Try chitosan as a clarification treatment for apple juice.

Apple juice has a significant concentration of phenolic compounds, which are thought to help protect us from many diseases associated with aging, including heart disease and cancer. Aside from other obvious vitamins like vitamin C, apple juice also contains the mineral nutrient boron, which is thought to promote healthy bones.

Scientists in Poland investigated the changes that occur during the conventional clarification of orange juice. They wanted to determine what effects gelatin, bentonite, silica sol and water-soluble chitosan would have on the phenolic compounds, antioxidant activity and color of the juice. This research suggests that chitosan can be used as a conventional clarifying aid for apple juice. The treatment has no impact on the juice's biochemical parameters.

Two varieties of apple were used by scientists: Sampion and Idared. The researchers monitored changes in polyphenol composition--the procyanidins, hydroxycinnamic derivatives and dihydrochalcones--through the clarification process.

The Sampion apple control juices contained more total polyphenols than did the Idared apple juices. In the Sampion variety apple juice, the dominant polyphenols were the flavan-3-ols (86% of total polyphenol content), the hydroxycinnamic acids (9.7%), the dihydrochalcones (3%) and the flavonols (1.3%). In the Idared juice, the hydroxycinnamic acids, especially chlorogenic acid, were dominant, constituting about 48% of total polyphenol content. The flavan-3-ols constituted 40% of the juice.

However, the concentration of polymeric procyanidins in the Sampion juices was 62.8% and 46.3% less when chitosan and gelatin treatments were used, respectively. Adding Aktivbentonit and Puranit (bentonite) to the juices when they were clarified had some protective effect on polymeric procyanidins, but only with the chitosan iron-based coagulant treatment. This effect was not observed in Idared apple juices, which had almost eight times less polymeric procyanidin than did the Sampion juices.

The antioxidant activity, as measured by the stable free radical DPPH (1,1-diphenyl-2-picrylhydrazyl), ranged from 0.20 mg TEAC per mL in Idared apple juice to 0.30 mg TEAC per mL in Sampion apple juice. The clarification of apple juices with these clarifying agents statistically had no significant influence on antioxidant capacity.

Further information. Jan Oszmianski, Department of Fruit, Vegetable and Cereal Technology, Agricultural University of Wroclaw, ul. C.K. Norwida 25, 50-375 Wroclaw, Poland; phone: [phone]; fax: [phone]; email: [e-mail].