The Nature and Fermentability of Last Runnings in High Gravity Brewing
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MBAA TQ vol. 48, no. 1 • 2011 • pp. 9–12 The Nature and Fermentability of Last Runnings in High Gravity Brewing Graham G. Stewart1, John M. H. Andrews2, Michaela Miedl1, and Richard J. Taylor3. 1. The International Centre for Brewing and Distilling (ICBD), Heriot-Watt University, Edinburgh, EH14 4AS, Scotland. 2. Briggs of Burton plc, Derby Street, Burton-on-Trent, Staffordshire, DE14 2LH. 3. Wells & Young’s Brewing Company Ltd., Havelock Street, Bedford, Bedfordshire, MK40 4LU. ABSTRACT SÍNTESIS Last runnings are traditionally regarded as the final liquid at mash- La última agua es tradicionalmente considerada como lo último que off flowing into the kettle following the separation of sweet wort from fluye de la mezcla a la paila de cocción después de separar el mosto spent grains. As the gravity decreases in the last runnings, the major dulce del afrecho. Al disminuir el porcentaje de extracto en esta úl- portion of the extract is fermentable sugars. Potentially detrimental tima porción, la mayor parte del extracto es azúcar fermentable. Sus- substances, such as proteins and polyphenols, have been diluted such tancias potencialmente dañinas, tales como proteínas y polifenoles, that they are not ‘harmful’ if added to the kettle. If this material is han sido diluidas de manera que no sean objetables al mosto en la discharged into the sewer, not into the kettle, the effluent costs be- paila. Si este material se botara directamente a la alcantarilla, los cause of high COD and BOD concentrations could be significant. costos del efluente aumentarían por su alta concentración de DOB y Wort collection can probably continue as long as the brewer does not DOQ. La recolecta de esta última agua podría continuar mientras no mind diluting the wort in the kettle for the sake of a small amount of importe que se diluya demasiado el mosto para recuperar una pequeña additional fermentable extract compared to the discharge costs. Al- porción de extracto, reduciendo a su vez el costo de la descarga a los though full-scale trials are required, the volume of last runnings from efluentes. Si bien esta última agua tenía la misma composición, tanto the lauter tun was higher than from the mash filter. However, the com- para un filtro lauter y un filtro de placas, el volumen de la última agua position of the last runnings from the two wort separation systems was del filtro lauter era mayor (aunque falta esto confirmar con pruebas similar. This study did not address the question of the organoleptic adicionales). Si bien no se estudiaron las características organolépticas characteristics of beer under controlled taste panel conditions. How- bajo condiciones controladas, un estudio preliminar indicó que existe ever, preliminary taste panel assessment indicates little difference in muy poca diferencia entre las cervezas producidas con última agua the beers produced with added last runnings compared with no added adicional que sin agua adicional. last runnings. Palabras claves: azucares del mosto, calidad y estabilidad de la Keywords: beer quality and stability, fermentability, last runnings, cerveza, fermentabilidad, filtro de mezcla, filtro lauter, última agua lauter tun, mash filter, wort sugars Introduction • Add it to the rest of the sweet wort in the kettle. • Add it to the mash mixer for use in a subsequent brew. Questions regarding the character and quality of last run- • Add it to the foundation liquor in the lauter tun for use in nings from mash sparging have been debated for many years a subsequent brew. (11). What are last runnings? They are the final liquid at mash- • Place the last runnings in the sewer, which will contribute off flowing into the kettle following the separation of sweet to the effluent costs. wort from spent grains. This debate has been exacerbated with Studies on the disposal and quality of last runnings have the advent of high gravity brewing (12). How does a brewer been ongoing for many years and there have been a number of dispose of last runnings?: relevant published quotations on this subject: • “Brewers should note that extract recovered at the end of sparging is not simply diluted first wort; last runnings Corresponding author Graham Stewart spent a good part of his contain little of interest to brewers making quality beer” (6). career at Labatt as technical director in London, ON, Canada. He was most recently a professor of brewing and distilling and director • “Prolonged sparging and use of last runnings will improve of the International Centre of Brewing and Distilling (ICBD) at yield but reduce quality due to increasing proportions of Heriot-Watt University, Edinburgh, Scotland. Currently, Stewart is undesirable materials in beer” (1). emeritus professor in brewing and distilling. In 2008, Stewart • “Weak-wort recycling risks haze problems due to extrac- founded GG Stewart Associates, a