TLE COOKERY 10 Lesson 2 LO1 PREPARE CEREAL & STARCH Sources of Starch

Summary

The video lesson focuses on the preparation of cereals and starch dishes, highlighting sources of starch from plants, including cereal grains, roots, and tubers. It explains the types and classifications of starches—native, modified, and purified. The lesson covers the molecular structure of starch, including amylose and amylopectin, and their roles in cooking. Key reactions such as gelatinization, retrogradation, and dextrinization are discussed, along with the functional properties of starch in food preparation. It emphasizes the nutritional value of cereals and their importance in a balanced diet.

Takeaways

• 🌾 The main sources of starch come from seeds, roots, and tubers, including cereal grains (corn, wheat, rice, etc.) and tubers like potatoes and cassava.
• 🧬 Starches are composed of two fractions: amylose (contributes to gelling) and amylopectin (contributes to thickening).
• 🥔 Starches can be classified into native starches (naturally derived), modified starches (chemically altered), and purified starches (separated by wet milling).
• 🍚 Native starches are found naturally in plants, while modified starches are chemically altered to change their properties.
• 🔬 Starch molecules are polysaccharides made up of glucose molecules. The organization of these molecules in starch granules creates crystalline patterns observed under polarized light.
• 🍮 Gelatinization is the process where starch granules swell and absorb water, increasing viscosity as starch breaks down when heated.
• 🍯 Sugar influences the gelatinization process by competing for water, which affects the texture and structure of starch-based foods.
• 🍽️ Starch has many functional roles in food, such as acting as a thickener, binder, stabilizer, moisture retainer, and fat substitute in processed foods.
• 🍞 Dextrinization is the process where starches break down into dextrins during dry roasting or heating, such as in toasted bread or sauces.
• 🌾 Cereals, especially whole grains, provide essential nutrients like carbohydrates, proteins, fats, vitamins, and minerals, and enriched cereals offer added vitamins and minerals.

Q & A

What are the common sources of food starch?

The common sources of food starch include cereal grains such as corn, wheat, rice, sorghum, and oats, as well as roots and tubers like potatoes, sweet potatoes, arrowroot, and cassava (tapioca).

What is the difference between native starch and modified starch?

Native starch refers to starch as it is naturally derived from its plant source, while modified starch has been altered physically or chemically to change its key chemical or physical properties.

How is purified starch obtained?

Purified starch is obtained from grains and tubers through a process called wet milling, which uses grinding, screening, and centrifuging to separate starch from fiber, oil, and protein.

What are the two main fractions of starch molecules?

The two main fractions of starch molecules are amylose, a long chain-like structure responsible for gelling characteristics, and amylopectin, a highly branched molecule that contributes thickening properties but does not form a gel.

How do starch granules behave when heated in water?

When heated in water, starch granules undergo gelatinization, where they absorb water, swell, and disrupt their organized structure, increasing the mixture’s viscosity.

What is retrogradation in the context of starch?

Retrogradation is the process where starch molecules, particularly amylose, reassociate into an ordered structure after gelatinization, resulting in a crystalline texture.

What is dextrinization, and how is it achieved?

Dextrinization is the process of forming dextrins, which are partially hydrolyzed starches. It is typically achieved by dry roasting starches, such as toasting flour or bread.

How does sugar affect starch gelatinization?

Sugar influences the temperature and rate of gelatinization by competing with starch for water, which can slow down or alter the process.

What are the functional roles of starch in food?

Starch functions as a thickener, moisture retainer, binder, stabilizer, and fat substitute in foods. It is used in products like gravies, sauces, processed meats, and puddings.

What nutritional value do cereals provide?

Cereals provide carbohydrates, protein, fats, vitamins, minerals, water, and cellulose. Whole grains, in particular, are important for a balanced diet and contribute valuable nutrients like thiamine, niacin, riboflavin, and iron.