Abstract
The plant cell membrane permeabilizing action of high pressure may be
utilised in juice processing to improve juice yield and the amount of phenolic
compounds released into the juice (1, 2). The reactions of the cell wall
degrading enzymes used to improve yields in conventional juice processing, may
be inhibited or enhanced by high pressure treatment (3).
In the first part of this work the effect of high pressure treatment of
bilberry pulp on juice yield and phenolic content was studied. The juice yield
or the content of phenolic compounds in the juice was not improved by high
pressure treatment. The juice yield tended to decrease with increasing
pressure, even though mechanical damage is expected to increase with
increasing pressure.
The work was continued by evaluating the possibilities of utilising the high
pressure technology as part of the enzyme-aided juice production process.
Three different types of processes were investigated. In the first process the
bilberry pulp was high pressure treated together with added cell wall
degrading enzymes. In the second process the pulp was high pressure treated
without added enzymes before conventional enzyme treatment (2 h at 45°C). In
the third investigated process the bilberry pulp was first conventionally
enzyme 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 or
total phenolic content of the obtained juices was not significantly improved.
One reason for the reduced juice yields after high pressure treatment may be
the gelatination of the soluble pectins that are released from the berry
matrix during pulping and pressurization. The pectin depolymerising enzyme
polygalacturonase is according to literature easily inactivated at moderate
pressures. Pectinmethylesterase, which produces demethylated pectin that forms
gels with calcium, is known to be much more pressure resistant and can even
be stabilized in the pressure range studied in this work. With increasing
viscosity of the berry pulp the extraction of phenolic compounds becomes more
difficult. Our future work will concentrate on finding a way to utilise the
high pressure technology for mechanical disruption of the berry matrix without
increasing the viscosity of the pulp too much.
REFERENCES
1. 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 in
Food Science 9, 5 (1998).
Original language | English |
---|---|
Publication status | Published - 2004 |
Event | 2nd International Conference on Biocatalysis of Food and Drinks - Stuttgart, Germany Duration: 19 Sept 2004 → 22 Sept 2004 |
Conference
Conference | 2nd International Conference on Biocatalysis of Food and Drinks |
---|---|
Country/Territory | Germany |
City | Stuttgart |
Period | 19/09/04 → 22/09/04 |
Keywords
- high pressure
- juice
- enzymes
- bilberry