A survey of the dielectric properties of meats and ingredients used in meat product manufacture

Emerging non-invasive microwave and millimeter-wave imaging technologies for food inspection

The microwave and millimeter-wave (MMW) imaging technology is gaining increasing interest for food inspection. It allows for noninvasive, contactless, and fast scanning capabilities, while being cost-efficient and safe to human. This review paper introduces the fundamentals in the interaction of electromagnetic wave with food materials and the current MMW sensing and imaging systems used for foods. Then we present emerging technologies in MMW imaging for inspecting food quality and safety, aiming to meet the modern food industry's demand. According to the most recent technological advancements, it is expected that high-performance antenna, ultrawide bandwidth signal generation, nano-scale semiconductor technologies, radio frequency identification with inductance-capacitance resonator, and machine learning could significantly enhance the capabilities of MMW imaging systems for food inspection.

Analysis of the Effects of Microwave Combined Induction Heating on Steamed Pork with Rice Powder

This study investigates the application of microwave combined induction heating (MCIH) to steam ready-to-eat pork with rice powder, emphasizing the advantages of rapid and uniform heating. The experimental setup included a mixture of 180 g pork strips, 30 g rice powder, and 10 g water in a CPET tray using MCIH with 1080 W microwave (MW) and 130 °C induction heating (IH) for 150 s. The results showed a quick temperature increase rate of 0.56 °C/s that achieved pasteurization against a variety of pathogenic bacteria, such as Listeria monocytogenes, but not Clostridium botulinum, by lethality calculation. Compared to typical electric cooker steaming, MCIH significantly shortened cooking time (8.6 times faster). To address rice starch gelatinization, two-stage heating techniques to steam pork with rice powder were MCIH: 150 s, and then IH: 60 s (MW1), and MCIH: 180 s, and then IH: 30 s (MW2), with no significant differences seen in color or the nine-point taste scale between treatment groups. MCIH groups had smaller shear forces than control. After MCIH cooking, no microbial counts were detected in the MW1 and MW2 groups initially, and the pork with rice powder had a shelf life of 14 days at 4 °C based on aerobic plate count assay.

Radio Frequency Treatment of Food: A Review on Pasteurization and Disinfestation

Radio frequency (RF) is a novel technology with several food processing and preservation applications. It is based on the volumetric heating generated from the product's dielectric properties. The dielectric properties of each material are unique and a function of several factors (i.e., temperature, moisture content). This review presents a list of dielectric properties of several foods and describes the use of RF as an innovative technology for the food industry. This paper includes several examples of pasteurization, fungi inactivation, and disinfestation in selected food products. The aim of this review is to present the potential applications of RF in pasteurization and disinfestation and research needs that should be addressed. RF has been successfully applied in the inactivation of pathogens such as Salmonella spp., Listeria monocytogenes, and Escherichia coli in low- and high-moisture food. The disinfestation of crops is possible using RF because of selective heating. This process inactivates the insects first because of the different dielectric properties between the pests and the food. The products' final quality can be considerably better than conventional thermal processes. The processing time is reduced compared to traditional heating, and thermal damage to the food is minimized. The main drawback of the technology is the lack of uniform heating, mainly when the product is surrounded by a packaging material with different dielectric properties from the food.

Influence of microbial cell morphology and composition on radio frequency heating of simple media at different frequencies

The effect of Listeria monocytogenes, Salmonella Typhimurium, and Saccharomyces cerevisiae on RF heating was studied in sterilized Milli-Q water and saline solution during treatments at 27.0 ± 0.6 MHz and 3.0 ± 0.02 MHz for 30 min. The presence of microorganisms caused a significant increase in temperature (maximum to 54.9 °C), with no significant decrease in cell numbers being observed for any conditions. For both media and frequencies, heating rates followed the order S. Typhimurium ≤ L. monocytogenes ≤ S. cerevisiae, except for heating at 3.0 ± 0.02 MHz in saline solution, where heating rates for S. cerevisiae and S. Typhimurium were equal. Generally, heating rates for microorganisms were significantly higher at 27.0 ± 0.6 MHz than at 3.0 ± 0.02 MHz, except for the S. cerevisiae case. Observed phenomena were probably caused by differences in the cell lipid and peptidoglycan content, with interaction effects with salt being present. This study was the first to investigate the influence of the presence of microorganisms on heating behavior of simple media. On the long term, more research on this topic could lead to finding specific RF frequencies more suitable for the heating of specific media and products for various applications.

