Method of the oak barrel Regeneration

 

Sula R.A., Prakh A.V., Ageeva N.M., Guguchkina T.I., Zakharova M.V., Yakuba Yu.F.

Alcoholic beverages production and wine-making State scientific  institution.

 

The North-Caucasian zonal research institute of gardening and viticulture of the Russian Academy of Agricultural Sciences (Rosselkhozacademia)

 

     The oak wood is essentially important for wine-making. Fermentation of the grape must in contact with the oak stave allows complete realizing of the future wine potential. Further ageing of wine in the oak barrels or boots makes it possible to manufacture products of higher quality. However the oak barrels get depleted after certain period of use and have to be replaced with new ones, thus the problem of more rational use of the oak stave is currently rather actual [1]. First of all it is determined by the limited wood resources: the area of oak forests in France is about 500 thousand hectares, in the Caucasian Region – 900 thousand hectares, in central Russia (mainly in the Voronezh Region) – 300 thousand hectares [2], the resources of Belarus and Ukraine are significantly less. The technology of mechanical working of inner surfaces of the old oak barrel staves, consisting in manual removal of several millimeters of the wood layer, causes thinning of the walls and sometimes results in loss of their mechanical strength. Therefore tens of thousands of the oak barrels become rejected for re-use because they are not subject to regeneration with the help of such technology.

 

     The purpose of the present paper consists in the feasibility evaluation and experimental development of technology for treatment and regeneration of inner surfaces of the oak barrels, used for wine production, without any mechanical working, with the help of the oak extract solutions, produced from the oak wood. Implementation of such technology can prevent from oak forests cutting and thus contribute to improvement of forestry ecology.

 

     The materials of the experiments were as follows: the depleted barrels, used for ageing of white and red wines, wine bases, oak wood extracts "Tanol, dry”, manufactured at the enterprise "Dialog” Ltd. (city of Goryachiy Klyuch, Krasnodar Region, Russia). The dry extract had the following parameters (%, not less than): tannins – 43, lignin – 32, hemicelluloses – 14, quercetol – 4, mineral substances, not more than, % - 0.5; humidity about 8% [3]. For the reference sample there was used the oak barrel  and stave, inner surface of which was mechanically worked. 

 

     Qualitative composition and quantity of volatile components were analyzed by the method of capillary gas chromatography with the help of the instrument "Kristall-2000M”, content of organic acids was determined by the method of capillary electrophoresis with the help of the series "Kapel” instruments, as well as by means of the GOST R methods. There were applied the following developed methods for treatment of the depleted oak barrels:

 

  1. The oak stave, used for ageing of natural white wines: the oak barrels were steam treated and washed with heated up to 55 oC 0.8-1% water solution of formic acid, rinsed with softened water till neutral reaction, filled with heated up to 45 oC 0.2-0.4% water solution of oak extract, and the oak barrels were kept filled during 7-8 days, then the extract solution was drained, heated again up to 40-45 oC, and poured again into the woods for 7-8 days; the solution in the wood was stirred from time to time, after the specified period it was drained and the wood was rinsed with softened water.
  2. The oak barrel stave, used for ageing of natural red wines: the oak barrels were steam treated and washed with heated up to 55 oC 0.8-1% water solution of acetic acid, rinsed with softened water till neutral reaction, filled with heated up to 40-45 oC 0.2-0.4% water solution of oak extract, and the oak barrels were kept filled during 7-8 days, then the extract solution was drained, heated again up to 40-45 oC, and poured again into the barrels for 7-8 days; the solution in the barrel was stirred from time to time, after the specified period it was drained and the barrel was rinsed with softened water.

 

     The experiments used red and white table wines with typical young wine aroma. Physical-and-chemical, organoleptic and other parameters, characteristic for the method of the oak stave treatment, are detailed in tables 1 and 2.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Analysis of the results showed that:

 

  • application of the technology of successive regeneration of the oak barrel inner surface with further treatment of the oak stave inner surface with water solution of the oak extract resulted in essential changing of the organoleptic characteristics alongside with retention of principal physical-and-chemical properties of the red or white wines, subject to ageing in such barrel. The results were explained by the fact that after cleaning of the inner surface of the oak barrel with acetic (formic) acid solution the oak extract components were absorbed by the inner surface of the oak barrel in the process of its double filling with such extract. The oak barrel inner surface demonstrated strong sorptive capacity with intensive saturation of deep layers;
  • typical colour was obtained;
  • after treatment as compared to the reference sample the resulting mass concentration of acetaldehyde and esters did not change, content of furfural was 20-35% less, of acetic acid – 15-18% less, of the extract – 3-5% less. 

