Food Test Practical and Digestive Enzyme Experiment - Lab Report Example

FOOD TEST PRACTICAL AND DIGESTIVE ENZYME EXPERIMENT By Location Performance of food test for protein Procedure 2ml of the food substance which in this case is put into a test tube and the test tube is labelled A for identification. A control apparatus is also set up which is made by adding 2ml of a liquid that does not contain protein (such as water) into a test tube and this tube is labelled B. After this, 2ml of the Biuret solution is added to the tube containing milk sample, that is test tube A and the tube is shaken. Another 2ml of the Biuret reagent is added to the liquid that does not contain protein and in this case we chose water. The tube which is labelled B is as well shaken and serves as our control experiment for this assignment. Absolute care must be taken perhaps by putting on protective gloves to prevent direct contact of the Biuret reagent with the skin of even the finger nails because these parts of the body contain proteins and can hence react with the copper ions contained in the Biuret reagent. Results The colour in test tube A slowly but steadily turned into purple, especially after a minimal shaking. When the same Biuret reagent was added to test tube B containing water, the resultant solution retained the blue colour of the Biuret reagent. Discussion The change of colour from white milk to bluish mixture of the Biuret reagent and milk and then finally to the purple colour occurred as a result of the reaction between the peptide bonds of casein which is a protein found in milk and the Copper II ions found in the Biuret reagent. The reaction that occurs in this case results into a complex that has a purple colour, hence explaining our results. There was no unique colour change when Biuret reagent was added to water because water contains no peptide bonds that can react with the Copper II ions that are available for reaction in Biuret reagent. This set up is therefore used as a control and most of the time the control is used to assess for the quality of some of the reagents being used and the accuracy of the experiment (Uddin, Ahn, Kishimura & Chun, 2009). Testing for glucose in bread Procedure 1g of bread is properly mashed and mixed with 2ml of water to make a suitable solution that can allow a reaction to occur. The prepared bread mash is then transferred into a clean test tube which is labelled C for quick identification. 2ml of the Benedict’s solution is added to the test tube labelled C containing the test sample. Another test tube is labelled D and 2ml of water is added to the test tube D which serves as a control for this experiment. The two labelled tubes are held with a pair of tongs and heated on a Bunsen burner with the mouth of the tube facing away from the technician until boiling occurs. Results As heating continued, the contents of test tube C showed a general change of colour from bluish to orange red or brick red. On the contrary, even after heating for an elongated length of time, the contents of test tube D did not change in colour; the solution still retained the blue colour of Benedict’s solution. Discussion In our practical, we assessed the glucose content of bread by use of a simple test that makes use of Benedict solution. Benedict’s solution is a blued coloured reagent whose blue colour is as a result of the presence of Copper II ions in the solution. When a mixture of Benedict’s solution and a test sample that contains glucose or any simple sugar is heated, the mixture changes colour to orange red or more precisely, what is referred to as brick red. The reason as to why there is such a colour change is due to the ability of the simple sugars such as glucose to reduce other chemical agents such as the Copper II ions containing Benedict’s solution. In our practical case for instance, the glucose found in the bread was able to reduce the Copper II ions that are responsible for the blue colour in the Benedict’s solution to Copper I ions that brings about the characteristic change in colour (Bayané & Guiot, 2011). Analysing for Presence of Starch in Potato Starch is a polysaccharide as discussed earlier and is made up of several monosaccharides bound together to create a long chain of simple sugars interlinked. Procedure Around 1 g of potato is weighed using a weighing balance and mashed to come up with a solution of mashed potato suitable for analysis of starch. 2-3 ml of the mashed potato solution is added into a test tube which is labelled E and kept on test tube rack. Another test tube is labelled F and 2-3 drops of water are added to it; as we have always done it, this tube serves as the control of our experiment. 3-4 drops of iodine solution which is also known as Lugol’s reagent, are then added using a dropper into the solution in the test tube E and the same is repeated for the control which is set up in test tube F. Results The test tube E which contains our test sample experienced a colour change that was between blue and black while on the contrary, there was no colour change in the test sample. Discussion Potato is a very rich source of starch which is stored in the stem tuber by the potato plant from the conversion of excess glucose in the plant and is always availed for glucose metabolism when required by the plant. Diastase enzyme experiment Procedure 5 test tubes are labelled A to E and 2ml of starch sample is added to each test tube Another test tube is also labelled F that contains the control although this is optional A drop of iodine is added to the solutions in each of the test tubes The test tubes are then heated at regulated temperatures ranging from 5, 10, 20, 40 and 60 Degrees Celsius. Results Temperature Test tube Time in seconds 5 A 1513 10 B 780 20 C 1050 40 D 248 60 E 53 A Graph of Time in seconds (Y-) against Temperature (X-axis) in Degrees Celsius The results are also illustrated in the graph shown above. From the graph, it is obvious that the most appropriate temperature for effective functioning of the diastase enzyme is about 25 degrees Celsius. As