GB2026884A - Filtering alimentary liquids - Google Patents

Abstract

Beer or cider is filtered using at least one native starch, notably potato or manioc starch, as a filter aid. Starches may be mixed together or with other filter aids, and may be applied to filtering surfaces in a filter press or candle filter as a plurality of layers.

Description

SPECIFICATION Method and agent for the filtration of alimentary liquids, notably fermented liquids The invention relates to a method and an agent for the filtration of alimentary liquids, notably for the filtration of fermented alimentary liquids and, more particularly again, for that of beer and cider.

The preparation of alimentary liquids and notably of fermented alimentary liquids such as beer and cider includes, in industrial practice, a filtration step designed to clarify the liquid, conferring on it optimal transparency and brilliance, to eliminate to the maximum the micro-organisms present and to stablize said liquid by retaining the unstable colloidal particles which would finish up by precipitating during preservation.

Hitherto, recourse was had to carry out this filtration step, to filtration agents of a mineral nature or accessorily cellulosic, the agents of a mineral nature being selected essentially from among diatomaceous earths or Kieselguhrs, perlites, asbestos whereas the agents of cellulosic nature are selected from among filter papers, cardboards and bulk cellulosic fibers, it being understood that only the agents of a mineral nature have at present real success on the industrial scale and are selected principally from among the Kieselguhrs, which have undergone a preparatory treatment which comprises in particular a calcination step and a granulometric grading.

These Kieselguhrs correspond in fact to the conditions systematically placed first by technicians the art; given that they do not contain substances notably organic which could be entrained by the liquid to be filtered and which have sufficient bacteriological quality, a well determined particle size distribution or one which is at least adjustable at will and a desirable irregular shape of particle constituting, according to the prior art, a porous architecture ideal for filtration due to the fact that it retards clogging, these filtering agents enabling the realization, quite satisfactorily, of the three above-mentioned actions required from the filtering agent used for the treatment of alimentary liquids.

They have however a major drawback residing in the imminently polluting character of the filtration cake, that is to say of the residue constituted by the filtering agent and the body notably organic retained or absorbed.

In fact, this filtration residue imposes serious constraints due to the polluting character of its organic component.

It is therefore an object of the invention in particular to remedy this drawback.

Now Applicant company has had the merit of finding surprisingly and unexpectedly and in spite of their organic character, of their granulometric characteristics which are very far from those of Kieselguhrs and of the shape of their constituents particles a priori unfavorable, that natural or native starches, notably starches from tubers and, more particularly, from potato and manioc, not only constitute good filtering agents for alimentary liquids, but also lead to non-polluting filtering residues since they are useful profitably in animal and even human foodstuffs.

The method of filtration according to the invention consists therefore of resorting to at least one native starch, notably a tuber starch and more particularly, potato and manioc starches, as a filtering agent.

It is recalled that the native starches are those which have not undergone any chemical or physical modification after having been extracted, whatever their origin.

In an advantageous embodiment of the above-mentioned method, the filtration is carried out by resorting to a fluid-tight filter avoiding the escape of fermentation gases, notably of the filter press or candle filter type on which has been deposited a pre-layer constituted by at least 50% preferably at least 70% of at least one native starch, the complement to 100% being constitutable by at least one filtering adjuvant selected from among those of the group comprising Kieselguhr, filtering earths, conventional filtering agents, starch, on the one hand, and the filtering adjuvant, on the other hand, being arranged preferably in the form of two superposed layers of which the whole forms the above-mentioned pre-layer.

According to another embodiment of the above-mentioned method, the filtration is carried out by placing in suspension in the liquid to be filtered at least one native starch, notably a tuber starch and, more particularly, those of potato and of manioc, in a sufficient amount so that no clogging of the filter is produced.

According to yet another advantageous embodiment of the above-mentioned method, in the liquid to be filtered is placed in suspension an amount of the above-said native starch sufficient for it not to produce any clogging of the filter and on the filter is deposited a pre-layer constituted by the same starch if necessary mixed with at least one of the above-mentioned filtering adjuvants.

The filtering agent according to the invention is constituted by at least one native starch, notably from tubers and more particularly, those of potato or manioc, of a bacteriological quality compatible with its use in the filtration of food liquids and notably free from yeasts and molds.

The invention is aimed more particularly but not exclusively at the application of the abovesaid method and agent to beer processing.

It is aimed also at the filtration residue as a novel industrial product and at its possibilities of use in animal and human feeding.

It will be well understood from the additional description which follows and the examples, said additional description and examples relating more particularly to advantageous embodiments.

