Can I solve for different variables?

Yes! This calculator supports reverse solving. You can solve for: Blank titer (B), Effective weight (M), Normality of NaOH (N), Protein solubility percentage (P), Titer (T).

Protein solubility

Solve protein solubility relationships quickly using core chemistry formulas.

Formula shown4 inputs definedUpdated Nov 2025By Automated Chemistry GeneratorFree, no sign-up

Quick Summary

Use this when you need:

Quantify how formulation changes (pH, salt) affect protein solubility
Compare different purification buffers by their solubility limits
Document the threshold mass that can be dissolved per milliliter

You’ll need:Effective weight (M), Normality of NaOH (N), Protein solubility percentage (P), Titer (T)

You’ll get:Blank titer (B)

How this is calculated

Formula:

Solubility = mass of solute / volume of solvent

In plain language:

Protein solubility is often expressed as the amount of protein that dissolves per unit volume of solvent, so dividing the mass that dissolved by the solvent volume gives the solubility metric.

The formula is always visible so you can verify the math and explain your numbers to anyone who asks.

What these terms mean

Blank titer (B)

Blank titer (B) used in the calculation.

Effective weight (M)

Effective weight (M) used in the calculation.

Normality of NaOH (N)

Normality of NaOH (N) used in the calculation.

Protein solubility percentage (P)

Protein solubility percentage (P) used in the calculation.

Titer (T)

Titer (T) used in the calculation.

When to use this calculator

Quantify how formulation changes (pH, salt) affect protein solubility
Compare different purification buffers by their solubility limits
Document the threshold mass that can be dissolved per milliliter

Last updated: November 19, 2025

Protein solubility calculator explained

Protein solubility index (PSI) measures the percentage of protein that dissolves under standardized mixing and titration conditions. After dispersing a ground sample, soluble nitrogen is determined by Kjeldahl titration and compared with a blank. This calculator implements the commonly used formula
$PSI = 1.401 \\times 6.25 \\times 5 \\times (B - T) \\times N / M$ ,
where {blank_titer} $B$ and {titer} $T$ are NaOH titers for the blank and sample, $N$ is the NaOH normality {normality_naoh}, and $M$ is the sample mass {effective_weight}. The result is the protein solubility percentage {protein_sol_percent}.

Use it when characterizing soybean meal quality, comparing formulation buffers, or documenting how process changes alter protein dispersibility.

How the conversion works

The constants in the PSI equation come from the Kjeldahl nitrogen determination:

1.401 converts milliliters of 0.1 N NaOH to milliequivalents of nitrogen (14.007 mg/eq).
6.25 converts nitrogen mass to protein mass.
The factor 5 accounts for the 5 g slurry used in standard PSI tests.

Subtracting the sample titration volume from the blank isolates soluble nitrogen. Dividing by the effective sample weight normalizes the result to percent protein dissolved.

Units and conversions

Parameter	Units	Notes
$B$ (blank titer)	mL NaOH	Titration volume for the blank solution.
$T$ (sample titer)	mL NaOH	Volume needed to neutralize filtrate from the dispersed sample.
$N$	eq/L	Normality of the NaOH titrant, typically 0.100 N.
$M$	g	Mass of test sample in the slurry.
PSI	% protein solubilized	Output from the calculator.

Worked examples

Soy flour lot comparison
$B = 25.3\\ \\text{mL}$ , $T = 17.8\\ \\text{mL}$ , $N = 0.100\\ \\text{N}$ , $M = 2.00\\ \\text{g}$ .

PSI = 1.401 \\times 6.25 \\times 5 \\times (25.3 - 17.8) \\times 0.100 / 2.00 = 16.4\\%

The flour meets a 15% minimum PSI requirement.

Protein dispersibility for processed meal
$B = 28.0\\ \\text{mL}$ , $T = 12.0\\ \\text{mL}$ , $N = 0.100\\ \\text{N}$ , $M = 2.50\\ \\text{g}$ .

PSI = 1.401 \\times 6.25 \\times 5 \\times 16.0 \\times 0.100 / 2.50 = 28.0\\%

Higher PSI indicates less heat damage, so this lot is suitable for high-value feed.

Tips and pitfalls

Keep titrant normality calibrated; a 1% error in $N$ becomes a 1% error in PSI.
Run duplicate dispersions and report the average to reduce variability from mixing efficiency.
Degas and preheat water to the method-specified temperature to mimic official PSI protocols.
Correct the effective weight for moisture content if the method specifies dry basis results.

References and further reading

Frequently Asked Questions

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Calculator info

Version:: v1.0.0
Last reviewed:: Nov 15, 2025
Sensitivity:: low
References:: 1

Last updated: November 19, 2025

Protein solubility calculator explained

Use it when characterizing soybean meal quality, comparing formulation buffers, or documenting how process changes alter protein dispersibility.

How the conversion works

The constants in the PSI equation come from the Kjeldahl nitrogen determination:

1.401 converts milliliters of 0.1 N NaOH to milliequivalents of nitrogen (14.007 mg/eq).
6.25 converts nitrogen mass to protein mass.
The factor 5 accounts for the 5 g slurry used in standard PSI tests.

Subtracting the sample titration volume from the blank isolates soluble nitrogen. Dividing by the effective sample weight normalizes the result to percent protein dissolved.

Units and conversions

Parameter	Units	Notes
$B$ (blank titer)	mL NaOH	Titration volume for the blank solution.
$T$ (sample titer)	mL NaOH	Volume needed to neutralize filtrate from the dispersed sample.
$N$	eq/L	Normality of the NaOH titrant, typically 0.100 N.
$M$	g	Mass of test sample in the slurry.
PSI	% protein solubilized	Output from the calculator.

Worked examples

Soy flour lot comparison
$B = 25.3\\ \\text{mL}$ , $T = 17.8\\ \\text{mL}$ , $N = 0.100\\ \\text{N}$ , $M = 2.00\\ \\text{g}$ .

PSI = 1.401 \\times 6.25 \\times 5 \\times (25.3 - 17.8) \\times 0.100 / 2.00 = 16.4\\%

The flour meets a 15% minimum PSI requirement.

Protein dispersibility for processed meal
$B = 28.0\\ \\text{mL}$ , $T = 12.0\\ \\text{mL}$ , $N = 0.100\\ \\text{N}$ , $M = 2.50\\ \\text{g}$ .

PSI = 1.401 \\times 6.25 \\times 5 \\times 16.0 \\times 0.100 / 2.50 = 28.0\\%

Higher PSI indicates less heat damage, so this lot is suitable for high-value feed.

Tips and pitfalls

Keep titrant normality calibrated; a 1% error in $N$ becomes a 1% error in PSI.
Run duplicate dispersions and report the average to reduce variability from mixing efficiency.
Degas and preheat water to the method-specified temperature to mimic official PSI protocols.
Correct the effective weight for moisture content if the method specifies dry basis results.

Quick Summary

Calculator Tool

How this is calculated

What these terms mean

Blank titer (B)

Effective weight (M)

Normality of NaOH (N)

Protein solubility percentage (P)

Titer (T)

When to use this calculator

Protein solubility calculator explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

Related Calculators

pKa

Beer-Lambert law

Molarity

Mole

Neutralization

Normality

Was this calculator helpful?

Found an error?

Calculator info

Protein solubility calculator explained

How the conversion works

Units and conversions

Worked examples

Tips and pitfalls

References and further reading

Frequently Asked Questions

Related Calculators

pKa

Beer-Lambert law

Molarity

Mole

Neutralization

Normality

Was this calculator helpful?

Found an error?

Calculator info