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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
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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

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References

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