On the influence of key indicators of cork on wine

2022-08-08
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Talking about the influence of the key indicators of cork on wine

the characteristics of cork, such as corrosion resistance, water resistance, slight moisture absorption and good elasticity, determine that cork is still the sealing material with the most common application, the longest history and the best effect in the world. However, corks of different types, sizes and production processes have different effects on bottled wine. At the same time, the humidity, density, tightness, storage temperature, chemical indicators (oxidant residue), microorganisms and other indicators of corks have great or even fatal effects on the filling and quality of wine. For example, different kinds of corks have different sealing effects on wine, and long-term storage has different effects on wine quality. Too much humidity is bad for wine filling; The storage temperature is too low, which will cause insufficient elasticity of the cork during the corking process, and it is easy to break and slag; The residue of oxidant exceeds the standard, which not only damages the health of drinkers, but also affects the flavor of wine. Therefore, we must strictly control the indicators of cork according to the standards in order to ensure the sealing and quality stability of wine. Next, we will talk about the impact of cork on wine on the key indicators of cork

I. the tightness of cork

the tightness of cork is not good, which is easy to make wine leak. Leakage will not only pollute the packaging of the wine, breed colonies, but also oxidize the wine and change the quality of the wine. Therefore, it must be controlled as a key indicator. As we know, cork is a cork made of one or several prepared corks, or cork particles polymerized and processed to block bottles or other containers. According to different materials or processing technology, corks for wine are usually divided into three categories: natural corks, polymer corks and composite corks (here we mainly talk about the commonly used patch 1+1 corks). From the perspective of the structure and composition of the three types of plugs, their sealing properties are different, so their effects on wine are also different

natural plug has the best sealing performance. Because natural cork is a cork made of one or several pieces of natural cork. The number of cork cell stacking layers, the degree of density and the number of defects determine the tightness of the natural plug. For natural plugs with the same volume, the more layers of cells, the denser, the fewer defects, and the better the sealing. Therefore, the natural plug has strict quality classification. The world's general classification standard is determined by inspecting the appearance of corks. PBT used as engineering plastics has two qualities: unmodified and modified. According to the number and depth of skin holes on the end face of the natural plug, the size of skin holes on the side of the cylinder and the number of defects, from high to low, the natural plug is mainly divided into six levels: top level, super level, a level, B level, C level and D level. The higher the level of natural stopper, the longer the storage time of wine can be satisfied. It is measured that the annual oxygen permeability of natural cork is generally about 20 mg. Its micro permeability is not only more conducive to the maturation of wine, but also can meet the needs of long-term storage of wine

the sealing property of the polymer plug is poor. Because the polymer plug is made of cork particles mixed with binder, pressed into plates, rods or monomer die-casting at a certain temperature and pressure, and then processed. Because there may be a gap between cork particles and binder, inversion is easy to produce leakage. Excessive oxygen exchange also tends to spoil the wine. Therefore, wine sealed with a polymer plug is not suitable for inversion or lying down, but only for short-term storage. And because there is binder inside the polymer plug, although the binder meets the requirements of food hygiene, the long-term direct contact between the binder and the liquor will affect the flavor of the liquor, and it is not suitable for long-term storage

composite cork (patch 1+1 plug) has good sealing performance. Because the patch 1+1 plug uses a polymer plug as the plug body, and a piece of cork patch is bonded to both ends of the polymer to form a cork plug. To a certain extent, it has the characteristics of natural plug and polymer plug; Cork patches at both ends avoid the direct contact between polymer and binder and liquor, so they are suitable for sealed wine with long storage time. However, due to the limited shelf life of the binder in the intermediate polymer, it is difficult to store high-end wine for a long time

of course, the above conclusion is not absolute. In a short storage period of bottled wine, the sealing properties of the three corks may also be the same

the following is the tightness test of cork in our laboratory:

at present, there are three commonly used cork tightness test methods in the world: pressurization method, heating method and torsion breaking force method. The fastest and most accurate method of testing is the pressure method

take 20 corks at random, use special corking equipment to press the cork into the standard column similar to the bottle neck of the wine bottle, after standing for a period of time, inject 2mm-3mm color solution, apply pressure to the color solution through external pressure on the cork sealing tester, and observe the depth of the solution penetrating into the cork under different pressures and times according to the type of cork. The following are the results of our test and observation with reference to the international standard of cork in the past three years:

natural cork: 0.5bar, 1.0bar, 1.5bar pressure, hold the pressure for 2 minutes respectively, and observe that there is no leakage

polymer plug: 0.5bar, 1.0bar, 1.5bar, 2.0bar pressure, hold the pressure for 2 minutes respectively, and observe that there is no leakage; 2.5bar pressure, hold pressure for 5 hours, and observe that the sealing performance of corks produced from different places of origin, different materials and different processes is different; Even if the same supplier, the tightness of corks from different batches is inconsistent. That is to say, the sealing property of the polymer plug is unstable. Patch 1+1 plug: 0.5B can produce semi crystalline or amorphous flakes with a thickness greater than 500um, AR, 1.0bar, 1.5bar, 2.0bar pressure, hold the pressure for 2 minutes respectively, and observe that there is no leakage; 2.5bar pressure, hold for 5 hours, and observe that there is no leakage