In order consequently to carry out the filtration step provided in industrial methods of manufacturing fermented alimentary liquids, recourse is had to native starches, notably to tuber starches and, more particularly in the following, to those of potato and manioc, of a bacteriological quality compatible with the normal requirements of the industry of alimentary liquids and free in particular from yeasts and molds which are normally to be found therein.

To achieve the desired bacteriological quality, it suffices to subject the starch to long-term storage, that is to say for at least six months at the end of which living yeasts and molds no longer subsist.

By way of example, it is stressed that a potato starch which has been stored for about a year has a perfect bacteriological quality as is evident from table I below in which the results of analyses carried out on such a starch are assembled.

TABLE I Mesophile Germs Count on Thermophile Count (30"C) Germs (55"C) on 10g 1g 10g 1st 2nd Test Test Aerobic germs 20 Enterobacteria 0 Total aerobic spores and Coliforms 0 facultative germs 20 Faecal streptococci 0 Molds 20 1 Acidifying Spores 10 Yeasts 20 0 Non-acidifying Spores of CSR Spores 0 (clostridium- 5 sulfito-reducer On examining this table, the almost total elimination of yeasts and molds is noted.

It is however also possible to sterilize potato starch without altering more than in the preceding method its granular structure; to do this, it is possible to resort, for example, to treatment with ethylene or propylene oxide according to techniques well known to the man skilled in the art and permitted in certain countries or again to radio-pasteurization, that is to say to sterilizing treatment notably by means of gamma radiation.

The potato starch applied is formed of granules of ovoid shape, of a humidity of 18 to 20% generally and whose particle size distribution is given in Table II below at the side of which is that of a Kieselguhr conventionally used as a filtering agent. It is observed that on examining Table II how much the two granulometric distributions are distinct from one another, which factor is added to the differences of structure, the Kieselguhr particles being of irregular shapes whereas the particles of the starch are, as indicated above, of ovoid shape.

It also appears that the granulometric spectrum of the starch is displaced in the direction of the particles of large size with respect to the granulometric spectrum of the Kieselguhr. It results finally from Table II that the largest particles of the starch are less than about 100 microns.

As regards manioc starch, its constituent grains are also of ovoid shape, its granulometric spectrum being on the other hand slightly displaced towards the granulometries as is seen from the Table below.

TABLE Il Kieselguhr Starch potato manioc Particles less than 5 microns 20% 0.3% Particles comprised between 5 and 9 microns 36% 0.4% Particles comprised between 9 and 15 microns 30% 1.3% Particles comprised between 15 and 25 microns 6% 12% 4 Particles comprised between 25 and 40 mircons 4% 33% Particles larger than 40 microns and less than about 100 microns 4% 53% It is of course understood that in the case of need recourse can be had to special granulometric fractions obtained by cycloning in air (turboseparation) or by cycloning in a liquid.

The filtration is carried out by resorting to a filter of the filter press type or of the candle filter type, this filter having in any case to be of fluid-tight type, avoiding the escape of the fermentation gases contained in the liquid.

Generally, a pre-layer is deposited on the filter, this pre-layer being constitutable from several superimposed layers of decreasing granulometry starting from the filter, the constituent material of each layer being selected from among starches whose granulometric spectrum corresponds to that required for the individual layer contemplated.

Thus, it is possible to have successively, a starch layer of potato starch and a starch layer of manioc starch.

Between the potato starch layer and the filter, it is possible to place a filtering adjuvant layer as defined above.

The native starch pre-layer can be formed by previously passing over said filter a suspension of native starch in a liquid which can be constituted by water or the liquid to be filtered, the first amounts being recirculated in the second case to undergo a complementary filtration after formation of this pre-layer.

The filtering adjuvant pre-layer can be formed in the same way.

Most generally, one continues to resort during the whole filtration process to a suspension of filtering agent according to the invention in the liquid to be filtered, the amount of agent suspended being selected so that this agent is deposited sufficiently rapidly from the point of view of increasing the thickness of the layer so that there should be no sticking os said layer due to the fact notably of yeast and mold cells as well as colloidal substances retained.

In practice, good results are obtained by forming a suspension of about 50 to 200 g, preferably from 80 to 150 g of filtering agent per hectoliter of liquid to be filtered.

By the continuous deposition of the filtering agent according to the invention in the course of filtration, there is produced a filtering cake formed for example from starch and micro-organisms, which cake finds its use advantageously both in animal and human feeding and which hence does not constitute a waste and polluting product The proportion of filtering adjuvant possibly present in this cake is sufficiently low not to be prejudicial to the above-mentioned application.

