IE73466B1 - A process for manufacturing milk powder - Google Patents

Abstract

Milk powder is manufactured by pre-heating skim milk, holding the heated skim milk and evaporating water. The concentrate is re-heated in a first heater and held in a first holding tank prior to atomising with a first atomiser. The atomised concentrate is dried in a primary fluidised bed dryer. A second process loop comprising a second heater, a second holding tank and a second atomiser is simultaneously cleaned. When cleaning of the first process loop is required, the concentrate supply is connected to the second loop and the cleaning supply is connected to the first loop so that production may continue substantially without interruption. Powder from a secondary dryer may be introduced into the stream from the primary dryer to achieve a homogenous mixture.

Description

A process for manufacturing milk powder The invention relates to a process for manufacturing milk powder.

There are several difficulties in manufacturing milk powder to a high level of quality and with maximum operating efficiency.

One of the problems is in the limited capacity of a manufacturing plant to accommodate what may sometimes be wide variations in required production rates dependent on seasonality and market requirements.

This invention is directed towards providing an optimised process for manufacturing milk powder of high quality with optimum efficiency.

According to the invention there is provided a process for manufacturing milk powder comprising the steps of:preheating skim milk to a temperature of from 75°C to 120°C; holding the heated skim milk for a period of from 5 seconds to 240 seconds; evaporating water from the skim milk; re-heating the skim milk concentrate thus formed to a temperature of from 75°C to 80°C in a first heater; holding the heated skim milk concentrate in a first holding tank for a period of from 10 to 30 minutes; atomising the concentrate with a first atomiser; spray drying the atomised concentrate thus formed in a primary fluidised bed dryer to form milk powder; simultaneously cleaning a second process loop comprising a second heater, holding tank and atomiser from a cleaning supply; disconnecting the concentrate supply to a first process loop comprising the first heater, holding tank and atomiser; and connecting the concentrate supply to the second cleaned process loop to continue spray drying.

In a preferred embodiment of the invention, after connecting the concentrate supply to the cleaned second process loop, the cleaning supply is connected to the first process loop.

In one embodiment of the invention, the process includes the steps of adding other ingredients to the concentrate after re-heating and homogenising the mixture thus formed in a homogeniser in both the first and second process loops after the heater.

In a particularly preferred embodiment of the invention, the process includes the step of introducing milk powder from a secondary dryer into the primary spray dryer. Most preferably, the milk powder from the secondary dryer is introduced into the stream of atomised concentrate from the atomiser of the primary dryer.

In a particularly preferred embodiment of the invention, the process includes the step of removing spores from the skim milk prior to pre-heating. Typically, the spores are removed by centrifugation. In this case, preferably the skim milk is heated to from 57°C to 63°C prior to removal of spores. Most preferably, the skim milk cooled to from 7°C to 9°C after removal of spores.

The invention also provides milk powder, skim milk powder or fat filled milk powder whenever manufactured by the process of the invention.

The invention will be more clearly understood from the following description thereof, given by way of example only.

In a process for manufacturing milk powder according to the invention, cold milk is first heat treated and then separated into cream and skim milk. The skim milk is heat treated to a temperature of 72.5°C and subsequently cooled to a temperature of about 7°C.

The cooled heat treated skim milk is then pre-heated to a temperature of from 75°C to 120°C and held at this temperature for a period which may be from 5 seconds to 4 minutes. If the skim milk is to be used to produce skim milk powder, the milk is then evaporated to a total solids content of from 48 to 52% in an evaporator. After evaporation, the skim milk concentrate is re-heated to about 75°C and then held for about 20 minutes prior to introduction to an atomiser of a primary spray dryer. The primary spray dryer has an internal fluidised bed and the output from the spray dryer is delivered to an external fluidised bed. The milk powder thus formed is cooled to about 30°C prior to sieving and packaging.

In the case of fat filled milk powder, the preheated skim milk, after holding, is introduced to an evaporator and evaporated to from 38 to 42% total solids content and is then cooled to about 12°C . The skim milk is then agitated and crystallised over a period of 12 hours. The concentrate is re-heated to about 75°C and blended with additional ingredients. The blended mixture is held for about 20 minutes prior to homogenisation and introduction to the atomiser of the primary spray dryer for further processing in a similar manner to skim milk powder as described above.

