Abstract
Strawberry halves, with and without osmotic pre-treatment, were dried at 40 °C air temperature, with and without microwave application (0.2 W/g). Changes in volume, pectic fractions, mechanical behaviour and glass transition temperature due to dehydration treatments were evaluated. Microwave application resulted in an increased water soluble pectic fraction as a consequence of both protopectin and oxalate soluble pectic fraction reductions. This solubilisation leads us to obtain dried samples with a more rigid, firmer structure which, indeed, showed greater glass transition temperature values. Nevertheless, these samples are softer when rehydrated, thus indicating a greater structural damage. The sugar presence induced by an osmotic dehydration pre-treatment seems to reinforce the solid cellular matrix, which is evident from the mechanical behaviour of rehydrated samples. So, the greatest structural damage caused by microwaves may be reduced by an osmotic dehydration pre-treatment.
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The authors thank to the Ministerio de Ciencia y Tecnología and to the Fondo Europeo de Desarrollo Regional (FEDER) for the financial support throughout the project AGL2005-05994.
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Contreras, C., Martín-Esparza, M.E., Martínez-Navarrete, N. et al. Influence of osmotic pre-treatment and microwave application on properties of air dried strawberry related to structural changes. Eur Food Res Technol 224, 499–504 (2007). https://doi.org/10.1007/s00217-006-0345-6
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DOI: https://doi.org/10.1007/s00217-006-0345-6