Soups, cannelloni or pasta: until now, catering services and kitchens had to wait for hot foods to cool down in order to be able to pack them effectively under vacuum. This requires flexibility, time and, in the case of using active cooling, also energy. The alternative of the Multivac packaging specialist: the new SFP light steam sweeping system.
Fun fact: It is impossible to bake an egg on Mount Everest. The lower the air pressure, the lower the boiling point of water. On the highest mountain in the world – 8,848 meters above sea level – the water evaporates already at 70 °C. But it takes 83 °C to cook a hard-boiled egg. For climbers this is not a problem at all: either they give it up or they use a steam cooker. But for catering services, this physical principle poses a challenge when they want to vacuum pack hot food directly after cooking to ensure its durability. Why? This is where the steam pressure curve comes into play. The higher the negative pressure, the lower the boiling point: the same thing happens on the mountain. If, for example, the machine generates a negative pressure of 200 mbar, the proportion of water contained in the product evaporates already at 60 degrees and from this point the pressure can no longer continue to decrease.
When vacuum packaging hot products, there will always be a part of residual air with 21% residual oxygen in the upper space. And this residual part can decrease the durability of the food. “For this reason, many catering services and kitchens allow hot food to cool before vacuum packaging or use active refrigeration. But this means time or energy consumption”” says Dominik Eberhard, product manager of thermoforming machines at Multivac. “To support catering and kitchen services we have launched on the market a new steam sweeping system for small and medium batches called SFP light.” SFP stands for Steam Flush Packing or steam sweep packing.
SFP light is now available as an extension module for Multivac thermoforming machines. “Our thermoforming machines have been successfully used all over the world for decades. They open up new paths in terms of resource consumption, process safety, efficiency, flexibility, reproducibility and ease of use. SFP light brings another important advantage. The steam sweeping system makes it possible to vacuum pack hot food directly after it has been cooked.“
To do this, in a first step, the thermoforming machines form plastic film packaging cavities for the product, for example for five kilos of meat stew at a temperature of 60 °C. In the next step, the portions are moved to a hermetically closed sealing station. Now a hot jet of water vapor at 180 °C sweeps the station. If then the sealing takes place with a top film, which gives steam in the package.
The secret: gases have a considerably larger volume than liquids. If the water vapor turns back to water when it cools down, the container automatically contracts. “With SFP light it will be possible to package hot food without significant residual air inclusions. And all this without a vacuum source constantly limited by the vapor pressure curve”” explains Eberhard. “In addition, there is no danger that the products will boil or burst, since no negative pressure is generated in the product cavity.” An advantageous side effect of the steam sweeping system is that the gas at 180°C kills the germs on the surface of the food, thus prolonging the durability.
And why SFP light? “For thermoforming machines with a high production rate in the industry, Multivac has been offering an SFP system for some time. The new model is designed for small batches in kitchens and catering services. It is less complex and saves space and costs””