The chemical composition of pressed and extracted apple juice

Quality tests of the juices of 3 apple varieties /Jonathan, Golden Delicious, Starking/ showed that the composition of the product extracted at 56-58 C differs from the pressed product in the following parameters: the saccharose content is lower; the reducing sugar content related to the dry matter is higher; the total sugar content in the dry matter is the same; the acid content is lower by ca 5-10 o/o; due to the inactivation of the enzymes the pectin and polyphenol contents are higher; the colour and moist fibre content of the juice extracted from Jonathan apples is of better quality; if condensed water is used for estraction, the ash content does not differ from that of the pressed juice. If extraction is carried out with tap water, the ash content of the extracted juice is higher than that of the pressed juice. The above findings vary with the different apple varieties as follows: in Jonathan juice only the favourable characteristics /light colour, low fibre content/ were proven by mathematical statistical calculations, and this observation was supported also by sensory tests, the increase in pectin content is higher in Starking than in Jonathan or Golden Delicious juice; the reduction of the acid content was highest in the juice of Golden Delicious, the extracted juice of which was darker than the pressed one. An increase of the extraction temperature from 50 to 60 C affected the general conclusions in the following ways: the advantages of the extracted juice /higher sugar content related to dry matter, lighter colour/ over the pressed juice diminished while setbacks /darkening of colour, reduction of acid content/ were caused. As a conclusion Jonathan seems to be the most suitable variety for juice production; when choosing the most appropriate extraction temperature /56-58 C/ and suitable clarifying technology, it gives an extracted apple juice and a concentrate of good quality /Patkai, 1986/.