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New dairy processing handbookBách khoa toàn thư về công nghệ sản xuất sữa của tập đoàn hàng đầu trong ngành sản xuất sữa Tetra PakContents1 Primary production of milk 12 The chemistry of milk 133 Rheology 374 Microorganisms 455 Collection and reception of milk 656 Buildingblocks of dairy processing 736.1 Heat exchangers 756.2 Centrifugal separators andmilk fat standardisation systems 916.3 Homogenisers 1156.4 Membrane filters 1236.5 Evaporators 1336.6 Deaerators 1396.7 Pumps 1436.8 Pipes, valves and fittings 1536.9 Tanks 1616.10 Process Control 1656.11 Service systems 1757 Designing a process line 1898 Pasteurised milk products 2019 Longlife milk 21510 Cultures and starter manufacture 23311 Cultured milk products 24112 Butter and dairy spreads 26313 Anhydrous milk fat 27914 Cheese 28715 Whey processing 33116 Condensed milk 35317 Milk powder 36118 Recombined milk products 37519 Ice cream 38520 Casein 39521 Cleaning of dairy equipment 40322 Dairy effluents 415Literature 425Index 427
Flow controller The flow controller maintains the flow through the pasteuriser at the correct value This guarantees stable temperature control and a constant length of the holding time for the required pasteurisation effect Often the flow controller is located after the first regenerative section Regenerative preheating The cold untreated milk is pumped through the first section in the pasteuriser, the preheating section Here it is regeneratively heated with pasteurised milk, which is cooled at the same time If the milk is to be treated at a temperature between the inlet and outlet temperatures of the regenerative section, for example clarification at 55°C, the regenerative section is divided into two sections The first section is dimensioned so that the milk leaves at the required temperature of 55°C After being clarified the milk returns to the pasteuriser, which completes the regenerative preheating in the second section The regenerative energy-saving effect is in a milk pasteuriser typically between 90 and 96% Pasteurisation Final heating to pasteurisation temperature with hot water, normally of a temperature – 3°C higher than the pasteurisation temperature (∆t = – 3°C), takes place in the heating section The hot milk continues to an external tubular holding cell After the hold, the temperature of the milk is checked by a sensor in the line It transmits a continuous signal to the temperature controller in the control panel The same signal is also transmitted to a recording instrument which records the pasteurisation temperature Flow diversion A sensor after the holding cell transmits a signal to the temperature monitor As soon as this signal falls below a preset value, corresponding to a specified minimum temperature, the monitor switches the flow diversion valve to diversion flow In many plants the position of the flow diversion valve is recorded together with the pasteurisation temperature For the location of the flow diversion valve, various solutions are available to satisfy local regulations and recommendations Below are three alternatives which are commonly utilised: The flow diversion valve is situated just after the holding cell Where a booster pump is installed, the valve is located before the pump If the temperature drops under preset level the valve diverts the flow to the balance tank and the pump stops The flow in the regenerative and cooling sections thus comes to a standstill (even when no booster pump is integrated) After a short while, without temperature increase, the heat exchanger is emptied, cleaned and sanitised When satisfactory heating is possible the plant is restarted The flow diversion valve is located after the cooling section of the plant Following a drop of temperature the flow is diverted to the balance tank and the plant is emptied of product, cleaned and sanitised The plant is then ready for restart when the temperature conditions are acceptable again The flow diversion valve is located between the holding cell and the boster pump If the temperature drops the valve diverts the flow The booster pump is not stopped, but other valves around the heat exchanger will automatically be positioned so that the milk in the regenerative and cooling sections will be circulated to maintain the right pressure in the plant This also preserves a proper temperature balance When the heating conditions are acceptable the process can be resumed without intermediate cleaning Cooling After the holding section the milk is returned to the regenerative section(s) for cooling Here the pasteurised milk gives up its heat to the cold incoming milk The outgoing pasteurised milk is then chilled with cold water, icewater, a glycol solution or some other refrigerant, depending on the required Dairy Processing Handbook/chapter 195 temperature The temperature of the chilled milk is normally recorded together with the pasteurisation temperature and the position of the flow diversion valve The graph consequently shows three curves Centrifugal clarifier As the milk in the present example is not going to be separated into skimmilk and cream, a centrifugal clarifier is shown in figure 7.6 Some dairies specify centrifugal clarification of cold ([...]