A low-cost sensing system for quality monitoring of dairy products

The dairy industry is in need of a cost-effective, highly reliable, very accurate, and fast measurement system to monitor the quality of dairy products. This paper describes the design and fabrication works undertaken to develop such a system. The techniques used center around planar electromagnetic sensors operating with radio frequency excitation. Computer-aided computation, being fast, facilitates on-line monitoring of the quality. The sensor technology proposed has the ability to perform volumetric penetrative measurements to measure properties throughout the bulk of the product

On the use of dielectric spectroscopy for quality control of vegetable oils

Quality control of vegetable oils is becoming more stringent, and related laws are being enforced especially for avoiding adulteration. As a result, there is a substantial need for methods of analysis that could provide real-time in-situ monitoring, especially for quality control purposes during production process. In this regard, the present paper investigates the possibility of monitoring qualitative characteristics of vegetable oils through microwave dielectric spectroscopy, which is a highly versatile investigative approach. In particular, the Cole & Cole frequency-domain dielectric parameters are known to be strongly related to the compositional characteristics of various substances. This way, starting from traditional Time Domain Reflectometry measurements performed on oils, the corresponding frequency domain information is retrieved. Successively, through a minimization routine, the Cole & Cole parameters of each considered oil are extrapolated. Results show that different dielectric characteristics can be associated with different oils. It is important to point out that the characteristics of the proposed procedure can be automated and, therefore, it may represent a promising solution for practical monitoring applications

A Coaxial Line Fixture Based on a Hybrid PSO-NLR Model for in Situ Dielectric Permittivity Determination of Carasau Bread Dough

Food quality is crucial in today's processing industry. The organoleptic properties of most food materials are known to depend on their water content. The monitoring of food quality and moisture content calls for engineering solutions. To this aim, given their nondestructive nature and cost-effective features, microwave sensors are a valuable tool. However, for some peculiar food processing industries, suitable engineered microwave devices must be designed. Therein, we will focus on the case of the Carasau bread industry. Carasau bread is a typical food product from Sardinia (IT). In this work, we will present the design, realization, and characterization of a coaxial fixture, working between 0.5 and 3 GHz, for the determination of the complex dielectric permittivity of Carasau bread dough. Through a nonlinear regression model based on a particle swarm optimization routine, the scattering parameters are used to retrieve the electromagnetic properties of bread doughs. By making a comparison with the complex dielectric permittivity measured with an open-ended coaxial probe, an average error of 3% for the real part and 6% for the imaginary part has been found. The proposed device is driven by a Raspberry Pi that controls the acquisition of a pocket-vector network analyzer (VNA), thus representing a cost-effective electronic system for industrial applications

Identification of fibre content in edible flours using microwave dielectric cell: Concise review and experimental insights

The quality of edible intake decides the health of the human body and is also responsible for building a healthy immune system in the body. A healthy immune system can protect the body even from invisible attacks of viral or bacterial infections. The assessment of the quality of edible items is not well defined and standardized in many developing countries due to quality assessment difficulties in practice. An alternative well-defined quality assessment approach for edible flours is presented in this paper. Every edible substance has dielectric properties, and it varies from material to material in nature. Edible flours and liquid have different microwave absorption capabilities, based on their natural molecular structure. Based on the microwave energy absorption characteristics of materials, the attenuation constant of edible flours is derived by the waveguide method in this work. In this approach, microwave energy absorption of the edible samples of different types of wheat, rice and millets are observed, and the attenuation constant factors of the samples are then calculated from the tabulated values. The work focuses on the identification of fibre content present in the edible flours. Inferences are made based on the attenuation and its variations with the number of samples, dielectric loss and dielectric constant of the samples. A systematic and concise review of the topic is also included for the benefit of future researchers.Web of Science1516art. no. 564

