The fresh milk drawn from the cows udder is normally 6. More acidic implies more bacteria Therefore milk cannot be commercialized. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel.
Carousel Previous. Carousel Next. What is Scribd? Uploaded by Yuviraj Putten. Document Information click to expand document information Description: This presentation is about tests performed on milk to determine fat and protein content.
Did you find this document useful? Is this content inappropriate? Report this Document. Description: This presentation is about tests performed on milk to determine fat and protein content.
Flag for inappropriate content. Download now. Compositional Quality of Milk. Images Donate icon An illustration of a heart shape Donate Ellipses icon An illustration of text ellipses.
Determination of the specific gravity of milk; the percentage of acid and casein in milk; the adulteration of milk by skimming and watering; the percentage of water and salt in butter; the percentage of fat and water in cheese. Item Preview. EMBED for wordpress. Want more? Such a sample is placed in a properly labeled bottle and tested after a week or so.
The results obtained would give an average figure for the total amount of milk received during the period covered by the composite sample. The system is accurate, simple and saves labour and time. Since composite samples are kept for long periods, preservative needs to be added to prevent souring. The preservatives commonly used are mercuric-chloride 0.
Composite samples to which mercuric-chloride has been added should be coloured to prevent any body mistaking the bottles for normal milk as it is a violet poison. Composite samples should preferably be not kept for longer than ten days. The sample bottles be kept at a cool dark place not exposed to the sun. They better be kept locked so that they cannot be tempered with. Each bottle should be shaken daily to prevent its getting hard and dried on the top of the fluid. When it does become hard and dried, the best is to mix the contents with a small brush and warm the bottle but the heat applied should not be more than Why is it necessary to mix the whole body of milk before obtaining a sample from it?
What is a representative sample of milk? Differentiate between an individual sample and a composite sample of milk? Milk, when freshly obtained, is a white, opaque fluid when seen in bulk and has a characteristic faintly sweetish taste and peculiar odour.
Sweetness is due to its lactose milk sugar content. The taste and odour can be best appreciated when they are absent as in case of heated milk which loses some of its fine flavour. The taste of milk is satisfying, pleasant and somewhat sweet and the smell is reminiscent of the animal but not unpleasantly so.
The so called cowey odour is due to manure gaining access into milk and due to the absorption of the characteristic odour from the atmosphere of dairy sheds. The white colour of the milk is due to the calcium-caseinate content and the opacity is due to the same substance and fat.
Sometimes a more or less yellowish tinge is noticeable, that is due to a pigment lactochrome associated with the fat.
During the colostral period and near the end of the period of lactation, milk may acquire saltish or bitter taste and rancid animal like odour. This odour varies in intensity. The development of bitter taste in milk in late lactation is due to the activity of lipase enzyme which hydrolyses milk-fat. Abnormal odours may also be a result of the diseased udder or the growth of bacteria in milk.
Further, certain aromatic feeds also impart a chraceristic odour and taste to milk such as rape, cabbage, beets, turnips, carrots, etc. Among the wild plants the garlics have such strong oniony flavour that the milk of dairy animals which eat them may become quite abominably tainted.
In such cases it is desirable to take immediate steps to eradicate all such plants from the feed of milch animals.
A blue tinge in milk may indicate a low percentage of fat due to either skimming or watering. The activity of peptonizing bacteria in milk may produce a bitter taste due to the production of peptones and later a foul and unpleasant odour and taste due to decomposition.
Bacilli of the Coli aerogenes group, so commonly present in excreta of animals, may produce an unclean and even nauseating taste with a manure like odour, when they contaminate milk.
Lactic acid bacteria render the milk sour and acidic in taste. The so called soapy milk is caused by the development of specific microorganisms in milk Bacillus sapolacticum. Certain metals may have adverse effect on the flavour of milk which comes in contact with them. Thus copper and copper alloys such as nickel, brass, bronze, etc. The tallowy flavour may also develop due to exposure of milk to direct sunlight.
The amount of dirt in milk must be taken into account since it is a carrier of bacteria. Moreover visible dirt is an indication of the care exercised in milk production. In any report on the examination of milk, its general appearance must be mentioned along with any marked change in the normal odour, colour, consistency, etc.
General appearance: Note whether clear or any visible dirt or foreign matter is present. If so describe its nature. Odour: Record odour as normal, none, very mild, or strong cowey, manure like, fishy, turnippy, oniony, etc. Heat accentuates any undesirable odours present.
If the titre value exceeds 1. Add 3 drops of paraphenylene diamine and shake well. Change in colour of the milk to blue confirms that the milk is adulterated with hydrogen peroxide.
To 10 ml of milk sample in a test tube add drops of Vanadium Pentoxide reagent and mix. The development of pink or red colour indicates presence of hydrogen peroxide. Take 10 ml of milk in a test tube. Add 5 ml conc. If a violet or blue ring appears at the intersection of the two layers, it shows the presence of formalin. Note violet coloration usually does not appear when relatively large quantities of formaldehyde are present.
Add 5 ml of hydrochloric acid along with 0. Shake the test tube well and place it in a boiling water bath for 5 min. Appearance of red colour indicates the presence of added cane sugar in milk. Wheat flour, arrowroot, rice flour, etc. Take 3 ml milk in a test tube and boil it thoroughly. Cool the milk to room temperature. Change of colour to blue indicates that the milk is adulterated with starch.
Take 3 ml of milk in a test tube. Keep the test tube in a boiling water bath for 3 min and then cool it for 2 min by immersing it in tap water without disturbance.
Add 1 ml of phosphomolybdic acid and shake. If blue colour is visible, then glucose is present in the milk sample. If the solution turns distinct yellow in colour, then the given sample of milk contains urea. Control, normal milk may show a faint yellow colour due to presence of natural urea. Take 5 ml of milk in a test tube.
0コメント