Chocolate Cornstarch Pudding Lab

Aim: To study the effects of cornstarch in the preparation of a simple pudding

Pudding• A starch thickened

desert– A starch is a

polysaccharide made up of 2 fractions: amylose and amylopectin

• Amylose – linear molecule and gives gelling characteristics to cooked and cooled starch mixtures

– Gel: rigid, holds shape of container when unmolded

Pudding- High amylose

starches form films: property used to bind other ingredients

• Amylopection – highly branched and bushy; no gelling properties

• All starches are mixture of amylose and amylopectin

• Plants store starches in their seeds, roots and tubers

Starch Granules

• Starch stored in plant cells and organized in units called granules:– Microscopic, come in

different sizes and shapes depending on the type of starch

• Potato: 10 - 100 um• Corn: 5 - 25 um

Factors That Affect Starch1. Moist Heat → Gelatinization2. Temperature and Time of Heating3. Agitation and Stirring4. pH 5. Addition of Other Ingredients

Gelatinization• As you heat the

starch its granules absorb water and swell → viscosity and thickness increase

• After a period of time the granules gelatinize – Get rigid and take

shape, resulting in a starch paste

Temperature and Time of Heating

• Starch paste prepared most quickly at boiling temp for 1 minute

• Granules swell more quickly at high temperature

Agitation and Stirring

• Stir with uniform consistency for a smooth product

• If agitation is too intense → rupture of granules and decreased viscosity

Other Ingredients• Sugar

– raises temperature at which a starch gelatinizes

→ delays swelling of starch granules decreasing thickness of paste

– It competes with the starch for water

pH

• High acidity causes fragmentation of granules– Decreases the

thickening power

Other Ingredients

• Protein and Fat: – coat the starch

which delays swelling and lowers rate of viscosity development