ESL milk production processes: all variants offered by GEA TDS!

GEA TDS offers four process engineering variants for ESL treatment processes: direct heating, indirect heating, microfiltration and deep-bed filtration

(PresseBox) ( Büchen, )
Process sequence of the ESL direct heating plant

The starting product for the ESL direct heating plant is standardized and heat-treated milk or just milk with a standardized fat content buffered in a storage tank. In the ESL direct heating plant, the product is first regeneratively preheated to 70 °C - 85 °C and then heated to max. 127 °C by direct steam injection. The milk is held at this temperature for approx. 3 seconds and is then cooled down to 70 °C - 85 °C in a flash cooler. To ensure the product is well stabilized, aseptic homogenization is carried out at a temperature of approx. 70 °C.As a result of these extremely short heating and cooling times at a high heating temperature, the direct process offers the advantage of top product quality. Taste tests have shown that from an organoleptic point of view the product is virtually comparable with conventionally pasteurized fresh milk. Milk can be supplied to the filling line as finished milk via modified sterile tanks or via high-hygienic milk tanks designed especially for ESL milk. The storage temperature in the tanks should never exceed 5 °C. For the "ESL indirect heating plant" process a similar intermediate storage approach is required.

Process sequence of the ESL indirect heating plant

The pre-treatment of the milk corresponds to the process for the ESL direct heating plant. The product is supplied to the ESL indirect heating plant from storage tanks. The milk is first heated to 70 °C by regenerative heat exchange and then specially homogenized. Next, the product is preheated to approx. 105 - 107 °C by regenerative heat transfer and then heated to 124 °C in the heating section. The temperature holding time is approx. 2 seconds. Special tubular heat exchanger sections have been developed to ensure that the product quality achieved is comparable with the quality of ESL milk produced by direct steam injection.

Microfiltration process sequence

For the microfiltration process, ceramic membranes with pore sizes of 0.8 ?m - 1.4 µm are used. Bacteria removal rates of more than 99.5 % can be achieved. The process used here is cross-flow filtration, which produces a bacteria-reduced permeate and a bacteria-enriched retentate. The bacteria concentrate is 20 times or 100 - 200 times concentrated. Retentate that has been 20 times concentrated is high-heat treated and added to the permeate. 100 - 200 times concentrated retentate is not used for the production of ESL milk. In the first heat transfer section of the milk heat exchanger the raw milk is preheated and then cleaned and skimmed in the separator. The skim milk is then microfiltrated at skimming temperature. The cream required for fat content sterilization is high-heat treated together with the retentate yielded from microfiltration at approx. 105 °C - 125 °C for 4 - 6 seconds. After high-heat treatment the cream is mixed with the skim milk and homogenized in a separate stream. The standardized milk is pasteurized in the milk heat exchanger, then cooled down to 4 - 6 °C and made available for filling in the filling tanks.

Deep-bed filtration process sequence

For the deep-bed filtration process, polypropylene filter cartridges are used. The systems consist of a pre-filter with a nominal pore width of 0.3 µm and a main filter with 0.2 µm. The micro-organisms are retained in the depth of the filter medium. Filtration is carried out at separation temperature. Due to the low pressure drop in the filtration system, no additional pumps are required. No retentate is produced as is in microfiltration. Apart from retentate treatment, the process sequence in the heating plant corresponds to microfiltration processes. As the level of thermal stress to which milk is exposed is lowest in the filtration processes described, this milk is closest to the conventionally pasteurized fresh milk from an organoleptic point of view.

We will exhibit:

ANUGA FOODTEC in Cologne, 10 - 13 March 2009, GEA TDS at the GEA Group Stand in Hall 4.1, Stand No. G010 / H029
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