 

     The obtained results were explained by the effect of the absorbed extract components in the inner surface of the oak stave, causing full reproduction of basic chemical, physical-and-chemical and biochemical transformations, finally improving aroma and flavour characteristics of wine in the process of ageing. Quality of table wine was improved due to harmonization of composition of the aromatic and extractive components. The oak extract components were specifically absorbed in the intercellular space of the wood under direct affect of capillary forces. During further ageing there took place the process of complex mass exchange with the components of table wine, which was exactly like the similar processes in the conditioned oak barrels. Thus there was established complex interrelation between the capillary forces in the intercellular space, newly built hydrogen bonds in the structure and adsorptive processes.  

 

     White wine, produced according to procedure no.1, had specific floral aroma, strong full flavour and typical for white wine straw colour.  Red wine, subject to ageing according to procedure no.2, was characterized by light fruit aroma, clear and light tone of the oak barrel ageing, soft and full flavour, had typical red colour.  

 

     The suggested technology of the oak barrel regeneration enables multiple use of the oak barrels during wine-making. The described research work was patented with the RF patent no. 2428466 [4].

 

 

Literature

  1. Khiabakhov T.S., Method of regeneration of depleted oak barrel, the USSR invention certificate no.1721083, Bulletine no.11, 1992, p.86.
  2. Oganesyants L.A. Oak wood and wine-making. – M: Agropishchepromizdat, 2001. – 359p. 
  3. Yakuba Yu.F., Sula R.A. Treatment of the oak barrels with oak extract solutions / Storage and processing of agricultural raw materials. Theoretical journal. – 2007.      – no.4. – p.65-66.
  4. Sula R.A., Redka V.M., Prakh A.V., Guguchkina T.I., Ageeva N.M., Yakuba Yu.F., Method of the oak barrel regeneration, RF Patent no.2428466, Bulletin no.25, 2011.

 

 

 

 

 

 

 

 

The invention relates to the wine industry and may be used in the cognac spirit technology where oak wood is employed; the best cognac spirits are produced at ageing in barrels.

   It is well known that there is a method of wood processing, when the wood is exposed to the ultraviolet radiation from the mercury quartz lamp located at a distance of not more than 50 m from the wood being processed for 50 – 100 hours, depending on the species of oaks and air humidity to accelerate formation of the substances contributing to production of high-quality cognac spirit. 

  

   The method of processing the internal surface of stave of old barrels, unsuitable for filling in with cognac spirit, is the closest analogous solution. Barrels are disassembled, repaired, 2-3 mm of wood ply is planed away and then barrels are reassembled and used for cognac spirits technology (I.M. Skurikhin. Chemistry of Cognac and Brandies.-M: DeLi Print, 2005.-page 63).

   Time-consuming mechanical operations for barrel disassembly and subsequent processing of the internal surface are difficulties of the existing method. The barrels processed by this technology have thin walls that effects on the diffusion processes in the course of the cognac spirits ageing and, as a rule, it has a detrimental effect on their quality. Besides, repeated operation for the barrel internal surface renewal can result in the loss of mechanical strength and destruction.

   Technical result of the proposed invention involves processing of the internal surface of the stave of oak barrel by the oak extract without mechanical influence on it that makes it possible to carry out repeated operations for stave processing and produce high-quality cognac spirits.

   Technical result is achieved due to the fact that stave of the barrel is filled by 0.5-1.0% aqueous or low alcoholic solution of the oak extract heated to 40-45ºС and it is aged for 14 days, then the extract solution is poured out, heated to 40-45ºС, filled in again for 14 days with periodical stirring, and then stave is washed by softened water.

   The advantage of the clamed method is as follows: physic-chemical processes are not used for the stave surface activation; mechanical actions on the stave are excluded; minimal material expenditures are required. Besides, the proposed method is economically advantageous because stave wastes are not generated.

