When it comes to brewing beer, it’s not just energy costs and water that are expensive – so are hops. Given the annual uncertainty of the supply of alpha acid, which is extracted from hops and critical to beer’s bitter profile, brewers should rethink classic brewing processes to remain profitable, including how to use hop products more efficiently in the brewhouse and the cold block.
Why so bitter?
Volatile weather. Wild swings in the supply chain. Hoarding. Consumer demand for a wide variety of hop aromas and flavors and constantly changing tastes, which makes forecasting hop needs tricky, particularly in an industry where forward contracting is more often the rule than the exception. These are only a handful of scenarios that keep brewers – particularly craft- and microbrewers who consume a disproportionate share of hops – up at night. Supply and price challenges are then often compounded by the inefficiencies of traditional brewing processes which are energy-intensive and make poor use of hops resources – which is literally money down the drain for a brewer.
Alpha acids, a class of chemical compounds, are found in the resin glands of hop plant flowers. They can be isomerized to form iso-alpha acids via a combination of steps and processes, including the application of heat in solution, typically achieved by adding hops to the boiling wort – the liquid extracted from the mashing process during the brewing of beer. Although alpha acid is not very soluble in wort, the isomerized form, iso-alpha-acid, is very soluble. The degree of isomerization and the amount of bitter flavor produced is highly dependent on the length of time the hops are boiled, with longer boil times resulting in isomerization of more alpha acids and thus increased bitterness. However, in the conventional wort boiling process, complete isomerization is not achieved; in fact, roughly two-thirds or 60% of the hops added are not utilized as a result of short boiling times, losses due to the hydrophobic structure of alpha acid in aqueous solution and losses in trub and yeast.
Increasing the isomerization rate in the brewhouse
Traditionally, hops would be dosed in the wort kettle, however, with the HOPSTAR™ Iso, GEA has developed a patented process that thermally accelerates hop isomerization and with it the isomerization rate. The process works on the principle that the reaction speed doubles with every 10 Kelvin temperature increase. Additionally, the particle size of the hop product is reduced in order to create an increased reactive surface. When the process temperature is increased to 120 to 140° degrees Celsius, compared to 100°C during wort boiling, the process time is accelerated, totaling just 15 to 20 minutes with the isomerization rate reaching more than 92 percent. This is roughly a 30 percent improvement over traditional methods, reducing a brewer’s annual hop expenditure anywhere from 15 to 30 percent.
The HOPSTAR™ Iso offers brewers the following benefits:
- Reduced raw material demand due to increased isomerization yield
- Improved flavor stability due to reduced thermal stress
- Pleasant hop flavor (smell and taste)
- No harsh or astringent bitterness as aftertaste
- Energy savings due to lower total evaporation rate
- Flexibility when using a stable hop suspension
- Central hop production for affiliated breweries
Resource efficient, dynamic dry hopping in the cold block
Dry hopping is the process of adding hop aroma to beer, usually in a secondary step – common in pale ales and other beer types, given that during wort boiling, most of the hop oils evaporate. In classical dry hopping, hop cones or pellets are placed in the storage tank. This static process hinders extraction efficiency because there is less contact between the beer and hop particles and limited disintegration of the hop pellets. Also, insufficient solid separation in classical dry hopping processes occurs, for example, because many centrifuges used later in the process cannot handle the high solid load. Removing the hops at the end of the process is challenging for brewers and causes high beer losses (a reported 10-20% depending on the specific hop dosage).
With the HOPSTAR™ Dry GEA has developed a process that has been proven in trials, and in an increasing number of industrial applications, to significantly improve extraction efficiency – from 30 to 50 percent compared to a classical static process. The key is using dynamic extraction in an extraction vessel, wherein the pellet hops are suspended by a low-shear agitator and kept in motion via pumping. The solids are separated during a sedimentation step, keeping the particles in the extraction vessel. An additional fine filter catches the finer particles which do not sediment out of the cylindrical-conical tank (CCT). The extraction and sedimentation take place in variable cycles, giving the brewer excellent control in terms of contact time and extracted hop oil fractions. The increased extraction efficiency means cost savings on hops and beer losses reduced to <3%.
The skid-mounted GEA HOPSTAR™ Dry offers brewers several additional key features and benefits:
- Minimum solids transferred to the CCT; no beer losses via pellet solid sludge in the CCT
- Comes as pre-piped, pre-wired and tested unit
- Extraction tank design takes into account CCT volume and maximal pellet load
- Extraction tank installed separately beside skid with all peripheral installations
- Pre-piped skid has a standard design, only extractor is adapted
- One GEA HOPSTAR™ Dry system can be used for several storage tanks
- Process conditions (e.g. soaking or suspending of pellets; number of extraction cycles) can be adjusted individually to reflect pellet quality or hop variety
- Automation enables reproducible product quality
- Process under CO2 atmosphere to avoid oxidation
- Automation as stand-alone unit or integrated in existing installation
- Automation of all process steps and CIP meets highest standards of quality and hygiene