Milk analysis? investigate the proteins

  • Thread starter Thread starter CuriousSam
  • Start date Start date
  • Tags Tags
    Analysis Proteins
Click For Summary
SUMMARY

The discussion focuses on the necessity of neutralizing milk samples before adding formalin during Formol titration for protein analysis. Neutralization is essential because the proteins in milk are acidic, and direct titration with alkali would yield inaccurate protein content results. The reaction between formalin and the -NH2 groups of proteins forms methylene-amino groups, making the carboxyl groups available for accurate titration. The procedure outlined includes the addition of phenolphthalein, potassium oxalate, and NaOH before formalin to ensure precise measurements of protein content.

PREREQUISITES
  • Understanding of Formol titration methodology
  • Knowledge of protein chemistry, specifically amino acid functional groups
  • Familiarity with acid-base titration techniques
  • Experience with laboratory procedures involving NaOH and formalin
NEXT STEPS
  • Research the role of formalin in protein analysis and its chemical interactions
  • Learn about the effects of pH on protein solubility and reactivity
  • Study the principles of titration and how to calculate protein content accurately
  • Explore alternative methods for protein quantification in dairy products
USEFUL FOR

This discussion is beneficial for biochemists, laboratory technicians, and food scientists involved in protein analysis, particularly those working with dairy products and seeking to improve accuracy in titration methods.

CuriousSam
Messages
4
Reaction score
0
For protein analysis, why is milk sample neutralised before the addition of formalin in Formol titration?

could we say that...

The proteins are too weak to be titrated directly with alkali,if formalin is added, it reacts with the -NH2 groups to form the methylene-amino(-N=CH2) group and the carboxyl group is then available for titration.

HOOC.CHR.NH2 + HCHO ----> HOOC.CHR.N=CH2 +H2O

HOOC.CHR.NH2(neutral) HCHO(formalin) HOOC.CHR.N=CH2(acidic)

Also , the proteins(which are acidic) in milk will react with NaOH will produce a higher amount
of volume used which would made higher protein content value thus giving an inaccurate
result.

Thank you very much and please help
 
Last edited:
Physics news on Phys.org
I thought that a known amount of base was added to the neutralized protein and the excess base titrated after addition of formalin. Do I have the wrong method?
 
The procedure is this
1) Add 0.5ml of 0.5% phenophthalein indictator and 0.4ml of neutral saturated potassium
oxalate.
2) Mix , allow to stand for a few minute and neutralise with 0.1M NaOH.
3) Add, 2ml formalin , allow to stand for a few minutes and titrate with the new acidity
produce with the 0.1N NaOH to the same pink colour(a ml) .Then carry out a blank titration
by replacing the milk sample with 10ml of water (b ml) .The protein content of the milk is
1.7 (a-b)%. The question is , why must the milk sample is neutralised 1st?? is this base on the answers
i have derided in the 1st post or is it something else. pls enlighten me.
 
Last edited:
CuriousSam said:
The procedure is this
1) Add 0.5ml of 0.5% phenophthalein indictator and 0.4ml of neutral saturated potassium
oxalate.
2) Mix , allow to stand for a few minute and neutralise with 0.1M NaOH.
3) Add, 2ml formalin , allow to stand for a few minutes and titrate with the new acidity
produce with the 0.1N NaOH to the same pink colour(a ml) .Then carry out a blank titration
by replacing the milk sample with 10ml of water (b ml) .The protein content of the milk is
1.7 (a-b)%.


The question is , why must the milk sample is neutralised 1st?? is this base on the answers
i have derided in the 1st post or is it something else. pls enlighten me.


What do you think you were neutralizing after you added the potassium oxalate? Would the amount of NaOH required be the same regardless of your sample? After you add the formalin, you have generated more acid. What does this new acidity correspond to? Would the acidity neutralized after you added the oxalate interfere with this measurement?
 

Similar threads

Titration Questions: Finding Levulinic Acid Concentration
  • · Replies 5 ·
Replies
5
Views
6K