ASHRAE REFRIGERATION SI CH 42-2010 CHOCOLATES CANDIES NUTS DRIED FRUITS AND DRIED VEGETABLES《巧克力、糖果、坚果、干果和干菜》.pdf

1、42.1CHAPTER 42CHOCOLATES, CANDIES, NUTS, DRIED FRUITS, ANDDRIED VEGETABLESCANDY MANUFACTURE. 42.1Milk and Dark Chocolate. 42.1Hand Dipping and Enrobing . 42.2Bar Candy 42.2Hard Candy 42.3Hot Rooms 42.3Cold Rooms 42.3Cooling Tunnels. 42.4Coating Kettles or Pans . 42.4Packing Rooms. 42.4Refrigeration

2、Plant. 42.4STORAGE. 42.5Candy . 42.5Nuts. 42.7Dried Fruits and Vegetables 42.7Controlled Atmosphere 42.8CANDY MANUFACTUREIR conditioning and refrigeration are essential for successfulAcandy manufacturing. Proper atmospheric control increasesproduction, lowers production costs, and improves product q

3、uality.Every plant has one or more of several standardized spaces oroperations, including hot rooms; cold rooms; cooling tunnels; coat-ing kettles; packing, enrobing, or dipping rooms; and storage.Sensible heat must be absorbed by air-conditioning and refrig-eration equipment, which includes the air

4、 distribution system,plates, tables, cold slabs, and cooling coils in tunnels or similarcoolers. In calculating loads, sensible heat sources such as people,power, lights, sun effect, transmission losses, infiltration, steamand electric heating apparatus, and the heat of the entering productmust be c

5、onsidered. See Chapter 24 for more information. Table 1summarizes the optimum design conditions for refrigeration andair conditioning.Two of the basic ingredients in candy are sucrose and corn syrup.These change easily from a crystalline form to a fluid, depending ontemperature, moisture content, or

6、 both. The surrounding tempera-ture and humidity must be controlled to prevent moisture gain orloss, which affects the products texture and storage life. Tempera-ture should be relatively low, generally below 21C. The relativehumidity should be 50% or less, depending on the type of sugar used.For ch

7、ocolate coatings, temperatures of 18C or less are desirable,with 50% rh or less.In processing areas where lower relative humidity and tempera-ture are required and production demands are high, serious consid-erationshouldbegiventousingASHRAEextremeconditionsasthedesign criteria for the air-handling

8、equipment.MILK AND DARK CHOCOLATECocoa butter is either the only fat or the principal fat in chocolate,constituting 25 to 40% or more of various types. Cocoa butter is acomplex mixture of triglycerides of high-relative-molecular-massfatty acids, mostly stearic, oleic, and palmitic. Because cocoa but

9、teris present in such large amounts in chocolate, anything affectingcocoa butter affects the chocolate product as well.Because cocoa butter is a mixture of triglycerides, it does not actas a pure compound. Its physical properties, melting point, solidifi-cation point, latent heat, and specific heat

10、affect the mixture. Cocoabutter softens over a wide temperature range, starting at about 27Cand melting at about 34C. It has no definite solidification point; thisvaries from just below its melting point to 27C or lower, dependingThe preparation of this chapter is assigned to TC 10.9, Refrigeration

11、Appli-cation for Foods and Beverages.Table 1 Optimum Design Air ConditionsaDry-BulbTemperature, CRelativeHumidity, %Department or ProcessChocolate pan supply air 13 to 17 55 to 45Enrober room 27 to 29 30 to 25Single cooling tunnel 2 to 7 85 to 70Double cooling tunnelentering 10 to 13leaving 3 to 7Ha

12、nd dipper 17 45Molded goods cooling 2 to 7 85 to 70Chocolate packing room 18 50Chocolate finished stock storage 18 50Centers tempering room 24 to 27 35 to 30Marshmallow setting room 24 to 26 45 to 40Grained marshmallow(deposited in starch) drying43 40Gum (deposited in starch) drying 52 to 66 25 to 1

13、5Sanded gum drying 38 25 to 40Gum finished stock storage 10 to 18 65Sugar pan supply air (engrossing) 29 to 41 30 to 20Polishing pan supply air 21 to 27 50 to 40Pan rooms 24 to 27 35 to 30Nonpareil pan supply air 38 to 49 20Hard candy cooling tunnel supply air 16 to 21 55 to 40Hard candy packing 21

14、to 24 40 to 35Hard candy storage 10 to 21 40Caramel rooms 21 to 27 40Raw Material StorageNuts (insect) 7 60 to 65Nuts (rancidity) 1 to 3 85 to 80Eggs 1 85 to 90Chocolate (flats) 18 50Butter 7Dates, figs, etc. 4 to 7 75 to 65Corn syrupb32 to 38Liquid sugar 24 to 27 40 to 30Comfort air conditions 24 t

