Food Composition

Abstract

Food composition is commonly discussed from a nutritional point of view, focusing on the three main chemical groups present in foods, i.e., carbohydrates, proteins and lipids, and on their role as sources of macronutrients and of food energy. The approach adopted in this book differs somewhat from that convention. The first three topics discussed in the present chapter adopt a focus on those food components that represent, or contribute significantly to, food structure. Structure after all is the primary identifying feature of any object, including foods and beverages. Structure expresses the relationships between the individual components that make up complex systems. It plays an important role in various aspects of food quality, in particular, sensory quality attributes, such as appearance and texture, and the microbiological quality of foods. Texture relates to the ease with which a food may be manipulated in the mouth, e.g., chewability and swallowability, important in terms of foods targeted at young children. Man-made foods are often designed specifically to create textures that consumers find interesting or attractive, and these are not always modelled on familiar natural foods. For example, extruded snack products tend to be valued especially for their texture which, in the case of starch based products, is typically light and crispy. Gels, such as tofu, also provide man-made structures with textures attractive to consumers. Food structure affects the order and rate of release of flavour-active components from the food matrix during eating. Integrity of structure plays an important role in the access to foods by spoilage microorganims, and different areas and phases (aqueous, lipid-based) within complex foods allow different types of microflora to become attached to, and develop in them. Structure also affects the suitability of a food for different types of processing. Different cuts of meat demand different culinary treatment or processing, and different varieties of a fruit or vegetables have different suitability for processing, e.g., drying, freezing or heat preservation. Food processing often affects structure in a way that alters appearance. For example, meat and fish turn from a translucent to an opaque state as a result of heat- or freezing-induced protein denaturation.