Lecture quiz 5/03/23 (wednesday)

Question 1

What method do we use for analyzing crude protein

Answer 1

kjeldahl method

Question 2

Proximate analysis of crude protein

Answer 2

• digest small dried sample in concentrated sulfuric acid until all organic matter is destroyed
• Nitrogen from feed will be in a form of ammonium sulfate
• Ammonia = liberated by adding sodium hydroxide to the digest, distil off an collected in standard acid
• the quantitative content of nitrogen is determined by titration with sulfuric acid or hydrochloric acid
• this determines the amount of N in the sample

Crude protein % = %N X 6.25

Question 3

What is liberated by adding sodium hydroxide to digest, distill off and collected in standard acid?

Answer 3

ammonia

Question 4

What is converted in the form if ammonium sulfate?

Answer 4

Nitrogen

Question 5

How do we determine the quantitative content of nitrogen?

Answer 5

titration with sulfuric acids or hydrochloric acid

Question 6

how to wee calculate the crude protein%?

Answer 6

Crude protein % = %N X 6.25

Question 7

What are the limitations of kjeldahl method?

Answer 7

• the procedure does not differentiate between true protein and non protein
• gives no indication of amino acid composition or protein quality