Sunday, October 10, 2010

Milk Testing Procedure

Fat & SNF of milk is tested for each batch for each silo milk for standardization purpose and also for finished milk so as to ensure that milk is ready for dispatch. Fat and SNF is tested using a milcoscan. The temperature of the sample should be 84 degree F Heat. It is a latest technical machine for scanning of milk and uses I.R rays to analyze milk for Fat, SNF, Protein, Carbohydrate, TS.

• Draw milk sample from outlet valve and note the homogenization pressure.
• Take 10 ml milk in centrifuge and see for any fat separation.
• If doubtful, prepare a slide and observe under micro scope the size of fat globule should not be more than 2 microns.
• In case unsatisfactory, the matter and cause is seen into.

This test is based on the principle that methyl blue (an oxidation-reduction dye or indicator) which is blue in its oxidized state, is reduced to colorless compound (leuco form) as a result of the metabolic activities of bacteria in milk. When a solution of dye is added, the organisms present in milk consume the dissolved oxygen and lower O-R potential to a level where methyl blue or similar indicators are reduced or decolorized.
Take 10 ml of milk in a sterilized MBR tube. Add 1 ml of MBR dye. Plug with a sterilized cork. Invert the tube to mix the contents and incubate at 370C in a water bath. Check the tube for de-coloration first after 10 minutes and subsequently every hour milk. For pasteurized milk time should be 5 hrs or at least 4 hrs. Whereas for raw milk time is 30min.
Keep milk samples of first and final testing in sterilized 125 ml glass bottle in incubator at 37°C.Note the time. Check for COB after 3 hrs first and then every hour till it becomes COB positive. Note down the % TA. Note total hours taken for milk to become COB positive. Observe for any abnormality such as cream layer, fat or powder separation
Take 10 ml milk sample to it add 10 ml distilled water add Phenolphthalein and titrate against N/10 NaOH.
Acidity% = titrate value x.09
Titrable acidity of milk from PM silo should not be greater than .14.
Take 2 ml milk in a test tube and kept in a boiling water bath for 5 min. The formation of curd indicates the poor heat stability and hence the positive COB test.
To 2 ml Rosalic acid in a test tube add 2 ml of milk. Rose red color indicates neutralizer present in milk and formation of flakes indicates disturbed salt balance. The neutralizer test results of processed milk should be negative so as to ensure that there is no misappropriation or mishandling during processing. After ensuring that fat percentage is 3.05 and SNF 8.58 minimum and all other tests are giving satisfactory results the milk is send or marked for dispatch.
Procedure for Final Inspection & Testing of Milk
(1) Samples are drawn from filled dispatch tankers parked in the hard parking bay. Normally temperature of milk in tanker is checked from the sample drawn from delivery valve. If temperature is found more than 7°C it is confirmed by taking sample from the top. Sample of few tankers is checked from top also for observation, temperature and MBR.
(2) The sample are tested for neutralizer test and for fat and SNF. If sample meets the requirements, the tanker is accepted and recorded. Few tankers are also tested for MBRT and if the MBRT of a tanker is found to be less than 4 hrs, milk of tanker is called back from retain outlets.
(3) If it fails to meet Mother Dairy dispatch standards, the tanker is rejected and shift in charge is informed.
(4) The system is so made that weighment of milk for dispatch is done only when the test results are found correct so as to ensure that quality milk leaves Mother Dairy.

(1) Regeneration-I : The milk is pumped to the balance tank from there the milk is pumped to regeneration-I wherein it gets heated to about 40-45°C because of outgoing milk and hence reducing its temperature. Regeneration system helps in energy saving both for heating as well as cooling milk
(2) Clarification: Clarification is the process of removing suspended foreign by centrifugal sedimentation – clarifies are used for this purpose.
(3) Regeneration-II The milk from clarifier is sent to regeneration-II wherein the milk is further heated by the pasteurized milk hence raising the temperature of incoming milk and reducing the temperature of outgoing milk and also regeneration-II raises the temperature of milk so as to enable efficient homogenization which is the next step.
(4) Homogenization: - Homogenization is a process wherein fat globules are broken down to 2 microns or less under high pressure Homogenizer is a machine which causes sub-diversion of fat globules. It consists of a high-pressure piston pump that forces the milk and thereby subdivided into smaller particles of more uniform size.
Effect of homogenization
The fat globules of milk are surrounded by a membrane 5-10 mm thick. The membrane has properties of an emulsifier and keeps the emulsion, milk stable. During homogenization the original membrane is destroyed and the first result is a rise in interfacial tension soon falls again. The new emulsion therefore remains stable even after homogenization.
Homogenization effect is produced by three collaborating factors:
1. Passage through the narrow gap in the homogenizer head at high velocity subjects the fat globules to very powerful shear forces, which deforms elongate and shatter the spherical globules.
2. The acceleration of the liquid in the gap is accompanied by a pressure drop. This creates cavitations in which the globules are subjected to powerful implosive forces.
3. Further shattering takes places when the fat globules impact at high velocity in the homogenizing head"