STUDIES ON FREEZE CONCENTRATION OF WHOLE KIWI FRUIT

The freeze concentration process is generally applied to fruit juice.
In our process, the freeze concentration of Kiwi fruit (Bruno variety) was obtained by crushing the freezed whole fruit under high pressure without prior juice extraction.
The working conditions of the pilot screw press (OLIER ATLAS B2) are given.
If freezed kiwi fruit (at a temperature close to – 20°C) were directly supplied in the press, a slurrry was formed and conveyed without any juice extraction whatever the settings of the press were.
Using hand-peeled fruit or fruit of another variety (Hayward) did not change the result.
A two-fold concentrated juice can be extracted from deep frozen fruit (close to – 40°C) but with low yields, less than 9 % in weight and less than 16 % in dry matter.
In order to obtain a reasonable extraction of concentrated juice, pure ice flakes have to be added to whole freezed fruit.
The best results were obtained when the press was fed with a mix 60 % of whole fruit and 40 % of ice flakes, allowing a two fold concentration of juice with yields close to 50 % in weight and 80 % in dry matter.
The contents in sugars, total acidity, vitamin C, chlorophyll and the refractive index value of the different fractions obtained (initial fruit, concentrated juice and ice cake) are given for different trials and discussed.
A preliminary trial has shown that ice cake can be recycled and substituted for pure ice crystal flakes.

International Symposium on Fruit & Vegetables for Processing

M. VALENTE, G. DUVERNEUIL, J. NICOLAS

https://doi.org/10.17660/ActaHortic.1986.194.27