... flow 6 80°C 4a 4b 5 2 1 2 3 3a 3b 3c 3d 3e 3f 3g 4a 4b 5 Balance tank Feed pump Tubular heat exchanger Preheating section Correction cooler Heating section Final heating section Cooling section Cooling section Diverted flow cooler Stabilising holding tube Holding tube Steam injection head 226 9 7 1 3 8 10 3a 3b 6 7 8 3c Expansion chamber Vacuum pump Aseptic homogeniser 3d 3e 3f 3g 9 Aseptic tank 10 Aseptic... temperature 3a 3c 3b 3d 1 2 3 3a 3b 3c 3d 3e 4 5 6 7 8 Balance tank Feed pump Tubular heat exchanger Preheating section Medium cooling section Heating section Regenerative cooling section Start-up cooling section Non-aseptic homogeniser Holding tube Steam injection head Aseptic tank Aseptic filling 3e 4 5 1 2 Milk Steam Cooling water Ice water Diverted flow 6 1 Product tank 2 Positive feed pump 3 Scraped... sterilised before restart Dairy Processing Handbook/ chapter 9 Milk Steam Cooling water Hot water Diverted flow 4 7 1 5 2 3 3a 3b 3c 3d 3e 8 6 Fig 9. 23 Indirect UHT system based on tubular heat exchangers Indirect UHT plant based on scraped surface heat exchangers Scraped surface heaters are the most suitable type for treatment of highviscosity food products with or without particles A scraped surface... exposure of 1 500 Lux Carton Taste no loss Vitamin C Bottle Vitamin B2 –1 % – 1.5% –2 % – 2.5% – 2.8% 3 % – 3. 8% no loss Hours Taste 2 3 4 5 6 8 12 little evident strong strong strong strong Vitamin C – 10% – 15% – 20% – 25% – 28% – 30 % – 38 % Vitamin B2 – 10% – 15% – 18% – 20% – 25% – 30 % – 35 % Measured by the Dairy Science Institute at the Justus Liebig University in Giessen, Germany, in 1988 Sunlight flavour... 6 1 Product tank 2 Positive feed pump 3 Scraped surface heat exchangers 3a Preheating section 3b Final heating section 3c Cooling section 3d Cooling section 3e Cooling section 4 Holding tube 5 Positive pump 6 Aseptic tank 7 Aseptic filling 7 Fig 9.24 Indirect UHT system based on scraped surface heat exchangers Dairy Processing Handbook/ chapter 9 229 Finally, the cooled product is pumped to an aseptic... Des truc tion Destruction of spores of ly sine Logarithmic death value = 9 3% 90% Ps-p A Mesophilic spores (30 °C) B 10 6 Thermophilic spores (55°C) UHTregion 4 2 1 110 120 Dairy Processing Handbook/ chapter 9 130 140 150 Temperature °C Fig 9.5 Limiting lines for destruction of spores and effects on milk The values within brackets (30 °C and 55°C) express the optimal growth temperatures of the vital types... temperature zone where they are subjected to sterilising temperatures of the order of 132 – 140°C for 10 – 12 minutes With an overall cycle time of 30 – 35 minutes, a capacity of 12 000 units per hour can be achieved The rotary valve sealed steriliser can be used for sterilisation of plastic Dairy Processing Handbook/ chapter 9 3 4 2 1 5 7 6 bottles and glass bottles as well as flexible containers of plastic... slow process; some crystallisation still continues after four or five hours Crystallised fat has a lower specific volume than liquid fat, so °C Cryst fat % 70 60 50 40 30 Cooling 20 10 5 10 15 20 Dairy Processing Handbook/ chapter 8 25 30 35 40 45 50 55 60 120 min Fig 8.4 The crystallisation process for 40% cream at 8 °C 209 tension forces are generated in the fat globules during crystallisation This makes... content, usually 35 – 40% The treatment of the cream is the same as described for whipping cream, with the exception that the half cream is mixed with skimmilk to obtain the required fat content The cream is homogenised Fig 8.6 Production line for half and coffee cream 1 Fat standardisation tank 2 Product pump 3 Plate heat exchanger 4 Homogeniser 5 Holding tube 3 5 4 1 2 Dairy Processing Handbook/ chapter... materials used to manufacture new products, but it is important that the new products meet a real need Dairy Processing Handbook/ chapter 8 Functions of packaging: • to enable efficient food distribution • to maintain product hygiene • to protect nutrients and flavour • to reduce food spoilage and waste • to increase food availability • to convey product information 2 13 • Recovery of energy All packages