Spent hops

Brewers dried grains are the dried extracted residue of barley malt alone or in mixture with other cereal grain or grain products resulting from the manufacture of wort or beer and may contain pulverized dried spent hops in an amount not to exceed 3% evenly distributed IFN 5-00-516 Barley brewers grains dehydrated. 

When the wort is cast from the copper, it is necessary to remove spent hops and trub, and the method originally used was straining or sieving. With a small brewery, the wort was run into a pipe which was expanded at its end into a perforated ball. The solid material was retained and the clarified wort was run to the cooler. In larger breweries, this same idea was developed for the... 

Some brewers put fresh hops into the hop back in the hope that this will impart hoppiness to the final beers. From the hop back, the wort is pumped directly to the cooler or held in a buffer tank before cooling. A considerable amount of wort is left entrained in the spent hops and is normally recovered by sparging with hot water (8 1/kg spent hops or 0 8 gal/lb). Finally, spent hops and hot trub are removed from the hop back and cleaning may take place either after every brew or following several brews. 

Fig. 15.9 Hop separator. 1. Valve 2. Level control electrodes 3. Level control 4. Screw-conveyor 5. Strainer area 6. Compression chamber 7. Fasteners 8. Strainer basket 9. Three-way valve (wort return and sparge water) 10. Return pipe 11. Wort discharge 12. Clean-out valve. Spent hops are discharged at the top. (Courtesy of A. Ziemann, GmbH).

In many breweries, the removal of the spent hop material and the hot trub from the wort occurs in two separate stages. Hop separators (Fig. 15 9) receive the wort from the copper and strain it through wire mesh. The separated spent hops are scraped from the mesh by a screw-conveyor and transferred to a part of the separator where they can be compressed and sparged before being ejected. 

The most popular separation device applicable whatever the method of hopping, developed by the Molson Breweries in Canada, is called the whirlpool tank [22]. It comprises a vertical cylindrical tank into which the wort is pumped at fairly high velocity (Fig. 15.10). The batch of wort circulates within the tank and eventually the solids are deposited as a heap in the centre of the base. Clear wort can be run off and the trub plus any spent hop material can be recovered. There are considerable variations in the constructional details and modes of operation of whirlpool tanks, often leading to varying success with separation of the solids. 

Wort freed from spent hop material and trub is cooled in order that it can be pitched with yeast. In very old breweries, the wort is cooled in shallow open vessels, using only air cooling. These open coolers or coolships had three functions cooling, aeration of the wort and separation of cold trub. 

High quality beers were traditionally treated with dry hops normally Golding hops or other hops with an excellent nose were added at racking to the cask. The hops gave excellent aroma to the beer but washing out the spent hops completely from emptied casks was difficult. Hop pellets, enriched hop powder, or lupulin have replaced normal dry hops in some breweries but in... 

The wort is next boiled with hops, which give it a characteristic flavour and aroma the hops are then filtered off and after drying are sold as spent hops. The wort is then fermented in an open vessel with yeast for a mnnber of days, during which time most of the sugars are converted to alcohol and carbon dioxide. The yeast is filtered off, dried and sold as brewer s yeast. 

The by-prodncts obtained from the brewing process are therefore malt culms, brewer s grains, spent hops and brewer s yeast. 

Dried spent hops are a fibrous product and comparable to poor hay in nutritive value, but they are less palatable, probably because of their bitter flavour. This product is rarely used as a food for animals today, most of it being sold for use as fertiliser. 

In modern processes, the classical brew kettle is replaced by a whirlpool kettle with external cooker. Shorter boiling times and a better quality of beer are achieved with this system. Moreover, separation from the spent hops can be conducted in the same vessel. 

The technique for changing round extractors on a supercritical system is somewhat different from that used on a liquid plant since the concept of liquid transfer between spent and fresh extractors is not applicable, though the principal objective of transferring as much CO2 as possible to the fresh extractor at no energy cost still applies. There is also less incentive to install gas recovery systems since the amount of residual gas left in the extractor, once equilibrated to the work tank pressure, is much less because of the higher temperature and the consequent avoidance of spent hops that are wet with CO2. 

Hops Humulus lupulus, Cannabinaceae) are an ingredient with a critical impact on the bitter taste and characteristic odour of beer. Hops also form insoluble complexes with proteins and polypeptides, which contribute to the colloidal stabflity of beer, the stabihty of beer foam, and assure the bacteriological stabflity of beer. Hops are added to the wort, which is boiled for at least 1 hoiu. After cooling and removal of spent hops, yeast is added to the hopped wort to convert sugars into ethanol and carbon dioxide. 

Hopping. Hops (dried flowers of the hop vine) are added to the wort in the brew kettle to impart to beer its traditional odor and bitter taste. The mixture is then boiled to extract the aromatic components of the hops, and to sterilize and concentrate the wort prior to fermentation. After boiling, the hops are removed by passing the mixture through a strainer. The hopped wort is held in a tank where the excess protein settles out. Tannins from the hops react with the protein so that it comes out of solution. Otherwise, it might cause clouding of the beer. The spent hops are saved for use as a livestock feed ingredient. After the protein has been removed, the wort is piped to a cooler, then to an open fermentation tank. 

The main by-products derived from malting and brewing beer are malt sprouts and hulls, brewers grains, spent hops, and brewers yeeisL As feed for cattle and sheep, the first three by-products help to lower the cost of producing valuable, high protein animal foods for people. Brewers yeast is used eis a nutritional supplement for both people and animals. 

Spent hops with water in order to solubilize polyphenols and pectins. Hops extracts can also be produced with supercritical CO2 technology. Hops extracts are used primarily for bittering purposes. The advantage is that the extracts are obtained at a low temperature, which keeps the volatile compounds in higher concentrations (Bamforth 2003, Hardwick 1995, Hough et al. 1993, Pollock 1979, Priest and Stewart 2006). 

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