Doris Duncan
A Method For Preserving Home-made Herbal Plant Juices by freezing - With stability tests of fresh, frozen and thawed juices
Abstract
The project considers a method for producing herbal plant juices on a small scale, up to around 500 ml, and preserving the juices by freezing them as individual 10 ml lots as icecubes.
Juices were made of the following plants:
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1: Betula alba - Birch - leaves and very young branches
2: Galium aparine - Cleavers - aerial parts
3: Melissa officinalis - Lemon Balm - aerial parts non-flowering
4: Plantago lanceolata - Plantain - leaves
5: Taraxacum officinale - Dandelion - leaves
6: Urtica dioica - Nettle - aerial part before flowering
The frozen juices were researched in storage and stability trials.
After thawing the juices were stored at 10 degrees
in the refrigerator. Taste, appearance and smell were tested on each thawed juice.
The pH changes were monitored during frozen storage at -18° C over a variety of months and on thawed juices kept at 10° C in screw cap bottles.
Dry and wet solids were measured as an indication of juice concentration and sediment formation on storage.
The UV and visible light spectrum was measured for changes in the absorbance of the chemical components in the juices occurring during storage.
The total bacteriological count was carried out on juices containing all sediment, a 1:10 dilution of juices and clarified juices by centrifugation.
The fresh juices were analysed for Vitamin C (ascorbic acid) content. Also the changes of Vitamin C content in juices stored at -18° C and 10° C was recorded.
Protein changes in the juices on storage and protein content in fresh juice was demonstrated by polyacrylamide-electrophoresis and analytical method.
The research demonstrated that the juices keep their quality during frozen storage apart from a loss of Vitamin C.
There is a variety of keeping properties of juices stored at 10° C up to one week.
