Continuous Thermal Processing of Foods – Pasteurization and UHT Sterilization. Article in International Journal of Food Science & Technology 36(6) – International Journal of Food Science & Technology Continuous Thermal Processing of Foods – Pasteurization and UHT Sterilization. Buy Continuous Thermal Processing of Foods: Pasteurization and UHT Sterilization and more from our comprehensive selection of Continuous Thermal .
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Sterilization of milk and other products. In about half of the studies reviewed by Bergere and Cerf [ 74 ], the heat inactivation curves were not linear; two showed shoulders and 10 showed tails. This item doesn’t belong on this page.
Continuous Thermal Processing of Foods: Pasteurization and UHT Sterilization
In a trial with good-quality milk, Blake et al. Heating at high temperatures for short holding times favors high levels of bacterial destruction, while heating at lower temperatures for longer holding times result in high levels of zterilization change. Psychrotrophic strains of B. Reviews “Lewis and Heppell have provided a review of pasteurisation and UHT processes that is well organised and built on a foundation of engineering and thermobacteriological principles.
The microbiological issues can be divided into those related to the bactericidal nature of the heating conditions and those associated with post-processing contamination. Microbiological issues associated with heat-treated milks.
The relative importance of these for the shelf-life of ESL milk depends on whether the milk is packaged aseptically or under very clean, but not aseptic, conditions. In the factory, fouling deposits and stainless steel surfaces to which the spores can readily attach are the main sources [ 4950 ]. When attached to stainless steel, spores show enhanced resistance to cleaning solutions [ 53 ]. The chemical effect of a heat process can be assessed in several ways using the kinetics of various chemical reactions.
There was a close relationship between B. In addition, these isolates produced proteases and hence have spoilage potential. Effect of milk storage before pasteurization on the formation of flocs bitty cream by Bacillus cereus in pasteurized milk. It is recognized, however, that only the undenatured level is measured and the level in the raw milk from which the ESL milk is produced is seldom known.
Acknowledgments The author wishes to thank Mike Lewis for helpful comments during the preparation of this paper. In direct systems, heating occurs through direct contact between steam and the product and in indirect systems the heat is transferred to the product from steam or hot water through a stainless steel barrier in a heat exchanger. Table of contents Introduction.
It had a D -value of 1. The heat resistance of B.
This is further supported by the fact that the contaminating bacteria in ESL milk have been identified to be processor-specific [ 90 ], which is consistent with the above discussion, where B. The above discussion relates to the keeping quality of ESL milk as affected by the bacteria in the raw milk that are not killed by the heat process. Several authors have reported a seasonal effect on the incidence of B. The spore cycle; pp.
Aerobic psychrotrophic spore forming bacteria in heat treated milk. Alternative Direct Heating Systems 2.
Bacillus cereus and other Bacillus species. Indirect heating involves the use of plate or tubular heat exchangers for all heating and cooling stages.
Optimum Thermal Processing for Extended Shelf-Life (ESL) Milk
These fast-germinating spores of B. Such a line was published by Kessler [ ] and reproduced by Chavan et al. The ESL heat treatment can also activate spores to germinate and thus allow their vegetative cells to grow during storage. Heat resistance data, D – and z -values, have been reported for the spores of several B. Their growth in pasteurized and ESL milk is evidence of their growth at low temperature, but Scheldeman et al.
Indirect Heating Indirect heating involves the use of plate or tubular heat exchangers for all heating and cooling stages.