The food, beverage, and confection industry, often referred to simply as the food industry, accounts for a considerable percentage of the gross domestic product in the US, making it one of the largest industries. Most scientists and engineers employed in the food industry fall into three broad categories: chemists; microbiologists; and food, mechanical, and chemical engineers. Chemical scientists improve or maintain the nutritional quality, safety, sensory quality, stability, and/or convenience of food products. Employment opportunities range from large multinational companies, which include ingredient and packaging suppliers, to small local companies.
Food chemists are concerned with the composition and properties of food products and the chemical and physical changes they undergo during postharvest handling, processing, storage, and preparation. Developing and maintaining the quality of food products is accomplished primarily through the application of analytical chemistry, biochemistry, organic chemistry, and physical chemistry; but molecular biology and the biological sciences also are relevant.
In addition to those specifically educated in food chemistry, analytical chemists, organic chemists, natural product chemists, physical chemists, biopolymer chemists, biochemists, and chemical engineers are employed in the food and related industries. Polymer physicists and materials scientists are increasingly in demand.
Foods are complex, heterogeneous biological materials. Some may be respiring (meat, fruits, and vegetables), although no longer growing; some may be capable of growth (seeds and eggs). Food products are most often made from disrupted tissues such as flour; fruit and vegetable purees and juices; and isolated carbohydrates, proteins, and vegetable oils. Food chemists also deal with milk, a biological fluid, and single-cell sources of food such as eggs, yeast, and other microorganisms. Food products are often highly hydrated, but their moisture content may vary from more than 95 percent to less than 4 percent.
Appearance, color, flavor, and texture are important aspects of the organoleptic quality of foods. Texture is the response to forces involved in chewing, swallowing, cutting, or spreading. Texture may be described by qualitative terms such as crispness, firmness, or cohesiveness, and/or quantified by physicochemical measurements. Instability of foods, which limits their shelf life, can be caused by chemical reactions, biochemical reactions, or physical changes. Stability and instability are related to the composition of the food and the physical states, spatial arrangements (supermolecular networks, emulsions, foams, or films), and dynamics of its components.
Desirable and undesirable changes may occur in the texture, flavor, color, nutritive value, and/or safety of the product. Changes in texture may be such things as either a toughening or a softening, a loss or gain in solubility, or a loss or gain in water-holding capacity. Typical flavor changes may be caused by the development of hydrolytic or oxidative rancidity, other off-flavors, cooked or caramel flavors, or other desirable flavors. Typical color changes include darkening or bleaching and the development of desirable colors and off-colors. Changes in nutritive value may arise from either increases in bioavailability or losses of proteins, starch, vitamins, lipids, or minerals. Changes in safety may arise from the development or loss of substances that are protective of health or the generation or inactivation of toxic substances.
The impact of chemistry on food products occurs at all points in the system - during postharvest storage, processing, postprocessing storage, transportation, supermarket and home storage, and preparation. The chemistry may include enzyme- and non-enzyme-catalyzed reactions, which may be desirable or undesirable; changes in physical states of molecules and supermolecular structures; changes in the structures themselves, which are created or broken down via changes in inter- and intramolecular forces; thermodynamics of the reactions and phase changes; kinetics of the reactions and phase changes; and various physicochemical phenomena such as rheology.
Examples of desirable and undesirable reactions that must be controlled can be found in the formation of colors and flavors. In some foods, such as bakery and breakfast cereal products, the formation of brown color (and associated flavors) is desirable (up to a point), whereas in fruit and vegetable products, browning is undesirable. The flavors produced by culturing milk to make yogurt and by frying when making French fries are desirable, whereas the rancid flavor resulting from oxidation of fats and oils, such as in roasted peanuts, is undesirable. Physical changes may be related to glass transitions and, sometimes, subsequent melting of partially crystalline biopolymers. Physical changes also occur in oil-in-water and water-in-oil emulsions, and they may also involve the formation of foams and films. Crystallization is important in either a positive or negative sense in many products. Controlling crystal size is important for forming the right texture in ice cream and chocolate.
Reactions and changes in physical state are functions of processing and storage conditions - for example, normal thermal processing versus ultra-high-temperature processing versus minimal thermal processing, freezing, baking, and refrigeration. The nature of the processing conditions and the resulting chemistry depend on the nature of the end product: canned, frozen, dehydrated, or ready-to-eat meals.
Chemists must be concerned with the public's fear of food additives, which is tied to a fear of chemicals, even though additives are used to improve the quality, variety, convenience, and nutritive value of our food and have been determined to be safe. At the same time, chemists guard against adulteration of food. Over the past two centuries, concern about adulteration of the food supply in the US has been almost eliminated, but food processors must be vigilant in ensuring the purity, safety, and quality of ingredients supplied to them.
Ensuring the safety of food means that chemical and microbiological aspects must be monitored. Chemical safety is ensured primarily by analyzing food for trace residues of pesticides. The most common way to provide microbiological safety, other than thermal processing, is by reducing water activity or lowering the pH, but both influence other attributes such as flavor, color, and texture. Biostatic agents may also be added.
Team approaches are most often used in problem solving. For example, a team might look into a new formulation, devise a new processing scheme, determine the factors affecting storage stability, and troubleshoot problems arising from a new ingredient source or climatic conditions affecting an ingredient. A chemist might have to determine the properties related to safety and quality, decide which specific chemical and biochemical reactions influence the quality or wholesomeness of the product, and apply this knowledge to control these reactions.
Producing more healthful foods is a major thrust of food companies. The variety of approaches includes fortification of foods, work toward understanding the physical and chemical basis of digestibility and nondigestibility, development and use of non-nutritive sweeteners and fat sparers (fat mimetics and replacers), and determination of the physiological role of dietary fiber. Included in this effort is the development of therapeutic and functional foods, that is, foods with definite, specific effects on the prevention, control, or cure of certain diseases.
ChemCenter
Pubs Div. Home Page
