About 67 million tons grapes produced in the world during 2008-09. Countries all over the world produce grapes and the import/export of grape products extends over borders, oceans and continents. Major grape producing countries are Italy, China, USA, Spain, France etc. India ranks 11th in grape production with production of 1.8 million t grapes from an area of 80,000 ha. The major consumption of grapes in India is as fresh followed by raisins, wine and juice. While at global level 78-80% grapes processed in to wine followed by raisin, fresh grapes and juice. Total grape export from India was 118132 t during 2009 out of which 38,688 t was exported to Europe. The value addition in grapes and diversification of grape products also provide good returns to growers. The raisin industry is also gaining good results. A quantity of 105000 t raisins was produced during 2009. But, it is not possible without active involvement of food industry in value addition sector. Adding value to grapes may be as simple as creatively packaging the grapes. This might be washing and packaging the fruit for a ready-to-eat snack or placing the fruit in a decorative container either alone or with other fresh fruit as a “farm fresh gift basket.”
A. Value added products
The dried grapes are known as raisins. The Thompson Seedless white and thin skinned grape variety has monopoly in the production of best quality raisins. At global level, about 90% of raisins produced by drying of Thompson Seedless and clones. In India, grape drying is performed under raisin sheds. Before drying, the grape bunches treated with grape dying oil. It is prepared by mixing of 15 ml ethyl oleate and 25 g potassium carbonate in one liter of water. The grape bunches dipped in this solution for 2-5 minuets. Then spread ion single layer on mesh under sheds. In some countries the “Drying on Vine (DOV)” practice is used for grape drying. During drying, water in the grape berry moves through the cells to the cuticle. It must then pass as vapor through the wax platelets and escape from the outside surface. High air temperature and rapid air movement lower relative humidity are suitable climatic conditions for faster drying of grapes. Larger berries and thicker skins increase drying time. Various factors such as drying structures, climatic conditions, dipping treatments, sulphur fumigation etc. are deciding factors of raisin quality. In some seasons, under persistent wet and humid conditions, mould begins to spread through the fruit on the racks. The green coloured raisins fetched more price in market than dark brown coloured. The colour of raisins depends on drying temperature, presence of sunlight and high humidity. Generally, raisins with moisture content of 12-15% found suitable for storage. Lower moisture contained raisins become hard and high moisture contained raisins looses quality during storage.
Wine is produced through process of must (red wine) or juice (white wine) fermentation which initiated by adding yeast. During this process of fermentation the sugar contained in the must / juice is transformed into alcohol along with the output of carbon di-oxide gas. Yeast is only able to fulfill its task between 4 °C and 36 °C. Fermentation stops completely when the sugar is completely transformed, but may also be stopped artificially by lowering the temperature of tanks. The grape skins give the colour to the wine. Rose wine can be made from juice of red grapes. The white wines made from fermentation of grape juice from white wine grape varieties. Fermentation and maturation can be completed in steel or oak containers. The suitable temperature for fermentation of grapes for making white and red wines is 15-17 and 18-22 °C, respectively.
The fermentation period lasts from a few days, for lighter wines and up to 30 days for stronger wines. The longer the contact of the juice with the skins is maintained, the stronger the colour and tannin content of the wine. This can give the wine a fuller body and potentially a longer life span in the form of age reachable. Too much tannins can, however, ruin a wine. At this point the red wine is separated from the skins and seeds and begins the aging process in barrels and later bottles. White wine differs from red not only in terms of colour. Traditionally they are fermented without maceration, have lower tannin content, a lighter body, a higher acidity and a shorter aging time compared to red wines. Several fermentation conditions such as fermentation temperature, skin contact time, and skins to must ratio (berry size) influence the extraction of anthocyanins and other phenolic compounds. The wines have several health benefits.
Various factors like sugar level, acid content and flavor constituents decide the juice quality. The specific composition of the juice from any cultivar varies from year to year and changes continually during ripening. The composition of a specific cultivar also affected by one area of growth to another and from one vineyard to another since composition is affected by several factors such as soil, climatic conditions, biotic and abiotic stress and vineyard management practices. In general, color of grape juice is the result of anthocyanin pigments located in or near the skin. Grape juice can be extracted using either a hot-press or a coldpress technique. Extraction temperature has a significant effect on quality parameters of juice. The hot-press method also yielded more juice than cold pressing. Within a cultivar, pressing method had no effect on soluble solids but did cause significant differences in pH and color density.
Browning increased with increased extraction temperature. Crushing the grapes and adding polygalacturonase and SO2, followed by holding the grapes for 24 hr at room temperature prior to low temperature extraction, resulted in juice with good color and flavor. Color is especially affected by storage temperature. All color parameters changed more in juices stored at 90°F than in those stored at 36° or 75°F. But pressing grapes without heating creates several problems: 1) enzymes that promote browning are not inactivated; 2) juice yield from the grapes is poor because of the thick skins; 3) color extraction of dark-skinned cultivars is low; and 4) a high percentage of the flavor remains in the skins.
The word vinegar means sour ("aigre") wine ("vin") in French. Vinegars can be made from a variety of raw materials. Wine connoisseurs may consider it a waste to convert good wine into vinegar, however, there are economic reasons why this could be a profitable plan. First, high quality vinegars often sell for more than the wines from which they were made.
