Evaluation of mild thermal processes for food pasteurisation

Hansriwijit, Suwijak (2019). Evaluation of mild thermal processes for food pasteurisation. University of Birmingham. M.Phil.

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Abstract

The objectives of this research were to evaluate the heat transfer behaviour of in-container pasteurisation using heated water, which was chosen as a first approach to the study of the heating dynamics of spray pasteurisation systems.

A series of experiments were designed to test the response of vessels using a variety of experimental setups. Thermocouples were placed in specified positions inside glass jars, filled with one of a variety of fluids, ranging from water to highly viscous CMC. Enzymic Time-Temperature Indicators were also tested. Two types of heating medium were used; a heated water bath and one of a series of spray heads. It is important that the spray is correctly designed to avoid wasting time and cost by using the correct flow rate. Otherwise poorly optimised processing will have excessive pumping and heating costs. The results demonstrated that heat transfer was primarily controlled by the internal behaviour of the system. Heat transfer is slowest within the packs, i.e. either convection (in low-viscosity systems) or conduction (for high viscosity products) is the controlling thermal process. The greatest effect on the overall heating rate was given by the viscosity of the system. However, external flow or temperature had some effect; heating in the water bath was in all cases faster than heating from the range of sprays used. The type and distribution of spray used had an effect, both in the rate of heating and the final temperature. Pasteurisation values (‘P-values’) for processes were calculated from the thermal data and used to identify the best process conditions. Suggestions for process operation and further work are made.

The results of this study will help in the understanding of pasteurisation processes exhibiting internally controlled heating dynamics, and they will be also valuable in the process of characterisation of the shower spray pasteurisation operations.

Type of Work:

Thesis (Masters by Research > M.Phil.)

Award Type:

Masters by Research > M.Phil.

Supervisor(s):