Milk Testing Equipments

We have discussed the general purpose instruments used in chemical and microbiological laboratories and also the instruments used to determine the physical and rheological properties of food and other substances. Sophisticated modern equipments/ instruments which can determine very low concentration of constituents with great precision like rancimate, GLC, TLC, HPLC, GCMS and LCMS have also been discussed. However, these instruments are of general use and can be used in any laboratory for example in pharmaceutical, forensic laboratory, food laboratory etc. On the other hand, there are some instruments which are specifically designed to be used in a dairy laboratory to determine the physico-chemical properties of milk and milk products. Some of these instruments are discussed below.

i. Gerber Centrifuge: Gerber centrifuge is used for the determination of fat in milk and milk products. This centrifuge is different from other centrifuge. It has provision to hold special glass tubes known as butyrometers, time adjustment clock and rotate at fixed speeds.

ii. Lactometer: Lactometer is a special type of hydrometer used for the determination of specific gravity of milk and to calculate the total solids and solid not fat (SNF) in milk. There are different types of lactometers such as zeal lactometer, Quevene type of lactometer and ISI lactometer etc. Lactometer consist a slender glas stem of uniform diameter connected to a large glass chamber, this chamber causes the instrument to float. At the lower end of the body is a glass bulb filled with lead shots or mercury which enable the instrument to sink to a proper level and also to float. Depending upon the specific gravity of milk the extent of sinking of the lactometer gives an idea of the purity of milk.

iii. Milko Tester: There are 3 models mark II, mark III and automatic. The instrument is used for fat determination in milk. It can analyse 80-120 samples/ hour and require very small sample of milk (1.6 ml). The instrument gives results which are comparable to reference method. The instrument determine the fat content on the basis of scattering of light by a diluted sample of milk. Calcium chelating agent eliminate the turbidity caused by the casein micelles, hence the scattering of light is due to the presence of fat globules. The size and number of fat globules influence the result therefore the sample is homogenized in a 4-stage homogenizer to reduce the size of the globules to a specific size.

iv. Electronic Milk Tester with Digital Read out: This instrument is manufactured in the country by the Rajasthan Electronic and instrument Ltd Jaipur. This is a electronic instrument used for determination of fat content of milk.The determination follows the well known principle of dilution, mixing,homogenization and photometric measurement of light scattered by the fat globules present in milk sample. Fat content is displayed quickly and accurately on a digital readout.

v. Infra Red Milk Analyzer (Milko Scan) Lactoscope: This instrument is used for simultaneous determination of Fat, Protein, solid not fat (SNF) and lactose in milk. The infrared milk analyzer measures absorption of infrared energy by carbonyl groups at 5.7 in the easter linkage of fat molecules, by peptides (at 6.46) linkages of amino acids in protein molecules, and by hydroxyl groups of lactose molecules (9.6). The SNF is determined by putting a constant to instrument values for protein and lactose. In 1975, Foss Electric co. intdouced the single cell, dual wavelength infrared milk analyzers (milko scan 203 and 300). In these instruments optical filters isolate the specific wave lengths absorbed by fat, protein and lactose and reference wave lengths not absorbed by these components, thus eliminating the need for a diffraction grating. The 100 series milko scan are the improved version of earlier milk scan. In this series milko scan 133-B is the latest micro processor controlled instrument.

vi. Lacto star Automatic Milk Analyzer: Lactostar-9 new, versatile, esy to operate, microprocessor based, fully automatic milk analyzer determines fat,SNF, proteins, lactose and freezing point of milk. The instrument is introduced in India by Funke Gerber, Germany. It applies a combined thermo-optical method to analyze the milk constituents. It determine the sum of fat and proteins by optical measurement (Turbidemetric), while fat and SNF content are determined by thermal analysis, whereas the lactose and proteins are determined by computationed analysis. The freezing point is predicted on the basis of protein and SNF content.

vii. Lactoscope: Lactoscope from Delta instrument determines fat, proteins,lactose, SNF and total solids in milk and milk products. The instrument is very sophisticated and built for self-service so that any maintenance that is required can be carried out via a modem connected to the manufacture’s head office.