Define observation or inference for picric acid test?
1. A mahogany red colour will be seen. The mahogany red colour indicates the presence of reducing sugar. All monosaccharides are reducing sugars and thus will give a positive picric acid test.
2. Maltose and lactose contain a free sugar group and thus can reduce picric acid in alkaline medium. Sucrose does not give this test as it does not have a free sugar group.
3. Starch with very few free sugar groups cannot reduce picric acid. Dextrin being a less complex molecule brings about partial reduction.