BREWING: NEW TECHNOLOGIES IN BREWING SCIENCE AND PRACTICE
CONTENTS 1 AN OUTLINE OF BREWING 2 MALTS, ADJUNCTS AND SUPPLEMENTARY ENZYMES 3 WATER, EFFLUENTS AND WASTES 4 THE SCIENCE OF MASHING 5 THE PREPARATION OF GRISTS 6 MASHING TECHNOLOGY 7 HOPS 8 THE CHEMISTRY OF HOP CONSTITUENTS 9 CHEMISTRY OF WORT BOILING 10 WORT BOILING, CLARIFICATION, COOLING AND AERATION 11 YEAST BIOLOGY 12 METABOLISM OF WORT BY YEAST 13 YEAST GROWTH 14 FERMENTATION TECHNOLOGIES 15 BEER MATURATION AND TREATMENTS 16 NATIVE AFRICAN BEERS 17 MICROBIOLOGY 18 BREWHOUSES: TYPES, CONTROL AND ECONOMY 19 CHEMICAL AND PHYSICAL PROPERTIES OF BEER 20 BEER FLAVOUR AND SENSORY ASSESSMENT 21 PACKAGING 22 STORAGE AND DISTRIBUTION 23 BEER IN THE TRADE MALTS MALTS ARE MADE FROM SELECTED CEREAL GRAIN, USUALLY BARLEY, (BUT SOMETIMES WHEAT, RYE, OATS, SORGHUM OR MILLET), THAT HAS BEEN CLEANED AND STORED UNTIL DORMANCY HAS DECLINED AND IT IS NEEDED IT IS THEN GERMINATED UNDER CONTROLLED CONDITIONS THEIR PREPARATION IS OUTLINED IN CHAPTER 2, AND IS DESCRIBED IN DETAIL IN BRIGGS (1998) THE GRAIN IS HYDRATED, OR `STEEPED', BY IMMERSION IN WATER DURING STEEPING THE WATER WILL BE CHANGED AT LEAST ONCE, AIR MAY BE SUCKED THROUGH THE GRAIN DURING `DRY' PERIODS BETWEEN IMMERSIONS, AND MAY BE BLOWN INTO THE GRAIN WHILE IMMERSED AFTER STEEPING THE GRAIN IS DRAINED AND IS GERMINATED TO A LIMITED EXTENT IN A COOL, MOIST ATMOSPHERE WITH OCCASIONAL TURNING AND MIXING TO PREVENT THE ROOTLETS MATTING TOGETHER DURING GERMINATION THE ACROSPIRE (COLEOPTILE) GROWS BENEATH THE HUSK AND ROOTLETS GROW FROM THE END OF THE GRAIN, ENZYMES ACCUMULATE AND SO DO SUGARS AND OTHER SOLUBLE MATERIALS THE DEAD STORAGE TISSUE OF THE GRAIN, THE STARCHY ENDOSPERM, IS PARTLY DEGRADED, OR `MODIFIED', AND ITS PHYSICAL STRENGTH AN OUTLINE OF BREWING BREWING NEW TECHNOLOGIES IN BREWING SCIENCE AND PRACTICE MILLING AND MASHING IN THE MALT, SOMETIMES PREMIXED WITH PARTICULAR ADJUNCTS, IS BROKEN UP TO A CONTROLLED EXTENT BY MILLING TO CREATE THE `GRIST' THE TYPE OF MILL USED AND THE EXTENT TO WHICH THE MALT (AND ADJUNCT) IS BROKEN DOWN IS CHOSEN TO SUIT THE TYPES OF MASHING AND WORT- SEPARATION SYSTEMS BEING USED (CHAPTER 5) IF DRY MILLING IS USED THE GRIST, POSSIBLY MIXED WITH ADJUNCTS, IS COLLECTED IN A CONTAINER, THE GRIST CASE AT MASHING-IN (DOUGHING-IN) THE GRIST IS INTIMATELY MIXED