   Employment of the proposed aggregate of essential features set forth in the summary of invention permits to reach the intended effect – regeneration of stave internal surface of the barrels and produce high-quality cognac spirits outperforming those produced in oak barrels processed by prototype method.

   Examples of Definite Application

   Example 1

   Depleted cognac barrels that had been used for two fillings with cognac spirit and dry oak extract "Tanol” produced by "Dialog” Company, Goryachy Kluch town, have been selected for the experiments. The barrel has been filled in with 0.5% aqueous solution of the oak extract heated to 40-45ºС and aged for 14 days with periodical stirring. 14 days after, the solution has been poured out and heated to 40-45ºС and the barrel has been filled in again for 14 days. Heating of the solution has been provided for sterilization and to increase the mass transfer rate between the oak extract solution and stave. Then the barels has been rinsed by softened water and filled in with young cognac spirit 65.8% strong produced by traditional technology. Young cognac spirit with the following mass concentrations of the components has been used for experiments (mg/dm3 a.a [anhydrous alcohol].): acetaldehyde – 311.0; total of esters – 540.0; acetals – 62.4; acetic acid – 77.4. Young cognac spirit was free from phenolic substances and aromatic aldehydes. Chemical measurements have been consecutively performed.

   Example 2

   The method has been realized in the same way as in example 1, except that 1% aqueous solution of the oak extract has been used.

   Example 3

   The method has been realized in the same way as in example 1, except that 1.5% aqueous solution of the oak extract has been used.

   Example 4

   The method has been realized in the same way as in example 1, except that 0.5% aqueous solution of the oak extract has been used in tail fractions of the  cognac spirit 15-20 vol.% strong. Spent alcohol solutions of the extract have been processed for spirit recovery.

   Example 5

   The method has been realized in the same way as in example 4, except that 1% aqueous solution of the oak extract has been used.

   Example 6

   The method has been realized in the same way as in example 4, except that 1.5% aqueous solution of the oak extract has been used.

   Example 7

The method has been realized as per the prototype method.

Physico-chemical, organoleptic and other indicators characterizing the method of the oak barrel stave processing are tabulated in Table 1-3.

 

Table 1 – Values of chemical composition of cognac spirit 1080 days after start of observation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2 – Aromatic aldehydes content in cognac spirit 360 days after start of observation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3 – Aromatic aldehydes content in cognac spirit 1080 days after start of observation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Analysis of the obtained results has revealed that:

   - employment of aqueous or low alcoholic solutions of the oak extract for processing the internal surface of the barrel stave has resulted in significant changes in the cognac spirit composition at all monitored values. This follows from the fact that as a result of double pouring into a barrel, the oak extract components have been absorbed by the barrel internal surface. Internal surface of the barrel has shown strongly pronounced sorption properties with the saturation of deep layers;

   - as a result of processing, mass concentration of acetic aldehyde has been increased by 5 – 7%, esters – by 11%, acetal – more than twofold, and aromatic aldehydes forming the characteristic aroma of the cognac – by several times;

   - Significant changes have been found in the aromatic aldehydes content: at the end of the first year of observation, all aldehydes have been present after processing by the proposed process variants as contrasted with the prototype method where only sinapic and lilac aldehydes have been recorded.

   After 3 years of ageing concentration of sinapic aldehyde has been increased by 4-7 times, coniferaldehyde – by 1.5-2 times, vanilline - by 15-20 times as contrasted with the prototype method. Concentration of lilac aldehyde after processing by the proposed variants of the method and by the prototype method was much the same;

   - The obtained results flows from the fact that complete physical and chemical, and biochemical transformations occur under the action of the oak extract components absorbed by the internal surface of stave of the barrel resulting in the improvement of the aged cognac spirit. Improvement of the cognac spirit quality is achieved due to tailored composition of the esters, higher alcohols, acetic acid, and especially aromatic aldehydes. The oak extract components have been specifically absorbed in the intercellular space of the wood with direct involvement of capillary forces. During subsequent ageing, complex mass exchange with cognac spirit has occurred entirely reduplicating the processes taken place in the oak barrels. Thus, complex interaction of the capillary forces in the intercellular space, generated hydrogen bonds and adsorptive processes has been achieved.

