ASHRAE REFRIGERATION IP CH 39-2010 BEVERAGES《饮料》.pdf

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1、39.1CHAPTER 39BEVERAGESBREWERIES 39.1Malting. 39.1Process Aspects 39.1Processing 39.3Pasteurization 39.6Carbon Dioxide 39.6Heat Balance 39.7Common Refrigeration Systems. 39.7Vinegar Production 39.8WINE MAKING . 39.8Must Cooling 39.8Heat Treatment of Red Musts. 39.9Juice Cooling . 39.9Heat Treatment

2、of Juices 39.9Fermentation Temperature Control 39.9Potassium Bitartrate Crystallization 39.10Storage Temperature Control. 39.10Chill-Proofing Brandies. 39.10CARBONATED BEVERAGES 39.10Beverage and Water Coolers 39.11Size of Plant . 39.11Liquid Carbon Dioxide Storage . 39.12HIS chapter discusses the p

3、rocesses and use of refrigerationTin breweries, wineries, and carbonated beverage plants.BREWERIESMALTINGMalt is the primary raw ingredient in brewing beer. Althoughadjuncts such as corn grits and rice contribute considerably to thecomposition of the extract, they do not possess the necessary enzy-m

4、atic components required for preparing the wort. They lack nutri-ents (amino acids) required for yeast growth, and contribute little tothe flavor of beer. Malting is the initial stage in preparing raw grainto make it suitable for mashing. Traditionally, this operation wascarried out in the brewery,

5、but in the past century, this phase hasbecome so highly specialized that it is now almost entirely the func-tion of a separate industry.Various grains such as wheat, oats, rye, and barley can be malted;however, barley is the predominate grain used in preparing maltbecause it has a favorable protein-

6、to-starch ratio. It has the properenzyme systems required for conversion, and the barley hull pro-vides an important filter bed during lautering. Also, barley is readilyavailable in most of the world.There are three steps to malting barley. In steeping, the raw grainis soaked in 40 to 65F water for

7、2 to 3 days. The moisture contentof the barley kernel increases from 12% to approximately 45%. Thewater is changed frequently and the grain is aerated. After two orthree days, the kernels start to germinate and the white tips of root-lets appear at the end of the kernels. At this time, the water is

8、drainedand the barley is transferred to where it is germinated.During 4 to 5 days of germination, the kernel continues togrow. The green malt is constantly turned over to ensure uniformgrowth of the kernels. Slowly revolving drums can be used to turnover the growing malt. In a compartment system, sl

9、owly moving,mechanically driven plowlike agitators are used for mixing. Cool(50 to 65F) saturated moist air is used to maintain temperatureand green malt moisture levels. At the desired stage in its growth,the green malt is transferred to a kiln.Kilning, the final step, stops the growth of the barle

10、y kernel byreducing its moisture level. Warm (120 to 150F) dry air is used toremove moisture from the green malt. Kilning is usually done in twostages. First, the malts moisture content is reduced to approxi-mately 8 to 14%; then, the heat is increased until the moisture isfurther reduced to about 4

11、%. Using this heating procedure reducesexcessive destruction of enzymes. The desired color and aroma areobtained by controlling the final degree of heat.After kilning, the malt is cleaned to separate dried rootlets fromthe grain, which is then stored for future use. The finished malt dif-fers from t

12、he original grain in several significant ways. The hardendosperm was modified and is now chalky and friable. The enzy-matic activity has been greatly increased, especially alpha amylase,which is not present in unmalted barley. The moisture content isreduced, making it more suitable for storing and s

13、ubsequent crush-ing. It now has a distinctive flavor and aroma, and the starches andenzymes are readily extractable in the brewhouse.PROCESS ASPECTSTwo distinct types of chemical reactions are used in brewingbeer. Mashing is carried out in the brewhouse. Starches in themalted grain are hydrolyzed in

14、to sugars and complex proteins arebroken down into simpler proteins, polypeptides, and amino acids.These reactions are brought about by crushing the malt and sus-pending it in warm (100 to 122F) water by means of agitation inthe mash tun. When adjuncts (usually corn grits or rice) are used, aportion

15、 of the malt is cooked separately with the adjunct. Afterboiling, this mixture is combined with the main mash, which hasbeen proportioned so that a combining temperature generally in therange of 145 to 162F results. Within this temperature range, thealpha and beta amylases degrade the starch to mono

16、-, di-, tri-, andhigher saccharides. By suitably choosing a time and temperatureregimen, the brewer controls the amount of fermentable sugars pro-duced. The enzyme diastase (essentially a mixture of alpha and betaamylase), which induces this chemical reaction, is not consumedbut acts merely as a cat

