Microscopic examination

Food Standard and Quality Control

Lesson 08 : Objective Methods - Chemical Methods

Microscopic examination

Microscopy techniques can be used to study the quantitative microstructures of materials, ingredients, and in-process and finished products. Images can be created for a broad range of food items, including macrostructures of meats and finished products, such as pizza, and microstructures of products, such as cheeses, doughs and baked goods, ice creams, fruits and vegetables, emulsions, foams, and gels. Microstructures characterized using high-quality imaging techniques illustrate chemical composition and thermo mechanical processing, genetic, and structural properties. Some of the other advantages are as below

Problems identification of finished products using Microscopy


Problem: Unexpected thinning of sauce after retorting.
Microscopic examination: Cooked starch granules are fragmented, and starch granules are overcooked.

Problem: Tapioca-like clumps and brown globules are present in a retorted cheese sauce.

Microscopic examination: The tapioca-like clumps consist of strong bi refringent crystalline particulates typical of certain gums. The brown globules consist of clusters of hydrated gum particulates.

Formed Meats:

Problem: Even though starches were used in a hot dog formulation, the packaged hot dogs are swimming in liquid.

Microscopic examination: Waxy and common starch granules are not optimally swollen; they are disrupted and, therefore, not able to retain liquid. Paper Sizing

Problem: Streaks on the surface of sized paper.

Microscopic examination: Residue from the edge of the trailing blade coater reveals it to be a high concentration of small and large retrograded amylose spherulites.

Tensile strength
An instniment used to find out the tensile strength of chapathi. One end of chapathi is attached to a stand and the other end is attached to a paper glass:
Water is added to the cup till the chapathi breaks. The more water required for the tougher the chapathi.

The compressimeter is related to the shear press, but it measures only compressibility not shear strength. The usual technique for operating the compressimeter is to apply pressure until the sample has been deformed a specific amount and then to measure the force that is required to accomplish this amount of deformation. The greater the force required, the firmer the product.

Warner-Bratzier Shear
It is a device used to measure the tenderness of meat. Meat samples of care­fully controlled dimensions are placed through an opening in a thin metal plate and the force required for two parallel bars to shear the meat as they pass down opposite sides of the place holding the sample is recorded.

Shear press
The shear press, a related device, is a machine that compresses, extrudes and shears the sample at the same time. This is a suitable method for measuring textual characteristics of some fruits and vegetables.

Universal Testing Machine
The Universal testing machine can provide a record showing seven aspects to texture from various food samples. These are cohesiveness, adhesiveness, hard­ness, springiness, gumminess, chewingness and fracturability.

Last modified: Thursday, 16 February 2012, 11:18 AM