• Poutanen, Kaisa
• Lille, Martina
• Mokkila, Mirja
• Mustranta, Annikka

Abstract

The plant cell membrane permeabilizing action of high pressure may beutilised in juice processing to improve juice yield and the amount of phenoliccompounds released into the juice (1, 2). The reactions of the cell walldegrading enzymes used to improve yields in conventional juice processing, maybe inhibited or enhanced by high pressure treatment (3).In the first part of this work the effect of high pressure treatment ofbilberry pulp on juice yield and phenolic content was studied. The juice yieldor the content of phenolic compounds in the juice was not improved by highpressure treatment. The juice yield tended to decrease with increasingpressure, even though mechanical damage is expected to increase withincreasing pressure.The work was continued by evaluating the possibilities of utilising the highpressure technology as part of the enzyme-aided juice production process.Three different types of processes were investigated. In the first process thebilberry pulp was high pressure treated together with added cell walldegrading enzymes. In the second process the pulp was high pressure treatedwithout added enzymes before conventional enzyme treatment (2 h at 45°C). Inthe third investigated process the bilberry pulp was first conventionallyenzyme treated and thereafter high pressure treated. The use of high pressure(50-600 MPa) was not beneficial in any of the studied cases, as the yield ortotal phenolic content of the obtained juices was not significantly improved.One reason for the reduced juice yields after high pressure treatment may bethe gelatination of the soluble pectins that are released from the berrymatrix during pulping and pressurization. The pectin depolymerising enzymepolygalacturonase is according to literature easily inactivated at moderatepressures. Pectinmethylesterase, which produces demethylated pectin that formsgels with calcium, is known to be much more pressure resistant and can evenbe stabilized in the pressure range studied in this work. With increasingviscosity of the berry pulp the extraction of phenolic compounds becomes moredifficult. Our future work will concentrate on finding a way to utilise thehigh pressure technology for mechanical disruption of the berry matrix withoutincreasing the viscosity of the pulp too much.REFERENCES1. Dornenburg, H. & Knorr, D.: Food Biotechnology 7, 1 (1993).2. Knorr, D.: Journal of Food Engineering 56, 2-3 (2003).3. Hendrickx, M., Ludikhuyze, L., Van den Broeck, I. & Weemaes, C.: Trends inFood Science 9, 5 (1998).

Topics

• impedance spectroscopy
• compound
• extraction
• viscosity
• Calcium