TIME AND STAGE OF HARVEST AND HARVESTING TECHNIQUES FOR GRAPES NextEnd

HARVESTING Grape is a non-climacteric fruit and hence harvesting should be done at full ripe stage to get maximum quality. Signs of ripening of grape include formation of waxy layer on berry skin, softening and development of typical colour of specific variety, easy detachment of berries from stem on pulling, changing of taste from sour to sweetness and thickness of juice reaching values up to 18 to 20 o Brix. PreviousNextEnd

Ripening process in grapes is highly influenced by auxin- ethylene relationship. Ethrel application (250 ppm) improves colour development, quality and uniformity in ripening. In case of raisin grapes, ultimate yield of dried product depends on drying ratio and hence it is advisable to allow berries to ripen fully on vine so as to decrease water content and increase Brix values. In certain areas, these are harvested one to two weeks after pruning canes which causes berries to abscise more easily from clusters. PreviousNextEnd

Table grapes are harvested by clipping bunches from vines with minimal handling after judging individual bunches for maturity. Harvesting is done two to three times over a period of several weeks. Ripening is judged mainly based on sugar-acid ratio, which determines proper blend for table purpose. Sugar- acid ratio might be a more reliable indicator for grape harvesting. However, the harvest of varieties with lower acid content (0.40 – 0.75%) could be based on TSS content alone, while for the varieties with high acid (more than 0.95%), the criterion should be acidity alone. PreviousNextEnd

The varieties with medium acid content ( %) should be harvested based on the TSS/acid ratio. The ratio must be higher for low acid varieties than for high acid varieties to maintain a given level of acceptability. This ratio should be 20 to 50, below which fruits are too acidic and beyond which they are too sweet. At the time of harvest the sugar: acid ratio should be 27 to 37. The TSS: acid ratios worked out for a few varieties are as follows. PreviousNextEnd Thomson Seedless32.83Bhokri31.95 Beauty Seedless17.54Pusa Seedless29.24 Delight44.75Hur31.77 Per I ette19.32Bharat Early27.98

PreviousNextEnd In wine grapes, harvesting time depends mainly on type of wine to be made. Refractometer reading is the most important parameter to be considered. pH of juice is also important but is very difficult to adjust in the winery and wines with pH above 3.6 are potentially unstable. pH measurement is an expression of the free or active acidity at any stage in the development and represents the state of balance of the chemical constituents at that time. During growth, the pH of grapes constantly undergoes change, starting with low in the immature grape and reaching a high value in the over ripe stage.

It would appear reasonable, therefore, to draw the conclusion that pH can serve as an indicator of maturity. Generally white wine grapes are harvested at 19-23° Brix, more than 0.7% acidity and pH above 3.3. Criteria for red wine grapes are ° Brix, more than 0.65% acidity and pH above 3.4. Random samples of a few hundred berries from different vines are often taken for lab quality evaluation at a few days intervals and harvesting time is fixed accordingly. PreviousNextEnd

Grape should not be harvested until they are fully ripe. There are fully ripe. There are many indicators to the proper stage of grapes for picking but the taste is the most valuable indication of the ripeness of the bunch. For this purpose, the greenest berries, which are always near the tips, should be tasted. If they are good to eat, the entire bunch is ripe for picking. Fully ripe bunches should be picked for local consumption while for distant markets, bunches should be picked when still hard ripe so that they do not spoil during transit PreviousNextEnd

Ripe grape bunches should be clipped with scissors without injuring the berries. During handling, the natural bloom on berries must not be rubbed off. Harvesting should be done during the coolest period of the day. Bunches should not be exposed directly to the sun. trimming, grading and packaging should be done in shade. Undesirable berries viz.unripe, over ripe, small, misshapen, sun burnt, decayed, soft and bruised ahould be trimmed. Bunches should be graded according to the fruit quality, maturity and size and different grades should be packed in different containers PreviousNextEnd

For nearby markets, mulberry or bamboo baskets can be used, where as for distant market, wooden boxes of 4-5 kg capacity or Corrugated Fibre Board (CFB) cartons should be used. PreviousNextEnd  A number of factors influence yield from grape vines, the main ones being variety, training and pruning methods, climatic and soil conditions, management practices and also age of vines.  About 6-10 t ha- 1 can be obtained from vineyards with proper management and care. Average yield in India (21.5 t ha- 1 ) is the highest in world.  Economic life of grape vines is about 20years. Yield

Storage The grape berries can be kept without spoilage for 7 days at room temperature. Grapes can economically be stored up to days in cold storage. The optimum storage temperature recommended is -2 to C. PreviousNextEnd

ASSESMENT 1.Grape is a ____________ fruit a). Climacteric b). Non-climacteric 2.Ripening process in grapes is highly influenced by ______________relationship (Auxin-ethylene). 3 Ripening is judged mainly based on___________, which determines proper blend for table purpose. a). Sugar-acid ratio b). Acid only c). Sugar only 4. The optimum storage temperature recommended is ___________ ( -2 to C) 5. Harvesting is done over a period of several weeks. (True/ False). PreviousEnd