By way of indication, it is indicated that when the filtered liquid is beer and the filtering agent is potato starch, the content of the potato starch suspension in the beer for filtration is of the order of 100 g/hl and the filtration residue is constituted by a mixture of starch and of retained yeast cells, the ratio of potato starch/cells being generally comprised between 1/0.2 and 1/3 according to the fermentation method applied.

Taking into account the water content of about 20% for potato starch and about 75% for yeast, an average ratio of 1/1 is equivalent, expressed in dry matter, to about 1/0.3.

This product may be used after a cellular lysing treatment in human foodstuffs as a flavoring substance for soups and sauces in particular and, in animal feeding, as a constituent of the alimentary ration, notably for pigs.

To illustrate the foregoing, there are described below examples of the application of the invention relating to advantageous embodiments.

EXAMPLE 1 This example relates to the filtration of beer in which the filtering agent is potato starch.

The filtering step comprised in the method of preparing a beer for current consumption is carried out atthe end of standing, that is to say at the end of the resting stage which follows fermentation.

The viscosity of this beer before the filtration was 1.6 cp at 20"C (measured by means of a vibrating sphere viscosimeter), its filtering temperature com-prised between 11 and 1 3 C, its content of yeast cells of the order of 105 cells per ml and its turbidity (which characterizes the clarity) 0.192 (value of extinction at 750 nm, for which wave length the color of the beer practically does not interfere with the reading of the clarity).

The filtration is carried out on- a filter plate filter having a filtering surface of 5 cm2, the filtering plate being a disc constituted by a filtering layer of cotton specially adapted for this use. Thefiltration pressure is 1 bar.

The amount of starch suspended was, in the course of the test, 100 g/hl.

The hourly filtration flow rate measured for the filtering surface used was 6.1 hl/m2/hour (average value deduced from a test arranged overfour hours).

The turbidity of the filtrate sampled between the 18th and the 21st minute of filtration was 0.008. This value was comparable with that of commercial beers.

Bacteriological analysis of the filtrate confirmed the absence of yeast cells.

Four concentrations of starch (respectively 80, 100, 120 and 140 g/hl) the log (volume filtered) = flog (time) was established and it was observed that these curves were straight, which confirmed the absence of clogging. It is recalled that with the conventional agents such as Kieselguhr, straight lines are also obtained.

The analogy in behaviour as filtering agents between Kieselguhr and the potato starch is hence manifest EXAMPLE2 This example relates to the filtration of a suspension of brewery yeasts in water, in which the filtering agent is constituted by potato starch; the pre-layer is also constituted by potato starch.

The filtration was carried out with a pilot filtration station constituted by an alluvionnable frame filter, in the event, that marketed by the GASQUET company with the identification "DC 50", and whose filtering surface was 2.81 m2. The alluviation was carried out by means of a metering pump with variable delivery rate.

The liquid to be filtered was constituted by a suspension of brewery yeasts in water whose concentration was of the order of 108 cells per liter.

The pre-layerwas a single one and formed by depositing on thisfilter potato starch in the proportion of 1800 g per m2 of filtering surface. The starch used contained 20% of water.

The amount of potato starch suspended in the course of the test was 100 g/hl.

The hourly filtering flow rate measured fo the filtering surface used was 2.8 hl/m2/hour.

At the end of the test, it was observed that the filtrate was clear and that the concentration of-yeast cel Is in thefiltratewas of the order of 50 cells per liter, which proves a good efficiency.

EXAMPLE3 This test was carried out under the same conditions and with-the same equipment as the test previously carried out, using "foam beer" as a filtering liquid.

Foam beer is the liquid emerging from the conditioning of beer casks, to which brewing yeasts are added to achieve a concentration of about 108 cells per liter.

At the end of the test, the concentration of yeastscells cells was of the order of 45 cells per liter, which confirms the good effectiveness of the filtration carried out with potato starch as afiltering agent.

The filtrate obtained was limpid and had a turbidity equal to that shown by the liquid before the addition of yeast, which also confirms the effectiveness of the filtration.

EXAMPLE4 This test relates to the filtration of a suspension of brewery yeasts (108 cells per liter) in water; the filtering agentwas a mixture of potato starch and manioc; the pre-layerwasformed by depositing on the filtera layer of potato starch, then a layer of manioc starch.

In this test the conditions and the equipment used were the same as in Example 2.

The pre-layerwas constituted by a first layer of potato starch, representing 50% by weight of the total pre-layer and by a layer of manioc starch representing also 50% by weight of the pre-layer.

