BT404 Handouts

Lecture 1

INTRODUCTION TO FOOD, DEFINITIONS AND BASIC CONCEPTS

Module 1: Introduction to Food, Definition and basic concepts

Food Science The study of food science involves understanding the nature, composition and behavior of food materials under varying conditions of growth, harvest, transportation, processing, storage, handling and use.

Food Technology: is the application of food science & engineering principles to the selection, preservation, processing, packaging, distribution, and use of safe, nutritious, and wholesome food.

Food Biotechnology:

Application of technology to modify genes of animals, plants, and microorganisms to create new species which have desired production, marketing, or nutrition related properties. Called genetically engineered (GE) or genetically modified (GM) foods.

Food Security: Food security is achieved when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life. (800 million people suffer from hunger).

Nutrition:

“The science of food, the nutrients and substances therein, their action, interaction, and balance in relation to health and dis-ease, and the process by which the organisms ingest, digest, absorb, transport, utilize, and excrete food substances” (The Council on Food and Nutrition of the American Medical Association).

Food is required for four main reasons:

as a source of energy; as a source of raw materials for growth and development; to supply minute chemicals that serve to regulate vital metabolic processes; to supply food components (phytochemicals) that retard the development and progression of degenerative diseases.

Module 2: Food composition

Carbohydrates

Carbohydrate is the collective name for polyhydroxyaldehydes and polyhydroxyketones, and these compounds form a major class of biomolecules that perform several functions in vivo, including the storage and transport of energy. Indeed, carbohydrates are the major source of energy in our diet. The name carbohydrate derives from their general empirical formula, which is (CH2O)n; however, the car-bohydrate group contains several derivatives and closely related compounds that do not fit this general empirical formula but are still considered to be carbohydrates. There are three distinct classes of carbohydrates: monosaccharides (1 structural unit), oligosaccha-rides (2–10 structural units) and polysaccharides (more than 10 structural units).

Module 3: Water Contents in foods

It exists in three forms in foods

1. Free Water: This is form of water that retains its physical properties and hence acts as dispersing agent for colloids and solvents of choice.

2. Chemically adsorbed water: This water is held tightly and it is componenet of cell walls or protoplast and is held tightly with proteins.

3. Chemically bound water: This is form of water that is bound chemically, i.e. lactose monohydrate or also in form of some salts Na2So4.10H2O etc.

Module 4: Carbohydrates Contents of food

The monosaccharides are also termed simple sugars, are given the suffix -ose and classified as aldoses or ketoses depending on whether they contain an aldehyde or ketone group. The most common monosac-charides are either pentoses (containing a chain of five carbon atoms) or hexoses (containing a chain of six carbon atoms). Each carbon atom carries a hydroxyl group, with the exception of the atom that forms the carbonyl group, which is also known as the reducing group. Monosaccharides are assigned optical configurations with respect to comaparison of their highest numbered asymmetric car-bon atom to the configuration of D-glyceraldehyde or Lglyceraldehyde. By convention, the carbon atoms in the monosaccharide molecule are numbered such that the reducing group carries the lowest possible number; therefore, in aldoses the reducing group carbon is always numbered 1 and in ketoses the numbering is started from the end of the carbon chain closest to the reducing group. Most naturally occurring monosaccharaides belong to the D-series, i.e. their highest numbered carbon has a similar optical configuration to D-glyceraldehyde.

Oligosaccharides

Oligosaccharides contain 2–10 sugar units and are water soluble. The most significant types of oligosac-charide occurring in foods are disaccharides, which are formed by the condensation (i.e. water is eliminated) of two monosaccharide units to form a glycosidic bond. A glycosidic bond is that between the hemiacetal group of a saccharide and the hydroxyl group of another compound, which may or may not be itself a saccharide. Disaccharides can be homoge-neous or heterogeneous and fall into two types:

Non-reducing sugars in which the monosaccharide units are joined by a glycosidic bond formed be-tween their reducing groups (e.g. sucrose and tre-halose). This inhibits further bonding to other sac-charide units

Reducing sugars in which the glycosidic bond links the reducing group of one monosaccharide unit to the non-reducing alcoholic hydroxyl of the second monosaccharide unit (e.g. lactose and maltose). A reducing sugar is any sugar that, in basic solu-tion, forms an aldehyde or ketone allowing it to act as a reducing agent, and therefore includes all

Of the disaccharides, sucrose, trehalose and lactose are found free in nature, whereas others are found as glycosides (in which a sugar group is bonded through its anomeric carbon to another group, e.g. a pheno-lic group, via an O-glycosidic bond) or as building blocks for polysaccharides (such as maltose in starch), which can be released by hydrolysis. Probably the three most significant disaccharides in food are su-crose, lactose and maltose.

Sucrose is the substance known commonly in households as sugar and is found in many plant fruits and saps. It is isolated commercially from sugar cane or the roots of sugar beet. Sucrose is composed of a-D-glucose residue linked to a b-D-fructose residue and is a non-