Radio frequency (RF) heating of food

Radio Frequency (RF) heating offers the possibility of fast heating in solid and semi-solid foods and can overcome the limits of uneven and slow heating inherent in conventional retorting. The objective of this study was to gain a better understanding of the dielectric heating process, to predict heating patterns within the heated region, to develop new product formulations and appropriate processes for treating food products.; In order to implement the study, a lot of literature relevant to dielectric heating (RF and microwave heating) such as fundamentals, computer simulations, dielectric properties and applications of RF heating are reviewed. Based on the pre-study and research, systems and equipment needed in this project were designed, manufactured and modified. Dielectric properties of heated objects are the principal parameters that determine the coupling and distribution of electromagnetic energy during dielectric heating. The dielectric properties of foods are often temperature dependent, and therefore, must be known over the full range of temperatures experienced by the product in thermal processes to allow prediction of heating behavior. With the dielectric measurement system, study of dielectric constants, loss factors, and penetration depths of several foods over a temperature range from 20 to 121.1°C at frequencies of 27, 40, 915, and 1800 MHz was conducted. In dielectric heating, the cold spot is different from that of conventional heating. Limited points of temperature measurement in dielectric heating may not be adequate in evaluating the temperature distribution within the packaged foods. The intrinsic chemical marker method can be used as a non-invasive technique to map heating uniformity within food. Based on the measurements of dielectric properties and kinetics of chemical marker M-1 formation, a study was conducted using a pilot-scale 27 MHz RF sterilization system to investigate the effectiveness of the new process concept in shortening process time and in improving product quality for foods hermetically sealed in 6-lb military group-ration polymeric trays.; The results of this study show that compared with the conventional retort method, the RF process produced better products using shorter time and less energy. RF heating is likely a better means of producing higher quality, shelf stable foods.