   - in the event that the stave has been processed as per examples 1 – 6, the development of complex aroma has been noted in the produced cognac spirits with resinous-cinnamomic flavour and distinct vanillic tint, and organoleptic characteristic higher than that provided by the prototype method.
   Processing of stave of the oak barrel by aqueous or low alcohol solution of the oak extract.
   Employment of the proposed method for the stave processing, as compared with the prototype one, has resulted in the significant improvement of organoleptic indicators of young cognac spirit aged in it, allowed to produce high quality cognac spirit due to the optimal composition of esters, acetals, acetic acid and aromatic aldehydes which are responsible for specific organoleptic properties of the ready-to-drink beverages. The processing technology has allowed multiple employment of the stave.
   The best results have been achieved when 0.5-1% aqueous solution of the oak extract has been used.

 

 

   SUMMARY
   Method of the stave processing provides its filling with 0.5-1.0% aqueous or low alcohol solution of the oak extract heated to 40-45ºС, ageing for 14 days, pouring the extract out and its heating to 40-45ºС, refilling and ageing for 14 days, periodical stirring and subsequent washing of the wood stave by softened water.

 

 

 

 

 

 

 

 

 

 

 

Roman Alekseevich SULA

1 GENERAL DESCRIPTION OF THE WORK 

      

1.1 Urgency of the issue. Russian scientists L. A. Oganesiants, I.M. Skurikhin, A.K. Rodopulo, I.A. Egorov, R.V. Avanesiants, T.S. Khiabakhov, M.S. Sachavo and others developed and introduced into production the technologies that contributed to significantly improvement of quality of the cognac distillates, brandy and Russian cognacs. Cognac distillates can be aged for 3 to 25 years and more. During this time, distillates loose up to 3-5% of anhydrous alcohol (a.a.) due to evaporation. At the same time, the content of tannins, lignin, hemicellulose and other valuable substances are decreased in oak wood. 

New technologies shall be introduced to reduce losses of spirits and to replenish valuable substances in the oak wood. These technologies are based on the action of different physical and physical-chemical means on the wine distillate and oak wood, as well as on the introduction of ageing accelerants to the distillate – extractive substances extracted from the processed or specially treated oak wood, for example, concentrates, oak extracts, etc. Introduction of the oak extracts for improvement of the wine distillates quality is allowed by France legislation and Russian state standards. Besides that, the extracts from the oak wood can be used to extend service life of oak barrel and stave, and to improve quality of the mature cognac distillates.

The existing episodal investigations of the oak extracts have left out of account their impact on the composition and resistance to cloudiness of the product. Besides that, the extracts production technology has been improving, new methods of hydrolysis, cleaning and dehydration of extracts are implemented. Meanwhile, those investigations are contradictory ones and they are not systematized. In this respect, the investigations focused on the substantiation of the use of oak extracts in the brandy production technology are of current concern and of great scientific interest.

1.2 Connection of the Work with scientific programs, plans, subjects. 

The Work in the form of individual projects has been performed according to plan of the Research Scientific Works for 1997 – 2005 in the State Scientific Institution "North-Caucasian Institute of Horticultural and Viniculture Research” of Russian Agricultural Academy on the subject: "Develop Packaged High Performance Technologies for production and stabilization of grape wines with the use of new and promising grape varieties and up-to-date methods of physical-chemical effects”.

       1.3 Research Objective – physical-chemical substantiation and development of brandy production technology.

       1.4 The following issues have been solved to achieve the stated objective:

- examine the oak extract effect on the formation of volatile components in the rectified spirits and young distillate;

- evaluate the oak extract effect on the  aromatic aldehydes content, composition of the volatile components of mature cognac distillate (aged for 3-5 years) and their organoleptic indicators;

- Define the concentration of alkaline and alkaline earth metals cations of cognac distillates and determine their effect on the distillates resistance to cloudiness;

- Substantiate the possibility to use oak extract to extend service life of oak barrels in the cognac distillates technology;

- Substantiate the applicability of the oak extract solution for enrichment of oak stave used for the cognac distillates ageing in tanks; 

- Develop improved technology for production of brandy and ordinary cognac distillates with employment of the extract, and oak stave enriched by the extract.

