The Dairy Science and Technology eBook. This is an educational area focused on milk, dairy products, and dairy technology, and is one book in our Dairy. The Dairy Science and Technology eBook. This is an educational area focused on milk, dairy products, and dairy technology, and is one book. Dairy Processing education at the Ontario Agricultural College, University of as Professor H. Douglas Goff, Dairy Science and Technology Education Series.
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(ebook) Dairy Science and Technology from Dymocks online store. Building upon the scope of its predecessor, Dairy Science. Spice Science and Technology, Kenji Hirasa and Mitsuo Takemasa. Dairy Technology: Principles of Milk Properties and Processes,. P. Walstra, T. J. Geurts, . Building upon the scope of its predecessor, Dairy Science and Technology, Second Edition offers the latest information on the efficient transformation of milk into.
Centrifugation; 9. Homogenization; Concentration Processes; Cooling and Freezing; Membrane Processes; Lactic Fermentations; Fouling and Sanitizing; Packaging; Milk for Liquid Consumption; Cream Products; Butter; Concentrated Milks; Milk Powder; Protein Preparations; Fermented Milks.
Remember me on this computer. Cancel Forgot your password? Dairy processing. Similar Items. Front Cover; Preface; Acknowledgments; Contents; 1. Principles of Cheese Making Cheese Manufacture; Cheese Ripening and Properties; Microbial Defects; Cheese Varieties; A.
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If your order has a status of "packed" or "shipped" we will not be able to guarantee any change in shipping details. There are two types of FDD:. This FDD can be cleaned in place and is more suited for automation.
At the pasteurized product discharge is a vacuum breaker which breaks to atmospheric pressure. It must be located greater than 12 inches above the highest point of raw product in system. It ensures that nothing downstream is creating suction on the pasteurized side. It is centrifugal "stuffing" pump which supplies raw milk to the raw regenerator for the balance tank.
It must be used in conjunction with pressure differential controlling device and shall operate only when timing pump is operating, proper pressures are achieved in regenerator, and system is in forward flow. The homogenizer may be used as timing pump. It is a positive pressure pump; if not, then it cannot supplement flow. Free circulation from outlet to inlet is required and the speed of the homogenizer must be greater than the rate of flow of the timing pump.
Magnetic flow meters shown on the right can be used to measure the flow rate. It is essentially a short piece of tubing approximately 25 cm long surrounded by a housing, inside of which are located coils that generate a magnetic field.
When milk passes through the magnetic field, it causes a voltage to be induced, and the generated signal is directly proportional to velocity. Application of the magnetic flow meter in the dairy industry has centered around its replacing the positive displacement timing pump as the metering device in HTST pasteurizing systems, where with certain products the timing pump rotors reportedly wear out in a relatively short period of time.
In operation, the electrical signal is sent by the magnetic flow meter to the flow controller, which determines what the actual flow is compared to the flow rate set by the operator. Since the magnetic flow meter continuously senses flow rate, it will signal the electronic controller if the actual flow exceeds the set flow rate for any reason. If the flow rate is exceeded for any reason, the flow diversion device is put into diverted flow.
A significant difference from the normal HTST system with timing pump comes into focus at this point. This system can be operated at a flow rate greater than residence time less than the legal limit.
However, it will be in diverted flow and never in forward flow. Another magnetic flow meter based system with an AC variable frequency motor control drive on a centrifugal pump is also possible in lieu of a positive displacement metering pump on a HTST pasteurizer. This system does not use a control valve but rather the signal from the magnetic flow meter is transmitted to the AC variable frequency control to vary the speed of the centrifugal pump.
The pump, then controls the flow rate of product through the system and its holding time in the holding tube.
These systems are used for time and temperature control of HTST systems. With operator control, changes can be made to the program which might affect CCP's; the system is not easily sealed. No computer program can be written completely error free in large systems; as complexity increases, so too do errors.
This gives rise to a need for specific regulations or computer controlled CCP's of public health significance:. While pasteurization conditions effectively eliminate potential pathogenic microorganisms, it is not sufficient to inactivate the thermoresistant spores in milk.
