Effects of Reducing Agents on Rheological Properties, Inhibition of Lysinoalanine Formation, and Spinnability of Soy Protein

Abstract

The relationships among the spinnability, the rheological properties, the spun fiber strength, and the inhibition of lysinoalanine (LAL) formation with the addition of reducing agents were studied to get safe, edible, fibrous soy protein, having excellent spun fiber strength, when a dope of 20% protein concentration was used as a normal dope. It was found that cysteine and 2-mercaptoethanol were effective in reducing LAL formation and the dopes prepared with the addition of these agents showed almost the same spun fiber strength as that of the normal dope prepared without agents. Especially, cysteine was the most effective agent for inhibiting LAL formation to get fibrous protein for meat analogues. The most suitable concentration for inhibiting LAL formation was 2% cysteine in the total protein. The dopes with the addition of 2-mercaptoethanol and Na₂SO₃ had lower viscoelastic values and their frequency dependence of G' was higher than that of the normal dope. However, the dopes with the addition of other reducing agents (NaHSO₃, glycine, reduced glutathione) had higher viscoelastic values and lower frequency dependence of G'. The viscoelastic values of the dopes with the addition of 2-mercaptoethanol, Na₂SO₃, and that of the normal dope were decreased with the lapse of time, but the dopes prepared by the addition of other agents had constant viscoelastic values.