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IMPACT OF CALCIUM ON VISCOELASTIC PROPERTIES OF FORTIFIED APPLE TISSUE
Author(s) -
SALVATORI DANIELA M.,
DOCTOROVICH ROMINA S.,
ALZAMORA STELLA M.
Publication year - 2011
Publication title -
journal of food process engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 45
eISSN - 1745-4530
pISSN - 0145-8876
DOI - 10.1111/j.1745-4530.2009.00550.x
Subject(s) - viscoelasticity , calcium , rheology , atmospheric pressure , creep , plasmolysis , chemistry , dynamic mechanical analysis , materials science , breakage , composite material , biochemistry , cell wall , metallurgy , oceanography , geology , polymer
The objective of this study was to analyze the linear viscoelastic behavior of calcium impregnated apples by creep and sinusoidal tests and to correlate the changes in rheological parameters with some structure features. The effect of different Ca concentrations of impregnation solutions (0, 0.1 and 0.53%, w/w), system pressure (vacuum or atmospheric) and process time was studied. All samples showed a viscoelastic solid behavior with the storage modulus ( G′ ) dominating the viscoelastic response. Treated apple samples with or without calcium showed a pronounced decrease in G′ as compared with fresh tissue. Instantaneous compliance ( J 0 ), decay compliances ( J 1 and J 2 ) and fluidity significantly increased after treatments, while retardation times were approximately constant. Impregnation at high calcium concentrations provoked severe folding of walls and/or a general inner disruption of cells with plasmolysis and membrane breakage in a different way according to the pressure applied and the treatment time, explaining the viscoelastic behavior. Changes in compliances and storage modulus values were significantly lower for apples treated under vacuum than when the treatment was performed at atmospheric pressure, suggesting that vacuum impregnation is an effective methodology to fortify apple tissue avoiding serious damage in viscoelastic properties and presumably in texture.PRACTICAL APPLICATION Incorporation of physiologically active food components (PACs) into vegetable matrices to obtain functional foods opens new product opportunities for the food industry. Impregnation processes performed at atmospheric pressure or under vacuum conditions may be employed to incorporate PACs, among them calcium. Because of alterations in structure, these processes can strongly modify rheological properties and hence texture of fruits. The results of this research can help to select operative impregnation conditions that allow the incorporation of great calcium quantities in apple tissue minimizing changes in viscoelastic properties. This objective is of primordial interest when designing minimally processed “fortified apples” preserved by refrigeration and to be consumed as is.