17、alyst. Some of the maltose is subsequentlychanged by another enzyme, maltase, into a fermentable monosac-charide, glucose.Mashing is complete when the starches are converted to iodine-negative sugars and dextrins. At this point, the temperature of themash is raised to a range of 167 to 172F, which i

18、s the “mashing-off” temperature. This stops the amylolytic action and fixes theratio of fermentable to nonfermentable sugars. The wort is sepa-rated from the mash solids using a lauter tub, a mash filter, or otherproprietary equipment (MBAA 1999). Hot water (168 to 170F) isthen “sparged” through the

19、 grain bed to recover additional extract.Wort and sparge water are added to the brew kettle and boiled withhops, which may be in the form of pellets, extract, or whole cones.After boiling, the brew is quickly cooled and transferred to thefermentation cellar, where yeast is added to induce fermentati

20、on.Figure 1 shows a double-gravity system with grains stored at theThe preparation of this chapter is assigned to TC 10.9, Refrigeration Appli-cation for Foods and Beverages.39.2 2010 ASHRAE HandbookRefrigerationtop of the brewhouse. As processing continues, gravity creates adownward flow. Hot wort

21、from the bottom of the brewhouse isthen pumped to the top of the stockhouse, where it is cooled andagain proceeds by gravity through fermentation and lagering.After the wort cools, yeast and sterile air are injected into it. Theyeast is pumped in as a slurry at a rate of 1 to 3 lb of slurry per barr

22、elof wort. Normally, oil-free compressed air is filtered and treatedwith ultraviolet light and then added to the wort, which is nearly sat-urated with approximately 8 ppm of oxygen. However, the wort mayalso be oxygenated with pure oxygen.Fermentation takes place in two phases. During the first phas

23、e,called the respiratory or aerobic phase, the yeast consumes the oxy-gen present. It uses a metabolic pathway, preparing it for the anaer-obic fermentation to follow. The process typically lasts 6 to 8 h.Oxygen depletion causes the yeast to start anaerobically metab-olizing the sugars in the extrac

24、t, releasing heat and producing CO2and ethanol as metabolic by-products.During early fermentation, the yeast multiplies rapidly then moreslowly as it consumes the available sugars. Normal multiplicationfor the yeast is approximately 3 times. A representative value for theheat released during ferment

25、ation is 280 Btu/lb of extract (sugar)fermented.Wort is measured by the saccharometer (measures sugar con-tent), which is a hydrometer calibrated to read the percentage ofmaltose solids in solution with water. The standard instrument is thePlato saccharometer, and the reading is referred to as perce

26、ntage ofsolids by saccharometer, or degrees Plato (P). Table 1 illustrates thevarious data deducible from reading the saccharometer.The same instrument is used to check fermentation progress.Although it still gives an accurate measure of density of the fer-menting liquid, it is no longer a direct in

27、dicator of dissolved solidsbecause the solution now contains alcohol, which is less dense thanwater. This saccharometer reading is called the apparent extract,which is always less than the real extract (apparent attenuation iscalculated from the hydrometer reading of apparent extract and theoriginal

28、 extract). In engineering computations, 81% of the changein apparent extract is considered a close approximation of thechange in real extract. Thus, 81% of the difference between the sol-ids shown in Table 1 for saccharometer readings before and afterfermentation represents the mass of maltose ferme

29、nted. Thisweight in pounds per barrel times 280 Btu/lb gives the heat of fer-mentation in Btu per barrel. (Each barrel has a capacity of 31 gal.)The difference between the original solids and mass of fermentedsolids gives the residual solids per barrel. It is assumed that there isno change in the vo

30、lume because of fermentation. The specific heatof beer is assumed to be the same as that of the original wort, butthe mass per barrel decreases according to the apparent attenuation.Bottom-fermentation yeast (e.g., Saccharomyces uvarium,formerly carlsbergensis) is used in fermenting lager beer. Top-

31、fermentation yeast (e.g., Saccharomyces cerevisiae) is used in makingale. They are so called because, after fermentation, one settles to thebottom and the other rises to the top. A more significant differencebetween the two types is that in the top-fermentation type, the fer-menting liquid is allowe

32、d to attain a higher temperature before acontinued rise is checked. The following characteristics of brewingale make it different from brewing lager:A more highly kilned darker malt is used.Malt forms a greater proportion of the total grist (less adjunct).Infusion mashing is used and a wort of highe

33、r original specificgravity is generally produced.More hops are added during the kettle boil.A different yeast and temperature of fermentation are used.Therefore, ale may have a somewhat higher alcohol content anda fuller, more bitter flavor than lager beer. With bottom-fermentationyeasts, fermentati

34、on is generally carried out between 45 and 65Fand most commonly between 50 and 60F. Ale fermentations aregenerally carried out at somewhat higher temperatures, often peak-ing in the range of 70 to 75F. In either type, the temperature dur-ing fermentation would continue to rise above that desired if

35、notchecked by cooling coils or attemperators, through which a coolingFig. 1 Brewery Flow DiagramFig. 1 Brewery Flow DiagramTable 1 Total Solids in Wort%Solids*SpecificGravityWeight per Barrel, lbSpecific Heat,Btu/lbFTotal Solids0 1.0000 258.7 0.00 1.0001 1.0039 259.7 2.60 0.9932 1.0078 260.7 5.21 0.

