Human Milk Pasteuriser Nest Test

31-03-2022 | Posted in General News

A pasteuriser Nest Test or Position Test is a crucial part of any Pasteuriser validation.

A Nest test is carried out by an independent scientific validation company using calibrated and traceable equipment.

The Nest Test document is required following a request from the manufacturer to test every available bottle
location at the same time during the same cycle.

This report is to show that each bottle position in the basket receives the correct treatment. Each position was fitted with a Type ‘T’ thermocouple probe and tested to meet the holder pasteurisation requirements as below.

Past time at 62.5°C = 30min to 35min
Rapid cooling to 25°C = 10minutes
Overall cooling to 4°C = 60minutes

PATH – A global non-profit improving public health highlight the importance of Independent Pasteuriser validation in the document below.

Sterifeed believes in a systematic approach to its machine design and therefore we follow the Quality by design approach in engineering our pasteurizers. The objectives and essential attributes of the pasteurizer and the process of pasteurization have been taken into consideration during the designing the Sterifeed range of pasteurisers. We test each machine after it has been manufactured and programmed to our design specifications to validate the performance of the machine in triplicate. The performance is achieved by various factors like selection of heaters, sensors, heat exchangers and compressors. The heat treatment according to the specifications is achieved with the major role of body design of the machine and the material of construction. It’s the design due to which required levels of water for the desired treatment are estimated. At the desired level of water, right volume displacement leads to submerging of bottles in accordance to the size of bottles (50ml/100/130 ml/ 250ml), and baskets (Single storey for T30, Double storey & combi baskets for S90) holding bottles, the material of bottles also plays a vital role eg: glass bottles/ BPA free plastic bottles.  Since there are many factors in achieving the desired programmed heat treatment for the liquid, it becomes important to actually monitor the heat treatment in both the hot and cold cycle inside the container. NEST test is used globally to measure the rate of temperature change in accordance with the time. Hence the final desired outcome of the heat treatment which has been programmed into the machine is validated with the NEST Test.  Passing a NEST test ensures that all these dynamic factors are working in tandem toward complete pasteurization.

In the process of pasteurization, equal heat and cooling treatment of each bottle has to take place to ensure that the bacteria are killed and spore formation is avoided. The heat treatment takes place by convection currents in the T30 and by a circulating pump and convection currents in the S90 pasteurizer.  In the NEST test, we place datalogger probes in each bottle and run pasteurization cycles in triplicates. This ensures that we get the minute-to-minute reading of the milk inside the bottles. The graphs are plotted and compared for any deviations. All Sterifeed models have to go through a nest test validation before they are released.

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