Q. Determine the gluten content in the sample of flour?
After undertaking this activity, you will be able to:
• assess the gluten content the given sample of flour,
• check the given sample for conformance to the standard for gluten content, and
• determine the water absorption power of the given sample of flour.
Principle
Gluten is made up of gliadin and glutenin. It is the water-insoluble portion of the wheat atta obtained by washing away the starch, as well as, the bran from the dough. Hydrated gluten contains about 66-67% water, and when dried, it becomes sticky or adhesive. During dough fermentation the gluten forms cells which retain CO2 and cause the bread to swell. Gluten is insoluble in water at pH 7 but is readily soluble in acidic or basic aqueous solutions of low ionic strength, therefore it should be noted that the water used for making the dough and washing away need not be distilled water but must be neutral and free from chlorine.
Materials Required
Collect the following material for conducting the activity:
• Sample of flour
• Flat-bottom dish - of stainless steel, porcelain, silica or platinum
• Weighing balance
• Burette
• Spatula
• Muslin cloth
• Butter paper
• Oven
Procedure
Now carry out the practical step-by-step as enumerated herewith:
1) Weigh 25 g of the flour sample. Put in china dish and add water from burette.
2) Measure the volume of water used to make a soft dough.
3) Keep the dough in a beaker filled with water for half an hour.
4) Now wash this dough with water and keep on removing the starch till clean water comes out.
5) Do iodine test to confirm that dough is free of starch.
6) Take this extracted gluten and weigh.
7) Dry it in oven maintained at 130 ± 1°C for 2 hours.
8) Keep in the dessicator, let it cool and weigh.
9) Calculate the gluten content of the sample using the following formula.