Radio Frequency Heated Research Articles

Effects of adding polystyrene blocks in rectangular containers on radio frequency heating rate and uniformity of watermelon seeds

Non-uniform heating is a main problem for applying radio frequency (RF) treatments to eliminate the seed-borne pathogens in seeds before commercial import/export. In this study, thermal and dielectric properties of watermelon seed coats and embryos with different moisture contents were measured for computer simulation. The simulation model of RF heated watermelon seeds with or without adding a polystyrene block was developed and validated based on experimental results using the commercial COMSOL software. The effect of adding different sizes of polystyrene block on RF heating rate and uniformity of watermelon seeds was also studied by the validated simulation model. The results showed that the difference in heating rate between first and second layers and average temperature of seeds increased from 0.63 to 18.78 °C/min and 40.74 to 58.60 °C with increasing thickness and height of polystyrene block increased from 5 to 30 mm and 4 to 28 mm. The volumetric RF heating uniformity index in seeds decreased with decreasing heating rate difference. Meanwhile, the height of 7.7 mm combined with thickness of 25 mm of the polystyrene block could provide the best RF heating uniformity for watermelon seeds. These findings from the established new methods to improve the heating uniformity could be used to develop an effective RF treatment protocol for controlling the seed-borne pathogens of watermelon seeds without reducing their quality.

Effect of surrounding medium on radio frequency (RF) heating uniformity of corn flour

Radio frequency (RF) heat treatment holds great potential for packaged food powder pasteurization by providing rapid and volumetric heating with a high penetration depth. Edge and corner overheating create high temperature differences throughout the product, which is a major drawback in its industrial applications. In this study, the effect of the surrounding media (air, DI water, and soybean oil), medium level, heating mode, electrode gap, and heating time on the heating uniformity was investigated by determining the thermal distributions, heating uniformity index, and heating rate at the top and middle layers of RF heated corn flour. The thermal images indicated that less edge and corner overheating occurred when corn flour container was immersed in soybean oil. A higher heating rate (7.77 and 9.86 °C/min at the top and middle layers, respectively) and a better heating uniformity (as indicated by lower heating uniformity indices: 0.047 and 0.037 at the top and middle layers, respectively) were obtained for the corn flour heated in soybean oil with an 11 cm electrode gap compared to those heated in air. The study proposed a method for improving the heating uniformity of RF heated food powders which can be easily implemented in industrial applications of RF treatment.

Kinetics of carbon nanotube-loaded epoxy curing: Rheometry, differential scanning calorimetry, and radio frequency heating

The isothermal curing kinetics of carbon nanotube loaded epoxy was investigated using rheometry and differential scanning calorimetry (DSC) at a range of temperatures. Rheo-kinetics was used to observe time-dependent rheological changes in elastic (G′) and viscous (G″) moduli, and complex viscosities of epoxy-CNT samples during isothermal curing. DSC measurements were also performed to monitor the curing reaction, in order to compare against the rheo-kinetic parameters. The Kamal-Sourour kinetic model describes the curing of the epoxy-CNT system for rheo-kinetics and DSC well. The activation energies of the curing reaction were found to be ∼36 kJ/mol and ∼33 kJ/mol using rheo-kinetics analysis and DSC, respectively. In addition, radio-frequency (RF) electromagnetic fields were used to heat and cure the epoxy-CNT sample; such heating techniques are valuable in a number of epoxy processing technologies. G′, G″, and complex viscosities of RF heated samples were measured to monitor RF-aided curing. This allows us to monitor the curing kinetics inside samples being heated by RF fields; the data indicate that RF-aiding curing is faster than curing rates for samples undergoing curing inside a measurement device such as a rheometer or DSC, because the heat generated is immediate and volumetric.

Diffusion Limited Cryopreservation of Tissue with Radiofrequency Heated Metal Forms.

Cryopreserved tissues are increasingly needed in biomedical applications. However, successful cryopreservation is generally only reported for thin tissues (≤1mm). This work presents several innovations to reduce cryoprotectant (CPA) toxicity and improve tissue cryopreservation, including 1) improved tissue warming rates through radiofrequency metal form and field optimization and 2) an experimentally verified predictive model to optimize CPA loading and rewarming to reduce toxicity. CPA loading is studied by microcomputed tomography (µCT) imaging, rewarming by thermal measurements, and modeling, and viability is measured after loading and/or cryopreservation by alamarBlue and histology. Loading conditions for three common CPA cocktails (6, 8.4, and 9.3 m) are designed, and then fast cooling and metal forms rewarming (up to 2000 °C min-1 ) achieve ≥90% viability in cryopreserved 1-2mm arteries with various CPAs. Despite high viability by alamarBlue, histology shows subtle changes after cryopreservation suggesting some degree of cell damage especially in the central portions of thicker arteries up to 2mm. While further studies are needed, these results show careful CPA loading and higher metal forms warming rates can help reduce CPA loading toxicity and improve outcomes from cryopreservation in tissues while also offering new protocols to preserve larger tissues ≥1mm in thickness.

