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Vegetable processing
Article index
Vegetable - Juice | ||
Vegetable - Heat treated and frozen | ||
Vegetable - Pickling | ||
Vegetable – Drying |
Vegetable - Juice
Significant quantities of juice are produced from vegetable sources such as carrot, celery, beetroot and cabbage. In general, the fresh vegetables are first washed and sorted before being coarsely milled and then pressed to extract the juice. Most vegetable juices have low acidity, i.e. a pH >4.5, and therefore they require a full sterilisation process or freezing to be rendered safe.Vegetable juices are sometimes acidified with organic or mineral acids to reduce the pH, so that a milder heat treatment (pasteurisation) is then possible. Some low acidity juices are blended with high acid juices such as tomato, rhubarb, citrus, pineapple or sauerkraut, so that they are acidic enough to only require pasteurisation. Some vegetables may be blanched prior to acidifying and extraction. Root vegetables are usually peeled before maceration and extraction.
Vegetable - Heat treated and frozen
Process conditions vary depending upon the vegetable type but preliminary operations for both heat treated and frozen vegetables are similar to those described for fruits and usually involve washing, grading and screening to remove extraneous matter such as stone and dirt.After washing, the vegetables are peeled and may be trimmed. After peeling the vegetables may be left whole or cut in a number of ways such as sliced or diced. Some vegetables are washed after slicing to remove the surface starch. Most vegetables require blanching; steam or water blanching are the most common methods. The product is then rapidly cooled. After cooling the product may be re-inspected and screened before being quick frozen or filled into cans or glass jars, usually with a hot brine (sugar, salt, acid), and then heat processed. Vegetables generally undergo a full sterilisation process as the pH is to high to inhibit microbial action.