Milk analysis? investigate the proteins

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Discussion Overview

The discussion revolves around the procedure for protein analysis in milk using Formol titration, specifically focusing on the necessity of neutralizing the milk sample before adding formalin. Participants explore the chemical interactions involved and the implications for accurate protein content measurement.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that milk proteins are too weak to be titrated directly with alkali and that formalin reacts with -NH2 groups, making the carboxyl group available for titration.
  • Another participant questions whether the method involves adding a known amount of base to the neutralized protein and titrating the excess base after formalin addition.
  • A detailed procedure is provided, highlighting the steps of adding phenolphthalein, potassium oxalate, neutralizing with NaOH, and then adding formalin before titration.
  • Participants inquire about the necessity of neutralizing the milk sample first and whether this is related to the previous claims about protein acidity and the potential for inaccurate results.
  • One participant raises questions about what is being neutralized after adding potassium oxalate and whether the amount of NaOH required would vary based on the sample.
  • Concerns are expressed about the new acidity generated after adding formalin and its potential interference with the measurement of acidity neutralized after adding oxalate.

Areas of Agreement / Disagreement

Participants express differing views on the necessity and implications of neutralizing the milk sample before formalin addition, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

Participants have not reached consensus on the specific reasons for neutralization, and there are unresolved questions regarding the effects of acidity and the titration method used.

CuriousSam
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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:
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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?
 

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