Dielectric study of milk for frequencies between 1 and 20 GHz

• Published in: Journal of food engineering 2006-09, Vol.76 (2), p.250-255
• Main Authors: Nunes, A.C., Bohigas, X., Tejada, J.
• Format: Article
• Language: English
• Subjects: ambient temperature; Biological and medical sciences; calcium; carbohydrate content; Composition; Dielectric properties; electric field; Food engineering; Food industries; food spoilage; food storage; frequency; Fundamental and applied biological sciences. Psychology; General aspects; Ionic loss; ions; low fat milk; Microwave; microwave radiation; microwave treatment; Milk; Milk and cheese industries. Ice creams; milk fat; milk proteins; Permittivity; shelf life; skim milk; spectral analysis; Spoil; storage temperature; storage time; UHT milk; water content; whole milk
• ISSN: 0260-8774; 1873-5770
• DOI: 10.1016/j.jfoodeng.2005.04.049

The complex permittivity of milk at room temperature (17–20 °C) was studied over the frequency range of 1–20 GHz. UHT whole, low fat and skim milk were examined, fresh from the container, and over a period of two weeks while they were allowed to spoil at room temperature. In addition, the spectrum of whole milk at various dilutions was also measured. Both the real and imaginary parts of the permittivity were found to be smooth, slowly varying functions of frequency over this range. The Debye relation, with an additional term for ionic conduction losses was fitted to the data, and six parameters were extracted. The variation of these parameters with fat content and dilution suggests that they may be useful to roughly determine the milk’s content in terms of groups of materials (ionic compounds, fats, and carbohydrates and proteins). Spectra also vary significantly with spoilage, but analysis is complicated by concerns of physical (phase separation) in addition to chemical changes.