Instrumental Methods

Food Standard and Quality Control

Lesson 07 : Determination of quality of foods- objective methods

Instrumental Methods

various parameters such as such as texture, colour and flavour can be assessed by various instruments. Sometimes chemical and physical methods need to be combined with instrumental analysis.

Measuring Texture
Evaluation of texture involves measuring the response of a food when it is subjected to forces such as cutting, shearing, chewing, compressing or stretching. Food texture depends on the rheological properties of the food. Rheology is the science of deformation and flow of matter or, in other words, reaction of a food when a force is applied to it. Does it flow bend, stretch or break etc. for example a good rasagolla( milk based product)when pressed between the figures it should compress and come back to original shape like a spring without any deformation.

There are various instruments to measure each kind of force, many with appropriate descriptive names but none exactly duplicate what occurs in the mouth. Many specialized test instruments have been devised to measure some attribute of texture.

These instruments are used to measure the texture of the liquid and semi liquid foods. The resistance or internal friction to the flow of liquids is normally known as viscosity. Viscosity or consistency is an important factor in influencing the quality of a large number of food products.

The more important among these are salad creams, tomato products, jellies, jams, mayonnaise, syrups, and fruit pulps where the acceptability largely depends on their having proper consistency or viscosity.
Measurement of this factor for the raw material or the product at various stages of manufacture serves as an aid in checking or predicting the consistency of the final product. Further, such quality control measurements also serve as indicators in calculating the amount of an ingre­dient (thickening agent, etc.) that should be added in a particular food product.

Duration and amount of heat applied in a process may also be suitably regu­lated to some extent by viscosity measurements as heat penetration and con­sistency are closely interrelated.

Pecent Sag : It is the unit for measurement of tenderness of product. The depth of a sample such as jelly is measured in its container by using a probe. The product then is unmolded onto a flat plate. The greater the per­cent sag, the more tender is the gel.

Percent Sag = depth in container - depth in plate x 100
Depth in container

Types of viscometers

Last modified: Thursday, 16 February 2012, 9:19 AM