Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 2
2.1.5.8.3 Description of techniques, methods and equipment
Pasteurisation temperatures commonly range from 62 to 90 °C, and pasteurisation times vary
from seconds to minutes. Batch wise pasteurisation uses a temperature of 62 to 65 °C for up to
30 minutes. High temperature short time (HTST) pasteurisation uses a temperature
of 72 to 75 °C for 15 to 240 seconds. High heat short time pasteurisation (HHST) applies a
temperature of 85 to 90 ºC for 1 to 25 seconds.
Batch wise pasteurisation is carried out in agitated vessels. Sometimes the product, i.e. beer and
fruit juices, is pasteurised after bottling or canning. Here the products in their containers are
immersed in hot water or fed through a steam tunnel. For continuous pasteurisation, flowthrough
heat-exchangers, e.g. tubular, plate and frame, are applied. These have heating, holding
and cooling sections. Table 2.2 shows examples of heat treatment combinations used in the
FDM sector.
Process Heating temperature/
holding time
Use
Bulk liquid pasteurisation 63 °C/30 min Vat pasteurisation of milk
High temperature short time 72 °C/15 s Continuous pasteurisation of
pasteurisation (HTST)
milk for food safety
Cooking of meat products 65 to 75 °C internal Ready-to-eat products, e.g. ham,
temperature
meat loaves and frankfurters
Blanching of vegetables Variable, e.g. 75 °C/5 min Enzyme deactivation and tissue
softening
In-bottle pasteurisation 60 °C/10 min* Shelf-life extension of beer
*the parameter may vary depending on the type of beer
Table 2.2: Examples of heat treatment combinations used in the FDM sector
[1, CIAA, 2002]
Generally for sterilisation, the product is canned or bottled and then heat-treated in a steriliser
with steam or hot water. Sterilisers may be batch or continuous. In sterilisation with moist heat,
temperatures generally range from 110 to 130 ºC with sterilisation times being
from 20 to 40 minutes. For example, canned foods are sterilised in an autoclave at about 121 ºC
for 20 min. Higher temperatures and shorter times may have similar effects, e.g. 134 ºC
for 3 min. However, if conditions do not allow the germination of spores, lower temperatures
and shorter times can also be applied. For example, with acid fruit juices, jam, or desserts,
heating up to 80 to 100 ºC for 10 minutes is normally sufficient.
For killing bacterial endospores by dry heat, longer exposure times and higher temperatures are
required than with moist heat, e.g. up to 2 hours at 160 to 180 ºC. Solutions containing
thermolabile compounds can be sterilised by filtration through mediums such as nitrocellulose
membranes, diatomaceous earth, e.g. kieselguhr, and porcelain. UV irradiation is used to keep
rooms partially sterile. Bacteria and their spores are killed quickly, but fungal spores are only
moderately sensitive to radiation. Ionising radiation, e.g. X-ray and gamma radiation, is used to
sterilise food and other compact materials. Chemical means may also be applied. Ethylene oxide
is used to sterilise food, plastics, glassware, and other equipment [87, Ullmann, 2001].
UHT treatment means a very short heat treatment at temperatures of 135 to 150 ºC for only a
few seconds. This results in a sterilised product with minimal heat damage to the product
properties. UHT treatment is only possible in flow-through equipment. The product is thus
sterilised before it is transferred to pre-sterilised containers in a sterile atmosphere. This requires
aseptic processing. For UHT treatment, indirect heating in plate and frame or tubular heatexchangers
is applied. Direct steam injection or steam infusion may also be applied.
40 January 2006 RHC/EIPPCB/FDM_BREF_FINAL