Analysis of taste, cordycepin, phenolic compounds, and water distribution of radio frequency heated Cordyceps militaris combined with electronic tongue and NMR

AbstractRadio frequency (RF) was applied to heat Cordyceps militaris for the purpose of quality evaluation and microorganism control. RF heating caused gradual temperature increases ranging from 59.6 to 63.8°C, resulting in good heating uniformity and uniform temperature distribution. Compared with conventional high pressure steam (HPS), RF heating resulted in significant (p < .05) higher total phenolic, flavonoids, and cordycepin contents of C. militaris. In addition to higher reduction of total aerobic bacteria counts, bitterness taste value increased from 2.35 (unpasteurized) to 4.79 (HPS). Umami value significantly decreased from 13.58 (unpasteurized sample) to 12.13 (HPS treated sample). Nuclear magnetic resonance analysis showed that 20 min of RF significantly reduced the loss of water mobility than HPS. Principal component analysis of taste characteristics indicated distinct differences between RF and HPS treated samples. Hierarchical clustering analysis also revealed higher similarity between RF heated samples and the unpasteurized one.Practical applicationsCordyceps militaris is an edible and medicinal mushroom with high nutritional quality. Results of the present study indicate that radio frequency (RF) contributed to higher umami taste, higher retention of bioactive compounds, and higher water mobility of C. militaris. Therefore, this process can be used to develop a promising alternative to conventional thermal method for the processing of C. militaris. It is highly possible that RF could be applied to healthy food industries.

Evaluation of Enterococcus faecium NRRL B-2354 as a potential surrogate of Salmonella in packaged paprika, white pepper and cumin powder during radio frequency heating

Salmonella contamination of various seasonings and spices has occurred in the last decade. Radio frequency (RF) heating has been shown to be a potential alternative inactivation method for pathogens in low moisture foods (LMF), including spices and vegetable powders. This study aimed to (1) determine the thermal resistance (D and z values) of Salmonella and Enterococcus faecium(E. faecium) NRRL B-2354 as a promising surrogate for thermal validation studies using paprika, white pepper, and cumin powders, and (2) evaluate the efficacy of RF heating on the inactivation of both microorganisms in packaged samples. Samples with initial water activity levels (aw,25°C) of 0.45 ± 0.05 were inoculated with Salmonella cocktail (S. Typhimurium, S. Agona, S. Montevideo, and S. Tennessee) and E. faecium NRRL B-2354 at approximately 8.5 log CFU/g. Inoculated samples were loaded in aluminum test cells and subjected to isothermal treatment in a water bath at 70, 75 and 80 °C. Samples (20 g) were also sealed in small polystyrene petri dishes and subjected to RF heating in a 27.12-MHz, 6-kW pilot scale RF unit with 105 mm electrode gap until the temperature at the geometric center reached 80 °C. The survival of both bacteria was enumerated and converted to log CFU per gram. The change in color of RF heated samples was also evaluated to assess the impact of RF heating on the product quality. Results showed that the thermal resistance of E. faecium at inactivation temperatures is higher than Salmonella in all three spices. Additionally, both microorganisms showed less thermal resistance in paprika than white pepper and cumin powder. The D80°C values of Salmonella and E. faecium were determined to be 1.21 and 1.82 min in paprika, 2.85 and 5.27 min in white pepper, and 4.47 and 9.53 min in cumin powder, respectively. Results also showed that E. faecium is a suitable surrogate for validation of RF pasteurization of Salmonella in spices and RF heating is an effective method to control the contamination of foodborne pathogens in spices.

