ITMI20101016A1 - METHOD AND PLANT FOR COATING OF EDIBLE PRODUCTS - Google Patents

Description

Description of the patent for industrial invention entitled:

â € œMETHOD AND PLANT FOR THE COATING OF EDIBLE PRODUCTSâ €

Description

The present invention relates to a method and a plant for the coating of edible products, in particular for the coating of such products. Although the invention is directed to the coating of edible products in general, for convenience in the present description specific reference will be made to the sugar coating, which in any case represents the preferred embodiment of the invention.

State of the art

Products coated with sugar-based coatings or coatings are well known, consisting of an edible central part and an external, always edible part called sugared almonds.

The central part can be made up of hard or soft candies (defined in jargon â € œhard boiled candiesâ € and â € œchewy candiesâ €) or chewing gum or even almonds or other nuts or chocolate.

The outer part consists largely of sugar, which is increasingly replaced by sugar alcohols and other additives.

Method and ingredients

In the method of obtaining the confectionery, the edible central part, also called center or core, a term that will be used in the following of this description, is loaded into a machine called bassina, whose essential element is a portion, usually cylindrical or similar. , rotating on the axis arranged horizontally called the drum of the pan.

An adequate amount of sugar syrup is applied to the cores while the pan drum rotates. The syrup, consisting of water, sugar and typically of binders, such as gum arabic and maltodextrin, disperses evenly on the surface of the cores due to the friction between them during rotation, after an adequate period of time the humidity It evaporated with a flow of air, while the syrup crystallizes on the souls.

To facilitate the crystallization, and therefore the evaporation of the water, crystallizing agents, usually in the form of an impalpable powder, are applied to the still moist syrup in one or more of the layers making up the covering.

This procedure can be summarized in the following phases:

a) introduction of a quantity of cores of products to be coated in the drum of a pan and start of rotation of the drum itself.

b) introduction into said drum of coating material of said cores in the form of liquids (syrups) and powders;

c) blowing of air into the drum and simultaneous aspiration from it of air mixed with powders, phases b) and c) being repeated at least once (in practice even up to 50 times) until a covering, weight and desired thickness, consisting of a plurality of layers. Flavors and dyes are typically added to the syrup.

In the conventional technique, the sugar coating can be divided into four subsequent steps following the loading of the cores into the drum. Each of the steps can consist of several repetitions of steps b) and c) above. These steps differ in the constitution of the syrups, in the use of the powders and in other process conditions used:

1. Gumming: in this first step the syrup applied is particularly rich in binders such as gum arabic or gelatin, in order to anchor the rest of the sugar coating to the core. This step is optional.

2. Thickening: in this second step the syrup has fewer binders than in the previous step, but it is richer in sugar or its substitute. Within this step, powders are usually also applied.

3. Smoothing: in this step the syrup is more diluted than in the previous ones, usually without or with few binders. The aim is to give a smooth finish to the confetti. Powders are not usually used. This part is also optional, but in fact it is used in most industrial productions.

4. Polishing: in this last step, no syrup is used, but a polishing agent such as carnauba wax, shellac, candelilla, in order to give the product shine and protect it from humidity. Finally, the coated products (sugared) are unloaded from the pan and sent for subsequent processing.

To obtain sugar-free products instead of this sugar are used polyalcohols such as: sorbitol, xylitol, isomalt, maltitol, mannitol, lactitol alone or in combination with each other. The method of obtaining the coverage is essentially the same as with products with sugar.

Further information on traditional confectioning systems can be found in â € œThe Science & Art of Candy Manufacturingâ € C.D. Barnett, Magazines for Industry Inc. (1978) Chapter 10.

A particular application form of the present invention relates to sugar-free chewing gums. Information on the state of the art can be found in â € œSugar Confectionery Manufactureâ € II edition, E.B. Jacson ed, (1999), Chapter 12 and in Silesia confiserie Manual n ° 4 J.A. Merl, K.W. Stock (1996) Silesia Gehard Hanke KG ed.