In the method of the invention, there are two separate process loops after evaporation, each of which comprises a heater, a holding tank, a homogeniser and an atomiser. In the case of skim milk, the homogeniser acts as a pumping unit. In the case of fat filled milk powders, the homogeniser acts as both a pumping unit and an homogeniser. While the skim milk concentrate is processed through the first process loop comprising a first heater, holding tank, homogeniser, and atomiser, the second process loop is connected to a cleaning supply which simultaneously cleans the second process loop while the first process loop is in line with the main process. When it is required to clean the first process loop or a change over from one product to another is required, the concentrate supply is disconnected from the first process loop and is re-connected to the second cleaned process loop to continue spray drying substantially without interruption. This is achieved using quick connect flexible pipe and electrical couplings. After connecting the concentrate supply to the cleaned second process loop, the cleaning supply is connected, again using quick connect couplings, to the first process loop.

In this way, the maximum throughput is achieved as there is minimum downtime for cleaning and/or changeover from one product to another.

Particularly at periods of high production demand, two spray dryers may be used at the same time producing products of different specifications. In this case, the milk powder produced from a secondary dryer which has a different specification than the primary dryer, may be introduced into the primary spray dryer. Most preferably, the milk powder from the secondary dryer is introduced into the stream of atomised concentrate from the atomiser of the primary dryer. A homogenous mixture with a high efficiency of throughput is achieved.

In the process of the invention, cooled skim milk may be treated to remove a substantial proportion of the spores which naturally occur in the skim milk prior to processing. In this case, the cooled skim milk is heated to a temperature of from about 57 to 63°C and the spores are removed, typically by centrifugation. The skim milk is then cooled to from 7 to 9°C prior to preheating and holding in advance of evaporation. These process steps have the considerable advantage of providing an improved finished product with minimum spore count.

Many variations on the specific embodiments of the invention described will be readily apparent and accordingly the invention is not limited to the embodiments hereinbefore described which may be varied in detail.

Claims (5)

1. A process for manufacturing milk powder comprising the steps of:preheating skim milk to a temperature of from 5 75°C to 120°C; holding the heated skim milk for a period of from 5 seconds to 240 seconds; evaporating water from the skim milk; re-heating the skim milk concentrate thus formed 10 to a temperature of from 75°C to 80°C in a first heater; holding the heated skim milk concentrate in a first holding tank for a period of from 10 to 30 minutes; 15 atomising the concentrate with a first atomiser; spray drying the atomised concentrate thus formed in a primary fluidised bed dryer to form milk powder; simultaneously cleaning a second process loop 20 comprising a second heater, holding tank and atomiser from a cleaning supply; disconnecting the concentrate supply to a first process loop comprising the first heater, holding tank and atomiser; and connecting the concentrate supply to the second cleaned process loop to continue spray drying.

2. A process as claimed in claim 1 wherein, after connecting the concentrate supply to the cleaned second process loop, the cleaning supply is connected to the first process loop.

3. A process as claimed in any preceding claim including the steps of adding other ingredients to the concentrate after re-heating and homogenising the mixture thus formed in both the first and second process loops after the heater.

4. A process as claimed in any preceding claim including the step of introducing milk powder from a secondary dryer into the primary spray dryer. 5. A process as claimed in claim 4 wherein the milk powder from the secondary dryer is introduced into the stream of atomised concentrate from the atomiser of the primary dryer. 6. A process as claimed in any preceding claim including the step of removing spores from the skim milk prior to pre-heating. 7. A process as claimed in claim 6 wherein the spores are removed by centrifugation. 8. A process as claimed in claim 6 or 7 wherein the skim milk is heated to from 57°C to 63°C prior to removal of spores . 9. A process as claimed in claim 8 wherein the skim milk is cooled to from 7°C to 9°C after removal of spores. 10. 11.

5. 12. A process for manufacturing milk powder substantially as hereinbefore described. Milk powder whenever manufactured by a process as claimed in any preceding claim. Skim milk powder whenever manufactured by a process as claimed in any of claims 1 to 10. Fat filled milk powder whenever manufactured by a process as claimed in any of claims 1 to 10.