Experiments on the behaviour of constituents of raw juice when precipitating them ¡have shown that several parameters which are attainable only with difficulties influence the precipitation by methyl alcohol (90 per cent by volume) of substances of high molecular weight. If the precipitate obtained by methyl alcohol is redissolved and precipitated again the influence of the volume of solution on the amount of precipitate is considerable. Furthermore the present electrolytes are important during coagulation. If calcium ions are present in varying concentrations, amount and composition of the coagulated substances vary considerably.
A fractionated precipitation of the constituents of raw juice by varying the concentration of calcium salts and methyl alcohol is not possible. The total amount of the precipitated colloids is increased if coagulation is carried1 out in steps.
By means of gel filtration it was possible to separate raw juice constituents in several fractions. These fractions with a different particle size have been subjected to the conditions of an industrial juice purification. It ¡has been shown that under the experimental conditions filtration was hindered by the fraction with a particle size between 400 and 2000 as well as by the supernatant liquid of the precipitation by methyl alcohol. Opposite to this no considerable influence of the substances with higher (>2000) or lower (<400) molecular weight has been stated. Furthermore retaining of important anions and cations in the several stages of industrial juice purification is studied1. Whilst oxalic acid and phosphoric acid as well as magnesium are removed completely or nearly completely during juice purification, tartaric acid, chloride ion as well as potassium and sodium pass the purification process up to the end. Differences found with two juice purification processes are given. Proceedings: CITS 1971 Page: 47–64 Language: GER pdf download: CITS1971-47-64.pdf