vacuum evaporation

is a modern, “no-boil” method of wort preparation. See boiling, wort. It is based on the physical relationship between a liquid’s boiling temperature and the ambient pressure surrounding it. The object of vacuum evaporation is ecological sustainability achieved by reducing the use of primary energy in the brewhouse. A secondary goal is wort quality improvements effected through the reduction of the shear factors that operate on the wort during a long, conventional, rolling boil. In vacuum evaporation, wort preparation is divided into two distinct steps, the simmering phase and the evaporating phase. During simmering, the wort is kept at just below the boiling point, at roughly 98°C (approximately 208°F), for about 50 to 60 min. This guarantees that all of the biochemical processes of a conventional boil take place, including wort sterilization, isomerization of hop alpha acids, the formation of flavor and aroma components, and the coagulation of excess proteins. See maillard reaction, melanoidins, and proteins. At the end of the no-boil heating phase the wort is pumped into the whirlpool for a conventional trub sedimentation phase. However, at this point, instead of being sent through a heat exchanger, the wort is pumped through an in-line vacuum evaporator with a constant vacuum atmosphere. There, the evaporation of the wort’s undesirable volatiles, especially dimethyl sulfide and its precursors, which are usually driven off into the kettle stack during a vigorous and highly energy-intensive boil, are being essentially sucked out of the wort. See dimethyl sulfide (dms). There is no need for the large amount of additional thermal evaporation energy that normally initiates the phase change from liquid to vapor. Aside from the substantial energy savings compared with conventional wort kettle treatments, a simmer-type vacuum evaporation technology has the additional advantage of reducing the thermal impact on the wort by reducing its oxidation potential. This, in turn, enhances the beer’s overall stability, especially its foam stability. Vacuum evaporation technology can be retrofitted to most conventional brewhouses and can thus serve as one way for environmentally conscious breweries to modernize and upgrade their older, energy-inefficient brewhouses without replacing the entire installation. Currently, there are two major manufacturers of vacuum evaporation brewhouse technologies, Ziemann of Ludwigsburg and Schulz of Bamberg, both from Germany. Schulz’s “GentleBoil” technology is designed to function entirely without a kettle boil. Under optimal conditions, it can reduce the primary energy consumption for brewhouse wort processing down to 1 l of fuel oil (or equivalent) per hl of wort, which equals energy savings of roughly 70% compared with conventional wort preparation techniques. In the environmental impact equation, this brings the carbon footprint of a hectoliter of wort down from about 9,000 to 3,000 g of CO₂ emissions for conventionally produced wort.