Opinion: The importance of dehydration in fruit and vegetable processing

May 12 , 2017

By OctoFrost Group marketing coordinator Carmen Popescu

What is dehydration and why is it so important for fruit and vegetable processors?

Dehydration is the process of water loss, no matter how you look at it. What interests us the most is what impact has the dehydration of fruit and vegetables during the IQF freezing process? In the case of IQF freezing, we see dehydration as the process of water loss through the fruits’ and vegetables’ membrane when they are exposed to cold airflow during freezing.

The reason why dehydration is so important for fruit and vegetable IQF processors is that all the moisture lost during the freezing process is actually product weight loss and product losses translate into money losses. Understanding dehydration can make the difference for your business by increasing your profitability.

Some may think that the product losses are too small to bother, but the truth is the opposite of this. Let’s look a bit deeper into the matter. 

In a mechanical freezer, the product dehydration level can reach 4% to 5%. Making a simple hypothetical calculation, if you process 10,000 tons of product every year and you lose 5% of your product due to dehydration, you will ultimately lose at least 500 tonnes of product per year.

So how do we minimize dehydration and the losses it will cause your business? This might sound easy but it’s actually an art of science. The answer to this question is short freezing time and the right, optimal aerodynamics.

The faster the temperature of the fruits and vegetables is dropped, the lower the dehydration time. With a short freezing time, the water from the product has less time to move into the air, as it will get frozen. The only way to short freeze fruits and vegetables is with the help of an IQF tunnel freezer that can fast freeze between 2 and 7 minutes, at a temperature of -260C.

However the most interesting part is about the aerodynamics. There is still a debate on how to measure the level of dehydration. There are methods such as weight-in-weight but they don’t normally provide accuracy, as it is sometimes impossible to weight the products right before entering the IQF tunnel freezer. Processors sometimes weight the products before the pre-treatment but that will already have changed the weight of the product and the results get inconclusive.

A more reliable aspect to look at when you are trying to understand the levels of dehydration is snow formation. An IQF tunnel is a closed system, and it is quite obvious that the snow formed inside the freezer can only come from the product’s lost moisture. The lost moisture results in more snow and thus more product loss. There are IQF freezers with a ‘snow room’ build inside the freezer so that the snow can land during production.

The first question that comes to mind is of course in what way is aerodynamics connected to the amount of snow formation? Aerodynamics in an IQF freezer are determined by key parameters such as air velocity, air pressure and relative humidity. Important to note is that the unique design of the OctoFrost tunnel is an important factor in creating the optimal air velocity and pressure, and ultimately optimal aerodynamics.

Our team of experts have learned to juggle with these parameters in a way that snow just doesn’t have the pre-conditions to form. This makes it possible for humidity in the air to stay constant and not precipitate in snow. This is why our equipment doesn’t have a snow room nor does it need one, because the aerodynamics of the OctoFrost together with the short freezing time don’t allow snow formation and thus reduces the product dehydration under 1%.

This level of dehydration can be verified through a number of methods, including weighting the snow after a full day of production.
Next time you’re looking for an efficient freezing equipment to provide you with premium quality IQF fruits and vegetables, don’t forget to ask the supplier for the dehydration levels in the freezer, because dehydration means product loss and product loss simply means money evaporating from your pocket.

www.freshfruitportal.com

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