15、o 27 60 to 50Note: Conditions given are intended as a guide and represent values found to be satis-factory for many installations. However, specific cases may vary widely from thesevalues because of factors such as type of product, formulas, cooking process, methodof handling, and time. Acceleration

16、 or deceleration of any of the foregoing changestemperature, humidity, or both to some degree.aTemperature and humidity ranges are given in respective order (i.e., first temperaturecorresponds to first humidity).bDepends on removal system. With higher temperatures, coloration and fluidity aregreater

17、.42.2 2010 ASHRAE HandbookRefrigeration (SI)on the quantity and hardness of cocoa butter and the time it is held atvarious temperatures. The presence of milkfat in milk chocolatelowers both the melting point and the solidification point of thecocoa butter. High-quality milk chocolate remains fluid f

18、or easyhandling at temperatures as low as 30 to 31C. Sweet chocolateremains fluid as low as 32 to 33C.Chocolate can be subcooled below its melting point withoutcrystallization. In fact, it does not crystallize en masse but rather insuccessive stages, as solid solutions of a very unstable crystalline

19、state are formed under certain conditions. The latent heat of crystal-lization (or fusion) is a direct function of the manner in which thechocolate has been cooled and solidified. Once crystallization hasstarted, it continues until completion, taking from several hours toseveral days, depending on e

20、xposure to cooling, particularly to lowtemperatures (subcooling).The latent heat of solidification of the grades of chocolate com-monly used in candy manufacture varies from approximately 84 to93 kJ/kg. Average values for the specific heat of chocolate may betaken as 2.3 kJ/(kgK) before solidificati

21、on and 1.3 kJ/(kgK) aftersolidification.Theaveragevalueforthespecificheatofcocoabutteris 2.1 kJ/(kgK); for milk chocolate, 2.0 kJ/(kgK); and for roastedcocoa bean, 1.8 kJ/(kgK). In calculating the cooling load, a marginof safety should be added to these figures.Cocoa butters cooling and solidificati

22、on properties exist in fivepolymorphic forms: one stable form and four metastable or labileones. Cocoa butter usually solidifies first in one of its metastableforms, depending on the rate and temperature at which it solidifies.In solidified cocoa butter, the lower-melting labile forms changerapidly

23、to the higher-melting forms. The higher-melting labileforms change slowly, and seldom completely, to the stable form.Commercial chocolate blocks are cast in metal or plastic poly-carbonate molds after tempering. During this process, it is desir-able to cool the chocolate in the molds as quickly as p

24、ossible, thusrequiring the shortest possible cooling tunnel. However, coolingblocks too quickly (particularly large commercial blocks, whichcan range from 5 to 23 kg) may cause checking or cracking, which,though not injurious to quality, adversely affects the blocksappearance and strength. Depositin

25、g chocolate into molds at 29 to32C is common.Dark chocolate should be cooled very slowly at 32 to 33C;milk chocolate, at 30 to 31C. Air entering the cooling tunnel,where the goods are unmolded, may be 4C. The air may be 17Cwhere the goods enter the tunnel. After the chocolate is depositedin the mold

26、, it can be moved into a cooling tunnel for a continuouscooling process, or the molds can be stacked up and placed in acooling room with forced-air circulation. In either case, tempera-tures of 5 to 10C are satisfactory. The discharge room from thecooling tunnel or the room to which molds are transf

27、erred forpacking should be maintained at a dew point low enough to pre-vent condensation on the cooled chocolate. Load calculations forthe cooling or cold room must account for transmission and infil-tration losses, any load derived from further cooling of the molds,and the sensible and latent heat

28、cooling loads of the chocolateitself.The tunnel is designed to introduce 4C air countercurrent to theflow of chocolate; the coldest air enters the tunnel where the cooledchocolate leaves the tunnel. Because the tunnel air warms on its wayout, the warmest air leaves the tunnel at the point where the

29、warmestmolten chocolate enters. The leaving chocolate is markedly coolerthan the entering chocolate, and the subcooling is greatly reduced.This in turn reduces the large temperature difference between thechocolate and the cooling air along the entire tunnel length.For any particular application, onl

30、y testing will determine thelength of time the chocolate should remain in the tunnel and the sub-sequent temperature requirements. Good cooling is generally afunction of tunnel length, belt speed, and the actual time the productcontacts the cooling medium.HAND DIPPING AND ENROBINGThe candy centers o

31、f chocolate-coated candies are eitherformed by hand or cast in starch or rubber molds. They are thendipped by hand or enrobed mechanically. The chocolate supply forhand dipping is normally kept in a pan maintained at the lowesttemperature that still ensures sufficient fluidity for the process.Becaus

32、e this temperature is higher than the dipping room tempera-ture, a heat source, such as electrically heated dipping pans withthermostatic controls, is required. Dipped candy is placed either ontrays or on belts while the chocolate coating sets.Setting is controlled by conditioning the dipping room a

