ASHRAE REFRIGERATION IP CH 41-2010 BAKERY PRODUCTS《烘焙食品》.pdf

1、41.1CHAPTER 41BAKERY PRODUCTSIngredient Storage 41.1Mixing 41.2Fermentation 41.3Bread Makeup 41.3Final Proof . 41.4Baking 41.4Bread Cooling 41.4Slicing and Wrapping. 41.5Bread Freezing . 41.5Freezing Other Bakery Products 41.6Frozen Pre-Proofed Bakery Products 41.6Retarding Doughs and Batters. 41.7C

2、hoice of Refrigerants . 41.7HIS chapter addresses refrigeration and air conditioning asTapplied to bakery products, including items distributed (1) atambient temperature, (2) refrigerated but unfrozen, and (3) frozen.Refrigeration plays an important part in modern bakery production.Some of the major

3、 uses of refrigeration in the baking industry are Ingredient coolingDough and batter temperature control during mixingRefrigerating dough productsFreezing dough for the food service industry and supermarketsFreezing bread for later holding, thawing, and saleFreezing fried and baked products for sale

4、 to consumersRefrigeration methods and equipment needed to accomplishthese uses includeNormal air conditioningDough mixers with jackets through which chilled water, low-temperature antifreeze, or direct-expansion refrigerant passesCO2chips or CO2fog placed directly into dough mixer bowlsCooling tunn

5、els with refrigerated air flowing counterflow to the productMedium-temperature cool rooms for storage of refrigerated dough productsFreezing tunnels for doughKettles for fillingsSpiral freezer chambers in which the product remains for about20 min to 1 h and is subjected to air at about 30F for freez

6、ingHolding freezers: 9 to 20FTotal plant air conditioning is increasingly used in new plant con-struction, except in areas immediately surrounding ovens, in finalproofers, and in areas where cooking vessels prepare fruit fillingsand hot icings. Total plant cooling was first used in plants producingD

7、anish pastry, croissants, puff pastry, and pies, and has expanded tonew-construction facilities for frozen dough operations and generalproduction. Flour dust in the air should be filtered out because itfouls air passages in air-conditioning equipment, seriously reducesheat transfer rates, and is a p

8、otential respiratory health hazard.INGREDIENT STORAGERaw materials are generally purchased in bulk, except in smalloperations. Deliveries are made by truck or railcar and stored in binsor tanks with required temperature protection while in transit andstorage.Flour. Flour is stored in bins at ambient

9、 temperature. Somebakeries locate these bins outside their buildings; however, insidestorage is recommended where outside temperatures vary greatly.This improves control of product temperature and decreases therisk of moisture condensation inside the storage bins. Pneumaticconveyance and subsequent

10、sifting before use generally increaseflour temperature a few degrees. Smaller quantities of other flours,such as clear, rye, and whole wheat, are usually received in bagsand stored on pallets.Sugars and Syrups. Sugar is handled in both dry and liquid bulkforms by many large production bakeries. Alth

11、ough most prefer liq-uid, many cake and sweet goods plants produce their own powderedsugar for icings by passing granulated sugar through a pulverizer.Refrigeration dehumidifiers are sometimes used to minimize cakingor sticking of the powdered sugar for proper pneumatic handling.Liquid sucrose (cane

12、 or beet sugar), generally with a solids contentof 66 to 67%, is stored at ambient temperature; however, it can becooled to as low as 45F without crystallizing out of solution. Cornsyrups and various blends of sucrose and corn syrups should bestored at 90 to 100F to improve fluidity and pumpability.

13、 Unlikesucrose, corn syrups become more viscous when cooled. High-fructose corn syrups are best handled at 80 to 90F. Lower storagetemperatures cause sugars to crystallize, and higher temperaturesaccelerate caramelizing. Dextrose (corn sugar) solutions containing65 to 67% solids must be stored in he

14、ated tanks at 130F to preventcrystallization. Many bakeries use high-fructose corn syrups.Because these syrups are stored at a lower temperature than conven-tional syrup, less thermal input is required during storage, and therefrigeration load during mixing is significantly reduced. Smaller-volume a

15、nd specialized sugars are received in poly-lined bags andstored at ambient temperature.Shortenings. Shortenings are stored in heated tanks or a “hotroom,” where the temperature is maintained at 10F above theAmerican Oil Chemists Society (AOCS) capillary closed-tubemelting point of the fat (AOCS 1999

16、, 2004). Lard, for example,should be stored at 120F to be totally liquid. Other shorteningsneed slightly higher temperatures. Fluid shortenings and oils arestored at room temperature, but they need constant slow-speed agi-tation to prevent hard fats from separating to the bottom of the tanks.Yeast.

