Horticultural Products: Heat, Sugar and Solar Drying [46]

Jam is a cooked fruit product with good keeping qualities deriving from the high sugar content, about 65 per cent. In it sugar plays the same part as salt in, say, salted meat products; it lowers the water activity so that micro-organisms cannot grow. The water content of fruit (without stones) ranges from about 78 to 90 per cent, the berry fruits containing say, 85 to 90 per cent, so that even if no water were added to facilitate cooking, it would be necessary to remove some to ensure a stable product. This was, and frequently still is, done by boiling in open pans or kettles. The packaging of jam and of preserved fruits in cans logically follows the trail set by the meat canners.

George Peacock, who arrived in Hobart in 1850 and became a grocer and fruiterer, is believed to have been the first to have made jam commercially from Tasmanian berry fruits. He was certainly the first in the Australian colonies to can jam, which he did in 1861. Within two years, three others also commenced and the export of canned jams from Tasmania began. The raw material came from the rich Huon valley; raspberries in reusable kegs, currants, gooseberries, and stone fruits in cases were transported by four fishing boats which found this more profitable than fishing. Jam was made in copper steam-jacketed kettles fitted with mechanical stirrers and with a capacity of 156 pounds of jam per hour. After boiling, the jam was drawn off into hand held fillers from which the individual 1 lb. cans were filled. After cooling overnight, the tops were soldered on, the cans washed and inspected for leaks, labelled and cased for export. The high sugar content and the low moisture, in short, the low water activity, plus the airtight seal, protected the product from the growth of the organisms, mainly moulds, which inevitably contaminated the jam before the cans were closed.

Peacock also canned fruit. Gooseberries, currants, and stone fruits were hand packed into cans topped up with condensate and the lids soldered on. They were then processed in water baths which, with the acidity of the fruit, would have been quite hot enough to ensure microbiological stability.

Peacock's cans were hand made from imported Welsh tinplate, using the mechanical aids for body formation and rapid soldering which were common in the meat in dustry. The cases were made from local woods and labels were designed and printed locally. It was an operation typical of the time and was duplicated by other jam makers both in Hobart and later on the mainland.

In 1879-80 Peacock began to process in Sydney. He sent apples, pears and quinces from Hobart and bought other fruit in New South Wales. Fresh fruit could be imported duty free into the latter colony, but when Peacock began to import berry fruit pulp, which he had seen shipped successfully over long distances in England, the New South Wales Collector of Customs assessed duty on this 'manufactured' product. The government reversed this decision but trouble flared in 1884, when some fruit imported in tubs as deck cargo was condemned as unfit for human consumption. This gave rise to considerable controversy and the episode has been discussed at length elsewhere;[47] it was noteworthy for four reasons. One, Peacock had introduced a technological improvement which helped him overcome time and distance in jam manufacture; two, bureaucracy lagged behind innovation as it always does; three, food microbiology was in its infancy; four, there was no provision for a portion of a sample taken for analysis by government officers to be given to the maker of the food sampled.

Australian Academy of Technological Sciences and Engineering