CCV brewing technology
Since brewing has moved into its industrial stage, the main trend has been the development of new technologies to boost gains. Almost all inventions were focused on reducing brewing cost (making the brewing process cheaper and employing less beer-makers) and speeding up equipment turnover (shortening fermentation and post-fermentation time inasmuch as possible).
An old classic German brewing rule read: "it takes a week for the wort to be fermented, and for the beer to be post-fermented – as many weeks as the percentage in the wort's primary extract content." But as early as the 19th century this rule outlived its usefulness. Driven by growing competition, brewers sought to speed up the beer production process as much as possible.
A striking example of such inquiries is solutions of the Swiss scientist Nathan 6) who invented and first applied super-fast brewing technology in the 19th century: the whole fermentation and post-fermentation process took him only 10-14 days (based on the primary extract content). By trying an unique temperature and process mode, Nathan increased yeast mass growth rate 2.5-fold. At an early stage, young beer was forced to remove carbon dioxide, which during this period contains volatile substances that cause the immature taste of the drink. Following this, the beer was carbonated with pure carbon dioxide and settled. This method has not taken root widely. According to a comment from Czech experts, the beer brewed by the accelerated method according to Nathan "failed to attain the traditional quality of Czech beer" (I think the same can be said about German beer without hesitation).
Nonetheless, this technology promised to boost equipment turnover to a huge extent, making it very appealing to many brewers with a strong profit-making spirit. This is a good indication of the value of reducing the overall brewing cycle time already attached at the time.
According to Zdeněk Šubrt, ex-technologist of Plsensky Prazdroj a.s., the first real-life CCМ was installed in 1928 in Europe at Kulmbach Brewery (Bavaria). The size of that vessel was far from as impressive as that of modern tanks: it was 3 m in diameter and 10 m high. The vessel's capacity was about 80 cubic meters (800 hectoliters). It is also Kulmbach specialists who are credited with the honour of breeding a new strain of yeast appropriate for CCV fermentation, where the height of the wort column (and therefore the pressure on the yeast cells) has increased significantly. At the same time, the relative size of the yeast cell was reduced by almost half.7)
Later, the pressure-assisted fermentation and post-fermentation technology was developed. It reduced the brewing cycle of light 11% beer to 14-15 days. The continuous fermentation method for industrial scale beer-making (in the USSR it was first introduced in 1973 at the Moskvoretskiy Brewery) was designed too. Today, the fermentation and post-fermentation process usually takes about 15-20 days, but the trend towards shorter production cycle times is continuing. The most significant obstacle in this case is the need to keep the beer made at the same (at least not lower) quality level. The best opportunities in this regard were found to be met by using cylindroconical vessels.
In addition, another factor played a significant role in giving priority to CCVs: as the brewing industry grew, the size of current fermentation vessels ceased to meet the increasing needs of brewers. An urgent need for larger and at the same time more cost-effective containers had arisen then. Unfortunately, for a number of operational (and technology) reasons, fermentation vats and lager tanks are limited in size. All these factors have provided important preconditions for the creation of cylindroconical vessels.
The first prototype model of a large-capacity fermentation tank (single-phase brewing method) was made as early as 1908. The "father" of this "CCV forerunner" was the mentioned Swiss scholar Nathan. It was 100 hectoliters in capacity and the entire production cycle took 12 days. It merits saying that the idea of using large-capacity containers in brewing did not take root at that time: there stemmed almost unsolvable (at that time) problems. The first major problem was the worsened yeast deposition (the technology was unfinished) and ensuring proper sanitation of equipment.
It should be noted that the first CCVs were made of ordinary black steel, covered with a special resin inside. Such protective coating needed to be refreshed at regular intervals. Today, CCVs are made exclusively of stainless steel. According to the Czech brewer F. Glavacek, for the first time in Europe, stainless steel was used in the manufacture of large-capacity containers in 1957. The widespread use of stainless steel led to a breakthrough in the further development of beer production technology.
In 1960s, the "CCV era" began, meaning the new technology rapidly spreading across countries and continents. As early as that time, the CCVs fell into cylindroconical fermentation vessels (CCVs), cylindroconical lager vessels (CCVLs) and uni-vessels (combining the main features of CCVs and CCVLs).
Thanks to a successful technical solution, CCVs were now built "open air". Before that, the idea of locating fermentation and lager vessels "open air", outside a brewery, sounded odd, to say the least. The opportunity to put it in place was viewed almost as groundbreaking. Fermentation and post-fermentation phases take most time in the brewing process, so fermentation and lager shops occupied most of brewery spaces. Traditionally, they consisted of separate rooms that housed wooden barrels or tanks.