Computer simulation modelling, evaluation and optimisation of radio frequency (RF) heating uniformity for peanut pasteurisation process

Non-uniform heating caused by uneven electromagnetic field distribution in a material is a major regulatory barrier for applying radio frequency (RF) heating in critical processes, such as pasteurisation of low moisture agricultural products. An earlier finite element model was adopted and validated to predict the temperature distribution in peanut kernels heated in a 6 kW, 27.12 MHz RF laboratory unit using 4.5 kg batches of peanut kernels. A temperature uniformity index (TUI) was used as a measure of the temperature distribution within the RF treated product load. The modelling results were used to demonstrate that the temperature distribution in RF heated peanuts could be improved by segregating samples into structured blocks with air gaps between them. The developed concept from this study can further be expanded to optimise industrial-scale RF treatment protocols for controlling microorganisms in agricultural products.

Developing a screw conveyor in radio frequency systems to improve heating uniformity in granular products

Radio frequency (RF) treatments have been increasingly studied due to the rapid heating, deep power penetration depth and high energy efficiency. However, the major challenges for commercial RF applications are non-uniform and run-away heating. The purpose of this study was to improve RF heating uniformity in three granular products (soybean, corn, and peanut) using a custom-made screw conveyor with sample movement and mixing. The results showed that soybean, corn and peanut samples in the screw conveyor were RF heated in a similar heating rate under the selected electrode gap and screw rotation speed, and the variations between the highest and lowest temperatures in the three samples were all clearly reduced as compared to the stationary treatments. The RF heating uniformity index was also reduced for soybean, corn, and peanut during and after the RF treatment. Therefore, the screw conveyor could improve RF heating uniformity due to stable, continuous, uninterrupted movement and mixing of samples. The small-scale screw conveyor used in RF systems would provide a solid basis for further large-scale industrial applications. Keywords: radio frequency (RF), screw conveyor, heating uniformity, movement, mixing DOI: 10.25165/j.ijabe.20191203.4227 Citation: Zhou H X, Wang S J. Developing a screw conveyor in radio frequency systems to improve heating uniformity in granular products. Int J Agric & Biol Eng, 2019; 12(3): 174–179.

Dielectric properties, effect of geometry, and quality changes of whole, nonfat milk powder and their mixtures associated with radio frequency heating

Radio frequency (RF) heating is a promising pasteurization technique providing a fast and more uniform heat generation throughout a sample. In this paper, the effect of composition, frequency (1–30 MHz) and temperature (20–90 °C) on the dielectric properties of whole, nonfat milk powder and their mixtures were studied to develop an effective RF pasteurization. Moreover, the effect of the shape and dimension of the container on RF heating were evaluated. Milk powders were loaded into rectangular and cylindrical boxes with the same volume and different heights (3, 6 and 9 cm), and heated in a 6 kW, 27.12 MHz pilot scale free-running oscillator RF oven. The heating rate, temperature profile, penetration depth, and electric field strength were determined. The quality of the RF heated milk powders was evaluated by measuring moisture content, water activity, solubility, and color. Overall, heating milk powder in the 6 cm height cylindrical box showed a relatively more uniform temperature distribution than 6 cm height rectangular box, with moderate heating rate as well as improved quality in the finished product with less changes in moisture content, water activity, solubility and color. Electric field strength increased with the increase in the height of the container.

RETRACTED: Transient Operation: A Catalytic Chemoselective Hydrogenation of 2-Methyl-3-Butyn-2-ol via a Cooperative Pd and Radiofrequency Heating Directed Kinetic Resolution

The effect of periodic temperature oscillations has been studied for the hydrogenation of 2-methyl-3-butyn-2-ol over a Pd-based catalyst in a micro-trickle bed reactor. This hydrogenation was investigated using a radiofrequency heated reactor under transient conditions using temperature cycling. The dynamic operation using this configuration was found to increase both conversion and selectivity towards 2-methyl-3-buten-2-ol compared to the steady-state operation with an improvement of up to 24% for the selectivity being observed. The developments made here also result in a lower activation energy in comparison to previous data, providing a starting point for radiofrequency heating to enhance reaction rate through the exploitation of thermal cycling at production scale.

