Beer - Getting Wild With Yeast & Bacteria
While on the subject of wild yeast and bacteria, anyone who has read an introductory level home brewing text knows that the aforementioned practices would likely pose a serious risk of contamination. Allowing wort to sit uncovered for several hours after it's been boiled is a surefire way to get all kinds of funky stuff growing in it. Slow cooling also results in increased levels of dimethyl sulfide (DMS) and its associated undesirable flavors and aromas. Although scientific knowledge was limited at the time, early brewers knew of the dangers of exposing wort in this way. They learned by trial and error what worked and what didn't, and took preventive measures where possible. But, in those days, the trusty coolship was really the only alternative.
In addition to problems with contamination, this method of cooling had a few other disadvantages. Because they were so shallow, these vessels had to be very large in order to have a sufficient volume to hold several barrels of wort. Thus, they required a lot of floor space. Because cooling time was largely dependent on the ambient temperature, brewers had to schedule brewing sessions based upon the weather. During the summer months brewing operations were often suspended. Occasional warm periods during spring and fall presented numerous challenges. Darkening of wort due to prolonged contact with air was another common problem.
As is the case today, however, problems often lead to solutions. Industrious brewers sought alternative means to cool their wort. Indeed, as early as the end of the 18th century, a cooling device that worked by pumping hot wort through pipes in a tank of cold water was patented. As alternative methods of cooling were developed, they were frequently used in conjunction with surface coolers to cool wort to pitching temperature.
Even after the development of refrigeration, however, the coolship still took up floor space in many breweries. Various improvements were designed to minimize contamination during cooling. Surface coolers were located in a separate room to minimize exposure to contaminants. The rooms housing coolers were often equipped with domed roofs and sloped walls, improvements designed to prevent condensation from dripping back into the wort. Instead, condensation was directed into troughs and, ultimately, to drains. In addition, large, specially designed fans were used to create strong air currents to remove condensation from the space above the cooler.
Once alternative cooling methods were developed, however, the coolship was largely relegated to the role of initial cooling and hot trub sedimentation. This was a role it was well suited for, and, as we will see later, one for which it is still being used today. In such a system, hot wort is pumped from the hopback to the coolship where it is held only long enough for the hot trub to settle. Depending on the ambient temperature, this takes from one to three hours. During this time the wort cools to 140 to 170 degrees F. From there, the wort is moved to a plate heat exchanger or some other type of cooler to cool to pitching temperature.