Lecture_22___condensed_milk_and_milk_powder

Lecture_22___condensed_milk_and_milk_powder - Concentrated...

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1 Concentrated and Dried Dairy Products Carmen I. Moraru Cornell University Condensed milk manufacturing Milk Centrifugal separation Evaporation (or RO) Preheating Homogenization Cooling Stabilization with Na 2 HPO 4 Packing Standardization 72-73ºC/15s 65ºC 22 and 5MPa 93-100°C/10-25 min or 115-128°C/1-6 min Stabilization with Na 2 HPO 4 Sterilization Homogenization Cooling 122-140ºC/15s-4min Cool to 60ºC 10ºC 10ºC Sterilization Aseptic packing 45MPa In–bottle evaporated sterile milk UHT evaporated sterile milk 120ºC/15min
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2 Raw material quality requirements Microbiological quality - High bacteriological quality is required, since under the evaporation conditions (vacuum, 65–70°C), spores and heat resistant bacteria can grow. Thermal stability - The initial milk has to have low acidity and a proper salt balance in order to withstand the intensive heat treatment. - Thermal stability can be enhanced by using stabilizers and applying a pretreatment to milk prior to evaporation and sterilization. Role of various processing steps Preheating - Increases the concentrated milk stability during sterilization. Most of the whey proteins are denatured and calcium salts are precipitated the protein complex of milk is stabilized, and thus can withstand subsequent thermal treatment without coagulation. This also decreases the chance of coagulation during storage - Decreases the initial microbial load - Modifies the viscosity of the final product - Energy savings - milk enters the evaporator at a high temperature Concentration - Typically done at low temperatures, under vacuum - Due to the low pressures, the boiling point of milk is lowered to 65- 70°C, which results in little to no cooked flavor - The end of the process is established by continuously monitoring the density of the condensed milk or its refractive index
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3 Homogenization - Disperses fat globules and prevents them from coalescing during sterilization - Too high homogenization pressures might affect protein stability and induce milk coagulation during sterilization - Sterilization in containers: homogenization pressure of 125–250 bar (two-stage) - In UHT processing, homogenization during the pre- treatment is normally low, in order to avoid separation during storage of the concentrate prior to sterilization. The main homogenization takes place after the UHT treatment. Stabilization - Ensures proper salt balance in milk, which affects the ability of milk to withstand intensive heat treatment. - The heat stability of condensed milk can be improved by adding stabilizing salts - usually disodium or trisodium phosphate. - Vitamins are also added at this stage. Sterilization - Primarily aimed at killing all bacterial spores and inactivating plasmin (a milk protease). -
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This note was uploaded on 05/02/2009 for the course FDSC 4250 taught by Professor Moraru during the Spring '09 term at Cornell University (Engineering School).

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Lecture_22___condensed_milk_and_milk_powder - Concentrated...

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