Influence of key indexes of the hottest cork on wi

2022-08-06
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The influence of 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 most widely used, oldest and best sealing material for wine 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. Excessive humidity is unfavorable to wine filling; If the storage temperature is too low, the cork will not have enough elasticity during the corking process, and it is easy to break and drop slag; Excessive oxidant residues not only damage the health of drinkers, but also affect the flavor of wine. Therefore, the indexes of cork must be strictly controlled according to the standards to ensure the sealing and quality stability of wine. The following is just about the impact of cork on wine on the key indicators of cork

I. sealing property of cork

cork has poor sealing property, which is easy to cause wine leakage. Leakage will not only pollute the wine packaging, breed colonies, but also oxidize the wine body and change the wine quality. Therefore, it must be controlled as a key indicator. As we know, cork is a cork made of one or several pieces of prepared cork or by polymerizing cork particles to block bottles or other containers. According to different materials or processing technologies, 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 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 the natural cork is a cork made of one or several pieces of natural cork. The number of layers of cork cells, the degree of density and the number of defects determine the tightness of the natural plug. For natural plugs of the same volume, the more layers of cells, the denser, the fewer defects and the better sealing performance. Therefore, the natural plug has strict quality classification. The world-wide classification standard is determined by inspecting the appearance quality of corks. According to the number and depth of the end surface leather holes of the natural plug, the size of the cylindrical side leather holes 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 wine can be stored. It is measured that the annual oxygen permeability of natural cork is generally about 20mg. 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 performance 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. As 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, the wine sealed with a polymer plug is not suitable to be placed upside down or horizontally, but only suitable for short-term storage. Moreover, because the polymer plug contains binder, although the binder meets the requirements of food hygiene, the long-term direct contact between binder and liquor will affect the flavor of 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 at both ends of the polymer to form a wood plug. It is easy to cause small piston damage and oil leakage, and has the characteristics of natural plug and polymer plug to a certain extent; The cork patches at both ends avoid the direct contact between the polymer and the binder and the liquor, so they are suitable for sealing and storing wine for a long time. However, due to the limited shelf life of the binder in the intermediate polymer, it is difficult to store high-grade wine for a long time

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

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 is the pressure method

take 20 corks at random, use special corking equipment to press the cork into a 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 on the cork sealing tester through external pressure, and observe the depth of the solution penetrating into the cork at different pressures and times according to the types of corks. The following are the results of our test and observation with reference to the international standards for corks in the past three years:

natural corks: 0.5bar, 1.0bar, 1.5bar pressure, respectively, for 2 minutes, no leakage was observed

polymer plug: 0.5bar, 1.0bar, 1.5bar and 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, observe that the sealing properties of corks produced from different places of origin, different materials and different processes are different; Even if the same supplier, different batches of corks have different sealing properties. That is to say, the sealing performance of the polymer plug is unstable

patch 1+1 plug: 0.5bar, 1.0bar, 1.5bar and 2.0bar pressure, hold the pressure for 2 minutes respectively, and observe that there is no leakage; 2.5bar pressure, hold for 5 hours, observe, no leakage

the above tightness tests are basically consistent with the sealing characteristics of corresponding corks

the following is our sensory experiment on cork bottled wine:

lying down and inversion experiment: in order to prevent the cork from increasing the air permeability and oxidizing the wine quality during long-term storage, the wine should be lying down or inverted. Kirin laboratory has collected wines from 24 manufacturers from 1999 to 2004, 119 to cup-shaped bottles sealed with different kinds of corks. From 2003, it has observed and recorded that there is no leakage in the standard natural plug, but there is side leakage in the filling plug with a short plug (40*24mm) and the lowest level of natural plug. The patch 1+1 plug did not leak, 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 basically consistent with their sealing characteristics

sensory evaluation: use the same bottle of dry white wine to soak the natural stopper, 1+1 stopper and polymer stopper in three goblets with covers. 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. And the corks provided by different manufacturers have different tastes after soaking. In this regard, we believe that the polymer plug is not suitable for sealing high-grade wine, nor can it be stored for a long time

II. Microbial indicators of corks

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 corks, corks must undergo strict selection, air drying, cooking and other processes to remove the peculiar smell, fungi and impurities in corks. The finished cork needs to be vacuumed and filled with sulfur dioxide for sealing 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 the import shipping process. In previous inspections, we found that there was a problem that the colony exceeded the standard, so we must carry out strict bacterial inspection on each batch of cork

at the same time, the storage environment and production environment of cork also have a certain impact on microbial reproduction, and it is easy to grow colonies in humid environment. Therefore, the warehouse and production environment shall be ventilated to prevent moisture. During storage, it shall not be stored with toxic or corrosive substances at the same time. The bottom layer shall be provided with a base plate to prevent 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 colony content exceeds the standard. If the colony exceeds the standard, it is necessary to re sterilize. In addition, when using the cork, it should also be noted that the cork humidity should be kept 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. oxidizer residue of cork

after the cork is grinded to the specified size, the surface shall be cleaned. First, remove the colonies on the surface, and second, beautiful appearance. The cleaning treatment uses a strong oxidant, hydrogen peroxide, which is commonly 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. Excessive oxidant residue (control standard: 0.1mg/piece) will oxidize the liquor. The color of 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 aroma will disappear

we have done this experiment: take several corks with an oxidant residue of 0mg/cork and a few corks with an oxidant residue of about 0.8mg/cork, immerse each cork in a covered goblet containing 100ml of dry Baijiu, and after 24 hours, take out the corks, observe and taste the liquor. The results show that the liquor soaked in the corks with a large amount 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, and the wine has no oxidizing taste except slight cork taste

in our previous tests, no excessive oxidant residue has been found in the cleaned corks directly imported from abroad. There may be 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 oxidised polyurethane waterproof coating, which was initially only used in the roof, kitchen and bathroom, has volatilized. However, in the domestic corks processed and cleaned, we have found that the oxidant residues exceed the standard. Therefore, as a key indicator, the residual amount of oxidant must be tested for each batch of cork

reprinted from: Huaxia wine daily

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