Food and nutrition.pdf

Chutneys, Pickles, Salted Vegetables and Sauces 249vegetables can be packed into a hot brine. The filled jars are sealed andpasteurized so that an internal vacuum forms when they are cool. Thesealed container then preserves the food by preventing re-contaminationand excluding air and sometimes light. Preservation depends on anadequate heat treatment and an air-tight (or 'hermetic') seal.There are three grades of syrup: a light syrup contains 200g sugarper"litre, a medium syrup 400-600 gil and a heavy syrup SOOg/I.The concentration of salt in brine is usually 15 gil. Acidic fruits requirerelatively mild heating conditions for pasteurization (e.g. 90-100°C for 10-20 minutes) to destroy yeasts and moulds, whereas less acidic vegetablesrequire more severe heat sterilization to destroy food poisoning bacteria(e.g. 121°C for 15-40 minutes, depending on the size of the container).Fruits can also be part-processed and stored until required in sugarsyrup or sodium metabisulphite solution (equivalent to 1000 ppm.) toallow production to take place for a larger part of the year.It is not advisable for inexperienced small scale processors to bottlevegetables unless they are acidified, because of the risk of poisoning frominadequately processed foods. Vegetables can however be processed bypasteurization if the acidity is first adjusted using citric acid or vinegar.'Double Jacketed' Pan for larger Scale Hoiling