33、ir. A dry-bulb temperature of 2 to 4C best promotes rapid setting and pro-vides a high gloss on the finished goods. However, the temperaturein the dipping room is raised for human comfort. Suggested condi-tions for hand-dipping rooms are 18C db and a relative humiditynot exceeding 50 to 55%. The pri

34、ncipal aim is to achieve uniform airdistribution without objectionable drafts. Loads for this room in-clude transmission, lights, and people, as well as heat load from thechocolate and heat used to warm dipping pans.In high-speed production of bar candy, the chocolate coating isapplied in an enrober

35、 machine, which consists mainly of a heatedand thermostatically controlled reservoir for the fluid chocolate.This chocolate is pumped to an upper flow pan that allows it to flowin a curtain down to the main reservoir. An open chain-type belt car-ries the centers through the flowing chocolate curtain

36、, where theypick up the coating. At the same time, grooved rolls pick up somechocolate and apply it to the bottom of the centers. Centers shouldbe cooled to 24 to 27C to help solidification and retention of theproper amount of coating.The coated pieces are transferred from the enrober to thebottomer

37、 slab and then pass into the enrober cooling tunnel. Thefunction of the bottomer slab is to set the bottom coating as rapidlyas possible, to form a firm base for the pieces as they pass throughthe enrober tunnel. The bottomer slab is often a flat-plate heat ex-changer fed with chilled water or propy

38、lene glycol or directly sup-plied with refrigerant. The belt carrying the candy passes directlyover this plate, and heat transfer must take place from the candythrough the belt to the surfaces of the bottomer slab. The bottomerslab is sometimes located before the enrober to create a good bottombefor

39、e full coverage.The enrober cooling tunnel sets the balance of the chocolatecoating as rapidly as is consistent with high quality and goodappearance of the finished pieces. Typical enrober cooling tunneltimes are approximately 7 to 8 min for milk chocolate, and can be aslow as 3 to 6 min for vegetab

40、le-fat-based coatings. The dischargeend of the enrober tunnel is normally in the packing room, where thefinished candy is wrapped and packed.Although not absolutely necessary, air conditioning the enrobingroom is desirable. Because the coating is exposed to the room atmo-sphere, the atmosphere shoul

41、d be clean to prevent contamination ofthe coating with foreign material. It is advisable to maintain condi-tions of 24 to 27C db and 50 to 55% rh; that is, low enough to pre-vent centers from warming and to help set the chocolate after it isapplied.BAR CANDYProduction of bar candy calls for high-spe

42、ed semiautomatic op-erations to minimize production costs. From the kitchen, the cen-ter material is either delivered to spreaders, which form layers ontables, or cast in starch molds. Depending on the composition ofthe center, the material may be delivered at temperatures as high as70 to 80C. Succe

43、ssive layers of different color or flavor may bedeposited to build up the entire center. These layers usually consistof nougat, caramel, marshmallow whip, or similar ingredients, towhich peanuts, almonds, or other nuts may be added. Becauseeach ingredient requires a different cooking process, each s

44、eparateChocolates, Candies, Nuts, Dried Fruits, and Dried Vegetables 42.3ingredient is deposited in a separate operation. Thus, a 3 mm layerof caramel may be deposited first, then a layer of peanuts, fol-lowed by a 20 mm layer of nougat. Except for nuts, it is necessaryto allow time for each success

45、ive layer to set before the next isapplied. If the candy is spread in slabs, the slab must be cooled andthen cut with rotary knives into pieces the size of the finishedcenter.HARD CANDYManufacturing hard candy with high-speed machinery requiresair conditioning to maintain temperature and humidity. C

46、andymade of cane sugar has somewhat different requirements from thatmade partly with corn syrup. For example, a dry-bulb temperatureof 24 to 27C with 40% rh is satisfactory for corn syrup (as the cornsyrup percentage increases, the relative humidity must decrease),whereas the same temperature with 5

47、0% rh is satisfactory for canesugar.Where relative humidity is to be maintained at 40% or less, stan-dard dehydrating systems using chemicals such as lithium chloride,silica gel, or activated alumina should be used. A combination ofrefrigeration and dehydration is also used.The amount of air require

48、d is a direct function of the sensibleheat of the room. Approximate rules indicate that the quantityshould be between 7.5 and 12.5 L/s per square metre of floor area,with a minimum of 15% outdoor air, or 15 L/s per person. The sen-sible heat in hard candy, which is at a high temperature to keep it p

49、li-able during forming, must also be taken into account.If concentrations of the finished product in containers or tubs arelocated in the general conditioned area, the quantity of air must beincreased to prevent the product from sticking to the container.Unitary air conditioners using dry coils are satisfactory if theyhave a sufficient number of rows and adequate surface. A centralstation apparatus using cooling and dehumidifying coils of similardesign may also be used. Good filtration is essential for air purity aswell as for preventing dirt accumulation on coo