Processing of Horticultural Crops (1+2)

Inoculation and Fermentation

Inoculation and Fermentation
The grape juice (must) after addition of sugar syrup is fermented by addition of a culture of pure wine yeast Saccharomyces cerevisae var. ellipsoideus as a starter @ 2-5%. For proper fermentation temperature should be maintained between 27-29^oC. A low temperature below 10^oC and higher than 38^oC, almost ceases the fermentation process. After three days the contents are filtered through muslin cloth and again allowed to ferment for another 10 days, so that yeast cells and other solids settle at the bottom. For other fruits the time taken for completion of fermentation varies between 15-20 days.

Aging and packaging: When fermentation is complete, the clear wine is siphoned out and further clarified with the help of fining agent like bentonite. When all the colloidal materials settle down along with bentonites, the clear wine is siphoned off and filtered if necessary. The clear wine is filled into bottles or barrels completely and sealed airtight to exclude air and allowed to mature for 6-8 months. During this aging process, the wine loses its raw and harsh flavour to a smooth and characteristic aroma. Generally, oak wood barrels are used for aging as they impart a finer aroma to the wine. During maturation dissolved carbon dioxide escapes and spontaneous clarification occur. The extraction of oak flavours and limited oxidation also occur during this process. Astringent tannic substances precipitate and result in slow smoothing of the taste. Generally wines are pasteurized at 82-88^oC for 1-2 minutes followed by bottling. To produce fortified wines, alcohol is added in the form of brandy or wine spirit. For improving the taste sugar may be added before final packing of the wine.

2. Cider: Cider is fermented apple juice, which is made from apples. In India, dessert apples are employed for preparation of good quality of cider. The alcohol content ranges from 4 to 6 percent in cider. Apples with high tannin (0.1 to 0.3%) contents are generally used for the preparation of cider.
Apples are crushed and pressed to extract juice, then its sugar content is raised to 220 Brix by addition of cane sugar. It is preserved with 100 ppm SO₂ and pure culture of wine yeast is added for fermentation. Sometimes di-ammonium hydrogen phosphate (DAHP) (0.02 to 0.05%) is added as a food supplement for the yeast. The method of fermentation is similar to that of other wines. The cider is aged in oak wood barrels after filtration. The matured cider is heated to 65⁰C filled into bottles, crown corked and pasteurized at 60⁰C for 30 minutes. Apple cider is also carbonated for better acceptability.

3. Vermouth: It is a fortified wine in which alcohol contents ranges from 15 to 21%, and flavoured with mixture of herbs & spices.

4. Brandy: Brandy is a distillate obtained from the distillation of wine and generally aged in small oak cooperage, example cognae and armagnae.

C). Vegetable juices: Generally fruit juices are consumed either fresh or processed form. Certain vegetable juices are also consumed in fresh form but for mostly medicinal purpose. Tomato juice is consumed in processed form either canned or bottled. Tomato is also used as soup, a warm beverage prior to meal.

D). Fruit juice powders: Fruit juice powder process includes the evaporation of water from fruit juices to bone dryness. These powders are highly hygroscopic in nature, therefore proper packaging is required. These powders are prepared from strained fruit juices by different drying techniques such as spray drying, double-drum drying, vacuum drying, freeze drying and foam-mat drying. The powder has a long shelf-life and is soluble in cold water. Reconstitution of the powder yields full strength fruit juice drinks.
During the drying process much of the characteristic fresh flavour is lost, which is compensated by adding natural fruit flavour in powder form. Mango, orange, lemon, guava, passion fruit and tomato juice etc can be dried into powder.

E). Fruit juice concentration and evaporation: Concentration is a process of removal of water from juice to increase concentration of soluble solids in fruit juices. It is also used to pre-concentrate a juice for further use in processing such as spray drying or drum drying. Concentration has the significant advantages to the processing, to reduce storage, packaging and transport costs, concentration of soluble solids aid in preservation by reduction in water activity. The juice concentrate can be used as base material for making various food and beverages formulation. Concentration of juice can be carried out by evaporation, freeze concentration by using reverse osmosis.

Evaporation is most commonly used for preparation of apple juice concentrate at commercial scale. The evaporator consists of a steam fed heat exchanger to heat the fruit juice to a desirable temperature for evaporation. There is a separator from which vapour is separated from the concentrated liquid phase, a condenser to effect condensation of the vapour and its removal from the system, and a fractionating still for aroma recovery. Generally, falling film evaporator is used to concentrate the apple juice. Final concentration is carried out in centritherm evaporator. Apple juice is concentrated to 6-7 folds from its initial total soluble solids. Apple juice concentrate is immediately cooled and stored in cold store in large barrels.

Advantages of concentration and evaporation

• Reduced weight and bulk compared to fresh juice result in economy in packaging, storage and transport.
• The whole crop of fruit is fully utilized during peak season, helps in lowering the prices.
• The product can be used as base material for making various beverages.

Concentrates of pure fruit juices particularly of orange, apple, pineapple and grape are highly popular.