1.5 Academic novelty. Dynamics of volatile components and aromatic aldehydes at the introduction of oak extract to young and mature cognac distillates have been investigated for the first time ever. Theoretically substantiated method of cognac oak barrels treatment without their subjection to mechanical influence has been proposed for the first time; dynamics of the distillate aromatic components in the processed barrels have been examined. Method of treatment the oak stave used for the cognac distillates ageing in tanks has been proposed and substantiated for the first time. Dynamics of the volatile and aromatic components of distillates produced by the developed method have been investigated.

1.6 Practical implications of the Work. Processing methods for enrichment of the depleted oak barrels and oak save used for the cognac ageing in tanks have been developed. Physical and chemical substantiation has been carried out; brandy production technology (including that with the use of rectified spirit) has been developed on the basis of introduction of the oak extract to the oak stave for cognac production. 

Economic effect of the technology is 7000 roubles /1 m3 of staff wood at 2006 values.

1.7 Approbation of the Work. Fundamental principles of the Thesis have been reported and approved at All-Russian Seminars of cognac production industry workers of Krasnodar branch of Standardization, Metrology and Certification Academy (Krasnodar, 2006–2007). 

To the full extent, the Work has been reported, discussed and approved at the extended meeting of wine-making center of State Scientific Institution "North-Caucasian Institute of Horticultural and Viniculture Research” on 19.01.2007.

2 applications have been filed for RF discovery (No. 2006128958 of 9.08.2006 and No. 2006137915 of 26.10.2006).

1.8 Publications: 8 scientific articles have been published on the basis of the Thesis.

1.9 Thesis structure and volume. The Thesis consists of Introduction, Literature Review, 3 Chapters of Experimental Part, Conclusions, List of References (167 items including 28 foreign ones) and Appendix. The Thesis text is set forth on 122 pages and includes 23 tables and 17 figures.

2 OBJECTS AND METHODS OF RESEARCH

Young and mature cognac distillates, brandies produced by the main stream technology at the Russian Federation enterprises have been used as the objects of research. Support material – oak wood extract "Dry Tanol” produced by "Dialog” company in accordance with the requirements of TU 9185-259-00334600-05 (Goryachy Kluch town, Krasnodar Region). Dry extract parameters (%, not less than): tannins – 43, lignin – 32, hemicellulose – 14, quercetol – 4, mineral substances– 0,5; humidity – about 8%.

GOST R, gas chromatographic analysis on chromatograph "Kristall-2000M”, capillary electrophoresis on "Kapel-103R” device have been used to determine basic indices of chemical composition. Experimental investigations have been carried out with the use of computer. Statistical processing has been performed by the variation statistics method.

 Scheme of the Thesis research is presented on Fig 1.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3 FINDINGS OF INVESTIGATIONS

3.1 Investigation of the oak extract effect on the formation of volatile and aromatic components in solutions of rectified spirit and young cognac distillate. Differences in the extract production technologies and continuous contact with the beverage (wine or cognac spirit) can lead to the formation of substances that result in the decrease of organoleptic indicator or those having harmful effect on the human health: acetone, methylethylketone, crotonic aldehyde, diacetyl (in amount of more than 20 mg/dm3 a.a.), surplus content of acetic acid and some others. In connection therewith, the oak extract "Tanol” solutions in water-alcohol solutions with a strength of 60% and 96.3% have been investigated (Table 1).

Table 1 – Effect of the extract on mass concentration (mg/dm3 a.a.) of main volatile components of the rectified spirit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The obtained results have testified that after introduction of the oak extract "Tanol” to rectified spirit and during its observation for 180 days, the substances that pose a hazard to human health have not been revealed. Significant changes in furfurol, esters and acetic acid concentration have been detected. Investigation of the oak extract effect on the formation of volatile components of young cognac distillate has given an evidence of significant change in concentration of main volatile components (Table 2).

Table 2 – Effect of "Tanol” on mass concentration (mg/dm3) of main volatile components in young distillate

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

It has been established that in young cognac distillate with "Tanol”, alongside with the changes in concentration of furfurol, esters and acetic acid, gradual increase of concentration of the aromatic components has been noted: phenyl ethanol, ionone, caproaldehyde and capraldehyde, which have positive effect on the organoleptic evaluation of the cognac products. Further research suggests that the wine distillate promotes much more rapid emergence of the aromatic aldehydes than the rectified spirit (Table 3). 

