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food test.docx

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Discussion. First question The table provides information about test food experiment on five types of substances. substance procedure The table above provides information how food test were done and what changes occurred. observation result Starch 2ml starch+2 drops of Iodine Deep blue-black colour + Mono- disaccharides 2 ml sugar+100ml benedict reagent(if non-reducing sugar for example sucrose 3 drops of HCL, NACO3 ) Red-brown color + protein KOH+CuSO4.it is c
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   Discussion. First question The table provides information about test food experiment on five types of substances. substance procedure The table above provides information how food test were done and what changes occurred. observation result Starch 2ml starch+2 drops of Iodine Deep blue-black colour + Mono-disaccharides 2 ml sugar+100ml benedict reagent(if non-reducing sugar for example sucrose 3 drops of HCL, NACO3 ) Red-brown color + protein KOH+CuSO4.it is called Biuret test Purple color appears + Lipid1 1 drop of oil+2ml ethanol +large quantity of water White milky solution + Lipid2 Oil +water two drop of Sudan 3 dye Lipid colored by sudan in red + Vitamin C 2ml DCPIP + ascorbic acid DCPIP lost color + Second question. The test for sugars was done in two stages. First stage is when Benedict reagent is added to to sugar the reduction of Cu(II ) to Cu(i) happens. In order to complete reaction the second stage was undertaken , so the solution was heated at the water bath. The red color appeared, because precipitation Copper oxide turn to this color. Reducing sugars like fructose, glucose and maltose had positive result, because they contain in their structure aldehyde or ketone groups. However, the sucrose solution did not showed positive result, because it is non-reducing sugar. So in order to break glycosidic bonds HCL was added and in order to neutralize the solution sodium carbonate was also added. So after this procedure the sucrose divided into glucose and frucrose. Then the solution showed positive result. Third question. This table shows the test on the unknown solutions.   Number oftest tubes Test for substances For Starch For Protein For Sugar For Vitamin C For Lipid 1 st  tube No expected result  No expected result Positive result No expected result  No expected result 2 nd  tube No expected result  No expected result Positive result Positive result No   expected result 3 rd  tube No expected result Positive result Positive result No expected result  No expected result The test examined three unknown substances. Every substance was observed by 5 food tests. When expected result was seen it means that this solution contain this type of biomolecules. As it is shown in the table the substance from first tube not contain any protein, starch, vitamin C and lipid molecules, but when the test for presence of sugar was undertaken the color of this solution changed to orange. This means that sugar might present in this solution. The same procedure was done with second and third unknown solutions. And during the test the second solution gave also positive result for sugar test and this means that it also contain sugar molecule. Interesting observation occurred with third solution , because it contained two types of molecules. The appearance of purple color shows that it contain protein and orange color indicates that there are sugar molecules present. This ends my report.   Lab Practical #6. Food test. Kaparova Zhamilya. Group D. Andy Hawkins. Nazarbayev University.(23.11.2012)   
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