In the production of chewing gum confetti according to the known technique, a chewing gum is made comprising a core formed by a gum base to which one or more sweetening substances are added, which is provided with a coating based on one or more layers of sugar or other sweetener. Since the application phase of said coating is technically known with the term "confection", the chewing gum thus obtained has been called chewing gum in the form of sugared almonds.

There are numerous known art documents relating to specific aspects of the sugar coating process, as well as to products obtained from syrups of suitable compositions. See, for example, EP 1,481,597; WO 03/00068; US 5,248,508.

Powders used in confectionery

The impalpable powders added in order to facilitate crystallization and drying can be made up of several single ingredients or mixed together or they can be made up of complex formulations.

In sugar-based confectionery, the powder is typically made up of milled sugar. In sugar-free confection, the powder can be made up of the same sugar substitute used for the syrup. For example, high purity fine maltitol powder is used in the maltitol coating, as EP 1,399,032 teaches.

In other cases, spraying mixtures are used, such as Quick-coat Xylitol®, supplied by Alfred L. Wolff GmbH, Germany, consisting of xylitol and gum arabic.

In other cases solid mixtures are used, for example IT MI20051005 teaches mixtures of acidifiers, sugar substitutes and anti-packings, in US 5,882,707 solid mixtures of carbohydrates, dyes and plasticizers are described.

Any type of powder can, however, be added, even for different purposes, for example in US 2,304,246 powdered activated carbon is added.

Powder coating and recovery machinery

The machinery for the production of roofs is also known. In recent technology, these machines, called bassine in technical jargon, have as their fundamental element a cylinder or a multi-sided polyhedron, called a drum, arranged with the axis horizontally. This cylinder can also have a multitude of holes suitable for the introduction and extraction of air. The cores are loaded inside the cylinder and this is set in rotation. Inside the cylinder there are one or more nozzles for the application of the syrup, delivery and suction openings for the drying air. The powders can be applied manually, but in the most recent machines the powders are applied by means of automatic dosing systems, both pneumatic and mechanical or combined.

Examples of the known art on the construction of the trays are US 4,586,457, GB 2,249,977, WO 84/13610. In all these documents particular importance is given to the incoming and outgoing air in order to maximize the yield of the machinery, but the problem of dust recovery is not addressed.

On the other hand, machinery for recycling powders, applied to plants and processes substantially different from those of the present invention, are known.

WO 03/028618 discloses, among other things, machines for producing tablets by compressing powdered material. Suction systems are applied to these machines to clean the pressing punches from dust residues; the sucked air can be passed through cyclones for the eventual recovery of such dust.

US 2007/0272598 teaches the use of cyclones for the recycling of dust generated by friction during the transport phases of plastic granules. The dust carried away by a flow of air is collected in discontinuous bins.

Technical problem

The use of powder increases the speed of the confectioning process, which is one of the most time consuming in the confectionery field. There is therefore an interest and a tendency to increase the use of powders. The use of automatic powder diffusion systems for large sugar-coated machines has facilitated the implementation of this trend. The presence of large quantities of cores in modern machines increases the friction between them during the coating and keeps under control the roughness that the use of too much dust would introduce. At the same time, however, the friction between the partially coated cores during drying produces more dust.

Both due to the excess of powder applied on the wet syrup and due to the dust generated in the friction of the rotating cores, the suction air carries with it in suspension the powder which is of a more complex composition than the virgin one. , introduced according to the known technique, because it also contains components of the sugared syrup (aromas, colors, intensive sweeteners, etc.).

This dust cannot be released into the atmosphere due to pollution problems. Traditionally, the air is filtered and the filters cleaned at intervals established by maintaining their efficiency.

The powders collected in this way cannot be recycled in a modern factory, where the same sugar coating plant is used to produce in sequence different products both for aroma and color and for main ingredients (sugar, xylitol, isomalt, maltitol, etc.) ), so that the dust recovered from the filters results in an inhomogeneous mixture and composition that is always different over time.

