Special Technologies used in Citrus Juices Production

In citrus juice production process-low-chart are, from some years, used rather sophisticated technologies that make possible to obtain new products or to produce in a better way traditional products. 

One of these technologies is debittering that allows to selectively eliminate bitter components from the juice stream without affecting juice properties and characteristics but with an improved organoleptic profile. 

We have already discussed the problem of "delayed bitterness" due to limonin in Navel and Biondo Comune oranges, and debittering really upgrades those juices; moreover we don not forget improvements possible for compounds and peel based products from which absorbers are able to eliminate also hesperidin and its bitter taste.

Absorbers are, usually resins having a stirene-divinylbenzene matrix, characterized by macroporous structure which are stable, safe, resistant and fully able to selectively absorb bitter components from juice stream. Mechanism involves Van Der Waals and London forces.

 Absorber resins are usually employed in columns with a "merry-go-round" system; plant is made by three columns, while column 1 is working, column 2 is standing-by and column 3 in in regeneration. When column 1 is getting exhausted column 2 is connected on ith outlet and works as police-filter. When fully exhausted, column 1 is disconnected and regenerated and just column 2 remains in-process; when necessary will be connected column 3 and so forth.

For an optimal process, absorber resins should be used with clear products, i.e. products totally free from suspended solids and from colloids; this is obtained through an Ultrafiltration Unit.

Ultrafiltration is a a pressure-driven unit operation in which particulates, colloids, emulsified oils, and macromolecules are separated from a liquid feed stream upon passage through a porous semi-permeable membrane. The separation is based primarily on the size of the species in the liquid relative to the size of the membrane pores (i.e. a simple sieving process) although geometry of the pores, geometry of the species to be separated, electric charge, and membrane surface chemistry may also play a part.

On the separation size spectrum, UF falls between Nanofiltration or NF ( membrane pore sizes below approximately 0.01 micrometer) and Microfiltration or MF (pore sizes greater than 1.0 micrometer; in general, see following image.

Operative pressures range from 20 to 100 psi for MF and UF, between 200 and 600psi for NF and from 400 to 1.000 psi for Reverse Osmosis. Membranes are made with polymer such as polyethersulfone, polysulfone, polvinylidene fluoride, or polyamide. With respect to configuration, see the following image.

Membranes are sensitive to essential oils, so it is necessary to fully eliminate oil contained into the juice before feeding into the unit.

(Many thanks to Koch Membrane Systems for images)

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