Factors influencing the determination of gluten in wheat flours.

The washing of gluten from wheat flour has a two-fold purpose. An approximate idea of protein content is obtained from the weight of dry gluten. The per cent of water imbibed by the gluten together with its coherence and other physical properties furnish the analyst with a rough index to flour strength.

Tap water is usually employed for gluten washing, but this has obvious disadvantages on account of its variation in concentration, composition, hydrogen ion concentration, and buffer action. When it is lacking in buffer action, the results of gluten washing are no doubt greatly influenced by variation in hydrogen ion concentration and buffer action of the flour itself.

The effects on gluten washing of solutions of various concentrations, of different composition and of various pH values have been investigated. Wet and dry gluten and total nitrogen in the dried gluten were determined.

It was found that there was practically no loss in protein when a washed gluten was kneaded under a stream of tap water (containing about 0.025 per cent total solids) for 45 minutes, while with freshly boiled and cooled distilled water there was a loss of over 25 per cent of the protein in that time. A modicum of electrolytes in the wash water is therefore essential in preventing dispersion of gluten proteins during washing.

Sodium phosphate buffer solutions of pH = 7.6 and of concentrations ranging from 0.01 to 1.25 per cent were next compared with tap water and boiled distilled water. A family patent flour was used. There was minimum protein dispersion with buffer solutions of 0.10 and 0.01 per cent concentration and with tap water. The dispersion was somewhat increased with buffer bolutions of concentrations of 0.25 per cent and above.