Since ancient time evaporated grape syrup pekmez has been traditionally and industrially produced in most Anatolian regions. Pekmez is produced in low heat evaporation steps, commercially sold and commonly consumed in viscous liquid and solid forms The liquid concentrated form of the pekmez contains minimum of 65 % total crystalline and soluble solids (45.3 to 75 °Brix). The viscosity of pekmez increases with increasing solids concentration and decreasing temperature. Grape pekmez is also produced and sold in thick, creamy and solid form. The color of the pekmez changes from dark brown to white depending on the processing conditions, concentration, types of bleaching agents, heat and mixing rate.
Verjus is the pressed, unfermented juice of unripe wine grapes. It was first used in the sixteenth century, probably “as a result of the right given to peasants to pick the unripe grapes from the second growth left on the vine by vineyard owners.
Verjus is the tart, fresh juice of unripe wine grapes. It is a culinary ingredient indigenous to the world's wine producing regions that is used in sauce making, for poaching fish and meat, and to dress lettuces, vegetables and fruit. Verjus or "verjuice" as it is sometimes called, literally means green juice in the sense that it's made from fruit that has yet to fully ripen — it's green. It is used to add acidity to foods, an important component in food and in cooking. The verjus is used any recipe that calls for lemon juice as a contrasting acid, in place of or in addition to broth or stock, to making a refreshing sorbet and add to beverages.
7. Sweet Spreads
The process of making grape jelly, jam, preserves, butter, or marmalade consists mainly of cooking the grapes and/or their juice in combination with sweeteners and pectins to the proper solids level. Jam, preserves, and grape butter are made from whole or crushed fruits. Preserves differ from jam, only in that the fruit pieces are usually larger. Muscadine butter is made by cooking the screened fruit (seeds and skins removed) to a smooth, thick consistency. It differs from jam in its ratio of fruit to sweetener and in the final solids concentration. Jelly is made from the fruit juice so that the product is clear and firm enough to hold its shape when removed from the container.
8. Other Dried Products
Drying involves the removal of moisture from foods to inhibit microbial growth and prevent spoilage. At the same time, it is important to preserve as much of the product’s nutritive value, natural flavor, nutraceuticals, and quality as possible. Fruit leathers get their name from the fact that, when dry, the product is shiny and has the texture of leather. Fruit leather is essentially the same as commercial fruit roll products. They are made by drying puree of fruit on a flat surface. A single fruit can be used or purees of more than one fruit can be mixed to give a mixed fruit flavor. Sugar may be added to the leather to reduce the tartness of the fruit, or sugar may be omitted to produce a product appropriate for use by those on a reduced sugar diet.
After grapes are pressed to remove the juice, the remaining press fraction, or pomace, consisting of skins and seeds, is a large percentage of the fruit. It is approximately 40% skin, 50% pulp and 10% seed. Thus for processing operations like juice, wine, and jelly production, approximately half of the fruit may be lost as press fraction. The pomace puree has been used in a variety of products including fillings and toppings for baked goods, fruit extenders and blends, fruit roll-ups, sauces, toppings, and as ingredients in fruit drinks, frozen fruit bars, cakes,muffins, candies, and breads.
A variety of grape seed extract products are coming into the ingredient market. Grape seed extracts are currently being used as nutritional supplements in fruit-flavored beverages and beverage mixes and will soon appear in hot and cold ready-to-eat cereals, meal replacers, snack bars, yogurts, and frozen dairy desserts.
Grape seed oil is a by-product of the grape industry. The oil can be extracted from the seeds in a variety of ways including pressing, soluble extraction, and through centrifugation. Grape seed oil is low in saturated fat and high in unsaturated fat (the heart-healthy kind). A tablespoon of grape seed oil has about 10 milligrams (14 IU) of vitamin E, slightly more than sunflower or safflower oil, which are also high in this vitamin. Grape seed oil has been used in soaps and paints and for food use. It can be used as a cooking oil since it has a high smoke point, meaning that it can be used to cook at high temperatures. The grape seed oil product is marketed as a heart-healthy alternative to mayonnaise, and its packaging includes a hang tag that refers to studies showing the oil’s ability to raise HDL cholesterol and lower LDL.
Pigments extracted from grape skins are other by-products of the juice and wine industry that are receiving considerable attention as food ingredients. Depending on the level of usage, these pigments have the potential to both color products and increase the nutraceutical content of the foods containing them. The large scale production of juice and wine from these grapes assures an abundant supply of these by-products.
Grapes are significant sources of several phytochemicals (chemicals found in plant foods) that have been associated with disease prevention in humans. High concentrations of gallic acid, catechin, epicaechin, ellagic acid, and resveratrol found in the seeds and skins give muscadines a high antioxidant capacity. A number of components contribute to the antioxidant capacity of muscadine grapes. Antioxidant compounds include vitamins, phenols, carotenoids, and flavonols. The most phenolics in the grapes were located in the skins and seeds.
Dr. Ajay Kumar Sharma, Senior Scientist
National Research Centre for Grapes,
P. B. No.3, Manjri Farm PO, Solapur Road, Pune-412 307