In canning we need to ensure the "cold spot" has reached the desired temperature for the desired time.
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With most canned products, there is a low rate of heat penetration to the thermal centre. This leads to overprocessing of some portions, and damage to nutritional and sensory characteristics, especially near the walls of the container. This implies long processing times at lower temperatures.
The milk may be packaged either before or after sterilization. The reduction in process time due to higher temperature UHTST and the minimal come-up and cool-down time leads to a higher quality product. Processing conditions are independent of container size, thus allowing for the filling of large containers for food-service or sale to food manufacturers aseptic fruit purees in stainless steel totes.
Both cost of package and storage and transportation costs; laminated packaging allows for use of extensive graphics. Complexity of equipment and plant are needed to maintain sterile atmosphere between processing and packaging packaging materials, pipework, tanks, pumps ; higher skilled operators; sterility must be maintained through aseptic packaging. With larger particulates there is a danger of overcooking of surfaces and need to transport material - both limits particle size.
There is a lack of equipment for particulate sterilization, due especially to settling of solids and thus overprocessing. Heat stable lipases or proteases can lead to flavour deterioration, age gelation of the milk over time - nothing lasts forever! There is also a more pronounced cooked flavour to UHT milk.
The product is heated by direct contact with steam of potable or culinary quality. The main advantage of direct heating is that the product is held at the elevated temperature for a shorter period of time. For a heat-sensitive product such as milk, this means less damage.
High pressure steam is injected into pre-heated liquid by a steam injector leading to a rapid rise in temperature. After holding, the product is flash-cooled in a vacuum to remove water equivalent to amount of condensed steam used. This method allows fast heating and cooling, and volatile removal, but is only suitable for some products.
It is energy intensive and because the product comes in contact with hot equipment, there is potential for flavour damage. The liquid product stream is pumped through a distributing nozzle into a chamber of high pressure steam.
This system is characterized by a large steam volume and a small product volume, distributed in a large surface area of product. Product temperature is accurately controlled via pressure. Additional holding time may be accomplished through the use of plate or tubular heat exchangers, followed by flash cooling in vacuum chamber. This method has several advantages:. The heating medium and product are not in direct contact, but separated by equipment contact surfaces.
Several types of heat exchangers are applicable:. Liquid velocities are low which could lead to uneven heating and burn-on. This method is economical in floor space, easily inspected, and allows for potential regeneration. All of these tubular heat exchangers have fewer seals involved than with plates. This allows for higher pressures, thus higher flow rates and higher temperatures. The heating is more uniform but difficult to inspect.
The product flows through a jacketed tube, which contains the heating medium, and is scraped from the sides with a rotating knife.
There is a problem with larger particulates; the long process time for particulates would mean long holding sections which are impractical. This may lead to damaged solids and overprocessing of sauce.
Robinson: Modern Dairy Technology
All handling of product post-process must be within the sterile environment. It is also worth mentioning that many products that are UHT heat treated are not aseptically packaged. This gives them the advantage of a longer shelf life at refrigeration temperatures compared to pasteurization, but it does not produce a shelf-stable product at ambient temperatures, due to the possibility of recontamination post-processing.
If raw milk were left to stand, however, the fat would rise and form a cream layer. Homogenization is a mechanical treatment of the fat globules in milk brought about by passing milk under high pressure through a tiny orifice, which results in a decrease in the average diameter and an increase in number and surface area, of the fat globules.
The net result, from a practical view, is a much reduced tendency for creaming of fat globules. Three factors contribute to this enhanced stability of homogenized milk: In addition, heat pasteurization breaks down the cryo-globulin complex, which tends to cluster fat globules causing them to rise. Auguste Gaulin's patent in consisted of a 3 piston pump in which product was forced through one or more hair like tubes under pressure.
It was discovered that the size of fat globules produced were to times smaller than tubes. There have been over patents since, all designed to produce smaller average particle size with expenditure of as little energy as possible.
The homogenizer consists of a 3 cylinder positive piston pump operates similar to car engine and homogenizing valve. The pump is turned by electric motor through connecting rods and crankshaft.
