Various measures are taken to contain the menace of adulteration; including regulatory monitoring, enhancing awareness in the communities, extensive testing/analysis of raw milk, etc. Analysis is one of the essential part of overall quality assurance system operated by dairy plants. Various analytical methods are used for the purpose of checking adulteration of milk including physical methods, instrumental methods and chemical methods
Physical methods
Methods based on physical properties of milk are density (lactometer reading), freezing point, refractive index, etc, which are easy to perform, but can be very easily manipulated due to natural variations in milk composition. Physical methods are simple, fast, easy, cheap and convenient. However, sensitivity of these tests are less in comparison to chemical and instrumental methods.
Freezing point can be significantly affected by seasonal and regional factors. Thus, considering geographical vastness of India and consequent seasonal and regional variation it cannot be a reliable means of adulteration detection.
The density (or specific gravity) depends on composition, temperature and temperature history of milk. As Indian dairy sector is still predominantly unorganized in nature; it is difficult to control most parameters affecting density. Therefore, density measurement cannot be a useful tool for adulteration detection.
Thus, physical methods suffer from some of the general limitations due to large natural variations, lower sensitivity, poor specificity, proneness to manipulation, etc.
Instrumental methods
Instrumental methods are one of the good option for quality control of milk and milk products. Though, it possesses several advantages like higher sensitivity, high specificity and reliability, it also suffers from several limitations as described below.
- Very limited adoptability for practical applications.
- Requires high initial investment, operational cost and expensive maintenance.
- Most methods are time consuming as it necessitates isolation, purification, concentration &/or derivatization of the target analyte.
- Impractical for routine analysis and field applications
As these methods require skilled manpower it is difficult to use as routine methods. Indian dairy industry is still characterised by small scale farming and small cooperative societies which may not be able to afford capital requirements for sophisticated instruments as well as its maintenance.
Chemical methods
The chemical methods are simple, fast, easy, cheap, convenient and have better specificity for adulterant/ chemical compounds being tested. However numerous qualitative tests are reported for detection of adulterants in milk with wide variation in procedure for a given test. There is lack of information regarding sensitivity between various reported qualitative tests. To overcome these limitations various reported tests and procedural variations were evaluated. The list of various reported tests with procedural variations is given in the Table 1. The test which was found most suitable is also mentioned.