Radio frequency heating as a disinfestation method against Corcyra cephalonica and its effect on properties of milled rice

Radio frequency (RF) heating has the potential to be developed as an alternative non-chemical disinfestation method. In contrast to microwave (MW), RF exhibited higher penetration depth, which helps RF to be a useful technique in disinfesting packaging foods. A 3 kW, 27.12 MHz RF system was used to validate the practical of radio frequency technology for rice moth (Corcyra cephalonica) control in milled rice. Rice samples were placed in the polystyrene bag and moved at a speed of 0.8 m/min, and heated in the RF system with intermittent mixing. Four electrode gaps and five sample thicknesses were chosen to confirm the optimal conditions of RF treatment. The results showed that the sample thickness of 15 mm and electrode gap of 40 mm could provide the optimum heating rate for rice. Mortality of each stage (adult, larva, egg) of C. cephalonica increased with increasing heating temperature and reached 100% while RF heated 180 s (45.8 °C), 300 s (56.9 °C), and 420 s (70 °C), respectively. No C. cephalonica was determined in the samples during 45 days storage incubation period at RF treatment to 70 °C. There were no significant differences between control and RF treated samples in quality parameters (moisture, protein, fat, gelatinization, and sensory attributes). Therefore, RF treatment may provide a practical and effective method for disinfesting milled rice without affecting product quality.

Radiofrequency inactivation of Salmonella Enteritidis PT 30 and Enterococcus faecium in wheat flour at different water activities

Salmonella persistence in low-moisture foods creates a significant need for effective pasteurisation processes, but conventional thermal treatments for low-moisture products are challenged by long treatment times and insufficient information on inactivation kinetics. Radiofrequency (RF) heating can reduce heating time and inactivate Salmonella without inducing significant quality damage. The objectives were to study RF heating of organic wheat flour, and evaluate Enterococcus faecium as a surrogate for RF inactivation of Salmonella. Temperature profiles and uniformity of the top and cross-section surface of RF heated flour were obtained with an infrared camera, using different electrode gaps, platforms, and different materials that surrounded the sample to make the electromagnetic field uniform. The flour was inoculated with S. Enteritidis PT 30 or E. faecium, equilibrated to a specific aw, and then RF heated for 8.5 (0.25 aw) or 9 min (0.45 and 0.65 aw) to reach ≈75 °C minimum temperature (no holding time); survivors were then enumerated. The best temperature uniformity was obtained using a 90 mm electrode gap, placing small polystyrene cylinders above and underneath the sample container, and using a platform of polystyrene Petri dishes. Salmonella reduction of 7 log was achieved at 0.45 and 0.65 aw at room temperature, while 5 and 3 log reductions were reached for Salmonella and E. faecium, respectively, at 0.25 aw. These data suggest that RF heating has potential as an inactivation treatment for Salmonella, and that E. faecium is a feasible surrogate to validate the efficacy of RF treatments.

Computer simulation analyses to improve radio frequency (RF) heating uniformity in dried fruits for insect control

Abstract In recent years, radio frequency (RF) heating has been explored as a new postharvest pest and pathogen control procedure for agricultural commodities and dry food ingredients. Non-uniform heating and, sometimes runaway heating, have been the major challenges with implementation of this technology. In this study, an experimentally validated computer simulation model was developed to predict the effects of different package geometries, electrode configurations, and use of forced air (60 °C) on improving the heating uniformity of raisins treated with RF for insect control. Higher temperatures (60–76 °C) were observed in the areas between the edges and corners on the top and bottom layers of the RF treated raisins held in rectangular and cylinder shaped containers, with lower temperatures (40–52 °C) observed in the central areas of each layer. The heating uniformity was improved by rounding the corners of the containers and reducing sharp edges on the packages, modifying electrode configurations, and applying forced air after RF heating. These modifications reduced the maximum temperature difference throughout a container of heated raisins to about 5 °C. Approximately 356 min were needed to raise the raisin temperature in a rectangular container from 23 °C to 55–60 °C using only forced air at 60 °C. In contrast, only 6 min of RF heating followed by 10 min of forced air treatment at 60 °C was needed for a similar filled container to reach a temperature of 55–60 °C. Shortening the electrodes length to 4 cm shorter than the horizontal dimensions of the rectangular containers also improved heating uniformity. This technique can be easily implemented to improve the uniformity of RF heating in the food industry for the control of insects in packaged dried fruits. Industrial relevance The results in this study provide essential information about the non-uniform heating inside the RF heated materials packed in containers with sharp areas, edges and corners, such as rectangular and cylindrical shaped containers. Rounding the edges and corners in the containers or bending the top and bottom electrodes is key parameters to control the electrical field inside the RF system. This technique can be easily implemented to improve the uniformity of RF heating in the food industry for the control of insects in packaged dried fruits.

