On the use of edible coatings to monitor osmotic dehydration kinetics for minimal solids uptake

During osmotic dehydration, extensive solute (i.e. sugar) uptake is an undesirable side effect, as it is counteracting water removal, while it modifies nutritional and/or organoleptic properties in a rather negative mode, damaging the natural, fresh product profile. Coating of whole strawberries with selected edible (polysaccharide) films before osmotic processing was found to favor water removal and prevent solute uptake. Among tested materials and coating procedures, double coating with a 0.5% sodium alginate (SA) solution gave the best results in terms of a high water loss (WL) to solid gain (SG) ratio (WL/SG), which is strongly related to the so called, “Dehydration Efficiency Index” (DEI). Single or double SA coating inhibited leakage losses upon freeze/thawing of osmotically treated strawberries. Lowering leakage losses was beneficial both in terms of higher product yield and in terms of marginally improved product texture. A higher process temperature (50 °C) caused significant color deterioration after the second hour of osmotic treatment.