Furthermore, the Applicant has found that these powders have a different particle size distribution from the virgin powders introduced into the drum. In particular, these powders are enriched with fractions having a higher particle size than the starting powder. The use of these powders would therefore also pose a qualitative problem of an aesthetic type, because the largest grains appear as irregularities (pimples in the jargon) on the smooth surface of the sugared almonds.

The object of the present invention is to eliminate the drawbacks illustrated above of the known art.

In particular, an aim of the invention is to provide a method for the coating of edible products, capable of recycling the powder present in the coated air efficiently with economic advantages (less new powder to buy) and logistics (no storage or disposal).

A further object of the invention is to provide a method which, by carrying out what has been described above, at the same time does not decrease the quality of the finished product of the confectionery.

Yet another purpose of the invention is to create a plant for implementing this method on an industrial scale that is simple and economical to make.

Description

These objects are achieved according to the invention with the characteristics of the attached independent claims.

Advantageous embodiments of the invention appear from the dependent claims.

Method description

Basically, the method for coating edible products according to the invention provides for the recovery of the coating powder present in the air sucked by the pan drum and its reintroduction into the coating drum in the powder application phases immediately following during completion. of the same bassinatura.

In a preferred aspect of the present invention, the method provides consequentially to the recovery from the air also the continuous sieving of the powders themselves and the deviation of the powders with a particle size higher than the desired one to the waste, while the powders of the desired particle size are always sent to the drum of the bassina.

Obviously, the recovered powders cannot by themselves satisfy the total amount of powder that is expected to be introduced into the drum at each stage of use. The missing part of this total quantity must be made up of virgin powder to be reintegrated with the recovery powder. In a preferred embodiment of the present invention there is a phase in which recovered powders and virgin powders are combined to form the total quantity necessary before being reintroduced into the drum. Alternatively, the recovered and virgin powders can be applied sequentially one after the other in the drum until the total quantity is reached without any union between the two.

The present invention also provides a method of diverting the powder before it is introduced into the drum towards a collection point. This method is implemented when necessary, for example at product changes or washing to empty the recovery line. In a preferential way, this method foresees the collection in small food containers in discontinuous way, so as not to mix powders coming from the basins of different products. The powders thus recovered in batch (a very small fraction compared to the total of the powder recovered continuously) can be reused in turn when the confection of the same type of product is resumed.

In a preferred embodiment, the method of the present invention is applied simultaneously with methods according to the known technique for treating the air introduced into the drum which allow the humidity and temperature of the air itself to be controlled.

Plant description

More in detail, the air with the dust sucked by the pan is fed into one or more devices for the continuous abatement of the poor. Such devices include for example continuous filters, cyclones and the like.

Among the similar devices we can mention, for example, the drum filters equipped with continuous suction similar to those marketed by Osprey Corporation and described in US 5,679,136, which however must be adapted to a non-fibrous particulate. Alternatively, it is possible to use cassette filters equipped with a continuous cleaning system by means of counter flow of air (Dantherm filtration), or polygonal filters electromechanically cleaned continuously or semi-continuously. However, these filters have the disadvantage of stopping dust on surfaces that cannot be cleaned 100% continuously, so that different dusts become contaminated. Furthermore, the creation of compact layers of powder causes the aggregates to grow, so that the difference between the granulometry of the virgin and recovered powder increases.

In a highly preferred embodiment of the present invention, the devices are one or more cyclones which can be arranged both in series and in parallel. Their number and size depend on the quantity of air flow out (suction) from the pan drum and on the suction power downstream of the same and on the dust abatement efficiency to be achieved.

These cyclones are equipped with continuous or semi-continuous discharges of the dust that collects in the cone. These means for unloading are known to those skilled in the art and allow unloading to be carried out without putting the bottom of the cyclone cone in communication with the environment.

The Applicant has found that cyclones do not compact the dust and minimize the contamination between powders of different composition which are separated at different times because they do not have absorbent parts. It is also possible to build the cyclones totally in steel allowing, in case of need, cleaning with water.

