2.3. Biochemical analysis
The pH of the samples was measured immediately after sample collection. Samples were centrifuged at 1279×g and the supernatant was kept frozen at −20 °C until required for analysis. Dissolved solids were estimated by measuring the refraction at room temperature of centrifuged sample using a sugar refractometer. Dissolved solids were recorded as grams of dissolved solids (expressed as sucrose) per 100 ml (% w/v). FAN was determined using the European Brewery
Convention method [12]. Ethanol was determined using the alcohol dehydrogenase method (UV test kits,Boehringer Mannheim, Germany). Organic acid levels were determined by HPLC analysis using an Aminex HPX 87H column, with a column temperature of 65 °C, flow rate 0.6 ml/min and injection volume 20 l. A refractive index detector was used at a wavelength of 215 nm. Samples were filtered through 0.45 m syringe filters before HPLC analysis. All analyses were carried
out in duplicate.