Protein Flashcards
What do proteins contain that most carbohydrates and lipids do not?
Nitrogen
What is the equation to convert total nitrogen to total protein?
Total protein = 6.25 x total nitrogen
Which type of barley generally contains higher total nitrogen?
Six-row barley
Who developed the Kjeldahl method and in what year?
Johan Kjeldahl in 1889
What is the first step in the Kjeldahl method?
Finely milled malt is heated with concentrated sulphuric acid and a catalyst
What compounds are transformed in the Kjeldahl digestion process?
Nitrogenous compounds into ammonium sulphate
In the Kjeldahl method, what is used to release ammonia gas?
Sodium hydroxide solution
What is the final product formed from ammonia gas in the Kjeldahl method?
Ammonium borate
How is total nitrogen (TN) calculated in the Kjeldahl method?
From the concentration of ammonia determined by titration
What is the temperature at which Dumas combustion takes place?
Around 1000°C
What are the non-nitrogenous products of combustion in Dumas combustion?
CO2 and water
What is the purpose of the thermal conductivity detector in Dumas combustion?
To measure the amount of nitrogen liberated
What method is used to prepare the sample for total soluble nitrogen (TSN) analysis?
Congress mash
What does free amino nitrogen (FAN) reflect in relation to barley?
The nitrogen level in the barley
What are the approximate FAN levels for ale malt using the IoB method?
110-135 mg/L
What is the purpose of the ninhydrin method in estimating FAN?
To react with amino acids and produce a yellow color
What wavelength is measured in the spectrophotometer for the ninhydrin method?
570nm
What is the formula for calculating the FAN result in the ninhydrin method?
Multiply absorbance by 2 and dilution factor, then divide by the absorbance of the blank
What does the TNBS method use to stain amino acids?
2,4,6-trinitrobenzene 1-sulphonic acid (TNBS)
At what temperature is the sample incubated in the TNBS method?
37°C
