Principle and regulations
The deep freezing of pre-cooked meals is done so that their temperature does not stay for more than 4h30 long between a value range of +65°C and -18°C.
The deep freezing is a fast freezing which avoids product's degradation due to macro-crystallization : water inside the product cells forming in big crystals after their enveloppe burst.
Macro cristallization effects
Macro cristallization phenomenon
Meat blast chilling / slow chilling microscopic views : 27 X magnification
Raw hamburgers frozen at – 18°C
To understand the interest of blast chilling, it is necessary to view the product at the cellular scale.
Microscopic views above allow to notice the impact of slow chilling (right picture) on product cells. The cells envelope is for the most part torned causing a conglomeration of free liquid. This effect is called macro cristallization because of the cristal sizes induced by a slow chilling. On the contrary, a freezing (blast chilling) allows to the cells envelop and the product (left picture).
Rapid descent to deep freezing
Deep freezing effects are particularely visible after the product's thawing : Above pictures of thawed shrimps, on the left deep freezed sample, on the right slow freezed sample.
After thawing, the deep freezed shrimps have preserved their volume and rejected a few quantity of water, on the contrary, the slow freezed shrimps have lost their original volume and a large quantity of water. To be noticed : a slow freezing leads to organoleptic degradation, taste denaturalization and stifness of the product.