The liquid then moves across the face of the valve seat the land and exits in about 50 microsec. The homogenization phenomena is completed before the fluid leaves the area between the valve and the seat, and therefore emulsification is initiated and completed in less than 50 microsec.
The whole process occurs between 2 pieces of steel in a steel valve assembly. The product may then pass through a second stage valve similar to the first stage. The second stage valve permits the separation of those clusters into individual fat globules.
Energy, dissipating in the liquid going through the homogenizer valve, generates intense turbulent eddies of the same size as the average globule diameter. Considerable pressure drop with change of velocity of fluid. Liquid cavitates because its vapor pressure is attained. Cavitation generates further eddies that would produce disruption of the fat globules.
The high velocity gives liquid a high kinetic energy which is disrupted in a very short period of time. Increased pressure increases velocity. Dissipation of this energy leads to a high energy density energy per volume and time. Resulting diameter is a function of energy density. Also to be considered are the droplet diameter the smaller, the more difficult to disrupt , and the log diameter which decreases linearly with log P and levels off at high pressures.
This membrane lowers the interfacial tension resulting in a more stable emulsion. During homogenization, there is a tremendous increase in surface area and the native milk fat globule membrane MFGM is lost. However, there are many amphiphilic molecules present from the milk plasma that readily adsorb: The transport of proteins is not by diffusion but mainly by convection. Rapid coverage is achieved in less than 10 sec but is subject to some rearrangement.
Membrane processing is a technique that permits concentration and separation without the use of heat. There are some fairly new developments in terms of commercial reality and is gaining readily in its applications:.
When a solution and water are separated by a semi-permeable membrane, the water will move into the solution to equilibrate the system. This is known as osmotic pressure.
If a mechanical force is applied to exceed the osmotic pressure up to psi , the water is forced to move down the concentration gradient i. The membrane configuration is usually cross-flow. In UF, the membrane pore size is larger than RO, thus allowing some components to pass through the pores with the water.
This schematic shows the process of diaflitration, as a step in ultrafiltration. The pressure used is generally lower than that of UF process. MF is used in the dairy industry for making low-heat sterile milk as proteins may pass through but bacteria do not.
The permeate of skim milk is used as "bacteria-free" skim although thee is no fail-safe guarntee as there could be pin-holes in the membrane since all of the milk components will pass through the membrane. In that case, the retentate, skim enriched in bacteria, is high-heat treated. MF skim can then be stadardized for fat with high heat-treated cream.
As the feed solution flows through the membrane core, the permeate passes through the membrane and is collected in the tubular housing. Imagine 12 ft long straws!
Similar to open tubular, but the cartridges contain several hundred very small 1 mm diam hollow membrane tubes or fibres. As the feed solution flows through the open cores of the fibres, the permeate is collected in the cartridge area surrounding the fibres. This system is set up like a plate heat exchanger with the retentate on one side and the permeate on the other. The permeate is collected through a central collection tube.
This design tries to maximize surface area in a minimum amount of space. It consists of consecutive layers of large membrane and support material in an envelope type design rolled up around a perforated steel tube. Electrodialysis is used for demineralization of milk products and whey for infant formula and special dietary products. Also used for desalination of water. Under the influence of an electric field, ions move in an aqueous solution.
The ionic mobility is directly proportioned to specific conductivity and inversely proportioned to number of molecules in solution. Charged ions can be removed from a solution by synthetic polymer membranes containing ion exchange groups. Anion exchange membranes carry cationic groups which repel cations and are permeable to anions, and cation exchange membranes contain anionic groups and are permeable only to cations. Electrodialysis membranes are comprised of polymer chains - styrene-divinyl benzene made anionic with quaternary ammonium groups and made cationic with sulphonic groups.
Amion and cation exchange membranes are arranged alternately in parallel between an anode and a cathode see this schematic diagram to the right.
