Predicting the dielectric behavior of orange and other citrus fruit juices at 915 and 2450 MHz

Abstract

Dielectric properties (DP: relative permittivity and loss factor) and electrical conductivity are important parameters for evaluating the microwave penetration depth and designing applicators for pasteurization processes. In this context, generalized equations that can predict the DP of a group of food products as a function of their characteristics are useful. The dielectric behaviours of eight citrus fruit juices (Pera, Lima, and Navel oranges, Ponkan tangerine, Murcott tangor, Mediterranean mandarin, Sicilian lemon, and Persian lime) and three Pera/Lima blends (25, 50, 75%) for temperatures between 0 and 90°C and frequency between 500 and 3000 MHz were studied. The results were correlated with temperature at frequencies of 915 and 2450 MHz. It was possible to quantify the ionic and dipolar contributions. DPs were modelled based on the behaviour of pure water in a semiempirical approach using correction factors, which were correlated with temperature and juice physicochemical characteristics (pH, Brix, conductivity). Polynomial regressions can successfully predict relative permittivity with mean absolute errors of 0.49±0.35% and 0.58±0.48% and the loss factor with errors of 4.1±3.9% and 2.8±2.3% at 915 and 2450 MHz, respectively, for juices with Brix/acid ratio between 1.26 and 29.9. ARTICLE HISTORY

Microwave heating impacts positively on the physical properties of orange juice‐milk beverage

“…In Figure 2a, an increase in temperature and frequency resulted in a decrease in the dielectric constant. These results are associated with reducing the polarisation under thermal agitation and the reduced dipole response under higher frequencies, respectively (Franco and Tadini 2017). This pattern is typical of water‐rich foods and has been massively reported in the literature for several liquid foods, such as grape juice (García et al .…”

Dielectric Properties of Beverages (Tamarind and Green) Relevant to Microwave‐Assisted Pasteurization

“…This trend was also similar to that reported by some authors in liquid foods as apple, grape, pear, orange, and pineapple fruit juices (Zhu et al., ), and natural green coconut water (Franco et al., ), at different temperatures. Franco, Tadini, and Gut () reported that decreasing in ε’ with increasing temperature may be considered a negative effect, due to molecular motion increases and the polarization of the material becomes less effective.…”

Model food for microwave‐assisted pasteurization of fruit juices and nectars at 915 and 2,450 MHz

“…The dielectric properties of 12 fruit juices, nectars and green coconut waters for temperatures 10, 30, 50, 70, 90 °C at 915 and 2,450 MHz were obtained from the literature: (1) apple juice, cloudy, Fuji standard variety, 12.1 °Brix (Siguemoto & Gut, ); (2) grape juice, Jufeng variety, 14.7 °Brix (Zhu, Guo, & Wu, ); (3) green coconut water, 5.2 °Brix (Franco et al, ); (4) green coconut water, concentrated 20 °Brix (Yamamoto, Franco, Gut, & Tadini, ); (5) green coconut water, concentrated 30 °Brix (Yamamoto et al, ); (6) lemon juice, Sicilian variety, 7.0 °Brix (Franco, Tadini, & Gut, ); (7) melon juice, Yellow variety, 11.7 °Brix (Barbosa, Cavalcanti, & Gut, ); (8) orange juice, Pera variety, 12.2 °Brix (Franco et al, ); (9) passionfruit nectar, 8.6 °Brix (Barbosa et al, ); (10) pear juice, Dangshanshu variety, 10.7 °Brix (Zhu et al, ); (11) pineapple juice, Bali variety, 10.6 °Brix (Zhu et al, ); and (12) pineapple nectar, 6.7 °Brix (Barbosa et al, ).…”