Food rheology

Food rheology
Many objective methods for measurement of food quality involve measurement of some aspect of texture, such as hardness crispness or consistency.

Texture is related to the rheological properties of food, which determine how is responds when subject to forces such as cutting, shearing or pulling.

Rheological properties can be divided into three main categories. A food may exhibit elastic properties, viscous properties or plastic properties or a combination.

There are many areas where rheological data are required by the food industry:

• Plant design: pumps and pipe sizing and selection, heat transfer calculations filler design and other process engineering calculations involving extruders, mixers, coaters and homogenizers.
• Quality control: both of raw materials and the product at different stages of the process (including ingredient functionality determination in product development an also shelf life testing).
• Evaluation of sensory attributes: quantitative measurement of consumer determined quality attributes by correlating rheology measurements with sensory data.
• Assessment of food structure and conformation of molecular constituents.

Food rheology is often confined to the behavior of liquid foodstuff. However, there is an increasing tendency to consider the response of both solid and liquid materials to applied stresses and strains as being two extremes of the same science.

There are in fact some foods that will exhibit either behavior depending on the stress applied; molten chocolate, fat based spread mashed potato and some salad dressings will exhibit a solid like behavior at low stresses and a liquid like behavior at high stresses.

This tendency is increasing as more food products are developed that would be classed by the consumer as being semisolid or semi liquid.

A more exact definition would therefore be the study of both the elastic and the plastic properties of foods.
Food rheology