Alcohols and alcohols mixtures as liquid biofuels: A review of dielectric properties

2018

Int J of Food Sci Tech

Summary Dielectric properties (dielectric constant ε′ and dielectric loss factor ε′′) of whole milk and skim milk with the lactose content of 4.56–6.44% and 4.57–6.47%, respectively, were measured over the frequency range of 20–4500 MHz at 25 °C using a vector network analyzer. The results showed that ε′ decreased with increasing frequency, and ε′′ changed with V shape and its minimum was noted at about 2000 MHz. Whole milk had lower dielectric properties than skim milk at almost same lactose content and a given frequency. ε′ had weak positive linear relationship with lactose content for whole milk, but had negative linear relationship for skim milk. No matter for which milk, ε′′ had very good negative linear relationship with lactose content below 1000 MHz and had good positive linear relationship above 2300 MHz. The study provides information on developing rapid lactose detector for milk in future.

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Effect of lactose content on dielectric properties of whole milk and skim milk

2018

Int J of Food Sci Tech

“…They are the real and imaginary parts, respectively, of the complex permittivity relative to free space, ε * = ε ′ − jε ″ . Some studies on dielectric properties of food materials and agricultural products, such as alcohols (Khaled, Novas, Gázquez, García, & Manzano‐Agugliaro, ), sugar (Franco, Yamamoto, Tadini, & Gut, ), honey (Guo, Liu, Zhu, & Wang, ), vegetable powders (Ozturk, Kong, Trabelsi, & Singh, ; Zhu & Guo, ), fruits (Barba & Lamberti, ), meats (Castro‐Giráldez, Dols, Toldr, & Fito, ; Tanaka, Mallikarjunan, & Hung, ), eggs (Lin, Zhang, Fang, & Liu, ; Soltani, Omid, & Alimardani, ), and so on, have shown that the dielectric properties are dependent on frequency and temperature. What is more, the dielectric properties also depend on the compositions of food, such as fat (Zhu, Guo, & Liang, ), protein (Zhu, Guo, Kang, Kong, & Zhu, ), water (Barba & Lamberti, ; Torrealba‐Melendez, Sosa‐Morales, Olvera‐Cervantes, & Corona‐Chavez, ), etc.…”

Section: Introductionmentioning

confidence: 99%

Dielectric properties of raw milk as influenced by frequency, salts, and salt contents

J Food Process Engineering

2018

To understand the effect of salts and salt contents on dielectric properties (dielectric constant ε′ and dielectric loss factor ε″) of milk, dielectric properties of raw cow's milk samples at the total salt content (in mass) of 0.75–0.87%, 0.75–0.93%, and 0.75–0.90% by adding NaCl, MgCl2, and KCl, respectively, were obtained from 19 to 3,000 MHz at 25 °C using an impedance analyzer. The results showed that ε′ decreased with increasing frequency, and ε″ changed with “V” shape and had minimums at about 1,500 MHz. At a given frequency and the same salt addition level in molar, the milk added with NaCl and MgCl2 had the smallest and the biggest ε″, respectively. At about 40 MHz, ε′ had a very good positive linear relationship with the total salt content of milk, whose coefficients of determination were 0.96, 0.98, and 0.95 for NaCl, MgCl2, and KCl, respectively. ε″ increased linearly with increasing total salt contents with the coefficients of determination higher than 0.99 below about 900 MHz and higher than 0.86 above 900 MHz no matter for which salt. Practical applications This work shows that there were linear relationships between dielectric properties and total salt contents. The study is helpful to understand the influence of salts and salt content on dielectric properties of raw cow's milk, and it offers useful information for developing portable salt detector based on dielectric properties in the future.

“…A large number of studies have found that the ε′ and ε″ of food and agricultural products, e.g., vegetable powders (Ozturk et al ., ; Zhu & Guo, ), eggs (Lin et al ., ; Soltani et al ., ), meats (Kent et al ., ; Castro‐Giráldez et al ., ), fruits (Guo et al ., ), honey (Guo et al ., ; Pentoś & Łuczycka, ), sugar (Franco et al ., ), alcohols (Khaled et al ., ), and so on, are dependent on temperature of materials and frequency of electric field. In addition, the ε′ and ε″ of materials also depend on their chemical compositions, such as water (Barba & Lamberti, ; Torrealba‐Melendez et al ., ), protein (Zhu et al ., ), fat (Zhu et al ., ), soluble solids content (SSC) (Guo et al ., ), etc.…”

Section: Introductionmentioning

confidence: 99%

Effect of solids‐not‐fat content on dielectric properties of skim milk

2018

Int J of Food Sci Tech

Summary Dielectric constant (ε′) and loss factor (ε″) of skim milk samples at different total solids‐not‐fat contents were measured over the frequency range of 20–4500 MHz at 25 °C using a vector network analyser. The results showed that ε′ of skim milk decreased as frequency increased, and ε″ changed from decreasing to increasing and had minimums at about 2000 MHz. There was a linear relationship between ε′ and solids‐not‐fat content with correlation coefficient higher than 0.940 below 50 MHz and keeping at −0.990 above 150 MHz. ε″ had positive linear relationship with solids‐not‐fat content, and their correlation coefficient was higher than 0.970 at all investigated frequencies. Penetration depth of electromagnetic wave in milk decreased as increased frequency or solids‐not‐fat content. The study is helpful to know the relationship between solids‐not‐fat content and dielectric properties, and it provides information for developing solids‐not‐fat detector could be used in on‐line detection for skim milk production.