The Dairy Science and Technology Book Table of Contents
The distance between the membranes is 1mm or less. A plate and frame arrangement similar to a plate heat exchanger or a plate filter is used. The solution to be demineralized flows through gaps between the two types of membranes. Each type of membrane is permeable to only one type of ion. Thus, the anions leave the gap in the direction of the anode and cations leave in the direction of the cathode. Both are then taken up by a concentrating stream. Concentration polarization. Deposits on membrane surfaces, e.
Ion exchange is not a membrane process but I have included it here anyway because it is used for product of protein isolates of higher concentration than obtainable by membrane concentration. Fractionation may also be accomplished using ion exchange processing. It relies on inert resins cellulose or silica based that can adsorb charged particles at either end of the pH scale. The design can be a batch type, stirred tank or continuous column.
The column is more suitable for selective fractionation. Following adsorption and draining of the deproteined whey, the pH or charge properties are altered and proteins are eluted.
Protein is recovered from the dilute stream through UF and drying. Selective resins may be used for fractionated protein products or enriched in fraction allow tailoring of ingredients. The removal of water from foods provides microbiological stability, reduces deteriorative chemical reactions, and reduces transportation and storage costs. Both evaporation and dehydration are methods used in the dairy industry for this purpose.
The following topics will be addressed here:. Evaporation refers to the process of heating liquid to the boiling point to remove water as vapour. The driving force for heat transfer is the difference in temperature between the steam in the coils and the product in the pan. The steam is produced in large boilers, generally tube and chest heat exchangers. The steam temperature is a function of the steam pressure. At its boiling point, the steam condenses in the coils and gives up its latent heat.
The product is also at its boiling point. The boiling point can be elevated with an increase in solute concentration. Because milk is heat sensitive, heat damage can be minimized by evaporation under vacuum to reduce the boiling point. The basic components of this process consist of:. It is sometimes a part of the actual heat exchanger, especially in older vacuum pans, but more likely a separate unit in newer installations. The condenser condenses the vapours from inside the heat exchanger and may act as the vacuum source.
They consist of spherical shaped, steam jacketed vessels. The heat transfer per unit volume is small requiring long residence times. The heating is due only to natural convection, therefore, the heat transfer characteristics are poor.
Batch plants are of historical significance; modern evaporation plants are far-removed from this basic idea. The vapours are a tremendous source of low pressure steam and must be reused. The heat exchanger, or calandria, consists of 10 to 15 meter long tubes in a tube chest which is heated with steam.
The liquid rises by percolation from the vapours formed near the bottom of the heating tubes. The thin liquid film moves rapidly upwards. The product may be recycled if necessary to arrive at the desired final concentration.
This development of this type of modern evaporator has given way to the falling film evaporator. They are similar in components to the rising film type except that the thin liquid film moves downward under gravity in the tubes.
A uniform film distribution at the feed inlet is much more difficult to obtain. This is the reason why this development came slowly and it is only within the last decade that falling film has superceded all other designs. Specially designed nozzles or spray distributors at the feed inlet permit it to handle more viscous products. The residence time is sec. The vapour separator is at the bottom which decreases the product hold-up during shut down.
The tubes are meters long and mm in diameter.
Each effect would consist a heat transfer surface, a vapour separator, as well as a vacuum source and a condenser. The vapours from the preceding effect are used as the heat source in the next effect.
There are two advantages to multiple effect evaporators:. Each effect operates at a lower pressure and temperature than the effect preceding it so as to maintain a temperature difference and continue the evaporation procedure. The vapours are removed from the preceding effect at the boiling temperature of the product at that effect so that no temperature difference would exist if the vacuum were not increased. The operating costs of evaporation are relative to the number of effects and the temperature at which they operate.
The boiling milk creates vapours which can be recompressed for high steam economy. Involves the use of a steam-jet booster to recompress part of the exit vapours from the first effect. Through recompression, the pressure and temperature of the vapours are increased.
As the vapours exit from the first effect, they are mixed with very high pressure steam.
