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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Assessment of uhht protein nitrogen index as an indicator of heat treatment for UHT milk and milk powder. An alternative measure is the undenatured whey protein index WPNIwhich is commonly used to indicate the severity of the pre-heating process in the manufacture of confinuous milk powder [ 97 ].
The native milk plasmin will not be inactivated under these heating conditions and, although it has low activity at low temperature, it is not inactive [ ].
Brody [ 93 ] cites defect rates for ESL product packaged in ultra-clean and aseptic fillers as 1 in and 1 in 10, respectively. As well as being potentially pathogenic, B. As discussed in Section 3. However, Stewart [ 47 ] and Bartoszewiez et al.
Optimum Thermal Processing for Extended Shelf-Life (ESL) Milk
These systems are described in ;asteurization publications, e. Strategies to control the outgrowth of spores of psychrotrophic Bacillus spp.
However, the reports are inconsistent. Diarrhoeal enterotoxin production by psychrotrophic Bacillus cereus present in reconstituted milk-based infant formulae MIF Lett. See details for additional description. The temperature of storage of the ESL milk has a major effect on its shelf-life. This indicates the importance of biofilms on equipment in the contamination of milk by B. This new book updates and expan ds Harold Burton’s classic book, UHT Processing of Milk and Milk Produ cts, to provide comprehensive, state-of-the-art coverage of thermal pr ocessing of sterilizatioh and particulate foods.
These higher-temperature treatments with very short holding times are still pasteurizatioh treatments in terms of their sporicidal effects, i.
Several authors have reported the effects of different ESL temperature—time combinations on tbermal shelf-life of the product. It is also instructive to indicate the position on Figure 1 for the temperature—time line of inactivation 9-log of spores of mesophilic spore-formers.
Bacterial ecology of high-temperature, short-time pasteurized milk processed in the United States. Spores in milk-problems associated with UHT processing. Table 1 Theoretical bactericidal and chemical effects 1 of possible temperature—time combinations for producing ESL milk. Dufeu and Leesement [ 65 ] reported the average generation times for the four strains to be 1. Continuous Thermal Processing of Foods: University of Pretoria; Pretoria, South Africa: Aseptic and extended-shelf-life packaging.
It has been shown that a germinant or germination factor is produced in milk by heat treatment [ 34theraml ]. Indirect heating involves the use of plate or tubular heat exchangers for all heating and cooling stages. To get the free app, enter mobile phone number. Thus more cooked flavor is produced in indirect systems than in direct systems for the same bacterial, including spore, inactivation.
Optimum Thermal Processing for Extended Shelf-Life (ESL) Milk
The latter is also the target for UHT milk [ 4 ] p. This condition applies to the holding tube only and hence, for ESL milk, closely reflects the heat input in a direct heating system but considerably underestimates passteurization heat input of interest in an indirect heating system.
Published online Nov Rowan and Anderson [ 60 ] reported that of 38 psychrotrophic B. Other stegilization in this series. It has been found in silage and feed concentrates and can enter the milk from these sources. Spoilage of microfiltered and pasteurized extended shelf life milk is mainly induced by psychrotolerant spore-forming bacteria that often originate from recontamination.
Continuous Thermal Processing of Foods: Pasteurization and UHT Sterilization
The germination medium as well as the temperature is significant. Published graphs should therefore be used as a guide to temperature—time combinations to use in processing but should not be assumed to apply to all strains of B.
It is therefore apparent that very long refrigerated shelf-lives can be achieved with aseptic packaging sterilizayion, provided the heat treatment is sufficient to inactivate the spores of proceseing psychrotrophic pathogenic spore-formers, such as B.
Similarly, Pfeifer and Kessler [ 81 ] reported increased 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. Pasteurization and Uht Sterilization by Michael J. It has a wide range of growth temperatures amongst its strains; most strains are mesophilic but some are psychrotrophic, which means they can grow in ESL milk during refrigerated storage.
Sterilization of milk and other products. This contrasts with the situation in pasteurized milk, where Gram-negative psyschrotrophs, principally Pseudomonads, are generally the most prevalent [ 89 ]. This approximately agrees with van Asselt and Zweitering [ 77 ]: This is similar cntinuous findings for contaminants in pasteurized milk [ 9192 ] and suggests the need for processor-specific remedial action to reduce bacterial contamination in market milk.
Food Engineering Pedro Fito. Lactulose, which is not present in raw milk, is formed from lactose during heating and is arguably the best chemical index of heat treatment [ 4 ] pp.
Analysis of whey protein denaturation: High spore numbers are found in very dry dusty conditions, wet and muddy conditions, and in the environs of housed animals, particularly when cows are fed silage. Effect of pasturing on the incidence of Bacillus cereus spores in raw milk.
The reported bacterial contaminants in thermally-produced ESL milk packed under very clean, but non-aseptic, conditions are mostly Gram-positive. Support Center Support Center.