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Food and Nutrition in Humans Food Test and Storage.

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Presentation on theme: "Food and Nutrition in Humans Food Test and Storage."— Presentation transcript:

1 Food and Nutrition in Humans Food Test and Storage

2 Food Test theory Heat is required ONLY for Benedict’s test for reducing and non-reducing sugars Reducing sugars are so called because they reduce blue copper sulphate (CuSO 4 ) in Benedict’s solution to a reddish precipitate

3 Food Test theory cont’d Simple sugars are reducing sugars Some complex sugars are also reducing sugars e.g. maltose Sucrose, a complex sugar is a non-reducing sugar

4 Food Test theory cont’d There is no direct test for non-reducing sugars A non-reducing sugar can be broken down to simple sugars by heating it with a dilute acid like HCl (hydrolysis) The resulting mixture is acidic and must first be neutralized by adding a small amount of alkali like NaHCO 3 The test for reducing sugar can then be carried out The red precipitate obtained confirms that a non-reducing sugar was originally present

5 Table summarizing the method and results of food tests FOOD SUBSTANCES METHODOBSERVATIONS FOR POSITIVE RESULTS Starch Add 2-3 drops of iodineBlue-black Reducing sugar Add Benedict’s solution and heatBlue-green, yellow, orange red precipitate Non-reducing sugar i) Add Benedict’s solution and heat to boiling ii) Add (to fresh solution) dilute hydrochloric acid and heat. Add solid sodium hydrogen carbonate until fizzing stops. iii) Add Benedict’s solution and heat I. Remains blue II. Blue-green, yellow, orange red precipitate Protein Add sodium hydroxide solution. Add 3-4 drops 1% copper sulphate solution Purple or violet Fat or Oil Test 1. Rub or place a drop on absorbent paper Test 2. i) Add alcohol and shake ii) Pour clean liquid into water Grease spot (translucent) White emulsion

6 Complete the following table to indicate where and in what forms the named organisms store food ORGANISMSFOOD STOREDSITE OF STORAGE Sugar cane Irish potato Onion Mango Man(i) (ii) (i) (ii)

7 Complete the blank spaces in the following tale which shows the method and positive results of selected food tests PROCEDURERESULTCONCLUSION Protein Present Add Benedict’s solution and heat Blue-black colour

8 Essay Type (a) State clearly how you would test a sample of flour for (b) Include the apparatus and materials you would use (c) Describe the procedure and the results expected if positive  Starch  Reducing Sugar  Protein  Fat

9 TYPE OF STORAGE ORGAN STORAGE AREAEXAMPLETYPE OF FOOD STORED Root tubersRootCassava, sweet potato Starch, small amount of protein Tap rootsRootBeetroot, carrotSucrose glucose Stem tubersStemYam, Irish potatoStarch, small amount of protein RhizomeStemGingerStarch, oils CormStemDasheenStarch BulbLeavesonionglucose

10 FOOD RESERVES AND SITES OF STORAGE IN SOME COMMON SEEDS STORAGE AREAPLANT EXAMPLETYPE OF FOOD STORED COTYLEDON(S)Peas and Beans Nuts Sunflower Seeds Cocoa Protein, Starch Protein, Oil Fat ENDOSPERMCorn, Rice Coconut Castor Oil Starch, Protein Oil Oil, Protein

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