17、Fresh yeast comes in 1 lb blocks packaged in cartons ofvarious sizes, in crumbled form in 50 lb bags, and in liquid creamform handled in bulk tanks. Refrigerated storage temperatures rang-ing from 45F to the freezing point of the product are required. Formaximum storage life, 34 to 36F is considered

18、 best. Active dry andinstant dry forms of yeast are available that do not need refrigeration.Egg Products. Liquid egg products (whole, whites, yolks, andfortified) are commonly used in small retail and large cake andsweet goods bakeries. They generally come frozen in 30 lb contain-ers that must be t

19、hawed under refrigeration or cold-water baths.Where large quantities are needed, liquid bulk refrigerated handlingcan be an economic advantage. Storage temperatures for liquid eggproducts should be less than 40F, with 35 to 38F being the idealstorage temperature range. Dried egg solids, which need n

20、o refrig-eration, are also used. A shelf-stable whole egg that requires norefrigeration has been introduced. This stability was achieved byThe preparation of this chapter is assigned to TC 10.9, Refrigeration Appli-cation for Foods and Beverages.41.2 2010 ASHRAE HandbookRefrigerationremoving two-thi

21、rds of the water from the eggs and replacing it withsugar, thereby lowering the water activity to the point that mostorganisms cannot grow.Other. Dried milk products, cocoa, spices, and other raw ingre-dients in baking are usually put into dry storage, ideally at 70F.Ideal storage is rarely achieved

22、 under normal bakery conditions.Refrigerated storage is sometimes used where longer shelf lives aredesired or high storage temperatures are the norm. This decreasesflavor loss and change, microbial growth, and insect infestation.MIXINGBread, buns, sweet rolls/Danish, yeast-raised doughnuts, andhoney

23、 buns are the most important yeast-leavened baked products interms of production volume. After scaling the ingredients, mixing isthe next active step in production. Proper development of the floursgluten proteins is what gives doughs their gas-retaining properties,which affect the volume and texture

24、 of the baked products. Tem-perature control during mixing is essential. Refrigeration is gener-ally required because of the heat generation and the necessity ofcontrolling dough temperature at the end of mixing. However,ingredient temperatures combined with room temperature mayrequire addition of w

25、arm water to produce the desired finisheddough temperature.Yeast metabolism is materially affected by the temperatures towhich the yeast is exposed. During dough mixing, the followingheat factors are encountered: (1) heat of friction, by which the elec-trical energy input of the mixer motor is conve

26、rted to heat; (2) spe-cific heat of each ingredient; and (3) heat of hydration, generatedwhen a dry material absorbs water. If ice is used for temperaturecontrol, heat of fusion is involved. Finally, the temperature of thedough ingredients must be considered. Yeast acts very slowly below45F. It is e

27、xtremely active in the presence of water and fermentablesugars at 80 to 100F, but all yeast cells are killed at 140F and at alower but sustained pace below its freezing point of 26F. Precisetemperature control is essential at all stages of storage and produc-tion, especially during mixing, because o

28、f its effect on downlineprocessing.MixersThe three most common styles of mixers are the horizontal, ver-tical or planetary, and spiral. Horizontal mixers are primarily usedby wholesale bakeries and are designed with horizontal agitatorbars. They range in capacity from 200 to 3000 lb. Because of thel

29、arge dough sizes, these mixers are generally jacketed with someform of cooling. Vertical mixers are more common in retail bak-eries and are categorized by their largest bowl capacity. Bowlsrange in size from 12 to 20 qt for tabletop models to as high as340 qt in some large wholesale plants. The bowl

30、s have no refriger-ation jacket and can be removed from the mixers. The hook or agi-tator revolves as it travels around the inside of the bowl. Spiralmixers are somewhat newer and are gaining in popularity withretail and specialty bread bakers. Here the bowl revolves, bringingthe ingredients to the

31、off-center spiral agitator. Bowls for smallermodels (50 to 400 lb) are not removable, but those for the largermodels (up to 1000 lb) can be removed. Like vertical mixers, spiralmixers are not jacketed.Where flour is pneumatically transferred to the mixer, liquid CO2can be injected directly into the

32、flour stream. This technique hasbeen used for mixers, such as vertical and spiral mixers, that are notjacketed for temperature control. Dry ice (CO2) chips have alsobeen used in frozen dough production, where dough temperaturesbelow 70F are required. Dry ice is used as an aid to other forms ofrefrig