A radiofrequency heated reactor system for post-combustion carbon capture

Several problems with stabilization of electricity grid system are related to the time lag between the electricity supply and demand of the end users. Many power plants run for a limited period of time to compensate for increased electricity demand during peak hours. The amount of CO2 generated by these power installations can be substantially reduced via the development of new demand side management strategies utilizing CO2 absorption units with a short start-up time. The sorbent can be discharged using radiofrequency (RF) heating to fill the night-time valley in electricity demand helping in the stabilization of electricity grid. Herein a concept of RF heated fixed bed reactor has been demonstrated to remove CO2 from a flue gas using a CaCO3 sorbent. A very stable and reproducible operation has been observed over twenty absorption-desorption cycles. The application of RF heating significantly reduced the transition time required for temperature excursions between the absorption and desorption cycles. The effect of flow reversal during desorption on desorption time has been investigated. The desorption time was reduced by 1.5 times in the revered flow mode and the total duration of a single absorption-desorption cycle was reduced by 20%. A reactor model describing the reduced desorption time has been developed.

Dielectric properties of peanut kernels associated with microwave and radio frequency drying

To develop advanced drying methods based on microwave (MW) and radio frequency (RF) heating, knowledge of dielectric properties is essential for understanding the interaction between electromagnetic fields and peanuts. In this study, dielectric properties of peanut kernels were measured between 10 and 4500 MHz using an open-ended coaxial-line probe and network analyser at temperatures between 25 and 85 °C and moisture contents between 10% and 30% on a wet basis (w.b.). The results showed that both dielectric constant and loss factor of peanut kernels decreased sharply with increasing frequency over RF range (10–300 MHz), but gradually over the MW range (300–4500 MHz). Both dielectric constant and loss factor increased with increasing moisture content and temperature. The rate of increase was greater at higher temperature and moisture levels than at their lower levels. Penetration depth decreased with increasing frequency, moisture constant, and temperature. The measured dielectric properties were finally applied to determine the temperature profiles of RF heated samples under three moisture levels using experiment and simulation. This study on dielectric properties may provide useful guidelines in developing effective dielectric drying methods with a suitable drying thickness for peanuts.

Investigation of the Effect of Dielectric Properties of the Biscuit on RF Power Uniformity using a Finite Element Computer Model

Background: Biscuit baking process is a major energy consuming and quality deciding process. In conventional biscuit baking process which rely on conduction, convection, radiation mode of heat transfer a condition called checking arises. Checking arises due to the build-up of stresses in the product being heated. The cause for the stresses is the differential moisture content between the outer surface and the centre bone of the biscuit and causes cracking of biscuit. Radio Frequency (RF) Post Baking is a proven solution to this problem. But the wide scale industrial use of RF post baking of biscuits is limited by energy efficiency and cost of the RF heating system. Energy efficiency can be improved by having better RF power uniformity/heating uniformity in the sample (biscuit) being RF heated. The uniformity of radio frequency power distribution defined by a metric called Power Uniformity Index (PUI) is used to evaluate the efficiency of the radio frequency heating. Methods: A finite element computer model of the RF heating system for post baking biscuits with staggered electrode configuration was developed using comsol multiphysics software. The dielectric properties of biscuit were varied from a scale of 0 till 80 and its effect on the RF power distribution and hence the heating uniformity in radio frequency post baking of was observed. Findings: The simulation results obtained indicate that the dielectric properties of the sample (biscuit) do have significant effect on RF power distribution and hence the heating uniformity when the values of dielectric constant and loss factor are lower than 10. Application: The results obtained give an insight into the effect of dielectric properties of biscuit on the RF power distribution in RF dielectric heating of biscuits.

Computer simulation of radio frequency selective heating of insects in soybeans

Radio frequency (RF) treatments have potential as alternatives to chemical fumigation for disinfesting legumes. This study was conducted to investigate the feasibility of RF selective heating of insect larvae in 3kg soybeans packed in a rectangular plastic container (30×22×6cm3) using a 6kW, 27.12MHz RF heating system. A finite element based computer simulation program-COMSOL was used to solve the coupled electromagnetic and heat transfer equations for developing a simulation model. Indianmeal moth larvae were selected as the target insect for experimental validation of the simulation results. Simulated and experimental temperatures of insects and soybeans after 6min RF heating were compared in top, middle, and bottom layers within the container. Both results showed that insect larvae were differentially heated with 5.9–6.6°C higher than host soybeans when RF heated from 25 to 50°C. These results revealed that the heating rate of insects was 1.4 times greater than that of soybeans. The validated simulation results demonstrated that placing the insect on the cold spot of each layer, or horizontally, and large insect size may cause less selective heating within the insect bodies. Dielectric properties of insects may also influence the preferential heating patterns. The selective heating of insects in soybeans may provide potential benefits in developing practical RF treatments to ensure reliable control of insect pests without adverse effects on product quality.

