Investigating the effects of temperature on the rate of clotting milk and Rennet

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GSCE Biology Coursework: Investigating the effects of temperature on the rate of clotting milk and Rennet

Introduction

 The following experiment investigates the effects of different temperatures on a mixture of rennet and whole milk. On having the choice between testing the mixtures reactions at various temperatures, or testing the mixture with various amounts of concentration of rennet, my partner and I decided upon the first option. We made this decision as we felt it would be valuable to our scientific knowledge if we had a better understanding of how different temperatures can effect the behaviour of an enzyme, such as Rennin, which is also known as Chymosin. Our scientific knowledge tells us that enzymes work most efficiently at specific temperatures, and this experiment helps us to discover exactly which temperatures they are.

   It is important to remember that the Rennet was mixed with milk, which is perhaps one of the most important sources of nutrition in the world, and drunk by billions of people everyday. It is particularly important to babies and growing children. It provides:

  • Calcium, to build strong bones and teeth
  • Protein, to build and repair muscle tissue
  • Potassium, to help regulate our body’s fluid balance
  • Vitamin A

And many other useful vitamins and nutrients which help to maintain a healthy body.

   As wonderful a necessity that milk is, it is also an extremely perishable food.  Milk is usually stored in the fridge, because it preserves better at a low temperature, but even so, once it has passed its sell by date, it is no longer suitable for consumption. Although the milk itself does not have a very long life, other foods and some dairy products can be made using it. Cheese would be the main example of this, which can be produced simply by the curdling of milk. Rennin, found in the substance rennet, is a milk-coagulating enzyme capable of assisting in the production of cheese. Therefore the temperatures at which the milk and rennet coagulate best at in this experiment, are going to be the most suitable temperatures for manufacturing cheese.

  Rennet can be obtained from the stomachs of young milk-fed mammals, namely calves where the lining of the fourth stomach (the abomasum) is a good source of the substance. Rennet contains the enzyme named Chymosin (Rennin). Chymosin plays a vital part in the digestion of milk inside the calf’s stomach. It’s job is to coagulate or curdle the milk, and if this wasn’t done then the milk would flow rapidly through the calf’s digestive system, not allowing the absorption of important proteins.

  Rennin having the ability to coagulate milk means that it was widely used in cheese making, as I mentioned before. A few of the cheese made by using animal rennet are:

*English Stilton
*Blarney Irish
*Blue Danish
*Cheddar Canadian Sharp
*Cheddar Tillamook
*Cheddar Wisconsin Aged
*English Cotswold
*Blue Castello
*English Huntsman
*Cheddar Wisconsin Black Wax
As cheese is made in such vast amounts in today’s world, there are not sufficient calf’s stomachs to supply the amount of Rennet required, so alternative sources have been found. For example there are liquid forms and tablet forms of Rennet which don’t actually contain Chymosin, but any form of enzymatic preparation that clots milk is called “Rennet”.

  The Rennet used in this experiment however is animal rennet, which does contain the enzyme Chymosin. By having the scientific knowledge prior to this investigation that enzymes are biological catalysts, it is clear that the Chymosin will be capable of speeding up a reaction of some sort.

 Enzymes can be used in both anabolism (the build up of simple chemicals into complex ones) and catabolism (the breakdown of complex chemicals into simpler ones). Enzymes are most commonly used in Catabolism, this particularly applies to animal digestive systems.

Most enzymes are proteins, and they can alter the rate of reaction without themselves being changed because they have catalytic properties. There are four key factors that affect enzyme activity and they are:

  1. The concentration of the enzyme
  2. The concentration of the substrate
  3. The temperature the enzyme is held at
  4. The pH
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  This experiment proves how key factor three (the temperature) really does affect the activity of Chymosin and how the enzyme works at particular temperatures.

  According to the kinetic theory, when the temperature of the surroundings increases, the molecules will move faster and the rate at which the product is made will also increase because the enzyme and substrate molecules meet more often.  

  Above 40 degrees Celsius the rate of reaction stops rising, and even though the enzymes might be causing a reaction to occur, they are doing it at a slower rate.

  At 60oC the ...

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