Process for the obtention of must from bunches of grapes comprising at least one phase of centrifugation

Abstract: A process for the obtention of must from bunches of grapes, comprising at least one phase of centrifugation of the said bunch, capable of bringing about separation of the must from the pomace prior to subjecting the must to fermentation.

Description: The object of this invention is a process for the obtention of must from bunches of grapes by pressing brought about by centrifugation of the bunch itself. It is known that the traditional method of processing grapes in order to obtain the must to be subjected to fermentation comprises phases of: crushing - for the opening, separation and breaking of the grapes; pressing - for the removal of the pomace (that is, the residual solid parts: skins stems and seeds) and, where necessary, disposal - that is, filtration of the solid residue effected through vacuum filters, plate filters or disc centrifuges. In greater detail, it is possible to distinguish two principal processes respectively termed red vinification white vinification. The first process, obviously applied to red grapes for the obtention of red wines, comprises the following processing phases: crushing with or without stemming (removal of stems), delivery to the fermentation tank via a pump, fermentation with or without temperature control, drawing-off, that is, drainage of the fermentation tank leaving in it only the fermented pomace, extraction of the pomace by means of suitable equipment, pressing of the pomace using hydraulic, screw or diaphragm presses. The wine obtained from drawing-off or that obtained from the pomace pressing phases is then placed in suitable tanks to bring about decanting of the solid residue or sediment, including the addition of clarifying agents. When the sediment settles on the bottom there is performed a second drawing-off operation and the sediment is sent to the distillery after filtering, to obtain the last wine from the sediment. White vinification, which is reserved for white grapes or for pink grapes used to make rosé wine, involves the following phases: crushing with or without stemming, subjection to the subsequent pressing phases, which may be of three types: a) demustering, which is very slight and serves to obtain "pure must". that is, a must of juice alone and without laceration of the skin; b) soft pressing which serves to obtain a must of optimum quality and with little processing of the skin. The latter may be carried out in a continuous manner with screw-type presses, and in a discontinuous manner with hydraulic or pneumatic presses. c) pressing to extract the last part of the must. often of poor quality and containing many lacerated skins. possible purification of the must, by removing the suspended substances, prior to being sent for fermentation. This purifying operation may be carried out by gravity with the introduction of adjuvants in the tanks, or by filtration or centrifugation. Once purified, or even if this operation is not performed, the must is sent to the fermentation vats where it is turned into wine. After vinification has completed, at the bottom of the tank there settles the fermentation "sediment" which is removed by "drawing-off". The sediment is then processed to extract its residual wine content. This operation is performed using either plate or vacuum filters, or using disc centrifuges or continuous horizontal-axis centrifuges known as decanters. For each of these phases it is, however, essential to use different machines which need to be linked to one another by conveyor systems for automatic production or, in the case of semi-automatic production, for collecting, transporting and feeding the products and the waste from each process to the next phase or for disposal as appropriate. Furthermore, the methods of known type for the industrial processing of grapes make it compulsory to use additives and special intermediate treatments to obtain a must of adequate quality. Inter alia there are commonly used techniques known by the name of flotation and consisting of the insufflation of gas into the crushed must tanks in order to bring about the rising of the solid particles still present in the said must, as well as the addition of chemical adjuvants to facilitate such rising of the particles. Decanters for producing must from grapes are known from article "Dekantereinsatz zur Traubenentsaftung" published in "Der deutsche Weinbau" (week 18/99) as well as in "Traubenentsaftung mittels Dekanter" published in "Mitteilungen Klosterneuburg" (week 43/1993) A process to obtain must from bunches is known from FR-A-2 477 383 that discloses a process in which a so-called "hammer filtering centrifuge" is used; it means that the liquid emerging from this machine will obviously contains a lot of solid matter and is therefore intended to be successively passed through a screw centrifuge. From CH-A- 622.820 it is also known a process to obtain must from bunches in which the grapes are guided into a centrifugal sieve working for filtration: this means that the liquid is extracted radially through the surfaces of the scroll and of the drum obliging to keep a low rotational speed to avoid stoppage of the sieve's holes. There is therefore posed the technical problem of providing a simplified process for the production of must from whole bunches of grapes which will make it possible to reduce to a minimum the intermediate processing phases and the relevant ancillary operations, as well as making it possible to reduce the number of machines necessary for such processing and to avoid the use of chemical adjuvant substances for the processing of the must to be subjected to fermentation, with obvious savings in money, floor space and operating personnel. The invention is defined by the features of claim 1. More particularly, provision is made for the centrifugation phase to be implemented by means of a continuous, horizontal axis scroll-type centrifuge. Further details may be obtained from the following description with reference to the attached drawings, which show: In figure 1 : a schematic flow diagram of the process according to the invention; and In figure 2: a schematic axial cross-section of a centrifuge for the implementation of the process according to the invention. As shown in figure 1. the process according to this invention is essentially comprised of a single centrifugation operation performed on the whole bunch as harvested. During centrifugation, performed with a machine which will be described later, there is obtained the separation of the must from the