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Ageing of milk

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AIM: To investigate the increase of enzyme production with the ageing of milk. Introduction: Milk is an opaque white liquid produced by the mammary glands in female mammals. Milk has many uses; milk is used to provide good nutrition to infants mammals that are usually fed through breast feeding (reference 1), furthermore it used industrially to make cheese, yoghurt, chocolate, butter, ice creams, cakes, it can be used therapeutically for skin and can be ingested raw. In 2005 14, 577 (1000 tonnes) of milk was produced and has risen since (reference 2). Pasteurization is used to kill harmful microorganisms by heating the milk for a short time and then cooling it for storage and transportation, this process is carried out because raw milk from cows contain a lot of bacteria by pasteurizing the milk, it means a lot of the harmful bacteria are killed. Milk can be heated further to extend their expiring dates and to preserve it, through ultra heated temperature which allows it to be kept un-refrigerated (reference 3). So how do we know when milk is going to go off? Expiring dates which indicates the products shelf life of a product, the shelf life is influenced by temperature, moisture, gas diffusion and physical impacts. This gave me the idea of carrying out an experiment involving the ageing of milk, and how the influence of temperature affects the ageing process. ...read more.


Place the first colorimeter tube with the methylene blue and milk solution in the colorimeter and press the test ("T") this should give a reading for the solution, repeat this for the rest of the other five solutions, once the readings have been recorded, discard of the diluted solutions and leave the original solutions in their appropriate conditions for another day. The next day repeat the same dilution procedure remembering to use the same colour filter, place all the diluted solutions in the colorimeter and take a recording of the readings, discard of the diluted samples and store the original samples in their appropriate conditions and leave for one more day. By the third day the colours should become noticeably different in contrast, repeat the same dilution procedure once again, remembering to use the same colour filter, place all the diluted solutions in the colorimeter and take a recording of all the readings, then discard of all the diluted solutions. If more readings need to be taken the original solutions can be left for another day and recorded to a get more accurate average of all the readings, if the solutions are no longer needed then all the original solutions may be discarded. (Reference 4) Prediction: My prediction is that the pasteurized milk will produce more enzymes than UHT milk, and will therefore decompose at a faster rate than the UHT milk making its shelf life much shorter than that of UHT. ...read more.


Dependent variable: In this experiment the methylene blue and milk solution was the dependent variable by leaving the solutions in a variety of conditions, in the incubator, at room temperature, and in the fridge, we are able to observe and analyse how temperature affects the rate at which the milk spoils. Using methylene blue dye the more enzymes produced by the increase in temperature, the clearer the dye would go until it went colourless, using a colorimeter to help collect accurate readings an results, by measuring the absorbance, the more enzymes that was produced the clearer the solution would go and the lower the absorbance readings, the absorbance of the solution was measured over a period of three days. Controlled variables: * The six solutions of milk were all made on the same day so the rate at which the milk spoilt stayed the same. * The same milk type was used for each of the solutions. * Each of the solutions was repeatedly left in the same conditions they originally were in. * All milk solutions were diluted with the same volume of water. Results: 1st day TYPES OF MILK CONDITIONS Pasteurized milk (A) UHT (A) Warm 0.56 0.60 Room Temp 0.58 0.64 Cold 0.60 0.78 2nd day TYPES OF MILK CONDITION Pasteurized milk (A) UHT (A) Warm 0.40 0.45 Room temp 0.47 0.54 Cold 0.56 0.76 3rd day TYPES OF MILK CONDITION Pasteurized milk (A) UHT (A) Warm 0.32 0.44 Room temp 0.42 0.50 Cold 0.53 0.70 ...read more.

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