Nitrogen dosage in fats at lab scale

We regularly talk about gas systems and liquid systems. This piece is about nitrogen dosing, but it is also an ode to Het Stempel. Het Stempel is a machine factory. And one of the old school. One where they know their customers and are loyal to their suppliers. That's how it happened that Het Stempel from Zwijndrecht has been a loyal customer of ours for 35 years. The order flow from Zwijndrecht is stable. Small, but stable.

Millions of components leave Teesing's doors every month. All through robotic storage systems. While assembly teams in the clean room are busy with high-tech liquid and gas systems that play with the boundaries of the physically possible. We are integrated via software in the supply chain of enormous multinationals. And: a box of Serto couplings is sent to Het Stempel. But what are the Serto couplings for?

Photo: Het Stempel makes machines for the food industry.

Set-up to perform lab experiments on dosing nitrogen in fatty dairy products.

Photo: set-up for doing experiments in the lab with dosing nitrogen in fat dairy products.

Machine factory Het Stempel

Het Stempel makes machines for the food industry. And especially for dairy products - there is no margarine factory without machines made by Het Stempel. They make all kinds of products. Both production machines and laboratory equipment for product development and testing. Albert Korres is an engineer and has been designing these kinds of machines for years.

The piping for gas dispensing

The apparatus Albert is now working on is intended for experiments in injecting nitrogen into a fatty emulsion.

The setup controls the supply of nitrogen with a needle valve, which is combined with a VA flow meter.

Before the nitrogen is introduced into the product via the injector, a non-return valve has been installed and the piping follows the course of a so-called siffon. Both to prevent unwanted mixing, because a classic problem of injecting a gas into a liquid is the liquid shock. The liquid shock is a temporary increase in pressure in the liquid and therefore in the gas. This pressure pulse is the result of pumping, which in the case of this type of product is done with a plunger pump that repeatedly makes a stroke and pushes a quantity of product into the pipe. Normally this does not cause any problems. But it does cause problems when a liquid and a gas are mixed, because a liquid cannot be compressed and a gas can. This means that the liquid has a tendency to flow back into the gas pipe. The non-return valve has to prevent this.

To make it easy to do different tests in a row, the whole setup must be easy to take apart. And the components are cleaned in a dishwasher. Because in a product development lab, flexibility is key.

Nitrogen dosage in fats

In practice, you regularly encounter gas dosing in fats. For example:

for aerating products
stirring without mechanical agitator
hydrogenation of oils and fats with hydrogen to improve the shelf life
oxygen removal by adding nitrogen

A good, even mixing of the liquid and gas is very important. It's a game of controlling pressure and temperature. Or, in fact, of 4 factors:

temperature of the liquid
pressure of gas and liquid
mechanical stress of the liquid
absorption capacity of the liquid

Backside of set-up to perform lab experiments on dosing nitrogen in fatty dairy products.

Gas can be dissolved in liquids, but if the pressure is too high it will outgas. And when there is too much mechanical stress on the liquid by an agitator, the gas you want will leave the liquid again and you will also add oxygen, which can have an oxidizing and spoiling effect on the product. In some cases sparging is a solution. With Mott's spargers made of sintered metal, the bubble size becomes incredibly small so that absorption is maximized. But for food applications this is not always possible because with thick substances the product stays behind in the pores.

Flow Meters for gas dosing

For a lab setup like this VA flowmeters are sufficient. The flowmeters are often delivered with different balls for different gasses and the reading of the flow is done by converting the value on the scale of the flowmeter via calibration sheets to the final measured value. This is of course a bit cumbersome, the customer often prefers a direct readable scale. In such a case a thermal mass flow meter would be very useful and accurate. And because those kind of instruments are calibrated, they are directly readable. Another advantage may be that they can be read digitally. Combined with a valve and control loop you get a Mass Flow Controller (MFC) which can run a complete preprogrammed test program. It depends a bit on the method used for the experiments in the lab what eventually gives the decisive answer, because MFC's do cost a lot more than a VA meter. Often a simple VA meter will do fine and sometimes the high cost of a thermal mass flow meter is justifiable.

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