The air coming out of the cyclones is sent to a suction pump and can be filtered before being released into the atmosphere as the cyclone abatement process can still leave a fraction of particularly fine dust still in the air.

The dust recovered from the air can be advantageously sent to continuous sievers which discard the particle size that is too large.

The powder, preferably the fine one coming out of the sieving machine, is continuously transported and reintroduced into the drum of the pan in the successive repetitions of the powder application phase of the same pan.

The transport of the powders recovered downstream of the cyclone towards the pan drum can take place according to any systems suitable for the purpose, including conveyor belts, bucket elevators, augers and others. A particularly preferred method is pneumatic conveying which will be described in the detailed description in the next paragraphs. The skilled technician will note that, regardless of the constructive aspect, for the purpose of the present invention the transport system must minimize the time between the recovery of the powder and its re-introduction into the drum.

In this way, the recovery powder is applied to the product itself with which it has been in contact or from which it comes, in the case of excess powder that has not anchored to the cores and has been carried away by the flow of water. € ™ air; or whether it is dust originated by rubbing between the cores themselves or between cores and walls of the rotating pan during drying by air. In both cases, the recovered powder is not of the same composition as the virgin one, bringing with it contamination of all the other ingredients present in the confection, some of which (for example aromas and colors) extremely variable between the various products. For this reason the recovery on the same cores represents the only one not to cause contamination between products, ensuring constant composition of the product itself.

The recovery powder, however, must be supplemented with virgin powder to ensure the total amount of powder necessary for the coating. This integration can take place inside a loading hopper into which recovery powder and poor virgin are introduced. Subsequently, this mixture of virgin and recovered powder can be applied in the pan drum by any method (see description below), not excluding manual dosages using traditionally used scoops, even if an automatic system that uses a flow of compressed air for the transport from the powder dosing hopper to the pan and a shaft dispenser with several nozzles for the uniform distribution of the powders along the entire length of the pan drum.

Alternatively, the integration can take place directly in the pan by applying in succession measured quantities of recovery powder through a system made up as follows:

a) pneumatic dosing system, which, drawing the recovery powder from a hopper on the load cell, measures the quantity of recovery powder introduced in real time and communicates the remaining quantity to be dosed to the next;

b) second pneumatic dosing system for virgin powders, which by drawing the virgin powder from a second hopper on the load cell, controls in real time the quantity of virgin powder reintegrated and doses it in the pan drum until reaching the expected total weight.

In some particular phases it may be necessary to eliminate the dust present in the recovery system without having to forcibly introduce it into the drum of the pan. These phases coincide with washing or product changes. For this purpose, the plant claimed in the present invention optionally comprises deviation points for the flow of recovery powder upstream of the pan drum. This deviation can simply be constituted by a diverter valve upstream of the cyclones described above that divert the air with the dust still in suspension to a suction pump equipped with filters that prevent its entry into the atmosphere. Alternatively, this deviation can consist of a deviation damper downstream of the cyclone which directs the dust towards a discontinuous collection point. Alternatively, this deviation can consist in a suction of the dust downstream of the above mentioned cyclones which conveys the dust itself to a cyclone which discharges discontinuously without reintroducing the dust into the drum.

Further characteristics of the invention will appear clearer from the detailed description that follows, referring to a purely exemplary and therefore non-limiting form of implementation, illustrated in the single annexed drawing, which is a diagram of a coating system according to the € ™ invention.

Detailed description of a preferred embodiment of the invention

In the diagram of the annexed figure 1 various dashed rectangles have been reported to indicate the various groups of the system according to the invention.

In particular, the rectangle C generically indicates the pan group, the rectangle B indicates an air treatment group before placing it in the pan, the rectangle D is a final filtration group of the sucked air, the rectangle A is the powder recycling group according to the invention, and finally the rectangle A1 enclosed in the rectangle A is the powder throwing group.

