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VARIATIONS IN FLEXURAL AND COMPRESSIVE FRACTURE BEHAVIOR OF A BRITTLE CELLULAR FOOD (DRIED BREAD) IN RESPONSE TO MOISTURE SORPTION
Author(s) -
CHANG Y. P.,
CHEAH P. B.,
SEOW C. C.
Publication year - 2000
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.1745-4603.2000.tb01018.x
Subject(s) - flexural strength , moisture , materials science , composite material , brittleness , brittle fracture , sorption , compressive strength , fracture (geology) , chemistry , organic chemistry , adsorption
Mechanical properties of dried bread (a cellular baked product) equilibrated at different water activities (A w ) were measured using three‐point bending and uniaxial compression to compare their responses to moisture sorption. The glass‐to‐rubber transition was clearly demarcated in all the mechanical property‐A w curves, although there were differences in critical A w (0.32–0.56) at which the dramatic changes in mechanical properties occurred. The role of water appeared to be strictly that of a plasticizer where flexural mechanical parameters were concerned, leading to reduced modulus and fracture stress but increased fracture strain with increasing A w . Uniaxial compression tests revealed moisture‐induced mechanical antiplasticization effects on the material in the glassy state which resulted in maximum compressive fracture stress but minimum fracture strain over the A w range from 0–0.56. Compressive modulus apparently was not affected much by moisture sorption up to an A w of 0.43, above which it decreased sharply.