Dielectric properties of grape marc: Effect of temperature, moisture content and sample preparation method

Sólyom, Katalin; Kraus, Stefan; Mato, Rafael B.; Gaukel, Volker; Schuchmann, Heike P.; Cocero, Marı́a José

doi:10.1016/j.jfoodeng.2013.05.005

Cited by 19 publications

(13 citation statements)

References 19 publications

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“…(Jia et al, 2003) for carrot and potato samples. The influence of temperature, moisture content and porosity on the dielectric properties are described in literature for several foods, exemplarily shown in (Ozturk et al, 2016;Solyom et al, 2013;Piyasena et al, 2003;Venkatesh and Raghavan, 2004;Sosa-Morales et al, 2010;Jha et al, 2011;Knoerzer et al, 2004), see also chapter 2. This shows the complexity of an accurate physical-principles-based simulation of a microwave assisted drying process even if only a "process modelling" is considered.…”

Section: Modelling Microwave Dryingmentioning

confidence: 99%

Microwave-assisted drying

Gaukel

Siebert

Erle

2017

The Microwave Processing of Foods

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AD is a common and well established industrial drying process. As idealised in Fig. 8.1, a typical drying curve of a foodstuff can be subdivided into three periods. After an initial phase (IP), a steady state is reached in which the drying rate (evaporated water over time) is constant. Therefore, this period is called "constant rate period" (CRP). In this period the product surface is still wet and the passing airflow transfers the heat for water evaporation to the surface. Simultaneously, the air is collecting the water vapour and is transporting it away from the product surface out of the dryer. This is a simultaneous heat and mass transfer. To keep the surface wet, enough water has to flow from the inside of the food to its surface. In the constant rate period this water flow is mainly capillary-driven and the surface temperature of the product is theoretically constant. As the water evaporation consumes energy, the surface temperature is typically significantly lower than the air temperature. The temperature profile in Fig. 8.1 A is adopted from a hot air drying process of carrot slices and it shows that this constant temperature period is not necessarily exactly reflected in real data. The factors that determine and limit the drying rate in the CRP are: the state of the air (temperature and relative humidity) as well as air velocity. By changing any of these parameters the drying process may be accelerated (or delayed) considerably.

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Section: Modelling Microwave Dryingmentioning

confidence: 99%

Microwave-assisted drying

Gaukel

Siebert

Erle

2017

The Microwave Processing of Foods

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“…Sipahioglu and Barringer [28] found comparable behavior for garlic samples with 57.3% moisture content. Sólyom et al [29] observed that when the temperature of milled seeds increased, the ε value gradually decreased, with a high amount of free water.…”

Section: Factors Affecting the Dielectric Properties Of Materials To mentioning

confidence: 99%

Microwave-Assisted Drying: A Review of the State-of-the-Art

2015

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Offering advantages of energy-saving rapid drying rates, short processing times, deep penetration of the microwave energy, instantaneous and precise electronic control, as well as clean heating processes, microwave-assisted drying (MWD) has become a popular method that is currently used for many materials and processes. This paper presents a systematic and comprehensive review of experimental and theoretical studies regarding the kinetic mechanisms of MWD. Factors affecting, methods for measuring, and applications of the dielectric property are discussed. From the experimental perspective, laboratory-and commercial-scale MWD systems are elaborated, including the equipment used and the stability, safety, and regulation of MWD systems. Theoretical investigations of thermal and non-thermal equilibrium models and moving-load computational models are discussed. Finally, some future trends in the research and development of MWD systems are suggested. Downloaded by [University of Otago] at 16:52 21 July 2015 2

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“…As expected, the moisture content affects the dielectric properties for all samples, but temperature was not shown to have a clear influence in both dielectric properties due to the presence of salt in the Marc grape. 3 The maturity effects on the dielectric properties of apples from 10 to 4500 MHz have been studied. It is shown that no obvious correlations are found between permittivity and firmness, moisture content or pH.…”

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confidence: 99%