereal1 Cereal I1 Jan 25 Jan 28 Feb 1 Feb 4 Feb 7 Feb 8 Feb 11 Feb 14 Feb 15 Feb 18 Feb 21 Feb 22
A
Course Description
The description of food cbemistry a s it appears in our college catalog is a s follows: A study of the chemistry of carbohydrates, fats, a n d proteins. The lecture and laboratory syllabi will show t h a t the course content is more extensive than indicated by the catalog description.
I. Lecture Syllabus Unit 1. Faod Laws and Standards. A discussion of modern food laws and their origin. Unit 2. Fat and Fat Food Stuffs. A study of the chemistrv of fats, fatty acids and their content in various food stuffs. Unit 3. Carbohydrates and Sugar Products. A study of carbohydrate chemistry and the sugar content of various food stuffs. Unit 4. Proteins. A brief study of protein chemistry. Unit 5. Cereals and Cereal Products. A discussion of the composition of various cereals and cereal products. Unit 6. Milk and Milk Products. A discussion of the composition of milk and milk products. Unit 7. Meat and Meat Products. A discussion of the compasition of meats and meat products. Unit 8. Food Additives. A discussion of the chemical nature and functions of food additives. Unit 9. Food Contamination, Deterioration, Preservation. A study of the causes and preventions of food contamination and deterioration. n. Laboratory Syllabus A. Chemical Analysis of Faod Stuffs Lab Exercise 1,Moisture Determination Lab Exercise 2, Crude Fat Determination Lab Exercise 3. Crude Fiber Determination Lab Exercise 4; Ash Determination Lab Exercise 5, Kjeldahl Nitrogen Determination (Crude Protein) 504
/
Journal of Chemical Education
Table 2. Chemical Analyses ot Animal Diets as Perlormed by Students
% Pro-
tein Rodent Chow
mrealrfaat
Cereal 1
22.0 23.6 22.9 23.5 11.5 11.1 10.7
38.3
The values listed are the results of single determinations
Lab Exercise 6, Carbohydrate Determination Lab Exercise 7, Detection of Some Food Additives Lab Exercise 8, Detection of Some Vitamins The methods used in these analyses were the official AOAC methods for grains, feeds, and cereals. (Association of Official Agricultural Chemists, Official Methods of Analysis, 9th Ed., 1960.) B. Animal Nutrition Study Weanling hamsters (23 days old), all of the same sex, were weighed and put into cages. Three animals were put in each cage, and were kept on a diet of commercial rodent chow for the first three days after weaning. The animals were again weighed at the end of this time. Then the diets in some of the cages were changed to popular dry breakfast cereal (one a wheat cereal, the other a cam cereal). Other cages of hamsters were kept on rodent chow as controls. Faod and water were supplied to all animals ad libitum. The hamsters were then weighed about every three days for a period of four weeks. While experiments of this kind usually involve white rats, I believe for this work the hamster is to be preferred esthetically. Students will enjoy working with hamsters rather than rats. 111. Outside Reading List The students were asked to read two books from the following list. 1. "The Chemical Feast," James R. Turner, Grossman Publisher, 1970.
Table 3. From Package Labels %Pro- % tein Fat W e n t Chow Cereal I (a wheat cereal) Cereal I1 (a corn cereal)
23.0 10.6 7.5
4.5 1.2
0.4
%Fiher 6.0
N.L. N.L.
%
%
Ash
CHO
9.0 N.L. N.L.
50.5 81.0 85.0
N.L., not listed on f a d package 2. "Let's Eat Right to Keep Fit," Adelle Davis, New American Library, 1970. 3. "Bio-organic: Your Food and Your Health," James Rorty and N. Philip Norman, Lancer Books, 1970. 4. "The Nuts Among the Berries," Ronald M. Deutsch, Ballantine Books, 1nc.~l961. 5. "The Jungle," Uptan Sinclair. In reading from this list the student will he exposed to views about food stuffs and the food industry not found in ordinary textbooks. Discussion Because of the limited amount of time allotted for this laboratory (one 3-hr periodlwk) each student could not carry out the complete animal nutrition study and chemical analysis of all the diets individually. Thus, a pair of students were assigned responsibility for care of one cage of animals on one particular diet. Each student was then required to perform the chemical analyses of the diet she
used for her cage of animals. All the data from the individual chemical analyses and animal studies were collected and organized by the instructor (Tables 1 and 2). This data was then distributed to the students and they were required individually to write reports on the total class experiment. From the collected data the students prepared graphs of weight versus time for each diet, and from these graphs assessed the nutritional value of each foodstuff. The students can do a limited statistical analysis of the data from the chemical analysis of the foodstuffs. This data can he compared with the values found on the food label (Table 3), and can be used t o partially explain the results of the animal nutrition study. This is a limited study and not all of the possible chemical analyses were performed. The weight changes of experimental animals is not the only criteria used for judging nutritional value of foodstuffs. Thus, the students were asked to descrihe experiments to obtain additional information that would allow a more complete evaluation of the nutritional quality of the foodstuffs used in this experiment. The experiments performed did give the students experience in quantitative chemical analysis. Also, part of the lecture instruction is a discussion of the many physiochemical methods used in the analysis of foods. Judging from student response I believe that the total experiment was valuable to these students. They said the program was relevent to their field of study, and they gained practical knowledge of food composition and analysis.
Volume 50, Number 7,July 1973
/
505
