Artificial cold stabilization

It is certainly true that spontaneous crystallization, under natural conditions, is an unreliable, unpredictable phenomenon. This is why the production process for many red and white wines includes artificial cold stabilization before bottling. This type of treatment is justified, especially as consumers will not tolerate the presence of crystals, even if they do not affect quality. 

These theoretical considerations, applied to a short treatment involving seeding with tartrate crystals, show that great care and strict snpervision is required to ensure the effectiveness of artificial cold stabilization. The following factors need to be closely monitored the wine s initial state of snpersaturation, the particle size of the added tartrates, the seeding rate, the effectiveness of agitation at maintaining the crystals in snspension, treatment temperature and, finally, contact time. 

TESTS FOR PREDICTING WINE STABILITY IN RELATION TO CRYSTAL PRECIPITATION AND MONITORING THE EFFECTIVENESS OF ARTIFICIAL COLD STABILIZATION TREATMENT... 

This traditional test is somewhat empirical. A sample (approximately 100 ml) of wine, taken before or after artificial cold stabilization, is stored in a refrigerator for 4-6 days at 0°C and then inspected for crystals. In the case of wines intended for a second fermentation, alcohol may be added to increase the alcohol content by 1.3-1.5% v/v. This simulates the effects of the second fermentation and makes it possible to assess the bitartrate stability of the finished sparkling wine. 

In practice, a rapid-response test is required for monitoring the effectiveness of artificial cold stabilization. The preceding results show quite clearly that the tests based on induced crystallization are relatively unreliable for predicting the stability of a wine at 0°C. 

The throughput, i.e. the average time in the crystallizer, is defined according to the wine s initial state of supersaturation, as well as the type of preparatory treatment (fining, bentonite, etc.) the wine received prior to artificial cold stabilization. The importance of preparation has already been mentioned (Section 1.6.4). 

It is true that, in contact treatments involving large-scale seeding, the wine s background is less important. Indeed, enologists do not always have this information if the wine has been purchased from another winery. In any event, wine must be well prepared and, above all, properly clarified, to ensure the effectiveness of rapid artificial cold stabilization treatments. 

Work has been done to find whether the very expensive treatment of wines with artificial cold could be advantageously replaced by the addition of inhibitors of the crystallization process of tartrate salts such as metatartaric acid, yeast mannopro-teins or carboxymethylcellulose (CMC). Such inhibitors indeed increase the width of the supersaturation field of both KHT and TCa in the wine, thus delaying tartrate salt precipitation in the bottle. Metatartaric acid is currently the product most widely used for this purpose, though its efficacy is low as this compound does not remain stable over time. Yeast mannoproteins possess stabilizing properties, which result in the spontaneous improvement of protein and tartaric salt stability, as can be... 

Whatever the technology used, and regardless of any treatment used preparatory to bitartrate stabilization, wine treated with artificial cold must be clean, i.e. not excessively contaminated with yeast or bacteria, as is often the case with wines stored in large vats. These wines should, therefore, be filtered on a simple continuous earth filter. Another advantage of filtration is the elimination of part of the protective colloids. Fine filtration is not useful at this stage, and is certainly not recommended, as there is a risk of eliminating microcrystals likely to act as crystallization nuclei. 

T5. Cooled from an elevated temperature-shaping process and artificially aged. Applies to products that are not cold worked after an elevated temperature-shaping process such as casting or extrusion and for which mechanical properties, dimensional stability, or both have been substantially improved by precipitation heat treatment. 

T8, Solution Heat Treated, Cold Worked, and Artificially Aged. This designation applies to products that are cold worked specifically to improve strength after solution heat treatment and for which mechanical properties or dimensional stability, or both, have b n substantially improved by precipitation heat treatment. The effects of cold work, inclu g any cold work imparted by flattening or straightening, are accounted for in specified property limits. 

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