consulting operation involved in tion of undesirable compounds, risk of flavor problems brewing and potable/industrial alcohol production. due to microbial contamination and risk of nitrosamine E-mail: [email protected] formation” (2). Based on a paper presented at the 123rd Annual Convention of the • “What is the economic threshold of last runnings? This is Master Brewers Association of the Americas, Providence, Rhode the point at which the value of additional extract stops ex- Island, June, 2010. ceeding the cost of energy required for evaporation of the extra water” (10). doi:10.1094/TQ-48-1-0118-01 • “The positive effects of maintaining high extract effi- © 2011 Master Brewers Association of the Americas ciency with recycled last runnings are particularly pro- 9 10 MBAA TQ vol. 48, no. 1 • 2011 Last Runnings in High Gravity Brewing nounced in conjunction with high gravity brewing while tion scale model and consequently reproduce its run-off char- the potential of negative effects upon beer quality and sta- acteristics. The lauter tun is operated according to standard bility should always be considered” (12). procedures with an initial settling period to brighten the wort A major problem regarding the question of last runnings is followed by running the wort into the kettle between 80–100 that whilst many publications recommend discarding this ma- L/hr. Sparging (at 76°C/169°F) began after 40 L of wort had terial because of its questionable quality, little research has been collected and raking began after collection of 50 L of been published on last runnings with respect to fermentable wort. Once the correct wort kettle gravity and volume had sugars, tannoids, sensitive protein content, etc. The recom- been achieved, sparging and raking were stopped and the mash mended gravity to stop running wort into the kettle has been an tun was drained (last runnings). This was collected until it area of major controversy for many years. The studies reported ceased running. With both wort separation systems, the last in this paper attempt to answer two questions: runnings were also sparged to a lower than normal gravity in • Do last runnings contain significant amounts of ferment- order to extract as much material as possible from the mash. able sugars? • Do last runnings contain higher proportions of undesirable Wort Analyses materials – polyphenols, silicic acid, nitrogen-containing As soon as the wort had been collected, the following analy- substances, and inorganic compounds? ses were conducted: These questions have led to the formulation of a number of • Present gravity (PG) was determined with a DMA 46 cal- objectives: culating digital gravity meter (Anton Paar). • Analyze last runnings and determine if they were detri- • pH with a 210 microprocessor pH meter (Hanna Instru- mental to the brewing process. What was the optional cut- ments). off point for running this material into the kettle? • The presence or absence of starch was tested with iodine • If the last runnings are not detrimental, are they beneficial solution. or neutral to the brewing process? • Levels of glucose, fructose, sucrose, maltose, and malto- • Could last runnings be used in the mashing process as wa- triose were measured by HPLC as described by Leiper et ter (liquor) in a subsequent brew? al. (5). • What are the economics of last runnings production and • Wort fermentability was determined by placing 1.25 g dis- use – cycle time, kettle wort dilution, and energy usage? tiller’s yeast (M strain, Kerry Biosciences, Menstrie, Scot- • If last runnings are not recycled, what is the cost of dis- land), in a 250 mL sterile conical flask containing 50 mL posal of weak worts – COD, BOD, and effluent treat- of wort sample. The samples were incubated on an orbital ment? shaker at 25°C (77°F) and 150 rpm for 48 h. The yeast • What are the differences in the composition of last run- was removed by filtration and the pH and the specific nings between the use of a mash filter and a lauter tun for gravity of the filtrate determined as described above. The mash separation? alcohol concentration of the filtrates was determined by distillation as described by Leiper et al. (5). Post-fermen- Materials and Methods tation wort sugars were determined as described above. • The total polyphenol content was determined with car- Wort Production in the ICBD Pilot Plant boxymethylcellulose reagent as described by Milyske et The malt (Optic) was provided by Pure Malt (Haddington, al. (8). U.K.) and stored at a constant temperature of 11°C (52°F) until • Tannoids from malt (with no hop material present), were use. All-malt wort was brewed to a specific gravity of determined using a Pfeuffer Tannometer as described by 16°Plato. The malt was either milled with a four hammer “Es- McMurrough et al. (7). Due to the polymeric nature of sex Major” mill (for use with the mash filter) or with a two these compounds it was not possible to determine their ex- roller mill (for use with the lauter tun).