Table 3 – Dynamics of aromatic aldehydes (mg/dm3) in rectified spirit and young distillate

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After 7 days of contact, the total content of aldehydes in cognac spirit has been found to be equal to 4.4 mg/dm3, while in rectified spirit, total amount of aldehydes was about 1 mg/dm3 after 60 days of observation (sinapic aldehyde was not detected). In all solutions (after 210 days of observation), lilac aldehyde prevailed – 58.6%. In the process of ageing, cognac distillates are enriched with cations of alkaline and alkaline-earth metals, which are intrinsic to the staff wood. Additional study has found that introduction of the extract has not resulted in alkaline and alkaline-earth metals increase, with the result that it has not deteriorated cloudiness resistance of the brandy produced afterwards. 

3.2 Effect of oak extract on formation of the volatile and aromatic components of cognac distillates aged for 3 years. Quite often, flavor profile of cognac distillates aged for 3-5 years fails to meet the requirements due to employment of the impoverished staff wood or other technological limitations. Introduction of the oak extracts is specified in many technological processes; meanwhile, detailed investigations of the oak extracts effect on the formation and transformation of volatile and aromatic components of cognac distillates aged for 3 – 5 years have not been carried out. Preliminary experiments have shown that optimal flavor profile of the cognac spirit is obtained when dry extract is applied to it in amounts of 1 g/dm3. Effect of the applied extract on the dynamics of main aromatic components of cognac distillates aged for 3 – 4 years is tabulated in Table 4.

It has been established that in cognac distillate aged for three years with the introduced extract, alongside with the changes in concentrations of furfurol, esters, fusel oil, acids, gradual increase of aromatic aldehydes concentration has been observed: lilac aldehyde by 15.4%, vanillin - fourfold, emergence of sinapic aldehyde and coniferaldehyde, which have positive effect on organoleptic evaluation of the cognac products. 

Table 4 – Extract effect on mass concentration (mg/dm3 a.a.) of main aromatic components of cognac distillates aged for 3-4 years

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

While investigating cognac spirit with the extract aged for four years, gradual increase of aromatic aldehydes concentration has been detected: lilac aldehyde – by 42,3%, vanillin – by 61%, formation of sinapic aldehyde and  coniferaldehyde, which were absent in the initial cognac distillate. Effect of the applied extract on the dynamics of main aromatic components of cognac distillate aged for 5 years is tabulated in Table 5.

Table 5 – Extract effect on mass concentration (mg/dm3 a.a.) of main aromatic components of cognac distillates aged for 5 years 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Alongside with the changes of concentrations of furfurol, esters, fusel oil, acids and phenylethanol, strongly pronounced increase of aromatic aldehydes concentrations (%) has been detected in cognac distillate enriched with the extract: lilac aldehyde – by 36.8, vanillin – by 55, sinapic aldehyde – by 100, coniferaldehyde – by 50.

Concentration of aromatic aldehydes of the initial spirit aged for 90 days has increased by 2.5-7.0 %. 

Introduction of the extract has had positive effect on the tasting assessment: colour has shown great improvement, full-bodied and at the same time delicate vanillic aroma with a touch of resinous and chocolate fragrance has appeared, harmonious and intense taste has been noted.

 

3.3 Application of oak extract for the enrichment of the oak wood used in the brandy production technology. High quality brandies are produced at their ageing in oak barrels. Expensiveness and deficiency of the barrel create the situation when new technologies for the alcohol based and other types of extracts production from waste woods are continuously developed and proposed. 

We have set up the experiments to study the possibility of processing the internal surface of depleted oak barrel with the oak extract without power influence on it. Aqueous and low alcoholic solutions of the oak extract have been used for enrichment and processing of barrels, processing conditions have been assessed on the basis of changes in the aged cognac distillate chemical composition. The barrel restored mechanically has been used as a reference specimen (Fig. 2, Tables 6 and 7).  

