Introduction: Retorts, batch kettles, and aseptic processes are a few thermal techniques used within industrial food production. Overall, aseptic processing is a superior method for fluid systems[1]. Aseptic processing offers shorter processing times, higher production rates, and better product quality[1-3]. Within aseptic processing, there are several different forms of heat transfer, including direct, indirect, ohmic, and microwave heat exchange[4]. Microwave thermal technology offers more consistent temperature profiles across fluid systems because of dielectric properties of a fluid[5-11]. Through testing of model fluids, temperature profiles were recorded at different velocities to compare the effects of dielectric properties[5-7]. …show more content…
When thermally processed, fluids exhibit irreversible changes like loss of texture, color, and nutrients in order to reach a desired level of sterility[1]. Added benefits of aseptic processing are shorter processing times, improved product quality, higher production rates, and reduced power requirements[1-3]. There are currently three main forms of heat exchange used in industry, which include direct, indirect, and ohmic[4]. Direct and indirect heat exchanges have added benefit of lower costs and versatility across different fluid systems[4]. Other advantages include: processing of viscous fluids, temperature control, rapid heating, and minimization of fouling[4]. Larger energy input is required because these systems heat through conduction and convection and can cause overheating of fluid products[5]. Microwave technology provides more consistent heating throughout the cross section of a fluid and therefore reduces overheating of …show more content…
When a high frequency field is applied to an aseptic system, the fluid system is heated by vibrating the chemical bonds within a food product[13,14]. There are two different properties in dielectrics that affect thermal processes: dielectric constant and dielectric loss factor. The dielectric constant is the ability of a material to store electromagnetic energy and dielectric loss factor is a measure of how well a material can convert electromagnetic energy to heat[5-11]. Figure 2 shows how electromagnetic fields are applied across a cross section of a pipe due to the dielectric properties associated with the fluid[7]. Fluids with higher dielectric properties exhibit more consistent cross sectional profiles as shown in Figure 2[7]. In food processing, process equipment must be sterilized before product can be processed. To prevent under heating or overheating, sterilization solutions must have similar dielectric properties to that of the final products of a production line[6]. Figure 3 shows temperature profiles as a microwave system switches from sterilization solution to sweet potato puree product at three different positions in the pipe[6]. The fairly uniform line shown in Figure 3 correlates to an even temperature profile along the cross section during the switch to
The MCE is typically in the range of (1-5) k/T (in terms of the adiabatic temperature change). This modest change in temperature is obviously not sufficient for applications such as domestic refrigeration etc. [24].
An Investigation Into How the Thickness of Insulation Affects the Time a Drink Takes to Cool Down
Acrylamide is not a concern when food is boiled, microwaved, or steamed. The food and drug admini...
The thermometer, containers, and iron ball were secured of any possible contaminants. The stopwatch was calibrated and checked to be correctly measuring the time in seconds and milliseconds, by comparison with other stopwatches. The thermometer was checked to be accurately measuring the temperature of lukewarm water, and was al...
The thermometer’s original temperature before coming in contact with an outside object is represented by T. ∆T/∆t is the average temperature of the digital thermometer. represents the temperature of the heat flowing object. In this lab, the temperature of the air is represented by Tair=T. To= Thand is the temperature of the hand.
Studies have shown that big changes in temperature do not affect the capability of insulation. In one experiment, materials were set to a high heat of 300 degrees Celsius. After six months in this environment, the substances were cooled to room temperature. The dielectric constant showing the level of insulation had not changed ("Teflon PTFE fluoropolymer resin" 28).
For this experiment, you will need 3 - ceramic bar magnets numbered 1 – 3 for identification purposes, 48 - 5/16” steel flat washers, tongs, goggles, gloves, stove, pot with boiling water, freezer, cooking thermometer, and freezer thermometer. Place the three magnets in the freezer overnight so that they reach a freezing temperature of between 0° - 32°. A freezer thermometer was used to verify temperature. After the magnets have reached the desired temperature, then place two even stacks of steel washers next to each other on a flat surface. Using one fro...
on how long it takes to heat up. If we heat a large volume of water it
Nano-thermal analysis methods are also known as micro-thermal procedures and they use the principle of characterizing highly localized materials on a micrometer. The characterization is then changed from a micrometer scale to a sub-micrometer scale with the temperature being regulated to the specified units. The application of nano-thermal analysis methods started towards the end of the 20th century. Although it has been applied in several other fields including microelectronics, its application in pharmaceuticals has not been that popular.
Methodology: A plastic cup was filled half way with crushed ice and mixed with four spoonfuls of 5 mL of sodium chloride. A thermometer was quickly placed inside the cup to take the temperature and the
A warm water was prepared by heating approximately 100mL of distilled water in a 400mL beaker along with few boiling chips to 45-50 ℃.
Pasteurization is a process that kills microbes mainly bacteria in food and drink such as milk, juice and others. Louis Pasteur was the first to discover inactivation of microorganisms by heating for the prevention of spoilage of wine in 1860 (Pescott et al., 1990). The purpose of pasteurization is not to sterilize a substance but to eliminate the disease causing pathogens. In food industry, particularly in dairy farming, many heating processes are present among the different types of fluids. Processes like sterilization, chilling of milk and pasteurization are strictly required to be cheap.
2007). Dielectric properties values for fresh chicken breast meat in the 10 to 1800-MHz frequency range at temperatures from 5°C to 65°C are shown in Figure 15. These curves show frequency dependence of the dielectric properties similar to those for tissues of fruits and vegetables. Probable potential for using dielectric properties to assess meat quality characteristics was indicated. Dielectric spectroscopy measurements were also taken on the albumen and yolk of fresh chicken eggs at weekly intervals during 5 weeks of storage (Guo et al. 2007b). Dielectric properties from 10–1800 MHz for the fresh eggs are shown in Figure 16, where the albumen has higher values for both the dielectric constant and loss factor than the yolk at any given frequency. Dielectric properties changed during the storage period, but they did not correlate well with traditional quality factors for the
- Temperature was measured after and exact time i.e. 1 minute, 2 minutes, 3 minutes.
The demand for easy to prepare and convenience of food create major scientific and technological challenges that cannot be fulfilled without experts scientific capable of understanding complex chemistry or biochemistry of food system and knowledge about method to preserved food which increases dependability of society towards ready-to-eat has led the greater responsibility for processors in terms of quality, safety and nutrition (McGill, 2011).