Investigation on Protein Denaturation

By y. c. pong Introduction When you heat an clump, the bullock block ovalbumin clump unneurotic and moody purity. It is beca accustom the protein in addict washrag undergoes denaturation, the cross linkage(the hydrogen bonds, bonce bonds and disulphride bonds) which economise the protein shape destructed, so protein lose its tertiary conformation. This denaturing serve up is very all-important(prenominal), because beforehand protein fanny be used in digestion they must be unfolded. trigger off A denaturation of musket ball uncontaminating Aim To examine the factors on the onus of denaturation of egg white.Principle As protein denaturation poop be cause by several(prenominal) factors such as temperature, pH, salt parsimony. In this experiment, we argon examining how these factors affect the denaturation of protein. We use egg white, which is actually a solution of protein in urine in this experiment. After the egg white had been dilute, the egg white solution h indquarters be put in 60? C and 80? C peeing bath to test for how temperature affects denaturation. It faeces be record by the time need for the first alter of appearance.To find out how pH of affect denaturation, we depose add dropwise the actetic mordant to the egg white solution. Beside, the NaCl can withal be add dropwise to egg white, to test for how salt concentration cause denaturation. Count the number of drop of solution added for an appearance change to occur. poster 60 ? C water bath After 15 minutes, a pale yellowed semi-solid make 80 ?C water bath After 2 minutes 30 seconds, a white jelly like solid formed. 1M acetic window glass After 10 drops of acid added, the solution become pale yellow and clumping of egg white occurs 5M NaCl After 27 drops of NaCl added, the solution become yellow and clumping f egg white occurs Add equal volume of water No evident change sermon Protein? s three dimension conformation is held by the interaction ami dst its amino acids. This interaction included hydrogen bonds, ionic bonds and disulphride bonds. But in virtually native condition, such as broad(prenominal) temperature, extreme pH, high salt concentration, the protein will be denaturate. It is because the cross linkage had been broken, the secondary and tertiary building are alter.The protein now has primary structure as peptide bonds are strong enough not to be destructed. In our experiment, we observed that the egg white clump together later onward denaturation (either by heat, pH or salt concentration). It is because subsequently the normal structure is destructed, several(prenominal) natural bonding may be formed between proteins. They can have a big clump of proteins hooked together. That is the curdling. In coagulation process, the egg white turned from transparent to a cloudy solution, because as the protein clump together, there are no much space for agility the pass through, so it looks more cloudy.Besides, in 80 ? C turn provide, the egg white turned white while at 60 ? C the egg white just now clump to a yellow semi-solid. It is because at higher temperature more kinetic energy is provided for the molecules to vibrate, so the bondings are disrupted more greatly. So it can be concluded that a high temperature will have a stronger effect on denaturation. vox B egg custard Aim To measure the phrase transitions that occurs in denaturation of egg and draw as affected by temperature change. PrincipleEgg and draw are the main ingredients of an egg custard, through baking an egg custard, we can examine the soma transition of transition of denaturation of egg and draw as affected by temperature. Result After baking the egg custard for 30 minutes, the egg custard set to a yellow smooth gel. Discussion The egg custard is at liquid phase before baking, and it turn to solid phase after baking. It shows that phase transitions of liquid to solid had occur in the denaturation process of egg an d milk as affect by high temperature. The egg custard has a smooth and spongy texture.In the experiment, our egg custard is made of egg, milk, sugar only. done applying of heat and manipulation, custards can become a cloying and semi-rigid gel, denaturation of the egg protein, causes a clumping of proteins, is primarily contri thate for the thickening of the custard. draw, although not as important as egg, but calcium ions present in the milk are also needed in order to form thicker custard. Sugar is also important to the viscosity and gel strength of custards. Sugar tends to increase the denaturation temperature of the egg proteins resulting in less stiff custard.The concentration of egg protein is proportional to the viscosity or gel strength of the custard. With increasing concentration, a custard sauce becomes more viscous and the gel strength of a baked custard firmer. A custard heated slow begins to thicken at a lower temperature, thickens gradually over a wider temperatur e range and result in a smoother texture. Slow prep can be achieved by placing the custard mixture in a water bath to warm to certain temperature before put into the oven which has been skipped in our experimentPart C denaturation of milk Aim To examine the factors on the effect of denaturation of milk. Principle Milk protein, similar with egg white, will also undergo denaturation in extreme condition. So acid and NaCl is added to milk respectively, to observe the changes and examine how pH and salt concentration affect denaturation. Then, they are place in a 80 ? C water bath, also a control tube is tube is put in water bath, to examine the effect of temperature on denaturation. Observation real milk pH= 6. 63 1 M acetic acid 60 drops of 1 m acid had been added The pH=4. 67 on that point are white ppt formed. Half quantity of 1 M acetic acid added 30 drops of 1M acid added there are no unmistakable change. And after heat for 2 minutes, there are white precipitat e formed. 1 ml of 5M NaCl No observable changes soon after summing up of NaCl. There are little white precipitate after heat for 8 minutes. control No observable changes even after 20 minutes Centrifugation tube 3 layers formed.The pep pill layer is translucent, the heart and soul one is white and the buns layer is white precipitate. Discussion There are 3 layers present in the centrifugation tube after centrifugation. The upper layer is the acetic acid we added, the middle layer is the milky serum, the bottom layer is the precipitate formed bring out by the addition of acid. There are 2 major components of milk, casein and serum .The casein contains phosphorus and will coagulate or precipitate at just about pH 4. 6. The serum proteins do not contain phosphorus, and these proteins remain in solution in milk at pH 4. 6. So, when acetic acid added the pH drop to 4. 69 the casein precipitate so white precipitate is seen. The addition of NaCl only cause a little p recipitation, shows change magnitude in pH has a greater effect on milk denaturation than increase in salt concentration. There are no observable changes in control because the protein are not yet denaturated in 80 ? C.Part D yoghourt Aim To experience the making of yoghurt and the conjecture of formation of yoghurt. Principle As immanent yoghurt is made from odoriferous milk without other ingredient added, it can be made by simply add a little yoghurt and milk together and incubate in 38 ? C incubator, which is a suitable temperature to touch yoghurt. Yoghurt can be available for tasting after 1-2 days. Results exclusively milk turned into yoghurt, the sample is no longer liquid but is in semi-solid. The yoghurt is a bit sour than the original sample. DiscussionYoghurt is made by fresh milk, but often some specific bacteria strains are introduce into the milk. The bacteria ingest natural milk sugars and released lactic acid as a waste product. The acid decrease the pH and ca use the denaturation of milk protein during which the cross linkage between protein break and protein uncoiled. Then, the protein will tangle into a solid mass, yoghurt formed In our experiment, we mixed the 50 ml milk with 5 ml yoghurt to made the sample yoghurt instead of milk only . the 5 ml yoghurt is to provide the bacteria.Only a small get along of live yoghurt can is needed to inoculate a new batch of yoghurt because the bacteria can reproduce and multiple themselves during the yoghurt making process. Besides the incubators temperature is 38 ? C because it is the optimal temperature of bacteria to reproduce. The yoghurt newly made is more sour than the original sample. It may be due to the long incubation hours, as we had kept it over 48 hours. The bacteria ingest a higher % of milk sugar and release more lactic acid. To stop the incubation we can place the yoghurt in a refrigerator.