GB603294A - Improvements in or relating to the processing of fruit and vegetables - Google Patents

Abstract

In the cooking, scalding or other similar processing of vegetables or fruit with hot or boiling water, there is used, to reduce darkening in colour, water to which has been added a soluble compound which will prevent formation of a coloured compound between iron or other metal, e.g., copper, lead, tin or silver, and organic constituents, such as certain tannins, already present in the vegetables or fruit. The added compound may be such as to form an insoluble compound with the metal and so precipitate it, e.g. a soluble phosphate forms an insoluble compound with iron in the water, to form with the metal a soluble compound which is colourless or nearly so and gives rise to a very low concentration of ions of the metal, e.g. p-hydroxybenzoic acid so combines with iron in the water, to form insoluble compounds with the organic constituents and so precipitate them, e.g. gluten or gelatine combines with tannins or other phenolic compounds of the vegetables or fruit, or to combine with the organic constituents preferentially to the metal to give colourless compounds, e.g. aluminium sulphate so combines with tannins or other phenolic compounds of the vegetables or fruit. By the employment of an appropriate mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate, e.g. in concentration equivalent to 0.2-0.4 per cent of sodium dihydrogen phosphate, there may be obtained also the pH value suitable for the particular vegetables or fruit undergoing the treatment.