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Sensory evaluation of apple cubes (Granny Smith var.) impregnated with concentrated grape juice (Victoria var.) subjected to convection drying - RIIIT
Sensory evaluation of apple cubes (Granny Smith var.) impregnated with concentrated grape juice (Victoria var.) subjected to convection drying
Fruit dehydration process generally uses high temperatures to reduce the moisture content in a short time. The high temperature modifies the sensory characteristics due to loss of thermolabile compounds, and chemical or enzymatic reactions that affect the acceptance of dehydrated fruits, being undesirable quality parameters. The use of osmotic dehydration has been used as a pre-treatment to enrich the food matrix with solutes that improve the nutritional composition, provide morphometrical and color stability. The aim of this work was to evaluate drying kinetics of impregnated apple cubes (Granny Smith var.) with grape juice concentrate (Victoria var.) in order to achieve a sensory acceptable snack. The impregnation pre-treatment was carried out with Victoria grape juice concentrate (40°Bx, 25°C, 4 g solution/g product, and 960 min); color, aw and drying kinetics of apple cubes (1.5×1.5×1.5 cm) subjected to convective drying (40°C and air velocity of 0.5 m/s) were investigated. Drying curves were modeled using selected models: Newton, Henderson & Pabis, Page, Weibull and Fick´s second Law. Dried pre-treated fruits were sensory evaluated using a nine-point hedonic scale. The results indicated that impregnated apples had a water loss of 0.53±0.12 g water/g product and solids gain of 0.07±0.00 g solids/g product. In addition, Page and Weibull models were found to be the most appropriate to describe the drying characteristics of fresh and impregnated samples, respectively. Effective water diffusivity of fresh and impregnated apple cubes was 11.4×10-10 and 0.50×10-10 m2/s, respectively. Fresh and impregnated samples required 440 and 850 min, respectively of convective drying to obtain a low moisture fruit (aw=0.26±0.04 for fresh-dry product and aw=0.36±0.01 for impregnated-dry product). No significant differences (p<0.05) were observed in the brightness and hue of the impregnated product due to the drying process (ΔE=7.98). It obtained an overall acceptability score of 8.57±0.16, being a sensory acceptable product, especially in taste and aroma.
Key words: apple cubes, convective drying, food impregnation, grape juice concentrate, sensory evaluation.
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