The Effect of Sodium Sulfite with Varying Concentration on the Separation of Gliadin from Gluten

Abstract

Gluten is a protein that gives a chewy characteristic to wheat flour-based foods. Gluten consists of glutenin and gliadin linked by disulfide bonds in which gliadin gives the viscosity and extensibility properties of gluten. Based on its properties, gliadin has great potential as a biomaterial and has been widely used in both the pharmaceutical and food industries. The separation between gliadin and glutenin generally uses alcohol such as 60-70% ethanol and 1-propanol. However, this method is inefficient and can cause environmental pollution. Another method is to add a food grade aqueous acidic medium where the separation occurs due to the difference in isoelectric point between gliadin and glutenin. Aim of the research to determine the effect of sodium sulfite with varying concentration on the separation of gliadin from gluten. In this study, gliadin was separated using 98% acetic acid, while sodium sulfite was used as a reducing agent to break the disulfide bond. To precipitate glutenin, the pH of the dispersion was adjusted to 4.4 using 5% ammonium hydroxide. The centrifugation was carried out at 8000 rpm to obtain the gliadin. The FT-IR spectrum showed that gliadin had absorption in the amide I band (C=O), namely α helix for the use of 0.1% and 0.15% of sodium sulfite and β sheet for 0.2% of sodium sulfite. The SDS-PAGE analysis on the use of all concentrations of sodium sulfite contained gliadin with a molecular weight of 25-40 kDa. After comparing it with marker proteins, it was estimated that it contains only α/β gliadin and γ- gliadin. The RP – HPLC chromatogram showed that the use of 0.1% and 0.2% sodium sulfite resulted in ω5 gliadin and ω 1,2 gliadin types, and at 0.15% sodium sulfite resulted in the most complete types, namely ω5 gliadin, ω1,2 gliadin and α /β gliadin, each containing glutamine, proline, phenylalanine, tyrosine and glycine. Overall, the use of 98% acetic acid at a certain pH with sodium sulfite as a reducing agent can separate gliadin from gluten. However, there was a change in the three-dimensional structure of gluten proteins so not all gliadin fractions can be identified completely.Keywords: 98% acetic acid; gliadin; isoelectric point; sodium sulfite