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

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 4 to 18C water for 2

7、 to 3 days. The moisture content ofthe 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 d

8、rainedand 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, slo

9、wly moving,mechanically driven plowlike agitators are used for mixing. Cool(10 to 18C) 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 barley

10、 kernel byreducing its moisture level. Warm (49 to 66C) 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 the

12、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 subs

13、equent 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 into

14、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 (38 to 50C) water by means of agitation in themash tun. When adjuncts (usually corn grits or rice) are used, a por-tion of

15、 the malt is cooked separately with the adjunct. After boiling,this mixture is combined with the main mash, which has been pro-portioned so that a combining temperature generally in the range of63 to 72C results. Within this temperature range, the alpha andbeta amylases degrade the starch to mono-,

16、di-, tri-, and higher sac-charides. By suitably choosing a time and temperature regimen, thebrewer controls the amount of fermentable sugars produced. Theenzyme diastase (essentially a mixture of alpha and beta amylase),which induces this chemical reaction, is not consumed but actsmerely as a cataly

17、st. Some of the maltose is subsequently changedby another enzyme, maltase, into a fermentable monosaccharide,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 75 to 78C, which is the “

18、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 (76 to 77C) isthen “sparged” through the grain be

19、d 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 fermentation.Figure

20、 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 HandbookRefrigeration (SI)top of the brewhouse. As processing continues, gravity creates adownward flow. Hot wort from

21、 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 4 to 12 g of slurry per litreof

22、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 11 mg/kg of oxygen. However, the wortmay also be oxygenated with pure oxygen.Fermentation takes place in two phases. During the first phase,

23、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 extract,

24、 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 fermentat

25、ion is 650 kJ/kg of extract (sugar) fer-mented.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 percen

26、tage 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 ind

27、icator 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 fermen

29、ted. This mass(in kilograms per cubic metre of wort at 10C) times 650 kJ/kg givesthe heat of fermentation. The difference between the original solidsand mass of fermented solids gives the residual solids per cubicmetre. It is assumed that there is no change in the volume becauseof fermentation. The

30、specific heat of beer is assumed to be the sameas that of the original wort, but the mass per unit volume decreasesaccording to the apparent attenuation.Bottom-fermentation yeast (e.g., Saccharomyces uvarium,formerly carlsbergensis) is used in fermenting lager beer. Top-fermentation yeast (e.g., Sac

31、charomyces 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 allowed to attain a higher temperat

32、ure 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 higher original specificgravity is

33、 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, fermentation is generally carried out b

34、etween 7 and 18Cand most commonly between 10 and 16C. Ale fermentations aregenerally carried out at somewhat higher temperatures, often peak-ing in the range of 21 to 24C. In either type, the temperature dur-ing fermentation would continue to rise above that desired if notchecked by cooling coils or

35、 attemperators, through which a coolingFig. 1 Brewery Flow DiagramFig. 1 Brewery Flow DiagramTable 1 Total Solids in a Cubic Metre of Wort at 10C%Solids*Total Density,kg/m3Mass of Solids,kgSpecific Heat,kJ/(kg K)0 999.6 0.0 4.191 1003 10.0 4.162 1007 20.1 4.133 1011 30.3 4.104 1015 40.6 4.075 1019 5

36、1.0 4.046 1023 61.4 4.017 1027 71.9 3.988 1031 82.5 3.959 1036 93.2 3.9210 1040 104.0 3.8911 1044 114.8 3.8612 1048 125.8 3.8413 1052 136.8 3.8114 1057 147.9 3.7815 1061 159.1 3.7516 1065 170.4 3.7217 1070 181.8 3.6918 1074 193.3 3.6619 1078 204.9 3.6320 1083 216.6 3.60*Saccharometer readings.Bevera

37、ges 39.3medium such as propylene glycol, ice water, brine, or ammonia iscirculated. In the 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 temp

38、erature of 7 to 13C. To avoid contaminationwith foreign organisms that would adversely affect subsequent fer-mentation, cooling must be done as quickly as possible, especiallythrough the temperatures around 38C. Besides the primary func-tion of wort cooling, other beneficial effects accrue that are

39、essentialto good fermentation, including precipitation, coagulation of pro-teins, and aeration (natural or induced, depending on the type ofcooler used).In the past, the Baudelot cooler was almost universally usedbecause it is easy to clean and provides the necessary wort aeration.However, the tradi

40、tional open Baudelot cooler was replaced by oneconsisting of a series of swinging leaves 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 admit

41、ted under pressureinto the wort steam, usually at the discharge end of the cooler. Theair 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 40 L of air per cubic metre of wort, which is the amountnecess

42、ary to saturate the wort, normal fermentation should result.The quantity can be accurately 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

43、heated effluent goes to hot-water tanks where, after additionalheating, it is used for 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 gl

44、ycol. Between these two, athird section may be used from which warm water can be recoveredand 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 all

45、ow a faster coolingrate and provide accurate control of the degree of aeration. Tomaintain 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 longe

46、r periods of circulation with cleaning solu-tions, such as 2 to 4% caustic at 80C. 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

47、 kettle to becooled in 1 or, at most, 2 h.The heat transfer surfaces to be apportioned 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

48、-ability should be balanced against the cost of refrigeration. Usualdesign practice is to cool the wort in the first section to within 6 Kof the available water.Usable heat should be recovered (effluent from the first section isa good source of preheated water). After additional heating, it canbe us

49、ed 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 mayvary in size from 5 to 100 m3and over, is ordinarily cooled in 1 or,at most, 2 h. Open coolers are made in stands up to about 6 m long.Where more length is needed, two or more stands are operated inparallel.Open cooler