Reduction of red blood spots in cooked marinated chicken breast meat by combined microwave heating and steaming

One of the defects commonly found in cooked marinated chicken breast products is a red blood spot (RBS), which is caused by undercooked blood in vessels. This problem was alleviated by microwave (MW) pre-heating for 6 to 7 min, followed by steaming. RBS formation decreased when samples were heated to a core temperature of 80°C and were completely eliminated at a core temperature of 82°C and 85°C when a MW pre-heating step was applied for 7 min. Based on synchrotron-based Fourier transform infrared spectroscopy (SR-FTIR), blood remaining in the blood vessel had a lower α-helical content when samples were cooked by the combination of MW heating and steaming as compared with those prepared by steaming alone (P < 0.05). MW pre-heating decreased cooking time by 28 to 48% as compared with steaming alone. Heating regimes had no effect on cooking loss, pH, water-holding capacity, and shear force. MW pre-heating for 7 min followed by steaming to a core temperature of 82°C appeared to be an effective heating regime to reduce the occurrence of RBS, with acceptable cooking loss.

A Resonant Coupler for Subcutaneous Implant

A resonator coupler for subcutaneous implants has been developed with a new impedance matching pattern added to the conventional loop antenna. The tuning element of a concentric metal pad contributes distributed capacitance and inductance to the planar inductive loop and improves resonance significantly. It provides a better qualify factor for resonant coupling and a much lower reflection coefficient for the implant electronics. Practical constraints are taken into account for designs including the requirement of operation within a regulated frequency band and the limited thickness for a monolithic implant. In this work, two designs targeting to operate in the two industrial, scientific, and medical (ISM) bands at 903 MHz and 2.45 GHz are considered. The tuning metal pad improves their resonances significantly, compared to the conventional loop designs. Since it is difficult to tune the implant antenna after implantation, the effects of tissue depth variations due to the individual's surgery and the appropriate implant depths are investigated. Simulations conducted with the dielectric properties of human skin documented in the literature are compared to measurements done with hydrated ground pork as phantoms. Experiments and simulations are conducted to explain the discrepancies in frequency shifts due to the uses of pork phantoms. The design method is thus validated for uses on human skin. A noninvasive localization method to identify the implant under the skin has been examined and demonstrated by both simulations and measurements. It can efficiently locate the subcutaneous implant based on the high quality-factor resonance owing to the tuning elements in both implant and transmitter couplers. The planar resonant coupler for wireless power transfer shows good performance and promise in subcutaneous applications for implants.

Dielectric properties of fresh rabbit meat in the microwave range

Dielectric properties (DPs) of fresh rabbit meat in the microwave range (0.5 to 20 GHz) were determined. Three different muscles (Biceps femoris, Tensor fasciae latae, and Longissimus thoracis) from California rabbits (male and female) were measured with the open-ended coaxial probe method at temperatures of 20, 40, and 60 °C. To assess the possible effect of age, females of 100 and 180 days old were analyzed. DPs were affected by frequency, muscle type, age, gender, and temperature (p < 0.05). Dielectric constant decreased with increasing frequency. Loss factor decreased from 0.5 to 2.5 GHz due to ionic conduction, followed by an increase up to 20 GHz, dominated by dipolar relaxation. PRACTICAL APPLICATION: These results are key parameters for further quality sensing applications and for heating processes of meat rabbit using microwaves. Longer penetration depths were achieved at 915 MHz; this frequency is recommended for further applications. Besides, dielectric properties have potential to be a tool for identification of gender and age for slaughtered rabbits.

