Hostname: page-component-7479d7b7d-qlrfm Total loading time: 0 Render date: 2024-07-15T03:52:01.212Z Has data issue: false hasContentIssue false
  • English
  • Français

Laboratory simulations of a commercial UHT treatment using an oil bath and a programmable, electronically temperature-controlled oven

Published online by Cambridge University Press:  01 June 2009

Robyn E. O'Connor  and
Colin O'Connor
Robyn E. O'Connor
Affiliation:
Queensland Food Research Laboratories, Department of Primary Industries, Hamilton, Queensland 4007, Australia
Colin O'Connor
Affiliation:
Department of Civil Engineering, University of Queensland, St Lucia, Queensland 4067, Australia
Get access Rights & Permissions [Opens in a new window]

Summary

Heat stability of secreted bacterial proteinase is normally assessed using an oil bath test in which the sample is heated at a temperature and time representing the commercial UHT treatment of milk. The temperature/time (T/t) profiles of the oil bath and the commercial UHT process being represented are not taken into account. Two laboratory procedures were used to simulate a commercial UHT process in which milk was heated to 140°C and held for 3 s in a Spiroflo heat exchanger. They consisted of a conventional oil bath test and the use of a programmable, electronically temperature-controlled oven. T/t profiles were established for each heat treatment. The T/t profile of the oil bath test was predicted accurately using the governing heat transfer equation. B* and C* values, which measure the severity of a heat process, were calculated from the T/t profiles and used to compare the three different heat treatments. B* and C* values of 4·95 and 1·92 respectively were calculated for the Spiroflo heat exchanger. An oil bath test, in which the sample was immersed in a bath at 136°C for 73 s, gave approximately the same B* and C* values as calculated for the Spiroflo heat exchanger. B* and C* values of 5·01 and 1·73 respectively were calculated for the oven procedure. The oven test gave the better laboratory simulation of the Spiroflo UHT treatment. Despite the slight difference in each of the B* and C* values between the oven and the Spiroflo, the T/t profile of the oven test closely resembled that of the Spiroflo. The T/t profile of the oil bath was completely dissimilar. Although it was possible to use an oil bath test to replicate simultaneously both the B* and C* values of this particular UHT treatment, this would not be the case for other commercial processes.

Type
Original Articles
Information
Journal of Dairy Research , Volume 56 , Issue 4 , August 1989 , pp. 593 - 602
Copyright
Copyright © Proprietors of Journal of Dairy Research 1989

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Alichanidis, E. & Andrews, A. T. 1977 Some properties of the extracellular protease produced by the Psychrotrophic bacterium Pseudomonas fluorescens strain AR-11. Biochimica et Biophysica Acta 485 424–433CrossRefGoogle Scholar
Barach, J. T., Adams, D. M. & Speck, M. L. 1976 Stabilization of a psychrotrophic Pseudomonas protease by calcium against thermal inactivation in milk at ultrahigh temperature. Applied and Environmental Microbiology 31 875–879CrossRefGoogle ScholarPubMed
Chism, G. W., Huang, A. E. & Marshall, J. A. 1979 Sensitive assay for proteases in sterile milk. Journal of Dairy Science 62 1798–1800CrossRefGoogle Scholar
Cliffe, A. J. & Law, B. A. 1982 A new method for the detection of microbial proteolytic enzymes in milk. Journal of Dairy Research 49 209–219CrossRefGoogle Scholar
Diermayr, P., Kroll, S. & Klostermeyer, H. 1987 Mechanisms of heat inactivation of a proteinase from Pseudomonas fluorescens biotype I. Journal of Dairy Research 54 51–60CrossRefGoogle ScholarPubMed
Fairbairn, D. J. & Law, B. A. 1986 Proteinases of psychrotrophic bacteria: their production, properties. effects and control. Journal of Dairy Research 53 139–177CrossRefGoogle ScholarPubMed
Griffiths, M. W. & Phillips, J. D. 1984 Effect of aeration on extracellular enzyme synthesis by psychrotrophs growing in milk during refrigerated storage. Journal of food Protection 47 697–702CrossRefGoogle ScholarPubMed
Griffiths, M. W., Phillips, J. D. & Muir, D. D. 1981 Thermostability of proteases and lipases from a number of species of psychrotrophic bacteria of dairy origin. Journal of Applied Bacteriology 50 289–303CrossRefGoogle ScholarPubMed
Jenness, R. & Koops, J. 1962 Preparation and properties of a salt solution which simulates milk ultrafiltrate. Netherlands Milk and Dairy Journal 16 153–164Google Scholar
Kessler, H. G. 1981 Pasteurization – sterilization heating methods, Food Engineering and Dairy Technology. pp. 139–207. Freising: Verlag A. KesslerGoogle Scholar
Law, B. A., Andrews, A. T. & Sharpe, M. E. 1977 Gelation of ultra-high-temperature-sterilized milk by proteases from a strain of Pseudomonas fluorescens isolated from raw milk. Journal of Dairy Research 44 145–148CrossRefGoogle Scholar
Mitchell, G. E. 1984 Proteolysis in milk by extra-cellular enzymes from psychrotrophic bacteria. M.App.Sc. Thesis, Queensland Institute of TechnologyGoogle Scholar
Mitchell, G. E. & Ewings, K. N. 1985 Quantification of bacterial proteolysis causing gelation in UHT-treated milk. New Zealand Journal of Dairy Science and Technology 20 65–76Google Scholar
Mitchell, G. E., Ewings, K. N. & Bartley, J. P. 1986 Physicochemical properties of proteinases from selected psychrotrophic bacteria. Journal of Dairy Research 53 97–115CrossRefGoogle ScholarPubMed
O'Connor, R. E. 1986 Studies on proteolytic psychrotrophic bacteria from raw milk and their role in the gelation of UHT milk. M.Sc. Thesis, University of QueenslandGoogle Scholar
Richardson, B. C. 1981 The purification and characterization of a heat stable protease from Pseudomonas fluorescens B52. New Zealand Journal of Dairy Science and Technology 16 195–207Google Scholar
Richardson, B. C. & Newstead, D. F. 1979 Effect of heat stable proteases on the storage life of UHT milk. New Zealand Journal of Dairy Science and Technology 14 273–279Google Scholar
Snoeren, T. H. M. & Both, P. 1981 Proteolysis during the storage of UHT-sterilized whole milk. 2. Experiments with milk heated by the indirect system for 4 s at 142°C. Netherlands Milk and Dairy Journal 35 113–119Google Scholar
Stepaniak, L., Birkeland, S. E., Sørhaug, T. & Vagias, G. 1987 Isolation and partial characterization of heat stable proteinase, lipase and phospholipase C from Pseudomonas fluorescens PI. Milchwissenschaft 42 75–79Google Scholar
Stepaniak, L. & Fox, P. F. 1985 Isolation and characterization of heat stable proteinases from Pseudomonas isolate AFT 21. Journal of Dairy Research 52 77–89CrossRefGoogle ScholarPubMed
Stepaniak, L., Fox, P. F. & Daly, C. 1982 Isolation and general characterization of a heat-stable proteinase from Pseudomonas fluorescens AFT 36. Biochimica et Biophysica Acta 717 376–383CrossRefGoogle ScholarPubMed