pomace. Because centrifugation of the must takes place at a speed of rotation such as to bring about centrifugal forces on the must exceeding 1500 times the force of gravity, during separation of the liquid from the solids inside the continuous horizontal centrifuge there are brought about two significant effects: a) the high pressure causes a larger quantity of gas extracted from the grape to pass into solution in the must, which is therefore enriched with natural gas and fragrance which enhance its quality, b) the high surface of free must under pressure which is obtained in the centrifuge is such that a larger quantity of air passes into solution, bringing about advantageous oxidation of all the oxidizable substances which are well known to detract from the quality of the must. When the must is extracted from the continuous horizontal centrifuge and pumped into the appropriate tanks, there occurs an instantaneous drop of pressure to ambient value so that the must is still oversaturated with natural gas and air, which are released in the form of bubbles which rise to the surface through the must, dragging with them the solid particles still present in the said must. Furthermore, the sudden drop in pressure also brings about breakage of the solid particles which release the gas contained therein, which gas becomes joined with the rising gas bubbles and facilitates the ascent of the solid particles to the surface. Under these conditions, flotation takes place within an average time of about 10-30 minutes, typically 15-25 minutes, and is performed without any addition of adjuvant substances, additives and/or the like and/or insufflation of gas. Such flotation takes place in tanks equipped with paddle assemblies which, on rotating in contact with the free surface of the must, collect the solid residue arriving at the surface and dispose of it. Such devices are self-evident and are not therefore shown in the figures. The pomace is instead extracted from the centrifuge and subjected to the subsequent operations of discharge and/or further processing for the recovery of second-quality must. As illustrated in figure 2, the equipment which makes possible the implementation of the process according to the invention is comprised of a fixed, substantially cylindrical housing 1, equipped approximately at one end with an annular section open at the bottom to form a radial outlet 1a, from which solid product "V" is extracted. Inside fixed housing 1 and coaxially thereto is located a rotary hollow drum 2, of substantially cylindrical form with a truncated-cone end. which is mounted at its driving end on bearings 2a to allow rotation with respect to housing 1, while such drum drive is comprised of a pulley 2b operated by belts 3a driven by a motor 3. Inside drum 2 and coaxially thereto is also located a scroll 4 substantially consisting of a body and formed by circumferential sectors 4a made integral with one another in order to form longitudinal slots 4c for the delivery of product 5 fed via a pump, not illustrated, and a duct 5a which enters into the body of the scroll, on the outer surface of which is made integral a helix 4b the purpose of which will be described more clearly hereinafter. Such scroll is supported at the opposite end by bearings 4d and 4e integral with drum 2, with respect to which scroll 4 may rotate as described hereinafter. The centrifugal extractor is also provided with drain apertures 16 for the discharge of liquid phases "M". At the opposite end drum 2 is made integral - via an end-closing disc 2c the hub of which runs in bearings 2d supported by wall 2e - with housing-crownwheel 7c of a gear, for example of epicycloidal type 7, to which it imparts movement with an equal number of revolutions; such movement is then taken up by a pulley 7a via a belt 8a which, as will be more clearly described hereinafter, is in turn fitted to a device for regulating the relative speed between the scroll and drum, not illustrated. To said gear 7 is also fitted a further belt 8b which, by means of a pulley 7b of gear 7, drives a shaft (not illustrated) acting on the satellites of epicycloidal gear 7, which satellites in turn actuate the secondary shaft of the gear which causes to rotate splined shaft 9 which drives scroll 4. The different number of revolutions of the scroll with respect to the drum is determined by the transmission ratio of gear 7 as well as by the sizes of the two pairs of pulley 7a, 14a and 7b, 14b linked thereto via respective belts 8a, 8b. The operation of the centrifugal extractor is as follows: the bunch fed via duct 5a (arrow "A") enters into hollow scroll 4 and, on emerging from slots 4c, is stratified by centrifugal action on the outermost peripheral area of drum 2 due to being of higher specific gravity with respect to the liquid phase, or to the two liquid phases, which are stratified on the solids according to their specific gravity. The liquid must drains out via outlets 16 (arrow "M"), while the solids consisting of the pomace are conveyed to outlet 6 of helix 4b of scroll 4, which has a relative rotary movement with respect to drum 2, the direction of relative rotation being closely linked to the direction of the helical surface and in any event such as to cause the forward movement of the solid product toward outlet la (arrow "V"). Many variants may be introduced in the implementation of the invention without departing from the scope of protection of this patent as described in the claims which follow.

Claims: A process for the obtention of must from bunches of grapes comprising at least one phase of centrifugation of the said whole bunches as harvested for the separation of the bunches into must and pomace prior to subjecting the must to fermentation, characterized in that the centrifugation phase is implemented by a continuous centrifuge equipped with horizontal-axis scroll and rotating at a speed such as to exert on the liquid a centrifugal force not lower than 1500 times the force of gravity. A process according to claim 1 characterized in that it conprises the following phases: - feeding of the bunches of grapes to a centrifugation device, - centrifugation for separating the bunches into must and pomace, - collection of the must. A process according to claim 1 characterized in that the horizontal-axis scroll centrifuge has one outlet for the must and one outlet for the solid residue.

Inventors: PIERALISI GENNARO, PIERALISI, GENNARO
Applicants: NUOVA MAIP MACCHINE AGRIC, NUOVA M.A.I.P., MACCHINE AGRICOLE INDUSTRIALI PIERALISI S.P.A.
Application year: 1995
Main classification: C12G1
IPC codes: C12G1