Freeze drying : Freeze drying is a method of drying involving freezing and then the sublimates of the ice under vacuum. Removal of water from a product while it is frozen by sublimation is called freeze drying. After the preliminary preparation of food is carried out as for other methods of drying and then the prepared food is frozen, placed in a vacuum chamber and a small amount of heat is applied. Fresh flavours and textures are better preserved by freeze-drying than by sun-drying or other procedures of artificial drying without vacuum. This method is costly. Freeze-dried fruits and vegetables generally have better texture and rehydration quality. In smoking drying is the main preservative factor, especially drying at the surface of the food.
Dehydration of grapes (Raisin making): The process of raisin making involves selection of raw material, preparation of bunches, lye treatment, dipping oil treatment, sulphur fumigation, drying in sun or shade or drier, separation of raisins, washing in luke warm water, curing, packing, storage for marketing. Work done at this institute indicated that apart from Thompson seedless, variety Arkavati is also suitable for raisin making. Grapes at 24 0 Brix produces best quality raisins.
The quality of raisins is determined to a greater extent by raw material composition and its maturity . The desirable characters of raisins are small size, round and plumpy shape, very sweet taste with greenish or light brown colour.
Freezing may preserve foods for long periods of time provided the quality of the food is good to begin with and the temperature of storage is far enough below (-180C) the actual freezing temperature of food for long preservation. In vegetables, enzyme action may still produce undesirable effects on flavour and texture during freezing. The enzymes therefore must be destroyed by heating ( blanching)before the vegetables are frozen.
In this case the lower temperatures is used –320 C to –400 C to freeze foods so rapidly that fines crystals are formed and the time of freezing is greatly reduced over that required in sharp freezing. In quick freezing, large amount of food can be frozen in a short period of time.
- The basic objective is to choose the location which minimizes the average production cost, including transport and handling. It is an advantage, all other things being equal, to locate a processing unit near the fresh raw material supply. It is a necessity for proper handling of the perishable raw materials, it allows the processing unit to allow the product to reach its best stage of maturation and lessens injury from handling and deterioration from changes during long transportation after harvesting.
- An adequate supply of good water, availability of manpower, proximity to rail or road transport facilities and adequate markets are other important requirements.
Various processed products can be made from vegetables are given below: Tomato - Canned whole or in form of pulp, puree, paste or juice and also in form of sauce or ketchup. Onion - Dehydrated(flakes, granules, powder), paste Peas - Canned, frozen, dehydrated Okra - Canned, frozen, dehydrated Watermelon - Ready to serve beverage Cauliflower - Frozen, dehydrated Carrot - Dehydrated, Frozen, juice Beans - Canned, dehydrated, frozen Mushroom - Canned, dried, frozen Pickles - mixed vegetables like cucumber, cauliflower, carrot, peas
Processing into pulp or puree.
Converting into beverages
16 plants were needed for conducting field trials in rose
What points one should remember in fertilizer management of vegetable seed crops for maximum seed yield and quality.
While fertilizing vegetable seed crops restraint should be exercised in the use of nitrogen. Excessive application of N may promote vegetative growth at the cost of reproductive growth. While liberal application of P and K is required to enhance seed production especially supply of P & K at later stages of growth has beneficial effect on proper seed growth and seed filling.
16 plants were needed for conducting field trials in tube rose.
Tomatoes can be processed into a simple and intermediate product like puree which can be used as a substitute for tomatoes or can be converted into ketchup, sauce etc., during later stages.
Whether foliar sprays of water soluble fertilizers could be given for vegetable seed crops. If so, which fertilizers, at what concentration, at what stage and how many sprays are to be given?
Yes. Foliar fertilization of water soluble fertilizers could be given to vegetable seed crops for enhancing seed yield and quality. Combinations like 19-19-19 or 13-46-0 could be very profitably used at a concentration of 0.5 percent. About five sprays during the grand growth and seed filling stage will be required.
What is the most optimum stage for harvesting in the case of vegetable crops to obtain higher seed yield and quality ?
Optimum harvesting stage is very important to obtain higher seed yield and quality in many crops. Early harvest may lead to unfilled, under sized and shrivelled seed. Delay in harvest may lead to shattering losses and field weathering of seed resulting in decline in the quality of seed. Optimum harvesting stage varies from crop to crop like Tomato at red ripe stage, brinjal at change of colour to bronze or yellow, chillies of red ripe and complete drying on the plant, capsicum at full change of colour from green to complete yellow or red stage with fruits becoming soft, onion at the appearance of black seeds in 1/4th of the umbel, okra at just full drying of the pods, i.e. before shattering starts, watermelon at full ripe stage of the fruit i.e. when the adjoining tendril dries, fruit turns yellow on ground side and gives dead sound instead of metallic sound, muskmelon at full slip stage i.e. fruit detaches from the vine, crucifers at the complete drying stage of pods.
Mainly two chemical preservatives are permitted.
- Potassium metabisulphite.
- Sodium benzoate