Dehydration during the freezing process can mean big losses for producers. In a mechanical freezer, dehydration can damage as much as 4% to 5% of fresh produce. For example, losses of 5% against 10,000 tons of produce can bring losses of 500 tonnes per year.
Dehydration is the process of water loss through the product’s membrane when exposed to cold airflow during freezing. All the moisture lost during product processing is product weight lost, and product losses mean financial losses. Therefore, understanding how to minimise dehydration can increase profitability.
"The good news is that dehydration can be minimized significantly through a combination of 2 factors: short freezing time and the right aerodynamics. This is why we believe that IQF technology is the solution. Depending on the product size of course, the freezing time in an OctoFrost IQF freezer with a freezing temperature of -26C can vary between 2 and 7 minutes. In other IQF freezers, the time is always closely connected to the freezing temperature and usually the time is more or less similar to the OctoFrost freezing time. All in all, IQF freezers provide significantly less freezing time when compared to 48 hours freezing process in a cold storage." shared Svetlana Plotean from the OctoFrost Group.
"A short freezing time is important for an obvious reason: the faster the produce temperature drops, the lower the evaporation time, as the water from the product has less time to move into the air as it gets frozen."
There is a lot of debate around how to measure the level of dehydration. There are methods such as weight-in-weight-out, but Svetlana said that these aren't very precise because it is not always possible to weigh the products right before they are frozen, so they are weighed before starting the pre-treatment which already changes the weight of the product, making the results inconclusive. Svetlana believes that measuring snow formation is a more reliable way to measure losses. The IQF tunnel freezer is a closed system, so snow formation inside the freezer can only come from the product’s lost humidity, therefore the more snow – the more product loss.
Some IQF freezers include a “snow room” as part of the design, a space where snow can land during production. However, questions have been raised as to how aerodynamics are connected to the amount of snow. Aerodynamics in the IQF freezer determine some key parameters such as air velocity, air pressure and relative humidity.
Svetlana said that OctoFrost has learned to juggle these parameters in such a way that the snow simply doesn’t have the pre-conditions to form, by keeping a certain air velocity and pressure. Therefore the humidity in the air stays constant and does not precipitate into snow – which would decrease the relative humidity and would dehydrate the products even more.
"The OctoFrost freezer does not have a snow room and doesn’t need one, because the aerodynamics of the OctoFrost IQF freezer, together with the short freezing time, does not allow snow formation and therefore reduces product dehydration to under 1%. This level of dehydration can be verified through a number of methods, including the weight of snow after a full day of production. So next time, when you look for efficient freezing equipment on the market, don’t forget to ask about the dehydration levels in that equipment, because dehydration means product loss and product loss means your loss." concluded Svetlana.