With reference to the attached figure, the reference number 1 has generically indicated a pan per se known and therefore not further described, for the confectioning of edible products. In this case, the pan 1 is provided with a cylindrical drum 30 which is rotated around its own horizontal axis, but this is not binding for the purposes of the present invention, in the sense that the pan 1 can assume any other known configuration.

The cores 31 of the product to be coated are loaded into the drum 30, which in the more modern construction pans is perforated on its shell, and are arranged on the bottom of the same. Inside the drum 30 there are provided, in a per se known manner, nozzles for the application of the syrup, usually grafted onto a shaft lying approximately on the axis of the drum, and delivery and suction for the drying air, indicated respectively with the arrows F1 and F2. In particular, a pump 2 is provided for sending air into the pan 1 in the direction of arrow F1.

In a preferred embodiment, the air F1 is generated by a plant, represented by the rectangle B capable of controlling its temperature and humidity. The temperature of the incoming air is varied to optimize drying in the various steps of the confectionery and can go, by way of example, from 15 ° C to 35 ° C. The humidity is kept at low levels (for example 2 g / kg). The applicant has in fact found that by maintaining adequate conditions of the incoming air (F1) the dust in the outgoing air (F2) remains freely flowing, despite being mostly made up of hygroscopic compounds such as hydrocolloids and polyalcohols and despite the Air carry with it all the humidity evaporated from the bed of damp souls through which it passes inside the drum (30).

The powders can be introduced into the cylindrical chamber 30 in any way and in the diagram of the attached figure an arrow F3 is indicated for their introduction, as will be better described later.

The air mixed with dust sucked from the cylindrical chamber 30 by means of a suction pump 4 is sent to a first cyclone 3, in which the dust that settles on the bottom, passing through a butterfly valve 5 is collected in a container 6, from which, by means of a further butterfly valve 7, an air current (arrow F4) is introduced into the flow, which has passed through a filter 8, and is sent to a rotary sieve 9 which discards the lumps and collects them in a container 10. These discarded lumps typically have a particle size greater than 1000 µ, preferably greater than 400 µ and even more preferably greater than 100 µ.

At the same time the finer powders, together with the air that transports them, are sucked up by means of a pump 13 and sent to a second cyclone 11 with incorporated filter. From the cyclone 11, the powders with the correct granulometry pass through a butterfly valve 12 and a diverter damper 14, to be sent alternatively to the virgin powder replenishment hopper 16 acting as a small lung from which the powder dosing system draws, or in one or more containers 15 of waste powders whenever there is a change of the product being processed. The containers 15 are preferably of food grade and can be stored to reuse the powders in the first compatible confection.

Alternatively the flow F4 can take air, instead of from the filter 8, from a detachment operated in the wall of the conical portion of the cyclone 3 or from a detachment operated in the delivery flow duct F1 or from a detachment operated in the flow duct F2 or by combinations of these modes. As it is evident for the skilled craftsman of the technique, the three ways of supplying the air of the flow F4 require a different balance of the suction power of the pump 13. However, the origin of the flow F4 in the cyclone 3 or in the pipeline flow rate of F1 have the advantage of keeping the powders in a flow at controlled temperature and humidity.

The arrow F5 directed into the hopper 16 indicates the integration of the consumed powders with virgin powders. The mode of transport of the powder from the cyclone 3 to the reintegration point 16 includes only pneumatic transport and is preferred for speed and cleanliness as it can be realized as a closed system towards the environment.

The mixture of virgin powders and recovered powders present in the hopper 16 is fed into a powder dosing hopper 18, as indicated by the arrow F6, which is sent into the pan 1 by means of an ejector 19 and a compressor 20, following the path of the arrow F3 previously introduced. The powders are applied on the product 31 by means of a distribution shaft equipped with suitable nozzles so as to be equally distributed along the entire length of the drum 30.

The powders are then continuously recycled and reintroduced into the drum 30 in real time to be used in the subsequent baking stages, while the coarser powders are discarded in the container 10 and at each product change the recovered powders are discarded in the container 15 .

