Flash ea1112 n analyzer

The total nitrogen content was determined in triplicate using the
Dumas method (Flash EA 1112 N analyzer, Thermo Fisher Scientific,
Waltham, MA, USA), according to the manufacturer’s protocol.
A calibration curve of methionine (1.00–20.00 mg) was used
for the nitrogen quantification. For WPI, a nitrogen conversion factor
of 6.32 was used.^{24 (link)} For the pea protein
samples, a nitrogen conversion factor of 5.4 was used, as calculated
from the average nitrogen conversion factor of the following pea protein
genotypes legumin A (P02857, UniProt Database), legumin J (P05692,
UniProt Database), legumin A2 (P15838, UniProt Database), legumin
K (P05693, UniProt Database), legumin B (P14594, UniProt Database),
and vicilin (P13918, UniProt Database).²⁵ The solubility of PPC, PLF, PVF, and WPI was determined at 25.0
g L⁻¹ protein in the diluted McIlvaine, pH 7.0.
The samples were prepared in duplicate, on which triplicate measurements
were performed. The solubility was determined by dividing the protein
content of the dried soluble sample by the protein content of the
dried total sample multiplied by 100. The samples were dried at 60
°C overnight.