33、eration. Because of expansion of CO2gas, horizontal mixersshould be left open slightly.Dough SystemsThe four principal types of batch dough mixes are straight, no-time, sponge, and liquid ferment. These methods are called doughsystems or dough process in the baking industry. The type of doughsystem

34、determines the stages in the process, the equipment needed,and the general processing parameters (times and temperatures).Straight dough and no-time dough systems are the two most com-mon in retail bakeries. All of the ingredients are mixed at one time.Straight doughs require fermentation, whereas n

35、o-time doughs donot. The no-time system is also used in wholesale or large plant bak-eries that produce hearth and specialty breads, in which fermenta-tion flavor is not as important as compared to white pan bread andbuns.The more common systems used in wholesale bakeries are thesponge dough and liq

36、uid ferment or liquid sponge. The spongedough process requires more equipment and longer fermentationtimes than the straight and no-time dough systems. Here, only a partof the total amount of flour and water required are mixed with all ofthe yeast and yeast food. The resulting mixture, or sponge, is

37、 thenfermented before it is given the final mix or remix with the remain-ing ingredients. This is done just before makeup, improving bothtolerance of schedule disruptions and dough machinability.The principal heat generated during mixing comes from hydra-tion, as the flour absorbs water, and from th

38、e friction of the mixer.To absorb this excess heat and maintain the dough at 78 to 82F, thedough-side water is usually supplied to the mix at 35 to 39F, andhorizontal mixers are generally jacketed to circulate a coolingmedium around the bowl.The liquid ferment or liquid sponge process has gained pop

39、u-larity with wholesale bakeries because of its excellent temperaturecontrol and acceptable product quality. Liquid sponge ingredientscan be incorporated and fermented in special equipment either inbatches or on an uninterrupted basis. To render the mixture pump-able, more water is incorporated than

40、 is used in a sponge. After fer-mentation, the liquid sponge (at required pH and titratable acidlevels) is chilled through heat exchange equipment from about 79 to88F to about 45 to 55F. The cold liquid sponge is then maintainedat the required temperature in a storage or feed tank until it isweighed

41、 or metered and pumped to the mixer, where it is combinedwith the remaining ingredients before being remixed into a dough.Regular sponges come back for remixing at about 84F. Often, it isnecessary to use the refrigerated surface on the mixer jacket in con-junction with ice water or ice to achieve th

42、e required dough temper-ature after mixing.Positive dough temperature control is achieved using a cold liq-uid sponge at 45 to 55F, which limits the need for the refrigerationjacket and eliminates using ice in the doughs. In cold weather,remaining dough water temperatures of 100F or higher are often

43、required.A fifth dough system, the continuous mix method, was devel-oped in the 1950s and requires specially designed continuous mixequipment for making bread and buns. Originally, a liquid ferment,then called a brew or broth, was formed, using 0 to 10% of the flour,10 to 15% of the sugar, 25 to 50%

44、 of the salt, all of the yeast, andyeast food in about 85% of the total water. Through the years, theamount of flour has increased to as high as 50% and the needed sugardecreased. Using mass flow meters, the liquid ferment is meteredinto an incorporator or premixer, where the remaining ingredientsar

45、e added. The resultant thicker batter finally passes through a devel-oper head/mixer, from which the finished dough is extruded anddeposited directly into a greased baking pan. Properly formulateddough can also be deposited onto floured belts that then pass throughconventional makeup equipment. Fina

46、l dough temperatures couldreach as high as 118F, though today, with higher levels of flour inthe ferment, they could be as low as 90F. It is estimated that lessthan 5% of the U.S. bread and bun market uses this system.Bakery Products 41.3Hot dog and hamburger rolls are also produced in quantity bypu

47、mping bun dough from the continuous mix developer directly tothe hopper of the makeup equipment. A coating of flour on outerdough surfaces affects gas development and retention, which in turnleads to a grain/texture more closely resembling that of spongedough products. External symmetry and crust ch

48、aracteristics aresimilarly changed.Dough CoolingSome dough mixers are cooled by direct-expansion refrigerant,but the most common means of cooling is with chilled water or anantifreeze such as propylene glycol. The temperature of the evapo-rating refrigerant or antifreeze supplied may often be as low

49、 as 30Fto maintain the dough at the desired temperature. When the doughmixers are cooled by evaporating refrigerant, the condensing unit isusually located close to the mixers. Table 1 lists the sizes of con-densing units commonly selected for mixers. The ingredient wateris cooled in separate liquid chillers, and when the mixer bowl iscooled by antifreeze, the liquid chiller may be remotely located.When large batches of dough are handled in the mixers, the re-quired cooling is sometimes greater than the available heat transfersurface can produce at 30F, an