Food Composition Fundamentals

Food Composition

• Food products originate from agricultural systems, progressing from farms to consumers.
• Food is composed of plant and animal cells.
• Food is primarily composed of carbohydrates, proteins, water, fat, and vitamins/minerals.
• The proportions and properties of these components influence food characteristics.
• Food composition guides preservation and processing techniques.

Common Food Molecules

• Common molecules include carbon, hydrogen, oxygen, and nitrogen.
• Other ions like calcium (Ca), iron (Fe), sodium (Na), and chlorine (Cl) are present.
• Carbohydrates, lipids, minerals, proteins, water, and vitamins collectively describe food composition.

Proximate Composition

• Proximate composition estimates nutritional composition.
• Components add up to 100%.
• Categorized, not specific molecules for easier determination of storage and shelf life.

Food Composition Examples

• Cooked turkey breast has a high water content, making it easily perishable.

Calculating Proximate Analysis

• Wet basis analysis considers the water content within a food sample.
• Dry basis analysis excludes water content, facilitating comparisons.
• Dry basis is common, particularly in nutrition tables.

Analytical Methods for Food Components

• Water: Determined by weight loss through drying.
• Protein: Measured using the Kjeldahl method, involving sulfuric acid digestion and converting nitrogen to protein.
• Lipids: Extracted using the Soxhlet method with solvent extraction.
• Minerals (ash): Measured via incineration in the muffle furnace.
• Carbohydrates: Calculated by difference after measuring other components.

Calculating Energy Value

• Each macronutrient (carbohydrate, protein, fat, alcohol) has a different energy value per gram.
• Carbohydrates = 4 kcal/g
• Protein = 4 kcal/g
• Fat = 9 kcal/g
• Alcohol = 7 kcal/g
• The energy value is obtained by multiplying the percentage of each macronutrient by its energy value per gram and then by the total serving size.

Carbohydrates: Macromolecules in Food

• Primarily composed of carbon, hydrogen, and oxygen (C_xH_2xO_x).
• Common linear or ring structures with 5 or 6 carbon atoms.
• Functions: Energy source, fiber, enhance flavor, and preservation.
• Simple Structures: Monosaccharides (e.g., glucose, fructose), disaccharides (e.g., sucrose), and oligosaccharides.
• Complex Structures: Polysaccharides (e.g., starch, cellulose, pectin), which have various functions in foods.

Proteins: Macromolecules in Food

• Composed of amino acids.
• Protein structure is determined by the sequence of amino acids, and affects shape and function.
• Organized in levels: primary (amino acid sequence), secondary (a-helix or b-pleated sheet), tertiary (protein 3D structure), and quaternary (multi-protein structures).
• Functions: Emulsifiers, foaming agents, gelling agents, thickeners, and binding agents.

Lipids: Macromolecules in Food

• Composed of fatty acids.
• Categorized as saturated or unsaturated.
• Functions: Source of essential fatty acids, caloric density, providing satiety, medium for heat transfer, and carry fat soluble vitamins.

Water: Essential in Food

• Crucial for all living organisms.
• Water content in food determines its preservation methods and characteristics.
• Water activity (Aw) describes the amount of free water available in food.
• Aw values help predict how food will react, and how microbial contaminants may thrive.

Vitamins and Minerals: Essential Micronutrients

• Primarily found in unprocessed or minimally processed foods.
• Vitamins regulate bodily function.
• Minerals play important roles in structure and energy transfer.
• Flour processing and other thermal processing may change the nutritional profile of foods.