Pasteurization in bread , biscuits and cakes
PASTEURIZATION IN BAKERIES
Traditional pasteurisation methods use hot air circulation, dripping hot water or direct steam injection into the treatment cabinet or tunnel for heating the packaged food. The temperature rise of the product is slow and non-uniform due to poor thermal conductivity of the packaging material, of the air or modified atmosphere contained in the package and within the food substrate itself. In order to reach a given temperature level in the coldest spot of the product a proportionally long heating time is required, affecting in particular the outside layers of food that are more exposed to heat. Consequently, the product looses its quality in terms of sensorial (colour, flavour, texture, etc.) and nutritional characteristics.
The drawbacks of conventional pasteurisation methods can be avoided thanks to the ability of radio frequency to rapidly generate heat volumetrically within the product. The heating process is fast, uniform and controlled, therefore product deterioration is minimised. When the RF generator applies high frequency alternating voltage between the capacitor plates, the dipolar water molecules of the product will vibrate and rotate attempting to align themselves according to the fast changing opposite plate polarity. This phenomenon causes intermolecular friction, which will in turn generate heat rapidly and uniformly within the whole product mass regardless of its size, weight, shape and thermal conductivity.
Microwave pasteurization is a gentle heat treatment usually at temperatures between 60 and 82 ºC, which has been applied to several foods, including bread. The main advantage of microwaves sterilization or pasteurization is the effective reduction in the time required for the heat to penetrate to the food centre
When using Infrared (IR) radiation, with a short penetration depth, almost all energy is converted to heat at the surface of the food. IR radiation does not destroy microorganisms directly, but by increasing the surface temperature microorganisms are destroyed by conventional thermal mechanisms. In most solid foods internal heat conduction is poor and IR can therefore be used to increase the surface temperature enough for desirable microorganism reduction without causing substantial increase in interior temperature. A holding time may be applied to ensure sufficient microbial reduction. IR treated products can be directly fed to a packaging machine. Products may also be surface pasteurised after packaging
It is used in all Information about bread, biscuits & cakes production
Typical parameters of the process
Source:Bayerisches Landesamt für Umweltschutz - Minderung öko- und klimaschädigender Abgase aus industriellen Anlagen durch rationelle Energienutzung - Großbäckerei (2000)