The steam entering the first effect calandria is at slightly less pressure than the supply steam. There is usually more vapours from the first effect than the second effect can use; usually only the first effect is coupled with multiple effect evaporators. Whereas only part of the vapour is recompressed using TC, all the vapour is recompressed in an MVR evaporator. Vapours are mechanically compressed by radial compressors or simple fans using electrical energy. There are several variations; in single effect, all the vapours are recompressed therefore no condensing water is needed; in multiple effect, can have MVR on first effect, followed by two or more traditional effects; or can recompress vapours from all effects.
It turns out more tonnage of dehydrated products than all other types of driers combined. It is limited to food that can be atomized, i. Evaporative cooling maintains low product temperatures, however, prompt removal of the product is still necessary. The liquid food is generally preconcentrated by evaporation to economically reduce the water content. The concentrate is then introduced as a fine spray or mist into a tower or chamber with heated air.
As the small droplets make intimate contact with the heated air, they flash off their moisture, become small particles, and drop to the bottom of the tower and are removed. The advantages of spray drying include a low heat and short time combination which leads to a better quality product. They provide a large surface area for exposure to drying forces:. The exit air temperature is an important parameter to monitor because it responds readily to changes in the process and reflects the quality of the product.
Generally, we want it high enough to yield desired moisture without heat damage. There are two controls that may be used to adjust the exit air temperature:. If heat damage occurs before the product is dried, the particle size must be reduced; smaller particle dries faster, therefore, less heat damage.
This can be accomplished in three ways:. It is essential for both economic and environmental reasons that as much powder as possible be recovered from the air stream.
Three systems are available, however wet scrubbers usually act as a secondary collection system following a cyclone. Bag filters are very efficient They are not recommended in the case of handling high moisture loads or hygroscopic particles. Cyclones are not as efficient Air enters at tangent at high velocity into a cylinder or cone which has a much larger cross section.
Air velocity is decreased in the cone permitting settling of solids by gravity. Centrifugal force is important in removing particles from the air stream. Higher centrifugal force can be obtained by using small diameter cyclones, several of which may be placed in parallel; losses may range from 0. A rotary airlock is used to remove powder from the cyclone. An example of a rotary airlock is a revolving door at a hotel lobby which is intended to break the outside and inside environments.
Wet scrubbers are the most economical outlet air cleaner. The principle of a wet scrubber is to dissolve any dust powder left in the airstream into either water or the feed stream by spraying the wash stream through the air. This also recovers heat from the exiting air and evaporates some of the water in the feed stream if used as the wash water. Cyclone separators are probably the best primary powder separator system because they are hygienic, easy to operate, and versatile, however, high losses may occur.
Wet scrubbers are designed for a secondary air cleaning system in conjunction with the cyclone. Either feed stream or water can be used as scrubbing liquor. Also, there are heat recovery systems available. Air is blown up through a wire mesh belt on porous plate that supports and conveys the product.
A slight vibration motion is imparted to the food particles. When the air velocity is increased to the point where it just exceeds the velocity of free fall gravity of the particles, fluidization occurs. With products that are particularly difficult to fluidize, a vibrating motion of the drier itself is used to aid fluidization; it is called vibro-fluidizer which is on springs.
The fluidized solid particles then behave in an analogous manner to a liquid. Air velocities will vary with particle size and density, but are in the range of 0. They can be used not only for drying but also for cooling. If the velocity is too high, the particles will be carried away in the gas stream, therefore, gravitational forces need to be only slightly exceeded.
In standard, single stage spray drying, the rate of evaporation is particularly high in the first part of the process, and it gradually decreases because of the falling moisture content of the particle surfaces.
In order to complete the drying in one stage, a relatively high outlet temperature is required during the final drying phase. Of course the outlet temperature is reflective of the particle temperature and thus heat damage. The two stage drier consists of a spray drier with an external vibrating fluid bed placed below the drying chamber. The product can be removed from the drying chamber with a higher moisture content, and the final drying takes place in the external fluid bed where the residence time of the product is longer and the temperature of the drying air lower than in the spray dryer.
The second stage is a fluid bed built into the cone of the spray drying chamber. Thus it is possible to achieve an even higher moisture content in the first drying stage and a lower outlet air temperature from the spray drier. This fluid bed is called the integrated fluid bed.
