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The effect of temperature on the setting time of Junket using rennet.

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The effect of temperature on the setting time of Junket using rennet Introduction When milk is mixed with rennet a reaction occurs and turns the milk into small lumps which then merge to form a lumpy thick liquid that is almost solid. If made in a test tube it can be turned upside down and none will come out. The best way of describing it is that it looks like baby sick. This substance is called junket. Some people mix it with sweet things and serve it as a pudding. The reason for this change is a reaction that goes on inside the test tube or whatever it is being made in. This reaction is because the rennet contains enzymes that convert caseinogen (a soluble protein) in to casein (an insoluble protein). It is found in young mammals including cows and humans. The stuff we use to make it obviously can't come from a human so it is probably cows or a vegetarian substitute. However small children do have it, it is found in gastric glands in their stomach lining the same place as all young mammals do. This is because all mammals share one common thing (well one that's relevant to this experiment) all the females have the ability to breast feed their young. But the milk would go through the digestive system way to fast for them to be able to get all they need from it. So this is where the rennet comes in, it curdles the milk (makes it more solid) ...read more.


* Scrape any solid off of the filter paper and weigh it. In a weighing boat on scales. * Repeat this 3 times for each temperature From the amount of solid gathered you can work out how much set in a minuet and therefore how long it would take to do the whole 5ml of milk. Prediction I would expect that as the temperature increases, the amount of solid would also as the speed of the reaction would increase. When a particular temperature is reached I believe the rate of reaction will dramatically decrease. I believe this because most reactions happen faster when the temperature is higher. This is because at higher temperatures molecules mover around faster, they have more energy and they collide more which makes it easier for them to react together, and because the enzymes are made of protein they work faster the warmer it is. Until they reach their optimum temperature where they are most productive then the rate of reaction starts to decrease. This is because the proteins start to denature and this makes them useless, so in affect you are lowering the amount of working enzymes so of course the reaction rate will go down until suddenly it will stop as there will be no reaction, as all of the enzymes will have denatured and none will be able to take part in the reaction. Actual method Because of a mistake on the preliminary experiment the method has changed back to the original of turning the test tube upside down. ...read more.


By 80OC the rennet was completely denatured. From this information I can conclude that the optimum operating temperature for the rennet is 50�C. Things to improve on I think this experiment did not go to plan as many things went wrong so if I did it again I would sort these problems out for a start. * Was given the wrong milk for first experiment Next time I would check before doing it that all the equipment is there and the right stuff. * Used to much rennet due to the mistake in the first experiment This just goes to show how important doing a preliminary experiment is. So obviously next time I shall take a bit more time and care into doing it better. * The water baths did not keep their temp for as long as they needed to in some cases and had to be cooled with ice or warmed with a Bunsen. Well in a perfect world with all the time and money then I would have electronic water baths with very sensitive thermostats. * Didn't really have enough time to complete the experiments as some went on for over an hour. Again in a perfect world then I could spend more time and then I could repeat the experiment more and get a more accurate average that would get rid of any weird results that may occur. * Some went so quick it was difficult to time If this wasn't coursework then I could have someone help me that would make it quicker as one could test while the other times and writes. Paul Randlesome Biology coursework ...read more.

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