Qualitative Food Tests

Topics: Starch, Glucose, Protein Pages: 5 (1577 words) Published: October 15, 2012
Name: Marcus Gonzales
Date: Wednesday 12th September 2012
Form: L62
Subject: Biology
Teacher: Ms. Hutton
Lab #: 1
Title: Food Tests
Aim: To test an unknown substance for various food substances. Apparatus/Materials:
* Unknown Solution X
* NaOH
* Iodine
* Ethanol
* Copper Sulphate
* Benedict’s Solution
* HCl
* Cold Water
* Syringe
* Beakers
* Bunsen burner
* Tripod stand
* Test tubes
* Dropper
Introduction: This Lab shows the detection of different food sources using different tests. Some of the food tests carried out was Benedict’s test, the test for non-reducing sugars, iodine test (test for starches), emulsion test and the biuret test. Carbohydrates include reducing and non-reducing sugars also starches. They have a general Formula of CnH2nOn.They can be classified into three main groups, Monosaccharide, Disaccharide and polysaccharide. Carbohydrates have many uses such as: for energy, for storage of food in both plant and animal cells e.g. Starch, chloroplasts, for structure in plant cells e.g. cellulose have a structural use in plant cell walls giving it structure. Carbohydrates are sweet and soluble in water with the only exceptions of starch and cellulose. Reducing sugars react with the copper in Benedict’s reagent to form a brick-red precipitate. Non-reducing sugars however do not react with Benedict’s reagent because the part that would react with the Benedict’s reagent is already in a glycosidic bond with another molecule. Therefore it is heated with HCl to break these bonds so that the benedict’s solution can be effective. Starch is made up of amylose and amylopectin, it is used as storage for food made in plants. Lipids can be classified as fats, oils, or anything similar to a fat/oil that is insoluble in water. There are different types of Lipids such as: Saturated, unsaturated, triglycerides and phospholipids Lipids are non-polar and insoluble in water. They are made up of Hydrogen Carbon and Oxygen, and are made up of a Glycerol molecule and three fatty acids. Lipids are used for many purposes one example is energy, considering their long fatty acid chains to store this high amount of energy also they are also part of the structure in cells. Proteins are made up of many amino acids linked together to form long chains of protein. Proteins are made up of a central Carbon atom, a –COOH (Carboxylic group), and amino group (H2N), a hydrogen atom and an R group that can be combination of C, N, H, O and S atoms. There may be over 100 amino acids bonded together to form one protein. They are bonded by peptide bonds. There are different ways in which proteins can be arranged such as: the order in which the amino acids are bonded, some chains form curls or some chains (alpha-helix) are laterally joined with other chains forming a sheet design (beta-pleated sheet). Sometimes these chains are folded due to different bonds within the chains to form a globular protein. Protein has many uses such as: as enzymes, structure (in cells, hair, bones, teeth, skin, etc.), energy, genetic identity, etc.

Table 1 Showing Method and Results of the Different Food tests Test/Procedure| Observation| Inference|
Benedict’s test (Test for Reducing Sugar)
2cm3 of Unknown Solution X was added into a test tube.•The same amount of Benedict’s solution was added to the solution.•The mixture was shaken well and then gently boiled in a water bath. | The Blue colour of the mixture turns to green, then to yellow, then to reddish orange colour.| The colour portrayed a moderate of reducing sugars as the reaction. Cu+2 + Reducing Sugar(electron donor) Cu+|

Test for Non- Reducing Sugars
2cm3 of Unknown Solution X was added into a test tube.•1cm3 of HCl was then added to the solution.•The mixture was then boiled in a water bath for approximately one minute.•The solution was neutralized with NaOH, using the same amount of HCl added.| The bottom...
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