A series of tables with examples from 1 to 21 are now reported.

Table I reports examples from 1 to 7 of powders that can be used in confectioning.

TABLE I

Powders usable in confectioning (%)

Powder Powder Powder Powder Powder Powder Powder Ingredient example example example example example example example 1 2 3 4 5 6 7

Milled sugar 20 79 Rice starch 80

Isomalt powder

impalpable <100 39>

Xylitol on rubber

arabica powder 100 64 impalpable

Maltitol powder <100> impalpable

Gum arabic in

dust <60 35 20> Anti

packaging <1 1 1> Table II shows examples from 8 to 12 of syrups that can be used in the thickening phase.

TABLE II

Thickening syrups usable in confectionery (%)

Ingredient <Syrup> Syrup Syrup Syrup Syrup Example 8 Example 9 Example 10 Example 11 Example 12

Sugar 39.5

Isomalt 65 - - -Xylitol - 75 - -Maltitol - - 64 -Sorbitol - - - 73 Water 28 19 24.29 40 23 Gum Arabica 1 5 10 20

Titanium dioxide 5 - 1 3 Allura red - 0.001 0.01 - Mint aroma 0.5

Orange flavor 1 - - - Strawberry flavor - 0,999 - - Mango / Peach flavor - - 0,7 - All Fruits flavor - - - 1 Aspartame (%

extra weight) 0.02 0.015 0.03 0.01 Table III shows examples from 13 to 17 of syrups that can be used in the smoothing phase.

TABLE III

Smoothing syrups usable in confectionery (%)

Ingredient <Syrup> Syrup Syrup Syrup Syrup Example 13 Example 14 Example 15 Example 16 Example 17

Sugar 70

Isomalt 60 - - -Xylitol - 65 - -Maltitol - - 64 -Sorbitol - - - 63 Water 35 32.999 30 30 32 Gum Arabica 0 2 4.99 0

Titanium dioxide 5 - 1 5 Allura red - 0.001 0.01 - Table IV shows with examples from 18 to 21 a comparison between coated compositions with recycling of powders according to the invention (examples 18, 20) and coated compositions traditional without recycling (examples 19, 21), highlighting the savings in the purchase of new powders.

TABLE IV

Confectioning composition -% dry

Example 18 Example 19 Example 20 Example 21 Ingredient

(inventive) (not inventive) (inventive) (not inventive)

40 40 60 60 thickening syrup

(example 10) (example 10) (example 9) (example 9)

25 25 25 25 smoothing syrup

(example 15) (example 15) (example 14) (example 14)

20 35 8 15 purchased powders

(example 3) (example 3) (example 2) (example 2)

recycled powders 15 7

<0.1% <0.1% <0.1% <0.1% other hedges

(polishing wax) (polishing wax) (polishing wax) (polishing wax)

% savings in the purchase of new powders

Example 18 Example 19 Example 20 Example 21 (inventive) (non-inventive) (inventive) (non-inventive)

- 43% 0 - 47% 0

From the above, the advantages of the invention appear evident, which allows a continuous recycling of the coating powders and therefore an economic saving of the use of the confectioning plant, as well as a lower environmental impact.

It is reiterated that although in the previous description we mainly talked about sugar coating, the method and the plant according to the invention can be used for the coating of any edible product, not necessarily to form a hard crust.

Naturally, the invention is not limited to the particular embodiment previously described and illustrated in the attached drawing, but numerous detailed modifications can be made to it within the reach of the person skilled in the art (for example, additional compressed air couplings for washing , sight glasses, automatic control systems), without thereby departing from the scope of the invention itself defined by the attached claims.

