The Freshness Alternative –
ESL Milk with Double Bacteria Removal using the Westfalia Separator® prolong Method

The production of ESL milk (Extended Shelf Life milk) is a question of freshness, naturalness, taste, vitamin content, and the number of actually necessary shelf life days. However, it is also a question of the costs for the installation and operation of suitable technologies and thus in the final analysis a question of the technology itself. GEA Westfalia Separator has now taken a tried-and-tested method which is familiar in cheese-making operations, and has adapted it for the production of ESL milk; the process has a wide range of advantages compared with the previous methods of heating and micro-filtration: double bacteria removal for fresh milk Westfalia Separator^® prolong with bacteria remocing separators connected in sequence.

Contents

• The Westfalia Separator^® prolong method
• Freshness and quality indicators
• Two bacteria removal separators connected in series
• Successful large-scale trials 
• Westfalia Separator^® prolong as sensible alternative
• Advantages of Westfalia Separator® prolong

So far, the normal procedures have aimed to achieve an extended shelf life of up to 30 days. This is nice to have, but are 30 days really necessary? At the manufacturers, the milk leaves the stores as quickly as possible. Retailers are of course also interested in maximising the rate of turnover of their articles and in making space for new articles. This leaves the consumer. Does the consumer really need the ability to store milk in his fridge for more than two weeks? This is probably not the case, because the consumer also wishes to experience the nature of freshness when drinking ESL milk. However, if stored at temperatures below 10 °C, ESL milk can only develop a bad taste approximately 20 days after production. This is however not necessarily due to bacteriological problems; on the contrary, this is due to the inevitable bacterial enzymes in the milk which, in the case of fresh milk, are not deactivated by high heat treatment.

In total therefore, 20 days plus x should probably be the optimum level of extended shelf life for fresh milk. And the Westfalia Separator^® prolong method can guarantee precisely this period. And it also has many other advantages.

The content of ß-lactoglobulin on the one hand and lactulose on the other are common parameters for the milk quality and heat indicators. The content of ß-lactoglobulin in raw milk is approx. 3500 mg/l. The greater the extent to which milk protein is denatured by means of heat treatment, the greater is the extent to which this value declines. In the case of fresh milk, it amounts to 3000 mg/l in conjunction with pasteurisation; in the case of micro-filtered milk, the figure falls to approx. 2500. In the case of milk subject to heat treatment, it falls further to 1000 to 1600 mg/l, and may even be lower than 1000 mg/l in conjunction with indirect heating. By way of comparison, the indicator in conjunction with the Westfalia Separator^® prolong process remains at the level of fresh milk of approx. 3000 mg/l.

On the other hand, lactulose is not present in raw milk. It is a by-product of the chemical reaction of a heat treatment. The intensity of heat treatment is directly related to the quantity of lactulose to be found in the milk. In the case of pasteurised fresh milk, lactulose attains a value of 10 mg/kg; in the case of filtered milk, this figure is 17, and in the case of UHT milk, the figure is between 25 and (in conjunction with indirect heating) 32 mg/kg. With the Westfalia Separator^® prolong process, this factor is also identical to the fresh milk factor of 10 mg/kg. Both indicators for freshness and quality thus clearly underline the benefits of the Westfalia Separator® prolong process.

Double bacteria removal with separators has a further advantage which should not be disregarded: it is a familiar process which has demonstrated its worth in the dairy processing industry, namely in cheese-making.

The selective centrifugal removal of bacillus cereus is made possible simply as a result of the fact that spore-forming bacteria in particular have a much higher specific weight than vegetative bacteria. Compared with cream or skim milk, their specific weight is even higher. In this way, centrifugal force can be used for readily separating vegetative bacteria and bacillus cereus.

For this purpose, two identical bacteria removing separators connected in sequence are generally used directly upstream of the skimming separator in order to achieve a high degree of reliability with regard to removing the spores. This ensures that bacteria are genuinely removed from the entire quantity of raw milk, including the cream. The milk is then treated in the skimming separator with fat content adjustment and traditional heating for a short period.

For the Westfalia Separator^® prolong method, self-cleaning milk separators of the CSE series with the flat belt drive which has demonstrated its worth for more than 20 years can be used for capacities in excess of 5000 l/h, or the CSI series with the latest integrated direct drive can be used for capacities in excess of 30000 l/h. With the prolong method, GEA Westfalia Separator has already conducted very successful large-scale trials in a German dairy. These trials attained shelf lives of up to 28 days, based on a storage temperature of 8 °C.

There is absolutely no difference between heat-treated milk from which bacteria have been removed by means of separators and fresh milk made in the traditional manner, in which the milk is heated for a short time. Accordingly, the taste and vitamin content are precisely the same as those applicable for pasteurised fresh milk which the consumer has known and appreciated for a long time.

The additional shelf life obtained compared with the normal shelf life of between 10 and 12 days provides retailers and consumers with valuable scope for shipping and storing drinking milk. Freshness, naturalness, taste and low costs are clear advantages of the Westfalia Separator^® prolong method.

Westfalia Separator^® prolong is the way to reduce the total bacteria count by up to 90 percent before pasteurisation and also for reducing the bacteria count of bacillus cereus to a level of less than one spore in 10 ml. This results in a product shelf life of at least 20 days. Westfalia Separator^® prolong helps to reduce the negative impact of heat on the fresh milk in order to provide an unchanged taste. This boosts consumer acceptance and guarantees premium quality. The process of reducing bacteria by means of centrifugal force with Westfalia Separator^® prolong results in energy savings, ensures very high-quality milk, considerably extends the shelf life of the milk, in conjunction with comparatively low operating costs, and without resulting in any changes in taste. An optimum solution.

• Removal of non-milk constituents and somatic cells
• Removal of bacteria and spores, in particular bacillus cereus
• Low energy consumption
• High degree of reliability due to the simple process
• No negative impact on taste
• Vitamin content identical to that of fresh milk
• ESL milk has properties equivalent to those of traditional fresh milk
• Multiple use (for cheese-making milk and ESL milk) also involves advantages in terms of costs
• Lowest total operating costs compared with other processes