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Effects of Shape and Size of Agar Gels on Heating Uniformity During Pulsed Microwave Treatment
Author(s) -
SotoReyes Nohemí,
TemisPérez Ana L.,
LópezMalo Aurelio,
RojasLaguna Roberto,
SosaMorales María Elena
Publication year - 2015
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/1750-3841.12854
Subject(s) - cylinder , microwave , materials science , slab , agar , microwave heating , spheres , microwave oven , thermal conductivity , agar gel , analytical chemistry (journal) , dielectric , chemistry , chromatography , composite material , geometry , biology , bacteria , optoelectronics , physics , mathematics , microbiology and biotechnology , quantum mechanics , astronomy , geophysics , genetics , geology
Abstract Model gel systems with different shape (sphere, cylinder, and slab) and size (180 and 290 g) were prepared with agar (5%) and sucrose (5%). Dielectric constant (ε′), loss factor (ε″), thermophysical properties, and temperature distribution of the model system were measured. Each agar model system was immersed and suspended in water, and then, heated in a microwave oven with intermittent heating until the core temperature reached 50 °C. The ε′ and ε″ of agar gels decreased when frequency increased. The density and thermal conductivity values of the agar gels were 1033 kg/m 3 and 0.55 W/m °C, respectively. The temperature distribution of sphere, cylinder, and slab was different when similar power doses were applied. The slab reached 50 °C in less time (10 min) and showed a more uniform heating than spheres and cylinders in both sizes. Agar model systems of 180 g heated faster than those of 290 g. The coldest point was the center of the model systems in all studied cases. Shape and size are critical food factors that affect the heating uniformity during microwave heating processes.