Effects of vacuum impregnation and erythritol usage on the drying kinetics and quality characteristics in the production of infused dried sour cherry

This thesis aimed to investigate the effect of sucrose, erythritol and sucrose + erythritol (1:1 v:v) in the osmotic dehydration (OD) stage for the production of infused dried fruit from sour cherry (Prunus cerasus L.), as well as the effect of the same substances in the OD stage on the resulting product. The objective was to examine the effects of control, ultrasound and vacuum impregnation pretreatments on the production of infused dried fruit from sour cherries (Prunus cerasus L.) and to analyse the drying kinetics and final product properties of the dried sour cherries obtained as a result of drying. The aim was to investigate whether erythritol, a sugar alcohol, can be used as an alternative substitute for sucrose. In this context, the time-dependent dry matter change in each method was analysed kinetically in order to determine the optimal OD time for sour cherries. Consequently, the optimal OD time was established as 15 hours. Subsequent analysis of the dry matter content of the OD samples revealed that the most effective method was vacuum impregnation. At the end of the drying process, a series of analyses were conducted to evaluate the final product. These included measurements of the total dry matter content, water activity (aw), rehydration rate, shrinkage effect, browning index, total colour difference (ΔE), bioactive substances, texture properties, morphological properties by scanning electron microscopy (SEM), and sensorial quality. The analysis of the kinetic change revealed that erythritol was the carbohydrate that exhibited the greatest increase in dry matter content during the OD stage. The aw, shrinkage value and browning index values of infused sour cherries subjected to OD with a sucrose + erythritol solution exhibited a decrease of 27%, 53% and 24%, respectively, in comparison to the control. It was determined that the sucrose + erythritol group samples exhibited the most similar ΔE to the control group when compared to the individual use of carbohydrates. The highest bioactive substance values were observed in the control group. The results of the texture analysis revealed that the fruits produced with sucrose exhibited a hardness value of 2.40 N, while those produced with erythritol demonstrated a value of 2.91 N. In contrast, the fruits produced with a sucrose and erythritol mixture exhibited a significantly reduced hardness value of 0.79 N. These findings indicate that the use of a sucrose and erythritol mixture resulted in a notable reduction in products' hardness values compared to the use of either sucrose or erythritol individually. The morphological properties of the products examined by SEM analysis revealed a correlation between the effectiveness of the applied processes. According to sensory analysis, the most preferred product belonged to the sucrose + erythritol group. Upon evaluation of the results, it was determined that vacuum impregnation pre-treatment accelerated the OD process, by affecting the mass transfer. The combination of sucrose and erythritol in the OD process was identified as a favourable application, exhibiting benefits in both the production stage and the final product properties of the infused sour cherry, due to the synergistic effect it provides.