Measurement of colour

Food Standard and Quality Control

Lesson 07 : Determination of quality of foods- objective methods

Measurement of colour

Colour is the first quality attribute a consumer perceives in food. Change of colour is generally accompanied by flavour changes.

Spectrophotometer: Visual matching of colours is subject to shortcom­ings of human observers. To overcome this spectrophotmeter can be used. In this, tube with the liquid is placed in a slot and light of selected wavelength is passes through the tube. This light will be differentially absorbed depending upon the colour of the liquid and the intensity of the colour. Two liquids of exactly the same colour and intensity will transmit equal fractions of the light directed through them. If one of the liquid is a juice and the other is the juice diluted with water, the latter sample will transmit a greater fraction of the incoming light and this will cause a proportionately greater deflection of the sensing needle on the instrument. Such an instrument can also measure the clarity, cloudiness of a liquid depending on the amount of light the liquid allows to pass.

Taste measurement:

The Electronic Tongue is designed for taste analysis of liquid matrices such as gels, syrups, solutions, emulsions or solids dissolved in liquid solution.

Principle: Chemical compounds responsible for taste are perceived by human taste receptors, and the seven sensors of electronic instruments detect the same dissolved organic and inorganic compounds. Like human receptors, each sensor has a spectrum of reactions different from the other. The information given by each sensor is complementary and the combination of all sensors results generates a unique fingerprint. Most of the detection thresholds of sensors are similar or better than those of human receptor s

Flavour measurement:

Electronic nose:
The electronic nose was developed in order to mimic human olfaction that functions as a non-seperative mechanism: i.e. an odor / flavor are perceived as a global fingerprint. Electronic Noses include three major parts: a sample delivery system, a detection system, a computing system

Last modified: Thursday, 16 February 2012, 9:36 AM