Student activity 1 : determining sugar content using a refractometer

paratus. In activity 2, students can use the equipment used by hobby winemakers – a vinometer – to measure the alcohol content of the must and wine. 3. A well balanced wine needs a certain amount of fruit acid; the total acid content is a very important measure, because it directly affects the flavour. In activity 3, the acid content is determined by pH titration. Four further activitiesw2 can be downloaded from the Science in School website: · Activity 1a: in an alternative to activity 1, students determine the sugar content of grape juice using density measurement instead of refractometry. · Measuring levels of carbon dioxide, one of the products of the fermentation, is a useful way to monitor the progress of the reaction. In activity C6H12O6 + 2 ADP + 2 Pi = 2 C2H5OH + 2 CO2 + 2 ATP The three main factors that determine the quality of the final product are sweetness, alcohol content and acid content. Using standard methods of a commercial wine laboratory, these three activities for the school laboratory explore how the quality of the starting grape juice and the must (fermenting grape juice) affect the final product. Each activity takes approximately 20-30 minutes. 1. In activity 1, students can determine the sugar content of grape juice using refractometry. Activity 1a (see below) offers an alternative, based on density measurement. 2. The exact determination of the alcohol content in commercial wines is performed by distilling the ethanol, then measuring the viscosity of the distillate using sophisticated apBy Thomas Wendt