The inlet air temperature can be raised resulting in a larger temperature difference and improved efficiency in the drying process. The exhaust heat from the chamber is used to preheat the feed stream. The results are as follows:. These processes have allowed the manufacturing of milk powders with better reconstitution properties, such as instantized skim milk powder.
Agglomeration Mechanism: Powder is wetted with water or steam. The surface must be uniformly wetted but not excessively. The powder is held wet over a selected period of time to give moisture stability to the clusters which have formed. The clusters are dried to the desired moisture content and then cooled e. Dried clusters are screened and sized to reduce excessively large particles and remove excessively small ones.
The agglomeration process causes an increase in the amount of air incorporated between powder particles.
More incorporated air is replaced with more water when the powder is reconstituted, which immediately wet the powder particles. This method uses powder as feed stock. Humidified air moistens powder, which causes it to cluster. It is re-dried and wetted. The clustered powder is then exposed to heated, filtered, high-velocity air. The dried clusters are then exposed to cooled air on a vibrating belt. It is then sized pelleted to uniform size and the fines are removed.
A multi-stage drying process produces powders with much better solubility characteristics similar to instantized powder. This method uses a low outlet temperature which allows higher moisture in powder as it is taken from spray drier with excess moisture removed in the fluid bed. The powder fines are reintroduced to the atomizing cloud in the drying chamber. The diagram below helps to explain the various principles involved in the thermodynamics of steam.
It shows the relationship between temperature and enthalpy energy or heat content of water as it passes through its phase change. As we increase the temperature of water, its enthalpy increases by 4. At this point, a large input of enthalpy causes no temperature change but a phase change, latent heat is added and steam is produced.
Once all the water has vaporized, the temperature again increases with the addition of heat sensible heat of the vapour. Steam is produced in large tube and chest heat exchangers, called water tube boilers if the water is in the tubes, surrounded by the flame, or fire tube boilers if the opposite is true.
The pressure inside a boiler is usually high, kPa. The steam temperature is a function of this pressure. The steam, usually saturated or of very high quality, is then distributed to the heat exchanger where it is to be used, and it provides heat by condensing back to water called condensate and giving up its latent heat. The temperature desired at the heat exchanger can be adjusted by a pressure reducing valve, which lowers the pressure to that corresponding to the desired temperature.
After the steam condenses in the heat exchanger, it passes through a steam trap which only allows water to pass through and hence holds the steam in the heat exchanger and then the condensate hot water is returned to the boiler so it can be reused.
The following image is a schematic of a steam production and distribution cycle. The following image is a schematic of a refrigeration cycle. It is described in detail below, so you may want to go back and forth between the diagram and the description.
Mechanical refrigerators have four basic elements: A refrigerant circulates among the four elements changing from liquid to gas and back to liquid. In the evaporator, the liquid refrigerant evaporates boils under reduced pressure and in doing so absorbs latent heat of vaporization and cools the surroundings. The evaporator is at the lowest temperature in the system and heat flows to it. This heat is used to vaporize the refrigerant.
(ebook) Dairy Science and Technology
The temperature at which this occurs is a function of the pressure on the refrigerant: The part of the process described thus far is the useful part of the refrigeration cycle; the remainder of the process is necessary only so that the refrigerant may be returned to the evaporator to continue the cycle. The refrigerant vapour is sucked into a compressor, a pump that increases the pressure and then exhausts it at a higher pressure to the condenser.
For ammonia, this is approx. To complete the cycle, the refrigerant must be condensed back to liquid and in doing this it gives up its latent heat of vaporization to some cooling medium such as water or air. The condensing temperature of ammonia is 29oC, so that cooling water at about 21oC could be used.
In home refrigerators, the compressed gas not ammonia is sent through the pipes at the back, which are cooled by circulating air around them.
Often fins are added to these tubes to increase the cooling area. The gas had to be compressed so that it could be condensed at these higher temperatures, using free cooling from water or air. The refrigerant is now ready to enter the evaporator to be used again. It passes through an expansion valve to enter into the region of lower pressure, which causes it to boil and absorb more heat from the load. By adjusting the high and low pressures, the condensing and evaporating temperatures can be adjusted as required.
