Freezing is an essential pre-treatment method
to achieve a crispy fruit chips texture in vacuum-frying processing.
After freezing, the moisture inside the
raw material cells will become ice crystal, and then cell structure become harder.
When the frozen raw material is fried the vacuum condition, the ice crystal could
be sublimed to gas directly and removed from the cells rapidly, the texture will be expanded and the chips taste crispy. In this
progress, freezing speed influence the frozen effect of raw material, like cell
structure. The moisture will become some big ice crystal in the slow freezing
condition, then destroy the cells. The oil will penetrate into the fruit and
vegetable chips. This is also one cause of high oil content in some clients’
vacuum fried chips.
Practice has proven that IQF in the -30℃ ~ -38℃ is the best processing method
to maximum the frozen effect. For big scale production, the raw material should
be storage in the refrigeration house(-18℃). You can finish
the vacuum frying program in a period of concentration.
In a word, rapid freezing, rapid
heating, rapid heat exchange, rapid removing, rapid condensation and rapid de-oiling…
you must get higher quality vacuum fried chips.