36、9863 1.0118 261.8 7.85 0.9794 1.0157 262.8 10.51 0.9725 1.0197 263.8 13.19 0.9656 1.0238 264.9 15.89 0.9587 1.0278 265.9 18.61 0.9518 1.0319 267.0 21.36 0.9449 1.0360 268.0 24.12 0.93710 1.0402 269.1 26.91 0.93011 1.0443 270.2 29.72 0.92312 1.0485 271.2 32.55 0.91613 1.0528 272.4 35.41 0.90914 1.057

37、0 273.4 38.28 0.90215 1.0613 274.6 41.18 0.89516 1.0657 275.7 44.11 0.88817 1.0700 276.7 47.06 0.88118 1.0744 277.9 50.03 0.87419 1.0788 279.1 53.03 0.86720 1.0833 280.2 56.05 0.860*Saccharometer readings.Beverages 39.3medium such as propylene glycol, ice water, brine, or ammonia iscirculated. In th

38、e past, these attemperators were manually con-trolled, but more recent installations are automatic.PROCESSINGWort CoolingTo prepare boiling wort from the kettle for fermentation, it mustfirst be cooled to a temperature of 45 to 55F. To avoid contamina-tion with foreign organisms that would adversely

39、 affect subsequentfermentation, cooling must be done as quickly as possible, espe-cially through the temperatures around 100F. Besides the primaryfunction of wort cooling, other beneficial effects accrue that areessential to good fermentation, including precipitation, coagulationof proteins, and aer

40、ation (natural or induced, depending on the typeof cooler used).In the past, the Baudelot cooler was almost universally usedbecause it is easy to clean and provides the necessary wort aeration.However, the traditional open Baudelot cooler was replaced by oneconsisting of a series of swinging leaves

41、encased within a removableenclosure into which sterilized air was introduced for aeration. Thismodified form, in turn, has virtually been replaced by the totallyenclosed heat exchanger. Air for aeration is admitted under pressureinto the wort steam, usually at the discharge end of the cooler. Theair

42、 is first filtered and then irradiated to kill bacteria, or it can be ster-ilized by heating in a double-pipe heat exchanger with steam. Byinjecting 0.167 ft3of air per barrel (bbl) of wort, which is the amountnecessary to saturate the wort, normal fermentation should result.The quantity can be accu

43、rately increased or diminished as the sub-sequent fermentation indicates.The coolant section of wort coolers is usually divided into two orthree sections. For the first section, a potable source of water is used.The heated effluent goes to hot-water tanks where, after additionalheating, it is used f

44、or subsequent mashing and sparging in the brewhouse. Final cooling is done in the last section, either by directexpansion of the refrigerant or by means of an intermediate coolantsuch as chilled water or propylene glycol. Between these two, athird section may be used from which warm water can be rec

45、overedand stored in a wash-water tank for later use in various washing andcleaning operations around the plant.Closed coolers save on space and money for expensive coolerroom air-conditioning equipment. They also allow a faster coolingrate and provide accurate control of the degree of aeration. Toma

46、intain good heat transfer, closed coolers may be flushed with hotwater between brews or circulated for a few minutes with cleaningsolutions. More thorough cleaning, perhaps done weekly, is accom-plished by much longer periods of circulation with cleaning solu-tions, such as 2 to 4% caustic at 175F.

47、Reverse flow of the cleaningsolution may also be used to help dislodge deposits of protein,hops, and other materials.In selecting a wort cooler, consider the following:The cooling rate should allow the contents of the kettle to becooled in 1 or, at most, 2 h.The heat transfer surfaces to be apportio

48、ned between the first sec-tion, using an available water supply, and the second section,using refrigeration, should make the most economical use of eachof these resources. Cost of water, its temperature, and its avail-ability should be balanced against the cost of refrigeration. Usualdesign practice

49、 is to cool the wort in the first section to within10F of the available water.Usable heat should be recovered (effluent from the first section isa good source of preheated water). After additional heating, it canbe used for succeeding brews and as wash water in other parts ofthe plant. At all times, the amount of heat recovered should beconsistent with the overall plant heat balance.Meticulous sanitation and maintenance costs are important.Wort cooler size is determined by the rate of cooling desired, rateof water flow, and temperature differences used. A brew, which mayv