REV
. 012018
5
1 Blast chilling and blast freezing
When products are kept at the correct temperatures and when they are cooked, chilled and frozen correctly, most of the
vegetative bacteria of raw materials can be destroyed and the remaining bacteria prevented from increasing. Depending on
the bacteria themselves their ability to tolerate different temperatures varies. According to their growing temperatures, they
can be classified e.g. as follows:
•
Termophiles +40… +90 °C
•
Mesophiles +10… +50 °C
•
Psykrotrofs 0… +35 °C
In different EU countries the exact limits vary a little as do the blast chilling times. Typically in the national legislation, the
dangerous temperature range is noted as +8… +60 °C. Freezing and cold storage prevent the bacteria from increasing
but do not destroy them.
The definition of freezing is to decrease the product temperature as quickly as possible below -18 °C. Freezing speed is a
critical factor to ensure to maintain the quality of the product. If freezing is too slow, water evaporating from the product
creates extracellular ice crystals which break down the product structure. When defrosting the structure deteriorates more
and a large amount of water exits. (Korhonen, J. 2013).
2 Capacity of blast chilling and blast freezing equipment
Traditionally the capacity of the equipment for blast chilling is advised to be + 70°C … +3°C in 90 minutes in 50mm layer
thickness (DHSS 1989) this however is advisory and not legislation. The EU Commission has published a new EN 17032
standard, within the ecodesign directive, to state the comparable capacity of equipment. The capacity in accordance with
this standard differs considerably from the present practice in professional kitchens. Table 1 illustrates the current guidance
for blast chilling and blast freezing across a selection of European countries:
Country
Start temp.
End temp
Storing temp.
Layer thickness
Time
Blast chilling
England
1
+ 70 °C
0… + 3 °C
0… + 3°C
max. 50 mm
90 min
Finland
2
Production
+ 6 °C
+ 6 °C
240 min
Sweden
3
+ 70°C
+ 8 °C
+ 8 °C
240 min
Germany (DIN)
+ 65 °C
+ 3 °C
90 min
Blast freezing
England
1
+ 70 °C
- 18 °C
Finland
4
Production
- 18 °C
150 min
Germany (DIN)
+ 65 °C
- 18 °C
270 min
Table 1. Blast chilling and blast freezing times and temperatures
1 Department of Health, Chilled and Frozen, 1989.
2 Maa- ja metsätalousministeriön asetus 1367/2011. 2011. Finnish ministry of agriculture and forestry, regulation 1367/2011
3 Sveriges Kommuner och Landsting. 2009. Livsmedelverket. 2016. KONTROLLHANDBOK FÖR STORHUSHÅLL del 2.
4 Eviran ohje 16049/1. 2016. Elintarvikkeiden pakastaminen ja jäädyttäminen elintarvikehuoneistoissa. Finnish Food Safety Authority Evira’s
instruction 16049/1. 2016. Deep-freezing and freezing of foodstuff in foodstuff apartments.
ENGLISH
