Soy in Food: What is that doing in there?

How does the chemical composition of soybeans impact the characteristics of soy-containing foods?
Have you ever looked on a food label and seen soy products on it, even though it wasn’t made from soybeans? This unit explores the various uses of soy in foods and how soy can be used to accomplish various functions in food science by asking students to measure the nutrient content of various foods, determine the function of soy in foods, and shows how fermentation of soy can be used to make different foods.

Lessons

Teacher background

The major macromolecules associated with foods are carbohydrates, lipids, and proteins. Soybean composition makes it a desirable ingredient in many foods (Lesson 1). The high protein levels in soybeans have made them important staples in vegetarian diets and in regional cuisines where access to animal protein has been historically limited. Students will find similarities in the processing of tofu and cheese based on the structure-function of proteins in soy and dairy. Soy also plays a major role in many foods due to lecithin, a cost effective emulsifier in foods (Lesson 2).

When considering the variety of soy-based foods that are available, students will be asked to note the differences in shelf life based on processing and formulation. In addition to the macromolecules, water is another major component of foods and a significant indicator of shelf life. Therefore, a correlation exists between shelf life and water activity so that changing the availability of water in a food will limit the ability of many spoilage microorganisms to grow (Lesson 3). Another method of shelf-life extension is fermentation wherein the growth of fermentative organisms leads to the production of metabolic byproducts (acid, ethanol, flavor compounds) that contribute to food’s sensory appeal, safety, and preservation. In this final activity, students will create a fermented soybean product, natto, that has significantly different attributes then unfermented soybeans and which has been consumed as a regional source of dietary protein (Lesson 4).

It should be noted that in the field of food science, the majority of experiments and activities are not destined for consumption by the scientist. Therefore, none of these activities produce food for students to eat. This is most important if the teaching space in not a food safe area, because allergies exist, and, in the case of Lesson 4, because fermentations which are not well controlled can lead to the outgrowth of pathogens.

Authors

Abigail B. Snyder
Ph.D. Student, Cornell University
Department of Food Science

Charles T.C. Day
Research Technician, Cornell University
Department of Horticulture

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