Food quality models: Ice cream under the microscope and ice crystal growth in the cold chain

Ice cream is a product whose quality is highly correlated to the storage temperature and temperature fluctuations.
There are limited data in the literature (see Figure 2) concerning modelling of the effect of temperature on texture, viscosity and ice recrystallization.
The National Technical University of Athens (NTUA), within the framework of the FRISBEE project, will conduct experiments in order to investigate the effect of static and dynamic storage temperature conditions (fluctuations
of temperature are a significant factor to be studied). Texture, viscosity and ice recrystallization will be studied using appropriate equipment and methodology.
The data obtained will be evaluated and modelled vs time and storage temperature. Equations will be developed to describe the effect of storage conditions on texture and viscosity parameters.
For the corresponding description of ice recrystallization, existing published equations will be used.
The validation of these models (concerning ice recrystallization) is of great significance since these equations have been assumed by simulating the cold chain of the ice cream. Real cold chain scenarios from collected data on the cold chain will be used.

Figure 2. Crystal growth as a function of temperature and amplitude. Source: Ben-Yoseph E. & Hartel R. W. (1998)

Air cycle refrigeration modelling: the potential in food cold chain applications

The refrigeration team at LSBU has extensive experience with air cycle refrigeration and heat-pump systems and this is now benefiting the FRISBEE project. A mathematical model of an air cycle system for combined heating and cooling has been developed and validated with previous experimental data.
It is now being used to assess the potential of this technology in food cold chain applications, and the team will go on to source and cost suitable components for the most promising applications.
Air cycle refrigeration can offer an environmental alternative to existing refrigeration systems in use in the food cold chain.
Air cycle is already used for certain niche applications like aircraft and train air conditioning (e.g. Figure 1), where it offers considerable benefits. In the food industry, air cycle compares most favourably with existing low-temperature refrigeration systems, especially where there is a need for heating
which can be served by the hightemperature heat rejected from the air cycle system.
Air cycle can also offer the potential for processing at far lower temperatures than those normally produced
by conventional vapour compression refrigeration systems, where the competition is currently limited to expensive and energy intensive total loss refrigerants such as liquid nitrogen.


Figure 1. Air cycle train air conditioning unit (Honeywell, UK)

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