the above sealing test is basically consistent with the sealing characteristics of corks of corresponding categories

the following is our sensory experiment on corked bottled wine:

lying down and inversion experiment: in the long-term storage process of wine, in order to prevent the cork from increasing the air permeability due to drying and oxidizing the wine quality, the wine needs to be lying down or inverted. Kirin laboratory collected 119 bottles of wine from 24 manufacturers from 1999 to 2004, which were sealed with different kinds of corks. The observation records have been made since 2003. From the observation results, there is no leakage of standard natural corks, but there is side leakage when using short corks (40*24mm) and filling plugs of the lowest level of natural corks. There was no leakage of patch 1 + 1 plug, but there was some wine turbidity. The polymer plug has more leakage and a large proportion of turbidity. The experimental observation of three kinds of corks is also basically consistent with their sealing characteristics

sensory evaluation: use the same bottle of dry white wine to soak natural cork, 1+1 cork and polymer cork in three covered goblets respectively. Each glass of wine is 100ml, soaked with a cork. After 72 hours, take out the cork and invite experts to taste it. The result is that the liquor soaked in natural cork has no other peculiar smell except a slight soft cork flavor. The liquor soaked in the polymer plug has a heavy dust taste, similar to the taste of rice bran. The liquor soaked in 1+1 stopper has a slight cork taste and is not unpleasant. Moreover, corks provided by different manufacturers have different tastes after soaking. In this regard, we believe that polymer plugs are not suitable for sealing high-end wine, nor can they be stored for a long time

small businesses are generally at 1800 yuan per cubic meter. 2. The microbiological index of cork

as we all know, the content of mold, yeast and bacteria exceeds the standard (control standard: mold 5cfu/piece, yeast ≤ 1cfu/piece, bacteria ≤ 1cfu/piece), which will change the flavor of wine and bring unpleasant taste. As a key indicator, it must be controlled in every link. We know that before making cork, cork must undergo strict selection, air drying, cooking and other processes to remove the odor, fungi, impurities and so on in cork. The finished cork needs to be vacuumed, filled with sulfur dioxide and sealed to inhibit the growth of colonies. Although the cork or cork stick is made through strict sterilization process, the cork may be infected with colonies due to the influence of temperature, humidity and environment during import shipping. In previous inspections, we have found that there is a problem that the colony exceeds the standard, so we must carry out strict bacterial inspection on each batch of corks

at the same time, the storage environment and production environment of corks also have a certain impact on microbial reproduction, and colonies are easy to grow in a humid environment. Therefore, the warehouse and production environment should be ventilated and protected from humidity. When storing, it should not be stored with toxic or corrosive substances at the same time. The bottom layer should be equipped with floor mats, etc., so as to avoid infection with colonies or other odors. After the storage period of semi-finished products and finished plugs exceeds 6 months, it is necessary to re check whether the content of colonies exceeds the standard. If the colonies exceed the standard, they should be disinfected again. In addition, when using cork, it should also be noted that the cork humidity should be maintained at 4% - 8%, and excessive humidity is easy to grow colonies. During corking, the inner wall of the bottle neck should be kept dry to prevent the formation of a liquid film between the cork and the bottle wall, resulting in microbial growth or side leakage of wine

III. oxidant residue of cork

after grinding the cork to the specified size, the surface should be cleaned, one is to remove the colonies on the surface, the other is to have a beautiful appearance. The cleaning treatment uses a strong oxidant, hydrogen peroxide, which is generally used internationally. In the past, hypochlorite was used for cleaning. Because the element of chlorine is toxic, and it is easy to produce a TCA substance, which has a foul smell, it is now prohibited to use. After cleaning, the residual oxidant on the cork must be removed. Too much oxidant residue (control standard: 0.1mg/piece) will oxidize the wine. Oxidized white wine will darken quickly, and the fruit aroma and taste will disappear. Oxidized red wine will turn brown or dull, and the fruit fragrance will disappear

we have done such experiments: take several corks with an oxidant residue of 0mg/cork and a few corks with an oxidant residue of about 0.8mg/cork, soak each cork in a covered goblet containing 100ml of dry Baijiu respectively, and after 24 hours, take out the cork, observe and taste the liquor. The results show that the liquor soaked in the cork with a lot of oxidant residue is darker, and the liquor has an obvious oxidizing taste. However, the color of the wine soaked in cork without oxidant has no obvious change. Except for the slight cork taste, the wine has no effective measurement range: 2% - 100% FS oxidized taste

in our previous tests, the residue of oxidant has not been found in the washed corks directly imported from abroad, which may be due to two reasons: first, the treatment process is relatively good, and the residual oxidant has been removed during treatment; Second, in the long-term transportation process, the residual oxidant has volatilized. In the domestic corks processed and cleaned, we found that the residue of oxidant exceeded the standard. Therefore, as a key indicator, the residual amount of oxidant must be tested for each batch of cork

reprinted from: Huaxia Wine News

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