the tempera increases above 25 degrees Celsius, the catalytic effect of the enzyme decreases. Discussion Diastase is actually salivary amylase and is responsible for the breakdown of starch into disaccharides. Iodine solution is used in this kind or reaction for detection of the point at which the enzyme works optimally and at this point the colour of the iodine becomes gray-black; the time taken for this to happen is noted. The activity of salivary amylase increases exponentially with increase in temperature until an optimal temperature of about 25 degrees Celsius is reached. Once this temperature is reached, the enzyme is denatured and can no longer catalyse the breakdown of starch into disaccharides. If there is any control that is used, no colour change would occur since there would be no enzyme to act on the starch (Li, Demisie & Zhang, 2013). Test for fats in milk Procedure A drop of milk is placed on a filter paper and spread evenly The filter paper is then left on the sun for 10 minutes After 10 minutes, the filter is observed through for and translucency Results The filter paper tested positive for the fats’ test Discussion Oil has some level of fat content and this is why it appears translucent when it is observed under the effect of light. Answering questions Salivary amylase stops working when food gets into the stomach because of the sudden change in pH in the stomach which drops to about 1.5-1.6. These pH conditions have denaturing effects on the enzyme salivary amylase hence its effect in the stomach will no longer be felt. According to the graph, pepsin has an optimal working pH of 2.5 while the optimal working pH of trypsin is 6.5. As the pH of pepsin rises from below 1 to the optimal pH, the effectiveness of the enzyme keeps on increasing but soon the optimal pH is attained and passed, the activity of the enzyme reduces to zero, the same applies to trypsin. Digestion is the chemical breakdown of food into tiny and fine particles that can be easily absorbed into the blood and this action is done by use of the digestive enzymes and juices. Absorption of food is the process by which the already digested food particles pass from the digestive system into the blood stream for further assimilation. Assimilation on the other hand is the capacity of the food that is absorbed in blood to traverse the cell membranes and get into the cells for conversion into beneficial energy (Li, Demisie & Zhang, 2013). Chymotrypsin is found within the pancreatic juice and its site of action is the duodenum where it acts on proteins cleaving the proteins into peptides. Lactase is an enzyme located in the small intestines which acts on lactose found essentially in milk breaking the lactose into glucose and galactose. Lipases are a group of esterase enzymes which act on fats to convert them into fatty acids and glycerol and they perform this role into the pancreas. Bile is located in the liver and it bile juice which contains sodium glycocholate and sodium tyrocholate which are salts responsible for fat emulsification (Uddin, Ahn, Kishimura & Chun, 2009). Digestion of carbohydrates starts in the mouth with starch which is a major carbohydrate in the food that we eat being broke down in the mouth by the action of the salivary amylase. Other carbohydrates are broken down in the small intestines and this is where absolutely the digestion of carbohydrates ends. Digestion of proteins begins in the stomach where the protein food substances are acted upon by digestive enzymes in the stomach including pepsin and chemotrypsin. These enzymes optimize the catalysis of the digestion of proteins when the pH is acidic and is as low as 2.5 as characterized by the stomach conditions. The chemical break-down of fats begins in the small intestines and at the duodenum the effects of the products of bile juice such as glycocholate and sodium tyrocholate which are responsible for fat emulsification are felt (Li, Demisie & Zhang 2013). After eating the snickers bar, the blood sugar level peaked after 10 minutes due to the achievement of optimum working conditions of salivary amylase hence total assimilation of glucose into the bloodstream. After some time, the blood sugar level started decreasing since the excess blood sugar was converted into glycogen for storage. A laxative that provides bulk is essential because it remains in the digestive tract until the entire laxative or food content in it is worked on by the enzymes. If the laxative provides no bulk, the victim would suffer from digestive complications since most of the food content will pass through the digestive tract without being digested. Moreover, if the laxative irritates the intestinal mucosa, it would interfere with the release of digestive juices that contain enzymes and the victim would suffer from indigestion (Bayané & Guiot, 2011). Mechanical digestion of food involves the physical breakdown of large food particles which occurs in the mouth through the chewing of food, a process known as mastication. Moreover, physical breakdown of food can also occur through peristalsis which involves contractions of soft muscles in the digestive tract. The chemical digestion on the other hand is the process that involves enzymes catalysing further breakdown of the various macromolecules (Uddin, Ahn, Kishimura & Chun, 2009). Bibliography Bayané, A. & Guiot, S.R. 2011, "Animal digestive strategies versus anaerobic digestion bioprocesses for biogas production from lignocellulosic biomass", Reviews in Environmental Science and Biotechnology, vol. 10, no. 1, pp. 43-62. Li, Y., Demisie, W. & Zhang, M. 2013, "The function of digestive enzymes on Cu, Zn, and Pb release from soil in in vitro digestion tests", Environmental science and pollution research international, vol. 20, no. 7, pp. 4993-5002. Uddin, M.S., Ahn, H., Kishimura, H. & Chun, B. 2009, "Comparative study of digestive enzymes of squid (Todarodes pacificus) viscera after supercritical carbon dioxide and organic solvent extraction", Biotechnology and Bioprocess Engineering : BBE, vol. 14, no. 3, pp. 338-344. Read More