Pectin is a big polysaccharide (MW between 20,000 and 400,000) abundant in apples, oranges and other fruits and vegetables. Its presence in jam and jellies is also well known. The main problem of
traditional pectin biosensors is the high viscosity of pectin solutions,which usually foul the electrode surface. By using plant tissue biosensors, this problem is overcome, as the tissue tolerates better the pectin absorption or, if not, it ismuchmore easily and cheaply replaced.Horie and Rechnitz (1995) developed a hybrid biosensor for pectin combining orange peel tissue, as pectinesterase source, and alcohol oxidase. Pectinesterase reacted with pectin producing methanol, which was oxidised by alcohol oxidase with the concomitant hydrogen peroxide production.