After mathematical treatment of the results of tasting the alcohol aged in the enriched barrels, considering the initial spirit composition, the regression equation has been obtained:

Tasting assessment = 8.29+0.028A-0.004E-0.023Ac-0.021AcA+0.016PhM (1),

Where: mass concentration (mg/dm3 a.a.): A - aldehydes; E - Ethers; Ac – acetals AcA – acetic acid; PhM – amounts of phenolic matters.  

The equation makes it possible to calculate the tasting assessment provided that current composition of volatile components of young distillate is known. Analysis of the obtained results has revealed that, as against the reference specimen, the employment of aqueous and low alcoholic solutions of the oak extract for processing the internal surface of the barrel stave has resulted in the increase of ethyl aldehyde – by 5 – 7%, esters – by 11%, acetal – more than twofold, and aromatic aldehydes forming the characteristic aroma of the ready-to-drink beverage – by several times.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The obtained data are derived from the fact that the oak extract components have been absorbed by the internal surface, which shows strongly pronounced sorption properties with saturation of deep layers. Development of complex aroma with resinous-cinnamomic and vanillic flavour, and with organoleptic characteristic higher than that of the reference specimen has been noted in the ready-to-drink beverage.

Table 6 – Dynamics of aromatic aldehydes in cognac distillate aged in barrel processed by aqueous solution of the oak extract

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 7 – Dynamics of aromatic aldehydes in cognac distillate aged for  3 years in barrel processed by low alcohol solution of the oak extract

 

 

 

 

 

 

 

 

 

 

 

 

 

Due to extensive use of ageing treatment in tanks, the possibility of the oak extract application for processing the depleted stave has been assessed. Stave has been subjected to the one-shot partial mechanical deformation by forge-rolling to form a large structure of microfractures and to extend the transfer surface. Then it has been placed to a vessel that has been filled through the height of the stave pile by 0.2-1.5% aqueous solution of the oak extract  heated up to 30-35ºC, and it has been aged for 7 days with periodic agitation. 

After second filling, the stave has been washed by softened water and filled up by young cognac distillate 69.4% strong produced by traditional technology, and aged. Traditional ageing in vessel has been used for reference (Fig. 3).

The highest tasting appraisal has been received by the cognac distillates in contact with the stave processed by 0.8-1.0 % oak extract solution. After mathematical treatment of the tasting results considering the initial distillate composition, the regression equation has been obtained:

Tasting assessment = 8.2+0.008A+0.006E–0.063Ec+0.064AcA– 0.009PhM (2),

Where: mass concentration (mg/dm3 a.a.): A - aldehydes; E - Ethers; Ac – acetals; AcA – acetic acid; PhM – amounts of phenolic matters.  

  The equation makes it possible to calculate the tasting assessment provided that initial composition of volatile components of cognac distillate is known.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Change in aromatic aldehydes in cognac distillate aged in contact with the depleted stave processed by the oak extract solution is tabulated in Table 8 

It has been established that, as against the reference specimen, the mass concentration of acetal aldehyde decreased by 20-22%, mass concentration of esters  increased by 17-20%, acetal – by 19%, and aromatic aldehydes forming the characteristic aroma of ready-to-drink beverages  increased by several times.

Table 8 – Dynamics of aromatic aldehydes in cognac distillate aged aged in contact with depleted stave processed by aqueous solution of the oak extract

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The obtained data have derived from the fact that as a result of double pouring into an oak barrel or tank, the oak extract components have been absorbed by depleted stave, which shows strongly pronounced sorption properties with saturation of both surface and deep layers, to which the extract components can penetrate due to partial deformation of the stave. Then, complex mass exchange on the extended surface of microfractures in wood has occurred when the oak extract components with young cognac distillate have been accumulated, at that the processes of cognac spirits ageing in vessels are duplicated. 

Fig. 4 illustrates the flow chart of the depleted oak stave processing.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In summary, integrated interaction of capillary forces of intercellular space, newly formed hydrogen bonds and adsorptive processes has been achieved in the structure. When depleted oak stave was processed by 0.8-1.0% solutions of the extract, harmonious aroma with a hint of vanilla has been noted in aged distillates with organoleptic characteristic higher than that of the reference specimen.