Claims (18)

CLAIMS 1. Method for the coating of edible products, in particular for the coating of such products comprising the steps consisting in a) introducing a quantity of cores (31) of products to be coated into the drum (30) of a pan (1) and subjecting said cores to continuous mixing by rotating the drum itself; b) introducing into said drum material for coating said cores (31) in the form of liquids and powders; c) introduce air into the drum and at the same time suck air mixed with dust from it, - in which steps b) and c) are repeated at least once, characterized in that it also includes the phase consisting in: - separating the powders from the air sucked in by said pan drum and recycling them in the drum itself for use in the subsequent repetitions of phase b) of the same coating. 2. Method according to claim 1 additionally comprising the step consisting in continuously discarding the powders with too large granulometry. 3. Method according to claim 1 or 2, characterized in that said powders separated from the suction air are integrated with virgin powders for feeding the pan drum. 4. Method according to any one of the preceding claims, characterized in that before the return of the powders separated from the air into said drum, the powders themselves are diverted to a discontinuous collection system, preferably in food grade containers. 5. Plant for the coating of edible products, in particular for the confectioning of such products, comprising a pan (1) equipped with a drum (30) suitable for receiving a quantity of cores (31), means for placing in said drum (30) of the coating material, both in the form of liquid and in the form of powder, of said cores (31), a unit (2) for introducing air into said drum (30), and a suction unit (4) air mixed with powder from said drum (30), characterized by the fact of providing, on the air suction path, at least one cyclone (3) or equivalent device for the abatement of the powders to be sent by means of a continuous transport system in the drum of said pan. 6. Plant according to claim 5 comprising downstream of said at least one cyclone at least one sieve (9) adapted to separate the coarse powders to be sent to the waste (10) from the fine powders sent in real time into the drum (30) of said pan ( 1). 7. Plant according to claim 5 or 6 comprising a hopper (16) continuously fed with said powder recovered from the suction air and in which said powder is integrated with virgin powder. 8. Plant according to claim 5 or 6 comprising two hoppers, one dedicated to the recovery powder and the other dedicated to the virgin make-up powder, said hoppers being connected to at least one powder metering device capable of introducing into the drum (30 ) the total amount of powder desired. 9. Plant according to any one of claims 5 to 8, also comprising downstream or upstream of said at least one cyclone (3) a deviation system suitable for diverting the dust towards an alternative collection system so as not to feed in a forced the drum (30) of said pan (1) when not required. 10. Plant according to claim 9, wherein said diverting system consists of a diverting shutter (14) downstream of said cyclone (3) which directs the powder towards one or more containers, preferably of food grade (15) for collection and the storage of powders. 11. Plant according to claim 9, wherein said diversion system comprises a three-way valve which opens access to a pipe to the flow (F2) upstream, or to the dust downstream of said at least one cyclone (3) in suction towards a suction pump (4) equipped with a filter. 12. Plant according to claim 9, wherein said diversion system comprises a three-way valve which opens access to a pipe to the flow (F2) upstream, or to the dust downstream of said at least one cyclone (3) in suction towards a cyclone for the recovery of powders not sent towards the drum of said pan (30). 13. Plant according to claims 7 and 8, characterized in that downstream of said a hopper (16) for integrating the recovered powders with virgin powders or of said two hoppers there is a hopper (18) for dosing the powders towards an ejector (19) which, by means of a compressor (20), feeds such powders to said drum (30) of the pan (1). 14. Plant according to any one of claims 5 to 13, in which means are provided for the pneumatic transport of the powders leaving said at least one cyclone (3) towards the subsequent components of the plant and a further cyclone (11) placed in suction by means of a pump (13) to separate the dust from the transport air. 15. Plant according to claim 14 in which the air for pneumatic transport is supplied by at least one of: a filter (8), the cyclone 3, the flow of air (F2) leaving the said drum (30) of the pan, the flow (F1) generated by the air inlet unit (2) and by combinations between them. 16. Plant according to claim 5, wherein said air generation unit 2 is capable of controlling humidity, temperature and quantity of air flow. 17. Plant according to any one of the preceding claims operating in a closed manner except for the reintegration of virgin powders. A plant according to claim 6 wherein the sieve (9) is a continuously rotating mesh sieve designed to operate in a closed flow pneumatic system.