Fruit juice processing

Processed fruit juices are usually manufactured to a maximum oil content of 0.03% v/v at natural strength. 

It was realised that the method of processing fruit juices significantly influences the specific flavom of the fruit and consequently the quality of the juice. When producing concentrate from a high quality fruit juice, the recovery and isolation of the aroma during the concentration process is essential for adding it back to the juice upon reconstitution of the concentrate. 

Uses Foam control agent tor food processing, fruit juice processing, paper coatings, pesticides, herbicides, fertilizers, industrial detergents, cosmetic cleansers Features Food grade... 

Apple juice [3" ]. As a general rule, fresh juices have better color and flavor than processed juices. An undisputed advantage of processed juice is its extended shelf life and convenience. An important aspect to consider when processing fruit juice is trying to retain its natural properties, such as color, flavor, and aromas. 100 kg/h of an apple juice with moisture of 92 % (w/w) will be mixed with 200 kg/h of an apple juice with 94 % moisture (w/w). After being well mixed, they are passed through an evaporator to obtain a concentrated product with 50 % solids (w/w). How much water should be removed in the evaporator ... 

The OMD process provides the great advantage of working at both constant (and low) temperature and atmospheric pressure, with a consequent reduction in both thermal and mechanical damage. These gentle operating conditions are very important, especially in the concentration of heat sensitive materials in biomolecules, in natural colours, or in food processing (fruit juice production, for example). 

Finally, levels of furfural and 5-hydroxymethyl-2-furfuraldehyde have also been monitored in processed fruit juices by a high performance liquid chromatography method using a reversed-phase macroreticular column and phosphate buffer as eluent [399], These aldehydes are degradation products of L-ascorbic acid. The detection limit of this method was reported as 0.05 mg r which was insufficiently sensitive to detect the presence of furfural. 

Freeze Crystallization. Freezing may be used to form pure ice crystals, which are then removed from the slurry by screens sized to pass the fine sohds but to catch the crystals and leave behind a more concentrated slurry. The process has been considered mostly for solutions, not suspensions. However, freeze crystallization has been tested for concentrating orange juice where sohds are present (see Fruit juices). Commercial apphcations include fmit juices, coffee, beer, wine (qv), and vinegar (qv). A test on milk was begun in 1989 (123). Freeze crystallization has concentrated pulp and paper black hquor from 6% to 30% dissolved sohds and showed energy savings of over 75% compared with multiple-effect evaporation. Only 35—46 kJ/kg (15—20 Btu/lb) of water removed was consumed in the process (124). 

The introduction of synthetic materials into natural products, often described as adulteration , is a common occurrence in food processing. The types of compounds introduced, however, are often chiral in nature, e.g. the addition of terpenes into fruit juices. The degree to which a synthetic terpene has been added to a natural product may be subsequently determined if chiral quantitation of the target species is enabled, since synthetic terpenes are manufactured as racemates. Two-dimensional GC has a long history as the methodology of choice for this particular aspect of organic analysis (38). 

The corrosive effects to be considered (mainly simple corrosion of metals) are, as would be expected from the edible nature of foodstuffs which are not excessively either acidic or basic but which may contain sulphur, less severe than those often encountered with inedible materials containing reactive substances. The importance of corrosive efiects where foodstuffs are concerned lies not so much in the action of the foodstuffs on the metal involved as in the resultant metal contamination of the foodstuff itself, which may give rise to off-flavours, in the acceleration of other undesirable changes (by the Maillard reaction for example), and in the possible formation of toxic metallic salts. Metal ions generally have threshold values of content for incipient taste effect in different liquid foodstuffs. Except in the case of the manufacture of fruit juices and pickles, process plant failure through corrosion must be rare. Nevertheless all foodstuffs, particularly liquid ones, should be regarded as potentially corrosive and capable of metal pick-up which may be undesirable. 

Role of pectin methylesterase in tomato fruit ripening and quality attributes of processed tomato juice... 

Figure 3 Size fractionation of EDTA-soluble polyuronides from Rutgers and transgenic fruit juice processed by cold- and hot-break methods. Pectin from processed juice was extracted as ethanol-insoluble solids and size fractionated on a Sepharose CL4B column. Under the same chromatographic conditions, elution of the branched dextrans with average molecular mass 2000, 500, 252, 151, 40 and 17.7 kD-peaked in fraction number 46, 50, 54, 62, 67 and 72, respectively. Modified from Thakur et al. [23].

In this presentation, we will take examples of different fruit juice processes and will try to relate enzyme activities, the role they play and the transformation they occur in terms of finished products. These examples will concern apple juice, french cider, pineapple and wine. 

Even if these liquefaction processes are still not accepted worlwide (for instance in Europe), they should grow within the next few years. We do really believe that they are the processes of the future, and especially the process of pressing / pomace liquefaction because it is an easy process, it allows the production of quality juice combined with high yields within a great flexibility. Such high yields, low production cost and flexibility to process different fruits make that fruit juice producers are more and more choosing the pomace liquefaction. 

Exogenous enzymes are used to produce fruit juices more easily during different stages of the process i.e. maceration, liquefaction or juice depectinisation These biochemical tools induce specific degradations that the processor can integrate into his process line to manage and valorize the fruits transformation into juice. 

Since many years, pectolytic enzymes have been widely used in industrial beverage processing to improve either the quality and the yields in fruit juice extraction or the characteristics of the final product [1,2]. To this purpose, complex enzymatic mixtures, containing several pectolytic enzymes and often also cellulose, hemicellulose and ligninolytic activities, are usually employed in the free form. The interactions among enzymes, substrates and other components of fruit juice make the system very difficult to be investigated and only few publications are devoted to the study of enzymatic pools [3-5], An effective alternative way to carry out the depectinisation process is represented by the use of immobilized enzymes. This approach allows for a facile and efficient enzymatic reaction control to be achieved. In fact, it is possible to avoid or at least to reduce the level of extraneous substances originating from the raw pectinases in the final product. In addition, continuous processes can be set up. 

Citrus (oranges, lemons, grapefruit) is processed into juice and oil for human uses and into molasses and dried pulp for use as animal feed. The fruit is first washed with a detergent and rinsed with water. The oil is localized in oil sacs on the surface of the fruit. The surface is scarified under a water spray to form an emulsion of oil and water. The oil is recovered by centrifugation. Altered to remove high melting point fats, and dried with sodium sulfate, which is removed by filtration. 

---