Chemistry: molecular biology and microbiology – Process of utilizing an enzyme or micro-organism to destroy... – Treating animal or plant material or micro-organism
Reexamination Certificate
2001-06-29
2003-09-23
Prats, Francisco (Department: 1651)
Chemistry: molecular biology and microbiology
Process of utilizing an enzyme or micro-organism to destroy...
Treating animal or plant material or micro-organism
C435S274000, C435S277000, C435S201000, C435S202000, C435S209000, C435S200000, C106S124100, C144S335000
Reexamination Certificate
active
06623953
ABSTRACT:
The present invention relates to an enzymatic composition and an aqueous bath for seasoning or maturing green wood, and also to a method using this enzymatic composition or this bath.
Introduction
The use of wood as a material in construction, carpentry or cabinet-making presumes prior drying in order to dimensionally stabilize this wood. For cooperage, there are also organoleptic requirements.
For most industrial applications, this drying takes place in a drying facility at controlled temperature and humidity.
For other applications, in particular when the wood will subsequently be in contact with foods, the drying takes place naturally, outside, over quite long periods of time, with the aim of eliminating certain undesirable compounds. The duration of this natural drying, or ageing, can be varied depending on the final use. This drying can take up to 2 years in order to obtain good organoleptic qualities.
In the case of natural drying, the wood is colonized by a fungal flora which can transform certain compounds of the wood. These transformations of the wood cannot, however, be controlled. Naturally dried wood exhibits great variability of quality.
On the other hand, with artificial drying in a drying facility, these transformations do not occur and the wood thus dried is not suitable for food applications since this drying does not make it possible to eliminate certain undesirable molecules (such as toxic or bitter molecules).
STATE OF THE ART
EP 0 001 540 A relates to the use of microorganisms or of enzymes (pectinase or cellulase) with the aim of modifying the structure of wood intended for decoration, by controlling the temperature, the water content of the wood, and the O
2
and CO
2
content in the wood's environment. In this method, the wood is pretreated before inoculation, post treated in order to terminate the microbiological process, and then dried.
This complex method does not use immersion of the wood in an enzymatic preparation.
DD 292 864 A relates to improving the impregnability of the sapwood of resinous wood using an enzymatic preparation (pectinase, cellulase and hemicellulase), at the same time as an aqueous mineral preparation intended to superficially protect this wood.
This method does not relate to the duramen of the wood, or to species other than conifers, or to a food application.
FR 2 421 039 A relates to the conditioning of wood in a solid medium, using microorganisms, with a view to facilitating the fragmentation and then the agglomeration of the elements of the wood.
This method does not use immersion of the wood or an enzymatic preparation, and does not relate to application in the food industry.
FR 2 705 607 A relates to the use of microorganisms having &agr;-amylase and &bgr;-glucosidase activities, with a view to improving the organoleptic qualities of oak intended for cooperage. The microbiological process is carried out in the solid state using a fungal leaven. The process, which is supposed to reproduce the effects of natural drying/seasoning, specifies neither the duration of bringing the microorganisms into contact with the wood, nor the temperature, nor the microorganism content. It does not describe a method of immersion of the wood, nor an enzymatic preparation, and it applies only to species of oak.
DESCRIPTION OF THE INVENTION
The aim of the present invention is to provide a method for seasoning wood which allows, once it has been used, notably shortened drying of the wood. This method is suitable for food applications and conserves the dimensions of treated wood.
A subject of the invention is an enzymatic composition for drying wood, comprising mainly enzymes of the cellulase class, and also an aqueous bath for seasoning wood, comprising an endocellulase activity of between 1×10
6
and 100×10
6
ECU (preferably between 3×10
6
and 30×10
6
ECU) per m
3
of wood to be treated, xylanase activity of between 0.6×10
6
and 60×10
6
BXU (preferably between 2×10
6
and 20×10
6
BXU) per m
3
of wood to be treated, a &bgr;-mannanase activity of between 0.4×10
6
and 40×10
6
MNU (preferably between 1×10
6
and 10×10
6
MNU) per m
3
of wood to be treated and an &agr;-amylase activity of between 1×10
6
and 100×10
6
&agr;
TU (preferably between 3×10
6
and 30×10
6
&agr;
TU) per m
3
of wood to be treated.
A subject of the invention is also a method for seasoning wood, prior to drying, comprising a step of bringing the wood into contact with an aqueous bath comprising the composition according to the invention.
Particular embodiments of the invention are described in the dependent claims.
The enzymatic composition used may comprise enzymes of the exocellular or endocellular type. The enzymes may be of bacterial or fungal origin, or of any other possible origin.
DETAILED DESCRIPTION OF THE INVENTION
The wood to be treated, the water content of which has ideally been brought to between 25 and 45% by being rapidly passed through a drying facility, is immersed in a bath containing water or any other suitable solvent, and varying amounts of enzymes mainly of the hydrolase class (International Union of Biochemistry (IUB) class 3), chosen from enzymes of the cellulase type (also known under the name glucosidases) (IUB classification subclass 3.2). In addition, enzymes of the lipase (subclass 3.1), peroxidase (subclass 1.11.1), etc. type, and mixtures of these enzymes, may be added. Among cellulases which can be used for the present invention, mention may in particular be made of cellobiohydrolases, endoglucanases, &bgr;-glucosidases, hemicellulases, &agr;-amylases, and xylanases, endocellulases, &bgr;-mannanases, etc., without losing sight of the fact that the enzymes often have secondary activities besides their main activity.
Depending on whether neutral or acid cellulases are used, the pH of the bath is adjusted to between 3 and 8, preferably between 4 and 7. The temperature of the bath is kept constant at between 20 and 70° C., preferably between 30 and 50° C. After this treatment by immersion, which can last from 30 minutes to 2 weeks, preferably from 1 hour to 1 week, depending on the strength of the effect desired, on the mixture of enzymes used, on the volume to be treated, on the volume of the bath, on the nature of the wood treated and on the temperature and pH of the bath, the wood is then placed in the drying facility at controlled temperature and humidity in order to carry out conventional drying which makes it possible to attain a water content of 15 to 20% for use in cooperage, starting from a wood having a water content of between 25 and 45%, preferably between 30 and 40%, before the bringing into contact with the enzymatic preparation.
The method according to the invention has proved to enable hydrolysis of soluble ellagitannins naturally present in wood, firstly ellagitannins linked to parietal polysaccharides, and also diverse aromatic molecules (such as digallic acid or heteroside coumarins) which are transformed, by the method according to the invention, into neutrally tasting molecules.
The method according to the invention therefore makes it possible to improve the impact on taste of the wood extracts by eliminating a significant portion of the undesirable compounds (such as certain phenol compounds) and hydrolysing forms judged to be bitter or astringent. This is particularly important for wood subsequently coming into contact with foods (typically, wood for cooperage).
This method superficially modifies the ultrastructure of the wood. By electron microscopy, a decrease in the cell wall is noted over 1 mm. Over 1 to 3 mm, the pores of the cells are open. The effects of the process are felt up to a depth of approximately 5 mm.
The present invention also has the advantage of providing a rapid method for ageing wood, while at the same time respecting all of the physicochemical reactions linked to the natural drying of wood.
In addition, the invention has the advantage of providing a reproducible method for seasoning wood and
ETS. Robert Stiernon S.A.
Olson & Hierl Ltd.
Prats Francisco
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