Starch plays various roles in different types of food. To use starch effectively, it’s important to understand how it works in each context. This requires monitoring changes that happen when starch is heated and then cooled, and how these changes affect the structure of the food. It’s also essential to recognize how cooked starch changes during storage and how this affects the food’s texture and appearance. Choosing the right starch for a particular use depends on the desired food properties and the processing and distribution stresses involved.
| Function | Foods |
| Adhesion | Battered and breaded foods |
| Binding | Formed meat, snack seasonings |
| Clouding | Beverages |
| Crisping | Fried and baked foods, snacks |
| Dusting | Chewing gum, bakery products |
| Emulsion stabilization | Beverages, creamers |
| Encapsulation | Flavors, beverage clouds |
| Expansion | Snacks, cereals |
| Fat replacement | Ice cream, salad dressings, spreads |
| Foam stabilization | Marshmallows |
| Gelling | Gum drops, jelly gum centers |
| Glazing | Bakery, snacks |
| Moisture retention | Cakes, meats |
| Thickening | Gravies, pie fillings, soups |
Starch Structures Relevant to Foods
Before cooking in water, starch granules are insoluble and can only absorb a limited amount of water. During cooking, the starch granules absorb water, swell, and break apart to different extents based on the intensity of heating and mechanical shear. The way the starch is distributed between swollen and fragmented granules and solubilized polymers determines the texture, appearance, and stability of the food. Changes can be made to the starch to enhance its performance in the desired form and placement within the food structure. This section explains the changes that occur during cooking and the necessary form that the starch must take to perform its intended function.
Gelatinization and Pasting
Starch undergoes changes when heated in water, known as gelatinization and pasting. Gelatinization is the disruption of molecular order within the starch granule, causing thickening and loss of opacity. Pasting is the phenomenon following gelatinization, where starch dissolves, involving granular swelling and eventually, total disruption of granules. Both terms are general and include various phenomena occurring during starch processing. To characterize a process or product, specific changes in structure, texture, or appearance of the starch paste or food should be referenced. These changes affect the contribution of starch to texture in different ways, necessary for various food functions.
Changes During Cooking
Heating starch in water causes it to swell as the bonds between adjoining polymers are broken. As the granule continues to heat up, it swells to many times its original size, impacting the properties of the starch slurry. Amylose can leach out of the granule during swelling, making the paste cloudy or opaque and causing gelation. Swollen granules are susceptible to disruption, and overcooking can result in rubbery gels, while undercooking produces opaque and watery gels. Achieving the optimum degree of swelling can be difficult due to factors such as heat, acidity, and shear. Unmodified starch has a narrow range of tolerance between undercooking and overprocessing. Some food applications require cooking until all granules are disrupted to achieve gelling, emulsifying, and mouthfeel enhancement.