The production of beverage milks combines the unit operations of clarification, separation for the production of lower fat milks , pasteurization, and homogenization. The process is simple, as indicated in the flow chart. These products are either produced by partially skimming the whole milk, or by completely skimming it and then adding an appropriate amount of cream back to achieve the desired final fat content. Vitamins may be added to both full fat and reduced fat milks.
During the separation of whole milk, two streams are produced: Cream is used for further processing in the dairy industry for the production of ice cream or butter, or can be sold to other food processing industries. A product known as "plastic" cream can be produced from certain types of milk separators. Creams for packaging and sale in the retail market must be pasteurized to ensure freedom from pathogenic bacteria. Whipping cream is not normally homogenized, as the high fat content will lead to extensive fat globule aggregation and clustering, which leads to excessive viscosity and a loss of whipping ability.
This phenomena has been used, however, to produce a spoonable cream product to be used as a dessert topping. When you whip a bowl of heavy cream, the agitation and the air bubbles that are added cause the fat globules to begin to partially coalesce in chains and clusters and adsorb to and spread around the air bubbles.
The whipped cream soon starts to become stiff and dry appearing and takes on a smooth texture. This results from the formation of this partially coalesced fat structure stabilizing the air bubbles.
The water, lactose and proteins are trapped in the spaces around the fat-stabilized air bubbles. The crystalline fat content is essential hence whipping of cream is very temperature dependent so that the fat globules partially coalesce into a 3-dimensional structure rather than fully coalesce into larger and larger globules that are not capable of structure-building. This is caused by the crystals within the globules that cause them to stick together into chains and clusters, but still retain the individual identity of the globules.
If whipped cream is whipped too far, the fat will begin to churn and butter particles will form. Below are scanning electron micrographs image of whipped cream. If you compare the schematics above with the "real thing" below, you should be able to fully understand whipped cream structure.
The structure of whipped cream as determined by scanning electron microscopy. Details of the partially coalesced fat layer, showing the interaction of the individual fat globules. Fat partial coalescence as it affects things like whipped cream and ice cream structure is an active area of our research here at the University of Guelph. Beverage milks can also be prepared by recombining skim milk powder and butter with water. This is often done in countries where there is not enough milk production to meet the demand for beverage milk consumption.
The concept is simple. Skim milk powder is dispersed in water and allowed to hydrate. Butter is then emulsified into this mixture by either blending melted butter into the liquid mixture while hot, or by dispersing solid butter into the liquid through a high shear blender device.
In some cases, a non-dairy fat source may also be used. The recombined milk product is then pasteurized, homogenized and packaged as in regular milk production. The water source must be of excellent quality. The milk powder used for recombining must be of high quality and good flavour.
Care must be taken to ensure adequate blending of the ingredients to prevent aggregation or lumping of the powder. Its dispersal in water is the key to success.
The sugar, cocoa powder and carrageenan are dry blended, and added to cold milk with vigorous agitation, and then pasteurized. Concentrated milk products are obtained through partial water removal. The benefits of both these processes include an increased shelf-life, convenience, product flexibility, decreased transportation costs, and storage.
There are several benefits to this treatment:. This process is based on the physical law that the boiling point of a liquid is lowered when the liquid is exposed to a pressure below atmospheric pressure.
This results in little to no cooked flavour. There are other benefits particular to this type of product:.In addition, heat pasteurization breaks down the cryo-globulin complex, which tends to cluster fat globules causing them to rise. The thin liquid film moves rapidly upwards.
All microorganisms require water but the amount necessary for growth varies between species. Using direct microscopic counts DMC , Coulter counter etc. There is no doubt that the book will have recognition by dairy scientists, students, researchers and dairy operatives and technologists. These would include temperature, relative humidity, and gases that surround the food.
The vapours from the preceding effect are used as the heat source in the next effect. Place one ml of dye solution in a sterile test tube, then add 10 ml of sample.
Very amphiphilic protein acts like a detergent molecule. Dalgleish, Douglas G.
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