WITH BREWING LIQUOR, BOTH FLOWING AT CONTROLLED RATES, INTO A MASHING VESSEL AT AN EXACTLY CONTROLLED TEMPERATURE BREWING NEW TECHNOLOGIES IN BREWING SCIENCE AND PRACTICE MASHING AND WORT SEPARATION SYSTEMS THE MAJOR MASHING SYSTEMS ARE, BROADLY, (A) THE SIMPLEST, NEARLY ISOTHERMAL, INFUSION MASHING SYSTEM, (TRADITIONAL FOR BRITISH ALE BREWERS); (B) THE DECOCTION SYSTEM, (TRADITIONAL FOR MAINLAND EUROPEAN LAGER BREWERS); (C) THE DOUBLE MASH SYSTEM, (COMMON IN NORTH AMERICAN PRACTICE); (D) THE TEMPERATURE-PROGRAMMED INFUSION MASHING SYSTEM THAT IS BEING WIDELY ADOPTED IN THE UK AND MAINLAND EUROPE (CHAPTERS 4 AND 5) A MASH SHOULD BE HELD AT A CHOSEN TEMPERATURE (OR AT SUCCESSIVE DIFFERENT TEMPERATURES), FOR PRE- DETERMINED TIMES, TO ALLOW ENZYMES TO `CONVERT' (DEGRADE) THE STARCH AND DEXTRINS TO SOLUBLE SUGARS, TO CAUSE THE PARTIAL BREAKDOWN OF PROTEINS, TO DEGRADE NUCLEIC ACIDS AND OTHER SUBSTANCES AT THE END OF MASHING THE SWEET, OR UNHOPPED WORT (THE SOLUTION OF EXTRACTIVES, MAINLY CARBOHYDRATES; THE `EXTRACT') IS SEPARATED FROM THE UNDISSOLVED SOLIDS, THE SPENT GRAINS OR DRAFF INFUSION MASHING IS CARRIED OUT IN MASH TUNS MASH CONVERSION AND THE SEPARATION OF THE SWEET WORT FROM THE SPENT GRAINS TAKE PLACE IN THIS VESSEL THE COARSELY GROUND GRIST, MADE WITH A HIGH PROPORTION OF WELL-MODIFIED MALT, IS MASHED IN TO GIVE A RELATIVELY THICK, PORRIDGE-LIKE MASH AT 63Ÿ67 ËC (145 4Ÿ152 6 ËF) AFTER A STAND OF BETWEEN MINUTES AND TWO AND A HALF HOURS THE WORT (LIQUID) IS WITHDRAWN FROM THE MASH THE FIRST WORTS ARE CLOUDY AND ARE RE-CIRCULATED, BUT AS THE RUN OFF IS CONTINUED THE WORT BECOMES `BRIGHT' (CLEAR), BECAUSE IT IS FILTERED THROUGH THE BED OF GRIST PARTICLES WHEN BRIGHT THE WORT IS EITHER COLLECTED IN A HOLDING VESSEL (AN UNDERBACK) OR IT IS MOVED DIRECTLY TO A COPPER TO BE BOILED WITH HOPS MOST OF THE RESIDUAL EXTRACT, INITIALLY ENTRAINED IN THE WET GRAINS, IS WASHED OUT BY SPARGING (SPRAYING) HOT LIQUOR, AT 75Ÿ80 ËC (167Ÿ176 ËF ) OVER THE GOODS DECOCTION MASHING IS CARRIED OUT WITH MORE FINELY GROUND GRISTS, ORIGINALLY MADE WITH MALTS THAT WERE UNDERMODIFIED THESE MASHES ARE RELATIVELY `THIN', SO THEY MAY BE MOVED BY PUMPING AND CAN BE STIRRED DECOCTION MASHING USES THREE VESSELS, A STIRRED MASH MIXING VESSEL, A STIRRED DECOCTION VESSEL OR MASH COOKER AND A WORT SEPARATION DEVICE, EITHER A LAUTER