Preparation Juice is prepared by mechanically squeezing or
macerating (sometimes referred to as cold pressing) 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
tomatoplant. Juice may be prepared at home from fresh fruit and vegetables using a variety of hand or electric
juicers. Many commercial juices are
filtered to remove fiber or
pulp, but high-pulp fresh orange juice is a popular beverage. Additives are put in some juices, such as sugar and artificial flavours (in some fruit juice-based beverages) or savoury seasonings (e.g., in
Clamato or
Caesar tomato juice drinks). Common methods for the preservation and processing of fruit juices include
canning,
pasteurization,
concentrating,
freezing,
evaporation, and
spray drying. Although processing methods vary between juices, the general processing method of juices includes: • Washing and sorting food source • Juice
extraction • Straining,
filtration and
clarification • Blending pasteurization • Filling, sealing and sterilization • Cooling, labeling and packing After the fruits are picked and washed, the juice is extracted by one of two automated methods. In the first method, two metal cups with sharp metal tubes on the bottom cup come together, removing the
peel and forcing the flesh of the fruit through the metal tube. The juice of the fruit then escapes through small holes in the tube. The peels can then be used further, and are washed to remove
oils, which are reclaimed later for usage. The second method requires the fruits to be cut in half before being subjected to
reamers, which extract the juice. After the juice is filtered, it may be concentrated in
evaporators, which reduce the size of the juice by a factor of 5, making it easier to transport and increasing its
expiration date. Juices are concentrated by heating under a
vacuum to remove water, and then cooling to around 13 degrees Celsius. About two-thirds of the water in a juice is removed. Pulsed electric field processing is a type of nonthermal method for
food preservation. Pulsed electric fields use short pulses of electricity to inactivate microbes. In addition, the use of PEF results in minimal detrimental effects on the quality of the food. PEFs kill microorganisms and provide better maintenance of the original colour, flavour, and nutritional value of the food as compared to heat treatments. This method of preservation works by placing two electrodes between liquid juices, then applying high-voltage pulses for microseconds to milliseconds. The high-voltage pulses have an intensity in the range of 10 to 80 kV/cm. The processing time of the juice is calculated by multiplying the number of pulses by the effective pulse duration. The high voltage of the pulses produces an electric field that results in the inactivation of microbes that may be present in the juice. The PEF temperatures are below the temperatures used in thermal processing. After the high-voltage treatment, the juice is aseptically packaged and refrigerated. Juice is also able to transfer electricity due to the presence of several ions from the processing. When the electric field is applied to the juice, electric currents are then able to flow into the liquid juice and be transferred around due to the charged molecules in the juice. Therefore, pulsed electric fields are able to inactivate microorganisms, extend shelf life, and reduce the enzymatic activity of the juice while maintaining similar quality as the original, fresh-pressed juice.
Emerging or aspirational technologies Fruit juices contain compounds that can be undesirable to consumers. Apple juices can be cloudy, and grapefruit juices can be bitter.
Enzymatic technologies, involving respectively
pectinases and
naringinase, address these problems. ==Health effects==