अंगूर का रस - स्वास्थ्य के लिए एक घूंट ले

India is ranked 12^th in the world in terms of grape production. About 78% of production in India is utilized as table purpose, 17-20% for raisin production and remain for juice and wine. Juicing is an excellent way to absorb the maximum nutritional content of fruits and vegetables. All the enzymes, water-soluble vitamins and minerals built-in in these foods are condensed into one glass of juice and, because of the deficiency of fiber; the vastly concentrated nutrients go straight into the bloodstream. Grapes are an excellent source of potassium, which encourages an alkaline blood balance and also stimulates the kidneys and regulates heartbeat. In addition to mineral elements of sodium, potassium calcium, phosphorous, iron, copper and manganese, grapes also contain biotin, niacin, inositol, pantothenic acid, pyridoxine hydrochloride, thiamine, folic acid, ascorbic acid, choline and trace amount of riboflavin and vitamin B₁₂. The restorative power of grapes is phenomenal, cleansing the liver and removing the uric acid from the body. Grapes also contain a phytochemical that appears to protect each cell's DNA from damage. Studies have shown a lower incidence of cancer in the areas of France where this grape fast is practiced yearly. The flavour of grape juice is the result of a combination of sugars, acids, anthranilate, volatile esters, alcohols and aldehydes. The polyphenol composition and antioxidant properties of different red grape cultivars viz.; Pusa Navrang, Ruby Red,Merlot, Cabernet Sauvignon, and Pinot Noir were studied at NRCG. The antioxidant properties were significantly high in whole grapes of Pusa Navrang followed by Pinot Noir, Ruby Red and Merlot. 

Total polyphenols in Indian grapes ranged between 3-58%. All the grape polyphenolic extracts caused a dose dependent of free radical. The inhibitory effect was compared to that observed with vitamin C but higher than that observed for a-tocophenol used as positive control. Maximum effects were in seed phenolic extracts of Pandheri Sahebi colourless grapes. Whole grape phenols of Banglore Blue coloured grapes showed higher antioxidant activity. Indian grapes exhibited chemopreventive properties (Pakhaleet al.2007). 

Due to consumption of fresh grape at high level, which is about 75-80% of total grape production, juicing of grapes is not properly attended in India. However, a lot of juice brands are available in market except grape. It is proper time to exploit this area in order to consider the common man health. There are some research gaps and can be filled by identification of suitable varieties, zone-wise identification of maturity indices, increment in juicing efficiency, development of suitable technology and packing and storage.

Fig.1: Fruit based beverage market in India (Anonymous, 2006)

Grape Varieties for juice purpose 

Nine varieties were evaluated for juice quality. Overall acceptance of the juice based on organoleptic score was better for Country Bangalore followed by Gulabi x Bangalore Purple, Concord, Arka Shyam and Pusa Navrang. However, juice yield per vine from these varieties ranged between poor to moderate. At IIHR, Bangalore, Arka Shyam was rated a good variety for juice purpose over Banglore Blue and Concord. Pusa Navrang is a double cropper under Pune conditions with minimum or negligible risks for plant protection. It is resultant of a cross between Madelien Angevine and Ruby Red, developed at IARI, New Delhi. The variety is teinturier hence the pigments are contributed both by the pulp and skin. The anthocyanin pigments are stable and juice can be kept up to 9 months even under ambient room conditions. Though this variety is rich in pigments but poor in flavour, hence blending with other aromatic variety such as Muscat, Black Champa etc is desirable. 

Table 1: Juice properties of some varieties studied at NRCG

 Table 2: Cultivation factors influencing juice quality (Bates et al,2001)

Table 3: Influence of fruit harvesting and handling on juice quality (Bates et al, 2001) 

Harvesting and crushing of grapes for Juice

To prepare quality juice, harvest the berries when they attained full maturity,maximum colour, TSS and flavour. Crush the harvested grapes within 24 hrs after picking in order to avoid decay and fermentation. The juice extraction method depends upon variety, scale of industry and location. It is mentioned in flow chart that for grape juicing usually two methods namely cold press and hot press followed. Application of enzymes increases the juicing efficiency.

Excessive extraction temperatures must be avoided to preserve the juice quality. 

A hot-press method yields more juice that contains higher total solids, more non-sugar solids, tannins, pigments and other substances than a cold-press juice operation. Grapes are unique from other fruits in that after juice extraction, the argols (potassium bitartrate, tartar in crude form) and tartrates must be precipitated. Otherwise, the argols will settle out upon cooling or even when filtered juice is refrigerated. These crystals, although harmless, are aesthetically unpleasant and can be mistaken for glass fragments (Bates et al, 2001). 

Colour is one of the most important qualities of grape products. A typical purple-red is associated with high quality `Concord' grape juice or other red grape juice, but changes in colour from purple-red to brown during processing and storage cause a drastic decline in quality. This is true of all cultivars and species of grapes. The red muscadine grape anthocyanin pigments are extremely unstable under conventional warehouse storage temperatures. Extraction temperature influences juice colour by affecting the activity of polyphenoloxidase (PPO), which accelerates the rate of degradation of anthocyanins (colour ingredient) in crushed grapes. Inactivation of PPO by heat prior to depectination prevents loss of anthocyanins during extraction and subsequent storage. Storage temperature and time are primary factors for stability of colour in long-term storage. Juice from mature grapes had better quality initially than juice from less mature grapes but declined in quality more rapidly during storage. Storage at 35°C resulted in a more rapid loss of quality than storage at 24°C (Bates et al, 2001). 

References

1.Anonymous, 2006. Fruit beverages. Modern Food Processing, 2(2): 36.
2. Bates, R. P.; Morris, J. R. and Crandall, P. G. 2001. Principles and practices of small - and medium - scale fruit juice processing. FAO, Rome, Italy. Pp 1-151. 
3.Pakhale, S. S.; Bhushan, B.; Karibsappa, G. S. and Ramchandani, A. G. 2007. Free radical scavanginy activity of polypgenols from Indian grapes by electron spin resonance spectrometry. Indian Journal of Expt. Biol. (Accepted).

Authors:

Dr. Ajay Kumar Sharma,

Senior Scientist, National Reseacrh Centre for Grapes,

P. B. No.3, Manjri Farm PO, Solapur Road, Pune-412307,

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