Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
Cold stabilisation by batch and stabulation is the oldest technique. It consists of bringing the
wine to a temperature below zero close to freezing point and then stabulating it in an isothermal
tank for a period of five to eight days.
Freezing point (ºC) = -
(alcohol (% v/v)/2) + 1
In continuous cold stabilisation, the stabulation tank is replaced by a cylindro-conical
crystalliser and an agitator, in which the wine will remain for only 30 to 90 minutes.
Cold stabilisation is carried out by crystal seeding, consisting of refrigerating at
between -1 and -2 ºC, and seeding at 4 g/l of tartaric crystals with agitation over 2 to 4 hours,
and later storage in tanks, followed by decantation after 12 to 48 hours.
2.1.7.2 Freezing (G.2)
2.1.7.2.1 Objective
Freezing is a preservation method. In freezing, the temperature of a food is reduced to below the
freezing point and a proportion of the water undergoes a change in state to form ice crystals.
The sector standard for freezing food is to reduce the temperature to around -18 ºC.
2.1.7.2.2 Field of application
Several types of food can be frozen, e.g. fruits, vegetables, fish, meat, baked goods and prepared
foods such as ice-cream and pizzas.
2.1.7.2.3 Description of techniques, methods and equipment
During freezing, the heat is first removed to lower the temperature of the food to the freezing
point. This includes removal of heat produced by respiration as in fresh foods. The latent heat of
crystallisation is then removed and ice crystals are formed. Table 2.4 shows the typical freezing
points of various FDM products.
FDM product Freezing point
Meat, poultry, and fish -0.6 to -2.0 ºC
Vegetables, e.g. peas, cauliflowers, onions, carrots and tomatoes -0.9 to -1.4 ºC
Fruits, e.g. pears, plums and apricots -1.8 to -2.5 °C
Berry fruits, e.g. strawberries and raspberries -0.8 to -1.2 °C
Milk -0.5 °C
Ice-cream -4.0 to -6.0 °C
Table 2.4: Typical freezing points of various FDM products
[37, Environment Agency of England and Wales, 2000]
A whole range of methods and equipment for freezing foods is available. The most common
freezers used are blast, belt, fluidised bed, cooled surface, immersion and cryogenic freezers.
Cryo-extraction and concentration by cold are also used.
In blast freezers, cold air at -30 to -40 ºC is circulated over the food at a velocity of 1.5 to 6 m/s.
In batch blast freezers, the food is stacked on trays in rooms or cabinets. In continuous
equipment, trays covered with food are stacked on trolleys or the food is moved through a
freezing tunnel by conveyor belts. Sometimes multiphase tunnels are applied with a number of
belts. The product falls from one belt onto another, this also breaks up clumps of frozen food.
The thickness of the food layer on the belts can vary from 25 to 125 mm. In blast freezers, large
volumes of air are recycled, however, this can cause freezer burn and oxidative changes to
unpackaged food. Moisture from the food is transferred, via the air, to the refrigeration coils,
which makes frequent defrosting necessary. Impingement freezing and cooling with air
velocities of up to 45 m/s and down to -50 ºC is also applied.
46 January 2006 RHC/EIPPCB/FDM_BREF_FINAL