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ON THE tanδ‐FREQUENCY RELATIONSHIP OF FOODS AND AGRICULTURAL COMMODITIES 1
Author(s) -
CAMPANELLA OSVALDO H.,
PELEG MICHA
Publication year - 1997
Publication title -
journal of texture studies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.593
H-Index - 54
eISSN - 1745-4603
pISSN - 0022-4901
DOI - 10.1111/j.1745-4603.1997.tb00138.x
Subject(s) - relaxation (psychology) , phase angle (astronomy) , logarithm , mathematics , range (aeronautics) , solidity , limit (mathematics) , phase (matter) , measure (data warehouse) , low frequency , frequency dependence , materials science , analytical chemistry (journal) , mathematical analysis , physics , chemistry , composite material , optics , nuclear magnetic resonance , quantum mechanics , chromatography , psychology , social psychology , database , astronomy , computer science , programming language
Published discrete relaxation times spectra of agar and alginate gels, alfalfa, apple and potato flesh, meat, cheese and wheat dough were used to calculate the frequency or frequencies where the phase angle δ(ω vs frequency, ω, relationship peaks. This was done by solving, numerically, the equation dtanδ(ω)/dω= O where d 2 tanδ(ω)/dω < O, with tanδ(ω) being an algebraic expression derived from the discrete Maxwell model of stress relaxation. The ω peak of the materials examined was in the range of 10 −3 to 10 −1 Hz band, setting a lower limit to the frequencies at which such materials can be compared by dynamic tests. This also indicates that the plot of tanδ(ω) vs ω in linear or logarithmic coordinates must have a negative slope at any frequency range above about 0.5 Hz. The frequency at which the peak appears, ω peak , is primarily determined by the relative weight of the elastic component and the elements of long relaxation times. The higher it is the lower ω peak is. Thus, the latter can serve as a measure of solidity, inherent to the material or caused by external conditions or through a textural modijication.