Food Composition and Proximate Analysis

Food Composition

• Food products originate from agricultural systems, moving from farms to consumers.
• Food is composed of plant and animal cells.
• Food is made up of carbohydrates, proteins, water, fats, and vitamins/minerals.
• The proportions and properties of these components influence the characteristics of food products.
• Composition guides food processing and preservation techniques.
• Common molecules include carbon, hydrogen, oxygen, nitrogen, and ions like calcium, iron, sodium, and chloride.
• Carbohydrates, lipids, minerals, proteins, water, and vitamins make up food composition.
• Proximate composition estimates nutritional composition, totaling 100%.
• Categories are used, not specific molecules, to determine shelf life.
• Water content affects the perishability of food.

Proximate Composition

• Estimates the nutritional content of a food.
• Adds up to 100%.
• Groups food by category rather than specific molecules.
• Used to determine food storage and shelf-life.

Calculating Proximate Analysis

• Wet-basis weight considers water content.
• Dry-basis weight removes water content for comparison.
• Dry-basis analysis is more common for nutritional tables.

Analytical Methods

• Water: Determined by weight loss during drying.
• Protein: Kjeldahl method uses sulfuric acid digestion to measure nitrogen, converting it to protein.
• Lipid: Soxhlet method uses solvent extraction.
• Minerals (ash): Determined by weight in a muffle furnace.
• Carbohydrate: Calculated by difference, subtracting the weights of water, protein, lipid, and mineral components from the total weight.

Energy Value of Food

• Each macronutrient has a specific energy value per gram.
• Carbohydrates: 4 kcal/gram
• Protein: 4 kcal/gram
• Fat: 9 kcal/gram
• Alcohol: 7 kcal/gram
• To determine the total energy value, multiply the percentage of each macronutrient in a serving by its respective energy value per gram.

Macronutrients in Food - Carbohydrates

• Primarily composed of carbon, hydrogen, and oxygen.
• Typically present in linear or ring structures.
• Functions include energy source, fiber component, and flavor enhancement.(hygroscopic).
• Types include simple sugars (e.g., glucose, fructose) and complex carbohydrates (e.g., starch, cellulose).
• Browning reactions (Maillard and caramelization) create characteristic flavours.

Macronutrients in Food - Proteins

• Composed of amino acids.
• Structure: primary (linear sequence), secondary (folding), tertiary (3D structure), quaternary (multiple polypeptide chains)
• Denatured by changes in temperature or pH.
• Functions: emulsifiers, foaming agents, gelling agents, thickening agents, and binding agents. Influencing flavour in foods.

Macronutrients in Food - Lipids

• Composed of fatty acids.
• Exist as oils (liquid at room temperature) and fats (solid at room temperature).
• Contain different ratios of saturated and unsaturated fatty acids.
• Important components for energy, flavor and texture.
• Types of lipids include triglycerides, phospholipids, and sterols.
• Functions include providing essential fatty acids, caloric density, satiety, carrying fat-soluble vitamins, fat transfer in cooking, and emulsification.

Water and Vitamins

• Water is essential for all life processes.
• Water removal is a major method for food processing and preservation to inhibit microbial activity and chemical reactions.
• Water can be extracted by squeezing, pressing, or cutting.
• Water activity (aw) relates to water availability in a food.
• Bound water cannot be easily extracted, and is essential to food quality.
• Water is crucial for dissolving flavors, vitamins, minerals, and is involved in lubrication for chewing and swallowing supporting nutrient digestion.

Micronutrients

• Primarily found in fresh, minimally processed food.
• Can be added through fortification in food processing.
• Micronutrients are essential components in the body (e.g., minerals/vitamins).
• minerals are represented as 'ash'.
• vitamins have functions to control reactions and formation in the body.