Journal
FOOD AND BIOPROCESS TECHNOLOGY
Volume 6, Issue 2, Pages 475-488Publisher
SPRINGER
DOI: 10.1007/s11947-011-0701-9
Keywords
Apple; Blanching; Osmotic dehydration; Rheology; Texture; Ultra- and microstructure
Categories
Funding
- University of Buenos Aires
- CONICET
- Agencia Nacional de Promocion Cientifica y Tecnologica of Argentina
- BID
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The objective of this work was to evaluate and correlate rheological properties (small-scale dynamic oscillatory and creep/recovery measurements and large-scale compression force-deformation testing), texture (sensory evaluation by trained panel) and structure (optical and transmission electronic microscopy observations) of apples osmotically dehydrated to water activity (a (w)) 0.97 with glucose, with or without previous blanching. All apple samples showed a solid behavior (G'aEuro parts per thousand > GaEuro(3)) dominating the viscoelastic response, but both dynamic moduli were reduced due to processing. The instantaneous elastic compliance (J (0)) and the retarded compliances (J (1) and J (2)) increased for treated tissues and the steady-state viscosity (eta (N)) was approximately 15% to 29% of the value of fresh apple. In general, compression parameters decreased for all treated tissues. Changes in structural features were mainly evidenced in heated samples. Partial least squares regression analysis regression models revealed that texture could be well predicted by rheological properties (compression and creep parameters). Juiciness, crispness and sensory hardness were negatively correlated to J (0), J (1) and J (2), and eta (N) was negatively correlated to sensory fracturability. Some mechanical parameters (fracturability, hardness 2, area 2, modulus of deformability and cohesiveness) were positively related to sensory fracturability, crispness and sensory hardness; and juiciness was negatively correlated to hardness. Compression and creep parameters showed ability to evidence structure differences (rupture of membranes, swelling of cells and degradation of cell walls) and to explain texture of treated apples.
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