Pigments on Fruits

Pigments on Fruits
Pigments, which are the chemicals responsible for skin and flesh, undergo many changes during the maturation and ripening of fruits. These include the following:

• 1. Loss of chlorophyll (green color), which is influenced by pH changes oxidative conditions and chlorophyllase activity.
  
• 2. Synthesis and elevation of carotenoids (yellow and orange colors)
  
• 3. Development of anthocyanins (red, blue and purple colors), which are fruit specific.

Beta carotene is a precursor to vitamin A and thus is important in terms of nutritional quality.

Carotenoid are very stable and remain intact in fruit tissues even when extensive senescence has occurred. Anthocyanins occur as glycosides in the cell sap.

They are water greater soluble, unstable and are readily hydrolyzed by enzymes to free anthocyanins, which may be oxidized by phenoloxidases to give brown oxidation products.
Pigments on Fruits

How grape juice is manufactured

How grape juice is manufactured
The Concord variety is chiefly used for the manufacture of grape juice. The grape are washed in acid or alkaline solution, then in water to remove spray residues, then destemmed and crushed by mechanical means. The crushed grapes are heated to about 180 F to extract pigment from the skins, after which the heated materials subjected to mechanical pressure while enclosed on cotton press cloths. The juice is then filtered, pasteurized by heating to 1790 F, and stored in bulk in covered tanks at about 40 F. This provides for the separation of tartaric acid slats. The juice is then siphoned off from the tartrate and treated with enzymes, which break down pectin, or with casein for purposes or clarification. It is then filtered and bottled. The bottles are capped and then pasteurized by heating in water at 170 F for 30 min.

To produce grape juice concentrate, grape juice is subjected to heat and evaporation until concentrated. Volatile components can be recovered from the process, and they can be added back to the concentrate. The concentrated juice may be frozen in retail sized containers, or it may be shipped in large tanks to food processors for remanufacturing process.
How grape juice is manufactured