Juice is a liquid that is naturally contained in fruit and vegetables. It is commonly consumed as a beverage or used as an ingredient or flavouring in foods. Juice is prepared by mechanically squeezing or macerating fruit or vegetable flesh without the application of heat or solvents. For example, orange juice is the liquid extract of the fruit of the orange tree, and tomato juice is the liquid that results from pressing the fruit of the tomato plant. Common methods for preservation and processing of fruit juices include canning,pasteurization, concentrating, freezing, evaporation and spray drying. A concentrate is a form of substance which has had the majority of its base component (in the case of a liquid: the solvent) removed. Typically this will be the removal of water from a solution or suspension such as the removal of water from fruit juice. One benefit of producing a concentrate is that of a reduction in weight and volume for transportation as the concentrate can be re-constituted at the time of usage by the addition of the solvent.
The following processes concerns mainly with the fruit to juice concentrate production. Thorough process outline will be presented in the final paper.
Oranges are harvested from large groves. When the mature fruit is ready to pick, a crew of pickers is sent in to pull the fruit off the trees. For higher picking rate companies on the other hand, use mechanical pickers instead of crew of pickers. The collected fruit is sent to plants for juice processing. The oranges are generally shipped via truck to juice extraction facilities, where they are unloaded by a gravity feed onto a conveyor belt that transports the fruit to a storage bin.
As the fruits are unloaded from the trucks, they are washed and loaded to belt conveyors proceeding inside the extraction plant. This process removes debris and dirt and reduces the number of microbes.
Selection and Sizing
Before extraction process, the fruits are manually selected and grouped based on size and color.
Proper juice extraction is important to optimize the efficiency of the juice production process as well as the quality of the finished drink. The latter is true because oranges have thick peels, which contain bitter resins that must be carefully separated to avoid tainting the sweeter juice. There are two automated extraction methods commonly used by the industry. The first places the fruit between two metal cups with sharpened metal tubes at their base. The upper cup descends and the fingers on each cup mesh to express the juice as the tubes cut holes in the top and bottom of the fruit. The fruit solids are compressed into the bottom tube between the two plugs of peel while the juice is forced out through perforations in the tube wall.
At the same time, a water spray washes away the oil from the peel. This oil is reclaimed for later use. The second type of extraction has the oranges cut in half before the juice is removed. The fruits are sliced as they pass by a stationary knife and the halves are then picked up by rubber suction cups and moved against plastic serrated reamers. The rotating reamers express the juice as the orange halves travel around the conveyor line. For massive industrial production, the most effective is the former method. The peels and pulps are collected to be used later for further steps in the production.
Pasteurization is still required to further retard spoilage. Pasteurization also inactivates certain enzymes which cause the pulp to separate from the juice, resulting in an aesthetically undesirably beverage. This enzyme related clarification is one of the reasons why fresh squeezed juice has a shelf life of only a few hours. Flash pasteurization minimizes flavour changes from heat treatment and is recommended for premium quality products.
Several pasteurization methods are commercially used. One common method passes juice through a tube next to a plate heat exchanger, so the juice is heated without direct contact with the heating surface. Another method uses hot, pasteurized juice to preheat incoming unpasteurized juice. The preheated juice is further heated with steam or hot water to the pasteurization temperature. Typically, reaching a temperature of 185-201.2° F (85-94° C) for about 30 seconds is adequate to reduce the microbe count and prepare the juice for filling.