Chemical Food Tests

Question 1

reagent in Benedict’s test

Answer 1

Benedict’s solutioin

Question 2

colour change in positive test for reducing sugar

Answer 2

blue to brick red

Question 3

describe the test for reducing sugars

Answer 3

add Benedict’s solution to a sample
heat the solution

Question 4

explain why a non-reducing sugar test can only be done on a solution which has tested negative for reducing sugars

Answer 4

the test may be positive for the monosaccharides that are already in the solution rather than the disaccharides that have been hydrolysed

Question 5

describe the test for non-reducing sugars

Answer 5

1. add hydrochloric acid to a solution that has tested negative for reducing sugars and heat to hydrolyse into monosaccharides
2. add sodium-hydrogencarbonate to the sample to neutralise it
3. add benedict’s solution and heat

Question 6

describe the test for starch and result if positive

Answer 6

add iodine to the sample
if contains starch, will change from yellow to blue-black

Question 7

reagent in test for proteins

Answer 7

biuret reagent

Question 8

does the test for proteins require the solution to be heated?

Answer 8

no

Question 9

colour change if proteins are present

Answer 9

blue to light purple

Question 10

name of reagent in emulsion test for lipids

Answer 10

ethanol

Question 11

does the test for lipids require the solution to be heated?

Answer 11

no

Question 12

negative result for lipids

Answer 12

no emulsion will form

Question 13

positve result for lipids

Answer 13

an emulsion will form

Question 14

describe the test for lipids

Answer 14

• add ethanol to a test tube containing the sample
• shake the test tube
• and the solution to water

Question 15

describe the test for proteins

Answer 15

• add three drops of biuret solution to the test tube containing the sample

Question 17

reagents used in the test for non-reducing sugars

Answer 17

beedict’s solution, hydrochloric acid and sodium hydrogencarbonate