Insight into the freezing of garlic cloves via dielectric relaxation characteristics and single-frequency dielectric properties

Le résumé fourni par la source

To explore the information that dielectric spectroscopy (DS) can provide on the freezing of fruits and vegetables (F&V), the freezing process of garlic cloves, employed as a representative, was monitored in real time by means of both dielectric scan in a frequency range of 50 Hz – 3 MHz and single-frequency dielectric characterizations. Four dominant β type dielectric relaxations were observed in the investigated frequency range throughout the freezing process, which are attributed to the interfacial polarization occurring at plasma membrane and tonoplast. The variation of the behavior of these relaxations sensitively reflects the alteration of the cellular composition and structure during freezing, where the variation of the relaxation intensity indicates the alteration of cellular structure and that of the characteristic relaxation time mainly denotes the freezing state of intra- and inter-cellular water. The dielectric properties at 10 4 , 10 5 , and 10 6 Hz are found changing synchronously during the freezing process, and their dependences on freezing time are found able to accurately determine important thermal properties including the nucleation point and the initial freezing point. Though a case study, this contribution strongly suggests that DS could become a very promising real-time monitoring method to investigate the freezing and frozen storage of F&V: the relaxation-based monitoring is capable of in-depth comprehension of the microscopic mechanism of the ice nucleation and crystallization in the matrix of F&V, and the single-frequency monitoring could be an ideal alternative to the cooling curve method and differential scanning calorimetry in the determination of important thermal properties of F&V. • Freezing process of garlic cloves monitored in real-time via dielectric spectroscopy. • Dielectric relaxation characteristics reveals compositional/structural change. • Single-frequency dielectric property can be used to determine temperature profile. • Deep insight into ice crystallization mechanism via dielectric spectroscopy feasible.

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