The filtering agent was constituted by a mixture of potato starch representing 75% by weight, and the manioc starch, representing 25% by weight.

It was observed, at the end of the test, that the filtrate was clear; the efficiency was such that the filtrate contained 40 cells per liter.

It was also observed thattherewas a better mechanical behaviour on the demolition of the filter, which facilitated the unsticking of the filtering cake. The quality and effectiveness of the filtration were also as good as in the preceding examples.

EXAMPLE 5 This test was carried out under the same conditions as Example 2, but the pre-layer was fabricated in two steps: - a first step consisting of depositing Kieselguhr in the proportion of 30% by weight of the total pre-layer, - then a second step in which the potato starch was deposited in the proportion of 70% by weight of the total pre-layer.

The Kieselguhr used had the following particle size distribution: 15% of the grains were less than 10 microns in diameter 18% of the grains had a diameter less than 18 microns and greater than or equal to 10 microns 22% of the grains had a diameter less than 25 microns and greater than or equal to 16 microns 24% of the grains had a diameter less than 40 microns and greater than or equal to 25 microns 21% of the grains had a diameter less than 100 microns and greater than or equal to 42 microns.

The filtering agent was constituted by potato starch.

The results obtained are similar to those observed in Example 2 (50 cells per liter).

As a result of which and whatever the embodiment adopted, there is thus provided a method and a filtering agent whose characteristics are apparent from the foregoing and which present, with respect to those existing hitherto, numerous advantages, notably that of leading to a filtering residue not only non-polluting, but on the other hand useful in human and animal feeding, hence of value.

As is self-evident and as emerges already from the foregoing, the invention is in no way limited to those embodiments which have been more especially envisaged; it encompasses, on the contrary, all modifications.

Claims (15)

1. Method of filtering alimentary liquids, notably fermented liquids, characterized by the fact that recourse is had to at least one native starch, notably from tubers, as a filtering agent.

2. Method according to Claim 1, characterized in that the native starch is potato starch.

3. Method according to Claim 1, characterized in that the native starch is manioc starch.

4. Method according to Claim 1, characterized by the fact that the filtering agent is constituted by a mixture of native starches.

5. Method according to one of Claims 1 to 4, characterized- by the fact that the filtration is carried out by resorting to a sealed filter avoiding the escape of fermentation gases, notably of the filter press or candle filter type, on which a pre-layer has been deposited constituted by at least 50%, preferably at least 70%, of at least one native starch, the complement to 100% being constitutable by at least one filtering adjuvant selected from among the group comprising Kieselguhr, filtering earths, conventional filtering agents, starch, on the one hand, and the filtering adjuvant, on the other hand, being arranged preferably in the form of two superposed layers of which the assembly forms the above-said layer.

6. Method according to Claim 5, characterized by the fact that the filtration is carried out by suspending the liquid to be filtered in an amount of at least one native starch in a sufficient amount so that no clogging of the filter is produced.

7. Method according to any one of Claims 5 and 6, characterized by the fact that a native starch is suspended in the liquid to be filtered in an amount sufficient so that no clogging of the filter occurs and that there is deposited on the filter a pre-layer constituted by the same native starch as that in suspension, or by a possibly different starch mixed with at least one filtering adjuvant.

8. Method according to any one of Claims 5 to 7, characterized in that the pre-layer is constituted by several superposed layers of decreasing granulometry starting from the filter, the constituent material of each layer being selected from among starches whose granulometric spectrum corresponds to that required for the individual layer envisaged.

9. Method according to Claim 8, characterized in that the pre-layer is constituted, starting from the filter, by a potato starch layer and a manioc layer.

10. Method according to any one of Claims 5 to 9, characterized by the fact that between the filter and the first starch layer, starting from the filter, is deposited a layer of at least one filtering adjuvant.

11. Method according to any one of Claims 5 to 10, characterized by the fact that the native starch in suspension is present in the proportion of 50 to 200, preferably from 80 to 150 g/hl.

12. Filtering agent for alimentary liquids notably fermented liquids, characterized by the fact that it is constituted by at least one native starch of bacteriological quality compatible with its use in the filtration of alimentary liquids and notably free of yeasts and molds.

13. Filtering agent according to Claim 12, characterized by the fact that the native starch is a tuber starch, notably potato starch or manioc starch.

14. Application of the method according to any one of Claims 1 to 11 and of the agent according to one of Claims 12 and 11 to the filtration of beer.

15. Novel industrial product constituted by the filtering cake obtained at the end of the method according to any one of Claims 1 to 11.