Fruit presses

In general terms, fruits are collected, soiled and washed, and then subjected to a type of mechanical compression appropriate to the fruit concerned. Although there are general fruit presses that can be used for more than one fruit type, fruits such as citrus, pineapple and stone fruits are usually processed in specially designed equipment. 

Figure 3.4 Horizontal rotary press Universal Fruit Press HP5000 (Bucher-Guyer).

The extractors work well on freshly harvested, early fruit which has a firm structure. However, as the degree of maturity of the fruit progresses and as the fruit becomes softer, the operation becomes more and more difficult due to the softness of the mash and the decreasing water permeability of the mash layer. Water extraction systems are more and more replaced by the simpler fruit presses. 

Mazaheri, H., Lee, K. T, Bhatia, S., Mohamed, A. R. Sub/supercritical liquefaction of oil palm fruit press fiber for the production of bio-oil effect of solvents. Bioresource Technol 2010, 101,7641-7647. 

In the past, expression presses were used in many processes for extracting oil and juice, generally from seeds and fruits such as olives. Batch presses were typically used in these apphcations, and hand unloading of the pressed cake was often required. Batch presses that require hand unloading or extensive cleaning between pressings are rarely used now descriptions of various types are presented in earlier editions of this handbook. This section, therefore, describes mainly continuous presses. 

Screw Presses Figures 18-155 and 18-156 show screw presses. The rotating screw shown in Fig. 18-156 is of constant pitch and has a constant diameter of about 0.3 m (12 in). Pressure to squeeze juice from fruit placed in the press comes from restricting the opening at the end of the barrel with a hydraulically adjustable cone and by making the spindle of the screw thicker toward the discharge end. 

FIG. 18-155 Cross section of screw press used for fruit juice ( 32j (Ij hopper, [1] perforated sheets, (oj nuiin. shaft, (4.) perforated ca e, (.5] driiinin cylinder, (Bj cone, i ] hv draiilic cvlinder, (8j driiinin cvlinder oil, (9j earliox. (Courtcsij of the h ivnch Oil MW Mnehinenj Co.)... 

Screw presses were traditionally used for seeds and fruits that had to be mechanically ruptured to release the liquid in the seeds or cells... 

The world demand for citric add around 1900 amounted to some 10,000 tonnes per annum. This was realised by pressing citrus fruits and precipitation of the citric add as calcium titrate. An Italian, government-led cartel had virtual monopoly of this process and as such the price of citric add was very high. 

Fig. 9.7 Bioluminescence of Panellus stipticus fruiting body (1) fluorescence of PM-2 in the presence of CTAB upon excitation at 440 nm (2) chemiluminescence of PM-2 in the presence of CTAB (3) chemiluminescence of PM-2 in the presence of 3-(dodecyldimethylammonio)propanesulfonate (SB3-12) (4) and chemiluminescence of the hot-water treatment product of PM-1 in the presence of SB3-12 (5). Curves 2-5 were measured in 2 ml of 50 mM Tris-HCl buffer (pH 8.0) containing 0.18 mM EDTA. Chemiluminescence was elicited by the addition of 5 p.1 of 50 mM FeSC>4 and 10 xl of 10% H2O2. From Shimomura, 1991b, with permission from Oxford University Press.

GOODWIN T w and goad l j (1971) Carotenoid and triterpenoids , in Hulme A C, The Biochemistry of Fruits and their Products, London, Academic Press, 305-28. 

Gross, J., Chlorophylls, in Pigments in Fruits, Gross, J., Ed., Academic Press Inc., London, 1987, chap. 1. 

Britton, G. and Hornero-Mendez, D., Carotenoids and colour in fruit and vegetables, in Phytochemistry of Fruit and Vegetables., Tomas-Barberan, T.A. and Robins, R.J., Eds., Clarendon Press, Oxford, 1997, 11. 

Takyi, E.E.K., Bioavailability of Carotenoids from Vegetables versus Supplements in Vegetables, Fruits andHerbs in Health Promotion, CRC Press, Boca Raton, FL, 2001. 

Gross, J., Pigments in Fruits, Academic Press, London, 1987. 

Inglese, P., Basile, E, and Schirra, M., Cactus for fruit production, in Cacti Biology and Uses, Nobel, PS., Ed., University of California Press, Berkeley, 2002, 163. 

Mazza, G. and Miniati, E., Anthocyanins in Fruits, Vegetables, and Grains, CRC Press, Boca Raton, EL, 1993. 

In conclusion, the technology of total liquefaction of apple allows to work with a continuous process with less labour and faster than with a classical one, to get a high and constant yield during the whole processing season at a very high level (93- 95%), to get a pulp with a low content of solids (about 20% in volume) which can be centrifuged instead of pressed (lower investment in equipment), to decrease the quantity of waste pomace, to decrease the production costs. Liquefaction technology allows to process different fruits with the same process, at last to liquefy fruits for which no equipment had been developed to extract the juice or for which the use of pectinases did not allow to get juice such as tropical fruits. 

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. 

The pineapple fruit is mainly processed for canning as slices or cubes. After cutting, the residual pulp is removed from the peel for cloudy juice production. Then, by-products are used to produce clear juice for slices cover or as clear concentrate. In the process of clear juice, by-products are crushed and pressed. The juice is pasteurized, cooled down and depectinized with enzymes at 50°C before ultra-filtration and concentration... 

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