Carried out investigations for employment of the oak extract in production technology for brandy produced on the basis of rectified spirit has found that the best degustation evaluation of brandy is made when the oak extract is introduced in cognac distillate with its short-term ageing, and only after that, it is used in the production technology. Introduction of extract to the cognac distillate and its short-term ageing has provided, as compared with other versions where the extract was immediately introduced into the composition, the increase of the following components (%) has been noted: ethyl acetate – by 40, ethyl acetal – by 84, furfurol – by 50, amounts of acids – by 36.8, phenylethyl alcohol – by 33.3, lilac aldehyde – by 11.6.

On the basis of carried out experimental investigations, the process flow chart has been developed for production of grape brandies, Fig 5.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 5 – Process Flow Chart

The Chart includes production of young cognac distillate (1), its pumping (2) to tank (3) for ageing with the possibility of the oak stave processing, delivery to the process vessel (4), production of ready-to-drink beverage in blending tank (5) with introduction of colorant (6), softened water (7), sorbents (8), storing (9), cooling (10), attainment of the required transparency (filtration 11) and resistance to cloudiness (12).

Cognac distillates production technology with employment of the oak extract has been tested at LLC Budennovsky Vinary («Vinzavod Budennovsky»), which is confirmed by appropriate Acts. Economic effect of the technology is composed of the price variance of new oak stave and expenditures connected with the processing of exhausted one by the oak extract, and it amounts to 7000 rub/1 m3 of oak stave at 2006 values. 

 

 

CONCLUSION

  1. Introduction of the oak extract to the rectified spirit and young cognac distillate during the whole observation period has resulted in increase of concentration of main volatile components responsible for the typicality and sensory characteristics.
  2. Young cognac distillate contact with the oak extract has promoted rapid emergence of aromatic aldehydes as compared to that of the rectified spirit. After 7 days of contact in cognac distillate, the total content of aldehydes was by 4.4 mg/dm3 higher than that in rectified spirit.
  3. It has been established that extract introduction to cognac distillates aged for 3-5 years results in increase of the concentration of furfurol, esters, fusel oils, acids as well as aromatic aldehydes – lilac aldehyde - by 15.4%, vanilline by 4 times, and emergence of aldehyde and coniferaldehyde. 
  4. The possibility of oak barrel regeneration by the oak extract solution has been substantiated. Wine distillate ageing in regenerated barrel has resulted in increase of the concentration of acetic aldehyde - by 5-7%, esters – by 11%, acetals – more than twofold, and aromatic aldehydes – by several times that form characteristic cognac aroma. With increase of the contact time (in experiment - up to 3 years) their concentration is increased by 7 - 20 times. 
  5. Advisability of depleted oak barrel regeneration by the oak extract solution has been proved. Concentration of main aromatic components, including aromatic aldehydes responsible for typicality and organoleptic perfections of the cognac products, has increased in wine distillate that has been in contact with the regenerated oak stave as compared to the reference specimen.
  6. Technology of the oak extract use has been developed for brandy production and oak barrel regeneration for cognac production. Economic effect of the technology is 7000 roubles/1 m3 of oak stave at 2006 values.

 

List of Works published on subject of the Thesis:

 

  1. R.A. Sula. Dynamics of Aromatic Aldehydes in Alcoholic Solutions of Oak Extract «Tanol» / R.A. Sula, Yu.F. Yakuba // Winemaking and Grape Growing.-2005.-No.6.-C.20.
  2. R.A. Sula. Effect of Oak Extract «Tanol» on Formation of Volatile Components in Spirit / R.A. Sula., A.G. Sula., Yu.F. Yakuba // Beverages Industry.-2005.-No.5.-C.54-55.
  3. R.A. Sula. Cognac Spirit: Effect of Oak Extract «Tanol» on Formation of Volatile Components in Young Spirit / R.A. Sula. Yu.F. Yakuba, M.V. Zakharova // Conformity Assessment Methods-2006.-No.8.- C.26-27.
  4. Yu.F. Yakuba. Effect of Oak Extract on Formation of Aromatic and Volatile Components of Young Cognac Spitit / Yu.F. Yakuba, R.A. Sula. .V. Zakharova // Winemaking and Grape Growing.-2006.-No.3.-C.32.

 

 

 

 

 

 

 

 

 

Oak stave Processing Method

PHYSICAL AND CHEMICAL SUBSTANTIATION AND BRANDY PRODUCTION TECHNOLOGY DEVELOPMENT