Application of microwave sensors to potato products

The first microwave measurement techniques uses an open ended coaxial probe with a purposely built sample holder to measure the dielectric properties of potato products from 500 MHz to 1 GHz. The second system utilises a waveguide cell with a purposely built sample holder to characterise potato products from 2.4 to 3.5 GHz. Common British varieties of raw potatoes such as Estima, King Edward and Maris Piper are used in this study. The two microwave measurement techniques are also used to measure the dielectric properties of potato products at elevated temperatures for these frequency ranges. Both measurement techniques are also used to study the effect of storage temperature on the dielectric properties of Saturna raw potato. For this part of the study, it is concluded that the microwave measurement techniques are unable to discriminate between potatoes that had a storage history of different temperature profiles. On the other hand, waveguide cells and open ended coaxial probes are able to measure the dielectric properties of raw potato, partial cooked fried potato and fried potato at the 500 MHz to 1 GHz and 2.4 GHz to 3.5 GHz frequency range. The measurement results show that both dielectric constant and loss values of fried potatoes decreased with frying time, due to the reduced moisture content during the frying process. Furthermore, the dielectric loss behaviour of raw and fried potatoes is dominated by the effect of the ionic conductivity at frequencies lower than 1 GHz. An apparatus has been designed and built in order to measure the dielectric properties of potato for both frequency ranges as a function of temperature. In the subsequent measurements it is found that the dielectric properties of potato products at elevated temperatures also depend on frequency and moisture content. For high moisture content potato (~> 70 %), at 2.45 GHz both the dielectric constant and loss are found to decrease with temperature, whereas at 915 MHz the dielectric constant decreases but the loss increases for the moisture content above 30%. For the intermediate moisture content (10%<MC<70%), all dielectric properties increase with temperature at the microwave heating frequencies 2.45GHz, whereas at 915 MHz all the dielectric properties increase with temperature for the moisture content range 10% to 30%. The increase in dielectric properties with temperature is small and marginal for fried potatoes with low moisture content (< 10 %). It is therefore apparent that moisture content is the primary factor in detecting the complex permittivity of potato products.EThOS - Electronic Theses Online ServiceMARDIGBUnited Kingdo

Dielectric properties of biological materials a physical-chemical approach

Dielectric heating of biomaterials was investigated from the physical, chemical, and electrical properties perspectives. Primary focus was on the electrical properties, especially dielectric properties. The dielectric constant (ε’) and loss factor (ε”) were studied at the molecular level of the materials’ composition; primarily water, carbohydrates, and proteins. Effects of components were investigated individually and in combination in aqueous media. Measurements were conducted using an open-ended coaxial probe connected to an impedance analyzer. Properties of food carbohydrates (starch, sucrose, glucose, and fructose) were investigated over the frequency range 10–1800 MHz at 20–60 oC, and to 100 oC for starch solutions. The influences of electrical field frequency (f), temperature (T), and concentration (C) on the dielectric constant and loss factor were thoroughly examined and theoretically interpreted. The dielectric constant’s response to frequency was fairly independent from 10 to 1000 MHz, but began a significant and progressive decline at frequencies beyond 1000 MHz. Influences of protein solutions (ovalbumin, bovine serum albumin, β-lactoglobulin, and lysozyme) were investigated in aqueous media at 450 selected frequencies between 5 MHz and 1800 MHz. All examined proteins exhibited similar dielectric dispersions for the selected concentrations (i.e., 5, 10, 20, 30, 40 and 50 mg/g) and results agreed fairly well with previously published data. Delta-dispersions (δs) between β and γ-dispersions for protein solutions were observed, although at higher relaxation frequencies than those previously published. Contribution of individual proteins to the dielectric loss, and consequently thermal generation in dielectrically heated biomaterials, was investigated and found to have greater effect at low frequencies, especially at 27 MHz. Theoretical calculation of the local dielectric constant (ε’) of individual proteins from their amino acid composition resulted in a mean value of 2.70. A derived mixture equation provided results that agreed with experimental data at frequencies close to the industrial microwave frequency (915 MHz). Dielectric measurements of protein-sugar aqueous mixtures were also conducted in the 10–1800 MHz frequency range. Rayleigh, Böttcher, and Berentsveig mixture models were utilized to predict the mixtures’ dielectric constants. Calculated values agreed with the experimental data, except for the three-component mixture result obtained using the Rayleigh model

Microwave enhanced processing of ores

Recent research developments have suggested that microwave assisted comminution could provide a step change in ore processing. This is based on the fact that microwave-absorbent phases within a multi-mineral ore can be selectively heated by microwave energy hence inducing internal stresses that create fracture. A detailed review of existing literature revealed that little or no information is available which relates and examines the influence of hydrated minerals on microwave assisted fracture despite the fact that most important ores are associated with phyllosilicates, the vast majority of which are hydrated. A study was carried out on two Kimberlite diamond ores containing various types of hydrated minerals but devoid of any semiconducting minerals which are known to be good microwave heaters. The results confirmed that dehydration of minerals containing interlayer adsorbed water induces significant micro and macro fractures after microwave treatment. The significance of microwave induced fracture on beneficiation was investigated by conducting liberation and flotation tests on two porphyry copper ores. It was demonstrated that microwave pre-treatment improves beneficiation at sizes suitable for flotation and that higher improvements in degree of liberation are attained in coarser particle sizes between 212 and 425 µm. Flotation tests demonstrated a potential for real economic benefits in terms of value proposition. An increase of 8-10% in copper sulphides recovery from coarse sized particles (-400+200 µm) and an overall increase in grade/recovery of between 1-2% was obtained. The results also showed that microwave pre-treatment enhances selective mineral recovery as the grade-recovery of iron sulphides decreased in all but one microwave treated samples. The major drawback to further developments towards industrial scale application was found to be the lack of an effective continuous processing microwave applicator. Any future applicator designs must be able to ensure localised hot spots and confinement of all the microwave energy