From now onwards, not being constrained by the size of inner spaces of a brewery, brewers started an unspoken "competition": to build a larger CCV, to make more beer and to be ahead of rivals. As early as that time, CCV capacity could reach 5 thousand hectoliters, the diameter of 5 m, and the height of 18 m. In the seventies, CCV beer-making technology dominated in most European countries.
The same years, the CCV cooling technology was developed and finalized, in particular, the activation mode and sequence of single cooling jackets and the cone (competent CCV cooling is known to contribute to good yeast settlement). It was also found that CCV helps attain the least loss of bitter substances (about 10%), enables maximum CO2 saturation of beer and disposal of the carbon dioxide formed during fermentation.
Major CCV advantages and disadvantages
Engineering sophistication of a cylindroconical vessel (and related equipment), provided that you have a good knowledge of the technology, allows achieving the same high, standard quality of even high-cube beer volumes. At the same time, it is relatively easy to automate the CCV beer fermentation process (alternatively, to computerize it). The same holds true for washing and sanitizing vessels.
Relatively high initial investments are commercially justified by the fact that with the aid of CCV and thus the product yield can be increased. That is why CCV technology is now the most common way of beer-making in all industrialized countries.
The CCV designers, having positioned fermentation and cold-aging vessels "upright" at the time, greatly increased the efficiency of utilization of production areas. Even today this factor is one of the most significant additional benefits of CCV brewing.
Some of the difficulties of depositing yeast cells in CCVs that the brewing pioneers used to face are now successfully resolved with the aid of validated cooling techniques and have moved to the category of routine operational issues from the problem category. Slower (relative to the classic version) reproduction of yeast cells is compensated by higher aeration of wort and higher doses of yeast administered.
CCV allows to noticeably improve the workplace environment, and in addition significantly increase labor efficiency and reduce production net cost. The ability to operate all cooling jackets in autonomous modes makes the CCV cooling mode viable and efficient. Another additional advantage of cylindroconical vessels is that you can swiftly remove the precipitating yeast from them.
Among the key drawbacks of CCV is the inability to extract fully the yeast covers that occur on the fermenting wort surface and a longer (compared to vats) yeas cell deposition time. Additionally, ca. 20% of the vessel's total volume must be reserved for the foam produced in the CCV, which significantly reduces the vessel's yield performance. Conversely, in traditional fermentation vats, about 20% of the free space is reserved too. This disadvantage is less inherent in CCVs (10% free space required).
If we talk about the most effective conditions for using CCVs, it should be stressed separately that the whole point of using CCVs is in the Nathan's effect discovered: an increase in the hydrostatic pressure of the beer column leads to the accelerated accumulation of CO2 in it during post-fermentation (in turn, the speed and degree of accumulation of CO2 directly affects the speed of formation of the organoleptic bouquet of beer, i.e. its maturation). This reduces the duration of the brewing cycle. The easiest way to increase the height of the wort column is to position the vessel in use "upright", thus getting a cylindroconical vessel rather than a horizontal one, which was exactly what Nathan had done.
It becomes evident in this sense why CCV's capacity (with standard vessel proportions) should be at least 20 hectoliters. Otherwise we won't get the beer column height required to start the process of accelerated carbon dioxide accumulation at high pressure. It is also worth considering that at 20-30 hectoliters the CCV's "impression" will only be observed. Beer maturation here will be accelerated for a few days. Starting from 150-200 hectoliters (a medium-capacity, not a mini brewery), CCVs become truly effective. The use of vertically placed fermentation vessels and post-fermentation vessels in mini-breweries can therefore be clarified, first of all, by the desire for more compact arrangement of the equipment indoors.
CCV constructive materials used
The first CCVs were made of ordinary black steel the inside of which was coated with special epoxy resin-based coating. Such coating needed to be refreshed at regular intervals. Today, CCVs are made exclusively of stainless steel (usually DIN 1.4301, but more durable and costly AISI 304 or AISI 316L can be used). As mentioned above, this material is quite neutral and resistant to the effects of beer and its fermentation products, as well as sanitizers.
Today, stainless steel is the optimum material. Nevertheless, its use does not always exclude the risk of corrosion. Corrosion factors:
- the presence of chloride ions or free chlorine molecules in a neutral or acidic medium (improper sanitizers);
- stainless steel was welded in a non-inert gas atmosphere (for example, argon). In this case there will be a drastic change in the properties of steel in areas exposed to high temperatures;
- in contact with ordinary steel. In this case, contact with a grated or rusty portion of conventional steel is sufficient for corrosion to occur.