PRESERVATION OF FRUIT

Otago Daily Times, Issue 22911, 19 June 1936, Page 10

PRESERVATION OF FRUIT

FOR JAM MANUFACTURE

RESEARCH AT LONG ASHTON,

(From Oun Own Correspondent) (By Air Mail) LONDON, May 13. The bulk preservation of fruit for the manufacture of jam is to-day solely effected by some form of sulphur dioxide treatment. Various methods of preservation have been the subject of research by the Agricultural and Horticultural Research Station at Long Ashton, Bristol, where a cold process treatment has been evolved for fruits whose nature was such that the hot process severely deteriorated the fruit.

The experiments provided data on which it was possible to base definite instructions for pulping fruit, and the cold process method has now become an accepted practice in .pulping procedure. The attention of Long Ashton was first directed to the preservation of fruit as a result of a difficulty encountered by jam mnmi facturers arising from a regulation by the Minister of Health imposing a maximum figure of 40 parts per million of sulphur dioxide in n finished jam offered for sale. This involved protracted boiling, which adversely reflected upon the fresh fruit flavour of the jam. An account of the research is given in the station’s annual report of 1034. The effect of the various means of preservation on the residual sulphur dioxide content of the jam was investigated. While this work was in progress on fresh plums, the most appropriate fruit avail able when the experiments were initiated, the question of the distribution of sulhpur dioxide in the different tissues of the fruit was raised, and a series of experiments was devised to determine whether any of the results observed in practice could bo explained ,by a consideration of this further point. In view of the tendency of sulphur diox'de to combine with a variety of organic compounds, it was thought possible that the different tissues of the plums, such as skins, flesh and stones, on account of their varying compositions and textures, might retain 1 the sulphur dioxide in varying proper-' tions. It has been stated in jam-making circles that in plum jam mopt of the preservative- resides in the, stones, and a short series of experiments was carried out to test the truth of this assertion and to determine whether any differences that may exist are related to the strength of the preserving solution. Considerable differences were noticed in the cond’tion of the fruit itself in the jam. In jams made from cold processed plup containing 1000 p.p.m. of sulphur dioxide, the fruits were nearly all in a whole condition, and were quite tender, but a stronger preservative resulted in a toughening of the skins, which was a distinct disadvantage. Many of the fruits had shrivelled and formed compact centres of hardened tissues. In the hot treatment, the plums were completely disintegrated under the conditions of the experiments, but the effects . of the larger proportions of preservatives were noticeable in the hardening of • the pieces of skin distributed throughout i the jam. j It was also shown that the stones con- ! tain considerably more sulphur dioxide than either the flesh or the skins of the preserved plums. The differences between the sulphur dioxide contents of the skins and flesh were in agreement in different expe dments on sim’larly treated fruit, but whereas the skins contained more sulphur dioxide than the flesh in the fruits treated with the weaker preservative, this was reversed when a 2000 p.p.m. solution was used. Work on the question of distribution is being continued.