ASHRAE REFRIGERATION SI 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 34C for freez

6、ingHolding freezers: 23 to 29CTotal 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 producing

7、Danish 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

8、potential 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 ambien

9、t 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. Alt

11、hough 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 (can

12、e or beet sugar), generally with a solids contentof 66 to 67%, is stored at ambient temperature; however, it can becooled to as low as 7C without crystallizing out of solution. Cornsyrups and various blends of sucrose and corn syrups should bestored at 32 to 38C to improve fluidity and pumpability.

13、Unlikesucrose, corn syrups become more viscous when cooled. High-fructose corn syrups are best handled at 27 to 32C. Lower storagetemperatures cause sugars to crystallize, and higher temperaturesaccelerate caramelizing. Dextrose (corn sugar) solutions containing65 to 67% solids must be stored in hea

14、ted tanks at 54C 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 and

15、 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 6 K above the Amer-ican Oil Chemists Society (AOCS) capillary closed-tube meltingpoint of the fat (AOCS 1999

16、, 2004). Lard, for example, should bestored at 49C to be totally liquid. Other shortenings need slightlyhigher temperatures. Fluid shortenings and oils are stored at roomtemperature, but they need constant slow-speed agitation to preventhard fats from separating to the bottom of the tanks.Yeast. Fre

17、sh yeast comes in 0.5 kg blocks packaged in cartons ofvarious sizes, in crumbled form in 25 kg bags, and in liquid creamform handled in bulk tanks. Refrigerated storage temperatures rang-ing from 7C to the freezing point of the product are required. Formaximum storage life, 1 to 2C is considered bes

18、t. 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 15 kg contain-ers that must be thawe

19、d 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 4.5C, with 2 to 3C being the idealstorage temperature range. Dried egg solids, which need no ref

20、rig-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 HandbookRefrigeration (SI)removing 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 21C.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 below7.2C. It is

27、extremely active in the presence of water and ferment-able sugars at 27 to 38C, but all yeast cells are killed at 60C andat a lower but sustained pace below its freezing point of 3.3C. Pre-cise temperature control is essential at all stages of storage and pro-duction, especially during mixing, becau

28、se of 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 90 to 1350 kg. Because of t

29、helarge 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 11 to 19 L for tabletop models to as high as 320 Lin some large wholesale plants. The bow

30、ls have no refrigerationjacket and can be removed from the mixers. The hook or agitatorrevolves as it travels around the inside of the bowl. Spiral mixersare somewhat newer and are gaining in popularity with retail andspecialty bread bakers. Here the bowl revolves, bringing the ingre-dients to the o

31、ff-center spiral agitator. Bowls for smaller models(23 to 180 kg) are not removable, but those for the larger models(up to 450 kg) can be removed. Like vertical mixers, spiral mixersare not jacketed.Where flour is pneumatically transferred to the mixer, liquid CO2can be injected directly into the fl

32、our 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 21C are required. Dry ice is used as an aid to other forms ofrefriger

33、ation. 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 de

34、termines 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 no-

35、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 liqui

36、d 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 t

37、henfermented 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 the

38、friction of the mixer.To absorb this excess heat and maintain the dough at 25.6 to 27.8C,the dough-side water is usually supplied to the mix at 2 to 4C, 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 26 to31C to about 7 to 13C. 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 29C. Often, it isnecessary to use the refrigerated surface on the mixer jacket in con-junction with ice water or ice to achieve the

42、 required dough temper-ature after mixing.Positive dough temperature control is achieved using a cold liq-uid sponge at 7 to 13C, which limits the need for the refrigerationjacket and eliminates using ice in the doughs. In cold weather,remaining dough water temperatures of 38C or higher are oftenreq

43、uired.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% of

44、 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 ingredientsare a

45、dded. 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. Final d

46、ough temperatures couldreach as high as 48C, though today, with higher levels of flour in theferment, they could be as low as 32C. It is estimated that less than5% of the U.S. bread and bun market uses this system.Bakery Products 41.3Hot dog and hamburger rolls are also produced in quantity bypumpin

47、g 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 charac

48、teristics 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 as

49、1Cto 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 1C, and t