Identifying Biological Macromolecules in Food Lab

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Identifying Biological Macromolecules in Food Lab
Stefanie Bogaert


Part 1: Test for Proteins
Biuret Test for Protein
Test TubeContentsColour ChangeConclusions
1Distilled waterClear to Blue tintThere are no proteins present because there was no significant colour change 2AlbuminWhite translucent to Purple/violetTherefore there are proteins present because of the significant purple colour exposed from the reaction of the Biuret solution 3PepsinBrown to Pink/brownThere is a little to none trace of proteins in the pepsin due to the slight pink colour created from the reaction with the Biuret solution 4StarchClear to Blue tintThere is no proteins in the contents because there was no colour change revealing the presents of proteins

Part 2: Test for Starch
Iodine Test for Starch
Test TubeContentsColour ChangeConclusions
1Starch suspensionWhite (starch) and brown (iodine) > dark blue-blackTherefore starch is present due to the change of colour in the solution 2Distilled waterTransparent (water) and brown (iodine) > translucent orange (diluted iodine)Therefore starch is not present due to the lack of reaction in the solution

Part 3: Tests for Sugars
Typical Reactions for Benedict’s Solution
ChemicalChemical CategoryBenedict’s Solution
(after heating)
Distilled waterInorganicBlue (no change)
(carbohydrate)Varies with concentration:
very low: green
low: yellow
moderate: yellow-orange
high: orange
very high: orange-red
(carbohydrate)Varies with concentration
(see results for glucose)
StarchPolysaccharide (carbohydrate)Blue (no change)

Benedict’s Test for Sugars
Test TubeContentsColour ChangeConclusions
1Distilled waterRemains translucent blueThere is no sugar in the new solution 2Glucose solutionGrass green, solution becomes opaqueThis solution contains a high concentration of sugars, to the degree of no longer being translucent, but...
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