Judging of milk refers to the evaluation of its "quality" on the basis of various attributes. Grading refers to the classification of milk into different grades. The ‘ quality' of any dairy product is determined by organoleptic/sensory tests, smell taste, touch and sound. Of these, taste and smell are the most important in judging and grading. Based on the quality as determined by the evaluation of the milk, samples could be broadly classified into two categories: acceptable and rejected.
The samples which are grouped under "acceptable category" can further be differentiated in grades. This classification is based on physical characteristics such as colour, smell, taste and presence of visible foreign material in milk. The evaluator makes use of the most sensitive organs viz. eyes, nose, tongue and hands.
The quality of milk of various grades is described here.
This includes the fresh milk completely free from off-flavours, abnormal colours and visible foreign materials, such milk when tested should give over five and half Methyl Blue Reduction (MBR) time.
Milk having off-flavours such as cowy/barny, flat, foreign, metallic, or rancid to a moderate degree and MBR time between two and half hours to five and half hours. Presence of small amounts of foreign material placed under this category. The off- flavours present in grade II milk could be easily removed by suitable processing techniques.
Milk having off-flavours such as acidic, bitter, weedy, oxidized, metallic and extraneous material distinctly visible in great amount is classified as grade III milk. This milk has less than two and half hours MBR time. It is difficult to remove completely the off-flavours by easy processing techniques. Such milk is not considered suitable for market milk operations. It is generally separated and cream is used for making ghee and skim milk for casein manufacture.
Fundamental Rules for Judging Milk
While judging 'the quality of milk, the evaluator must keep following points in mind. The person should :
-be in physically and mentally in sound condition before scoring.
-know the score card or ideal set up for each product.
-learn the grades of each product and defect intensities allowed in each grade.
-have the samples at proper temperature e.g. ice-cream at 20.6 to 23.3°C, butter, cheese and milk at l5o Centigrade.
-observe the aroma immediately after removal of the sample and introduce into the mouth a sufficiently large volume for tasting.
-observe the sequence of flavours and make a mental picture of the taste and smell reactions and concentrate upon the sample being examined.