The Thermo-Egg: A Combined Novel Engineering and Reverse Logic Approach for Determining Temperatures at High Pressure

Abstract

High-pressure thermal (HPT) processing is a novel form of thermal processing targeted at achieving commercial sterilisation of foods. During HPT processing, the final heating is generated volumetrically within the food as a result of rapid compression to pressures usually at or above 600 MPa. While the pressure within the process vessel is uniformly distributed, non-uniform temperature distributions can develop as a result of differences in the temperatures of vessel components and incoming fluids, and compression heating properties of the materials involved in the process. Therefore, a reliable system for recording temperature profiles in different locations of the high-pressure vessel is needed to determine process performance. In this work, a purpose-designed pressureresistant shell was engineered to protect a miniature temperature logger. The impact of the shell's thermal mass was analysed, and a numerical software routine developed, accounting for the delay in temperature readings. The reverse logic software algorithm was able to predict temperatures outside the shell with high accuracy from the temperatures measured by the logger inside the shell. This system is expected to contribute to the development and commercialisation of HPT processing by providing the reliable temperature measurement data required for thermal process validation.

The Application of High-Hydrostatic-Pressure Processing to Improve the Quality of Baked Products: A Review

“…Although it is considered a non-thermal treatment, adiabatic heating must be taken into account [ 38 ], which is approximately 3 °C per 100 MPa for water [ 39 ]. In addition, combined pressure and temperature treatments can be carried out using temperature control devices and insulated vessels [ 40 , 41 , 42 ].…”

Apparatus for the simultaneous processing of mesophilic spores by heat-only and by high pressure and heat in a high pressure vessel to investigate synergistic spore inactivation

“…1a) and a Thermochron iButton® DS1922T temperature logger (Maxim Integrated Products, Inc., Sunnyvale, CA, USA) placed in the sample space of the closed container. Delays in readings recorded by the logger were accounted for as reported previously by Knoerzer et al (2010). The paired sample containers were sealed in a retort pouch filled with 200 mL tap water (to reduce temperature loss during processing caused by convective heat transfer) and pre-heated to 80 or 85°C over 25 min in an external water bath.…”

“…Replicating the thermal profile delivered during a HPT process where compression rate is not near-instantaneous, nor which is isothermal or strictly isobaric during hold-time, as will be the case in a commercial setting, requires a different approach. Following on from previous development of a purpose-designed pressure-resistant shell engineered to protect a miniature temperature logger during HPT processing (Knoerzer et al, 2010), we sought to develop paired sample containers that would permit simultaneous processing of two samples in the same HPT vessel, one with pressure (HPT) and one without (heat-only), but both 'experiencing' the same thermal profile. Being inherently thermally equivalent both in lethality (F Z T ) and with respect to profile shape, this system would provide a means of direct comparison of inactivation as affected by pressure.…”