🍲 Food Composition — Carbohydrates

This lesson explains core food science and nutrition concepts with practical relevance to food quality, safety, and human health.

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Food Composition — Carbohydrates

Overview

Carbohydrates are the most abundant organic compounds in nature and serve as the primary source of energy in the human diet. They are composed of carbon, hydrogen, and oxygen and are classified based on the number of sugar units they contain. Carbohydrates provide approximately 4 kcal of energy per gram.

Classification

Monosaccharides

These are the simplest sugars that cannot be hydrolyzed further. Important monosaccharides include:

• Glucose — the most common sugar in nature, found in fruits and honey; serves as the primary energy source for the body
• Fructose — the sweetest natural sugar, abundant in fruits and honey
• Galactose — a component of lactose (milk sugar)

Disaccharides

Disaccharides are formed by the condensation of two monosaccharide units:

• Sucrose (glucose + fructose) — common table sugar from sugarcane and sugar beet
• Lactose (glucose + galactose) — milk sugar; some individuals lack lactase enzyme causing lactose intolerance
• Maltose (glucose + glucose) — formed during starch digestion and in germinating cereals

Polysaccharides

These are high molecular weight polymers of monosaccharides:

• Starch — the main storage polysaccharide in plants, found in cereals, tubers, and legumes; composed of amylose (linear) and amylopectin (branched)
• Glycogen — the animal storage polysaccharide, stored in liver and muscles
• Cellulose — structural polysaccharide in plant cell walls; indigestible by humans but important as dietary fiber

Dietary Fiber

Dietary fiber refers to the non-digestible carbohydrates and lignin that are intrinsic and intact in plants. It is classified as:

1. Soluble fiber — pectin, gums, beta-glucan; helps lower blood cholesterol and regulate blood sugar
2. Insoluble fiber — cellulose, hemicellulose, lignin; promotes bowel regularity and prevents constipation

The recommended dietary fiber intake is 25–30 g per day for adults. Major food sources include whole grains, legumes, fruits, and vegetables. Dietary fiber plays a protective role against cardiovascular disease, type 2 diabetes, and colorectal cancer.

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	Carbohydrates in food — monosaccharides, disaccharides, polysaccharides, and dietary fiber.
Section context	Revise this lesson with the rest of Principles of Food Science and Nutrition for stronger conceptual continuity.