Effect of Radio Frequency Assisted Thermal Processing on Quality and Functional Properties of Egg White Powder

Abstract. Traditionally, egg white powder (EWP) is stored in a hot room maintained at 58°C to 60°C for 10 to 14 days for pasteurization and to improve functional properties. This long and energy-intensive process limits plant production capacity. In this study, radio frequency (RF) assisted thermal processing was evaluated for pasteurization of EWP with the objective of reducing the storage period in a hot room, thereby reducing the energy requirement, while minimizing loss of functional properties. Spray-dried EWP (pH ~9.5) was RF heated to 60°C, 70°C, 80°C, or 90°C and maintained at the same temperature for different storage periods ranging from 1 h at 90°C to 3 days at 60°C in a hot air oven. The quality and functional properties of the RF-treated EWP, including color, foaming capacity (overrun), foam stability, solubility, gel firmness, and gel elasticity, were evaluated. RF pretreatment of EWP at 90°C followed by holding in a hot air oven for 8 to 24 h provided optimal functional properties. RF-assisted thermal treatment at all levels did not significantly reduce the color lightness (L* values), solubility (Haenni value), and moisture content when compared to traditionally processed EWP. However, RF-pretreated EWP had a significantly lower foaming capacity (overrun) when compared to traditionally processed EWP. It was found that RF pretreatment at 90°C and holding in a hot air oven for 8 h or longer resulted in similar foam stability, water holding capacity, gel firmness, and gel elasticity. Therefore, we recommend RF heating of EWP to 90°C followed by holding in a hot air oven for 8 h or longer to produce similar or better functional properties compared to traditionally processed EWP. This treatment process is estimated to achieve ≥7-log reduction of Salmonella spp. Thus, RF-assisted thermal treatment can be used to reduce the pasteurization duration from the current 10 to 14 days to less than 24 h. We demonstrated the feasibility of designing a high-temperature short-time (HTST) pasteurization process for EWP using RF-assisted thermal processing.

Effect of radio-frequency on heating characteristics of beef homogenate blends

The heating characteristics of different lean-to-fat ratios in ground beef (90/10, 85/15, 80/20, 73/27) was investigated using radio-frequency (RF) heating of ground beef homogenates. A homogenate model system was prepared with ground beef in phosphate buffer (pH 6.0). Homogenate blends were packaged in vacuum bags, immersed in pre-heated water at 10, 25 and 50 °C, and heated in the RF equipment to a target temperature of 60 °C. Beef homogenate blends with more lean and less fat (90/10 and 85/15) heated more rapidly, reaching the target temperature faster than the higher fat composition blends. The RF heating rates of the beef homogenate blends varied with water temperature; higher temperature resulted in rapid RF heating. The RF heating rate at 50 °C was the most rapid in heating all homogenate blends. The instrumental color characteristics for RF heated homogenate blends exhibited lower L* and a* values than uncooked homogenate blends. RF heating resulted in reduced redness and more oxidation of myoglobin (metmyoglobin formation) and lesser oxy- and deoxy-myoglobin redox forms in all beef homogenate blends independent of the initial water temperature. The results present scope to explore short time heating processes which will minimize quality deterioration in RF heated meat products.

Effect of Radio Frequency Heating on Yoghurt, II: Microstructure and Texture.

Radio frequency (RF) heating was applied to stirred yoghurt after culturing in order to enhance the shelf-life and thereby meet industrial demands in countries where the distribution cold chain cannot be implicitly guaranteed. In parallel, a convectional (CV) heating process was also tested. In order to meet consumers’ expectations with regard to texture and sensory properties, the yoghurts were heated to different temperatures (58, 65 and 72 °C). This second part of our feasibility study focused on the changes in microstructure and texture caused by post-fermentative heat treatment. It was shown that there were always microstructural changes with additional heat treatment. Compared to the dense and compact casein network in the stirred reference yoghurt, network contractions and further protein aggregation were observed after heat treatment, while at the same time larger pore geometries were detected. The changes in microstructure as well as other physical and sensorial texture properties (syneresis, hardness, cohesiveness, gumminess, apparent viscosity, G’, G’’, homogeneity) were in good agreement with the temperature and time of the heat treatment (thermal stress). The RF heated products were found to be very similar to the stirred reference yoghurt, showing potential for further industrial development such as novel heating strategies to obtain products with prolonged shelf-life.