TUN OR A MASH FILTER IN ONE TRADITIONAL MASHING PROGRAMME THE GRIST IS MASHED IN TO GIVE AN INITIAL TEMPERATURE OF AROUND 35 ËC (96 ËF) AFTER A STAND A DECOCTION IS CARRIED OUT, THAT IS, A PROPORTION OF THE MASH, E G , A THIRD, IS PUMPED TO THE MASH COOKER, WHERE IT IS HEATED TO BOILING THE BOILING MASH IS PUMPED BACK TO THE MASH MIXING VESSEL AND IS MIXED WITH THE VESSELS CONTENTS, RAISING THE TEMPERATURE TO, E G , 50 ËC (122 ËF) AFTER ANOTHER STAND A SECOND DECOCTION IS CARRIED OUT, INCREASING THE TEMPERATURE OF THE MIXED MASH TO ABOUT 65 ËC (149 ËF) A FINAL DECOCTION INCREASES THE MASH TEMPERATURE TO ABOUT 76 ËC (167 ËF) THE MASH IS THEN TRANSFERRED TO A LAUTER TUN OR A MASH FILTER THE SWEET WORT AND SPARGINGS ARE COLLECTED, READY TO BE BOILED WITH HOPS TYPICALLY, DOUBLE-MASHING USES NITROGEN- (`PROTEIN-') AND ENZYME-RICH MALTS AND SUBSTANTIAL QUANTITIES OF MAIZE OR RICE GRITS IT ALSO INVOLVES THE USE OF THREE VESSELS MOST OF THE MALT GRIST IS MASHED INTO A MASH-MIXING VESSEL TO GIVE A MASH AT AROUND 38 ËC BREWING NEW TECHNOLOGIES IN BREWING SCIENCE AND PRACTICE WORT CLARIFICATION, COOLING AND AERATION AT THE END OF THE BOIL THE TRANSPARENT, OR `BRIGHT' WORT CONTAINS FLOCS OF TRUB (THE HOT BREAK) AND SUSPENDED FRAGMENTS OF HOPS IF WHOLE HOPS WERE USED THEN RESIDUAL SOLIDS ARE STRAINED OFF IN A HOP BACK OR OTHER FILTRATION DEVICE AND THE BED OF HOP CONES FILTERS OFF THE TRUB, GIVING A CLEAR, HOPPED WORT HOWEVER, IF POWDERS, HOP PELLETS, (WHICH BREAK UP INTO SMALL PARTICLES), OR EXTRACTS WERE USED THEN HOP FRAGMENTS (IF PRESENT) AND THE TRUB ARE USUALLY SEPARATED IN A `WHIRLPOOL TANK' THE CLEAR `HOPPED WORT' IS COOLED TO CHECK CONTINUING DARKENING AND FLAVOUR CHANGES AND SO IT CAN BE INOCULATED (`PITCHED') WITH YEAST, AND CAN BE AERATED OR OXYGENATED WITHOUT A RISK OF OXIDATIVE DETERIORATION THE HEATED COOLING WATER IS USED FOR VARIOUS PURPOSES AROUND THE BREWERY DURING COOLING A SECOND SEPARATION OF SOLIDS OCCURS IN THE WORT THIS `COLD BREAK' IS COMPOSED MOSTLY OF PROTEINS AND POLYPHENOLS AND SOME ASSOCIATED LIPIDS IT IS OFTEN, BUT NOT ALWAYS, CONSIDERED DESIRABLE TO REMOVE THIS MATERIAL TO GIVE A `BRIGHT', COMPLETELY CLEAR WORT THE WORT IS AERATED OR EVEN OXYGENATED, TO PROVIDE OXYGEN FOR THE YEAST IN THE INITIAL STAGES OF FERMENTATION BREWING NEW TECHNOLOGIES IN BREWING SCIENCE AND PRACTICE