Dielectric properties of carrots affected by ultrasound treatment in water and oil medium simulated systems

The ultrasound treatment of vegetables can damage their tissue structure and release water and soluble solids altering the dielectric properties of the material. Changes in the dielectric properties will influence the microwave processing of ultrasound pretreated material. In order to investigate the effect of ultrasound pretreatment on dielectric properties, carrots were ultrasonicated in simulated water and oil systems. Microwave heating and microwave-assisted vacuum frying of carrot slices were also completed to explore the relation between dielectric properties of microwave pretreated samples and microwave absorption. Ultrasound of carrots in water simulated system showed that ε' and ε″ of carrots tended to decrease with the increase of ultrasonic power (from 480 W to 640 W) and time (from 10 min to 30 min). Ultrasound treatment of carrots in salt solutions increased ε' and ε″ of carrots. The combined pretreatment of microwave blanching with ultrasound in salt solutions increased ε″ (from 19.72 to 29.90). Conversely, in oil simulated system, the ε' and ε″ of carrots also decreased as the ultrasonication power and time increased. Besides, the dielectric properties decreased as the temperature of oil medium increased from 35 °C to 75 °C. With improved dielectric properties, the dehydration rate during frying of carrot increased due to the enhanced microwave absorption. Therefore, the combined pretreatment of microwave blanching with ultrasound in salt solutions largely improved the dielectric properties of carrots, and reducing the required time of microwave vacuum frying.

Analysis of Apple Candying by Microwave Spectroscopy

Process control in the industry requires fast, safe and easily applicable methods. In this sense, the use of dielectric spectroscopy in the microwave range can be a great opportunity to monitor processes in which the mobility and quantity of water is the main property to produce a quality and safety product. The candying of fruits is an operation in which the samples are first osmotically dehydrated and then exposed to a hot air-drying operation. This process produces changes in both the structure of the tissue and the relationships between water, the solid matrix and the added soluble solids. The aim of this paper is to develop a dielectric tool to predict the water/sucrose states throughout the candying of apple, by considering the complexity of the tissue and describing the different transport phenomena and the different transition processes of the sucrose inside the sample.

Effect of marination in gravy on the radio frequency and microwave processing properties of beef

Dielectric properties (the dielectric constant (ε') and the dielectric loss factor (ε″)) and the penetration depth of raw eye of round beef Semitendinosus muscle, raw beef marinated in gravy, raw beef cooked in gravy, and gravy alone were determined as a function of the temperature (20-130 °C) and frequency (27-1,800 MHz). Both ε' and ε″ values increased as the temperature increased at low frequencies (27 and 40 MHz). At high frequencies (915 and 1,800 MHz), ε' showed a 50 % decrease while ε″ increased nearly three fold with increasing temperature in the range from 20 to 130 °C. ε' increased gradually while ε″ increased five fold when the temperature increased from 20 to 130 °C. Both ε' and ε″ of all samples decreased with increase in frequency. Marinating the beef in gravy dramatically increased the ε″ values, particularly at the lower frequencies. Power penetration depth of all samples decreased with increase temperature and frequency. These results are expected to provide useful data for modeling dielectric heating processes of marinated muscle food.

Measurement techniques and application of electrical properties for nondestructive quality evaluation of foods-a review

Non-destructive systems are recent trends for quality evaluation of fruits and vegetables. Information on post-harvest variations in electrical properties is needed to develop new instruments for this purpose. Electrical properties are finding increasing application in agriculture and food processing industries. Knowledge of dielectric properties of foods as a function of moisture content and temperature is essential in the design and control of drying systems. As simple, rapid and non-destructive measuring techniques, dielectric spectroscopy provides information about the dielectric response of materials to electromagnetic field. Electrical properties of agricultural materials have been of interest for many years. The interest in dielectric properties of materials has historically been associated with the design of electrical equipment. This review paper covers theoretical aspects of different electrical properties, their measurement techniques, applications of dielectric properties in agriculture/food processing sector and potential applications of thermal imaging (TI) for quality and safety assessment in food processing. The values of dielectric properties of a number of products including food grains, fruits and vegetables, and meat and meat products are presented in table form. This comprehensive coverage will be useful for academic, scientific and industrial community in treating and applying the facts in developing/testing new processes and products based on electromagnetic energy application.