Free sugars determination by HPLC in pineapple products

Free sugars have been determined by HPLC in fresh pineapple fruit, freshly extracted pineapple juice (home-made), pineapple juice concentrate (for industrial use), commercial pineapple juices and nectars. In natural samples, intermediate products and commercial juices the dominant sugar was sucrose, followed by fructose and glucose, both of which were found in similar concentrations. However, the sugar content of nectars analyzed was highly variable. The presence of maltose in nectar samples is a clear indication of the addition of sugars from corn syrup. We have found a fructose/glucose ratio close to 1, and the coefficient fructose plus glucose/sucrose close to 1, both of which are a good index of authenticity of pineapple juices.