Increasing the Whiteness and Galactomannan Value of Flour

Flour contains a substance, a type of polysaccharide called Glucomannan, which has gelling properties and many other benefits.

Flour with a physically brown appearance is not highly preferred in the food industry. Therefore, it is necessary for the flour's color to be sufficiently white and for its galactomannan value to meet standard levels.

The following substances are required for this process:

As a bleaching agent, sodium metabisulfite
Ethyl Alcohol
Ascorbic Acid
Water

The browning in such flours results from the browning reaction during processing. To increase the commercial value of this flour, a bleaching process is necessary.

For this reason, sodium metabisulfite prevents browning reactions by inhibiting the melanoidin pigment that causes browning in the flour.

Another bleaching agent is ascorbic acid. One of its greatest advantages is that it is a reducing agent (electron donor). The fact that ascorbic acid leaves no harmful residues means there are no restrictions on its use for whitening flour in the food industry.

A bleaching solution is prepared from these substances.

What is the Mechanism of Action for Sodium Metabisulfite and Ascorbic Acid?

When treating with the solution, the galactomannan value increases as the soaking time increases. This is because the hydrogen sulfite anion (HSO3-) from sodium metabisulfite has the ability to break down the disulfide ions in proteins. As the treatment time in the solution extends, the effect of the hydrogen sulfite anion increases, thereby raising the galactomannan value.

Ascorbic Acid has no effect on the galactomannan value; it only has a preventive effect on browning reactions. Ascorbic acid inhibits the reaction by reducing ortho-quinones to phenolic compounds before brown pigments can form. As the immersion time in the solution increases, this reduction of ortho-quinones to phenolic compounds also increases. Consequently, the progression to a browning reaction is blocked.

What is the Effect of SMBS and Ascorbic Acid Concentrations?

The highest galactomannan value is achieved with a bleaching solution of sodium metabisulfite in 40% Ethanol. As the immersion time in the solution increases, both the galactomannan value and the whiteness level will rise. However, the amount of resulting sulfite also increases.

In the solution prepared with ascorbic acid, the galactomannan value did not change noticeably. However, it has a significant effect on the whiteness factor.

For flour development, a dosage of 50 ppm of Ascorbic Acid provides optimal efficiency. Using a higher concentration can lead to a reduction in mixing time requirements.