Abstract
The ferrous salt FeSO4 (NH4) 2SO4·6H2O (Mohr's salt) or calcium salt CaCl2·2H2O was added at various concentrations to an aqueous keratin hydrolysed solution and its fractions fractionated by membrane ultrafiltration.
The effects of added iron (II) or calcium on foam heights, foam stabilities, amounts of sediment before washing, and amount of water-insoluble precipitates were investigated. Calcium content in the water-insoluble precipitate and maximum concentration of added iron (II) which could not form a precipitate were also measured.
The foam heights and stabilities of keratin hydrolysate and its fractions increased with the addition of iron (II) or calcium.
The keratin hydrolysate and its fractions except that in the fractionated molecular weight (F.M.W.) range from 5, 000 to 10, 000 formed precipitates by the addition of calcium.
The main cause of precipitation of the fraction in the F.M.W. range from 500 to 1, 000 with the addition of calcium was found to result from the formation of insoluble calcium connected hydrolysed proteins. The precipitation of fractions in the F.M.W. range from 1, 000 to 5, 000 and above 10, 000 was due to the salting out effect or formation of soluble precipitates of hydrolyzed proteins which adsorbed calcium ions.
From measurements of ultraviolet and visible absorption spectra and change in color of metal containing hydrolysed protein solutions, the keratin hydrolysate and its fractions were shown to be connected to added iron (II) in a water-soluble chelate configulation, but not to added calcium in a soluble state in a pH range from 7.0 to 7.5, 25°C.
