Effects of Different Drying Methods on Drying Kinetics and Color Parameters of Strawberry Tree (Arbutus unedo L.) Fruit

Changing of drying kinetics and color parameters of strawberry tree fruits that were notreated (NPT), ethyl oleate pretreated (EO) and water blanched at 80 degrees C (WB) for one minute were evaluated during hot air drying at 50 degrees C, 60 degrees C and 70 degrees C and vacuum drying at 60 degrees C, 70 degrees C and 80 degrees C for halved and whole fruits. In addition to drying behaviors of strawberry tree fruits at different drying methods, tri-stimulus color parameters such as Hunter L*, a* and b* values were measured. HMF (formation of 5-hydroxymethylfurfural) occurring was also determined due to drying process. EO pretreatment was found highly effective on decreasing of drying time both for hot air drying and vacuum drying processes while WB pretreatment found to be more effective to keep color properties of strawberry tree fruits. Color properties were found to be better in half samples compared to whole dried fruits. HMF values verified this result. Hot air drying process caused to shorter drying time. High drying air temperatures (70 degrees C for hot air drying and 80 degrees C for vacuum drying) for all samples caused to occur HMF while HMF occurred in only whole dried NPT and WB treated fruits for hot air drying process at 60 degrees C. All these data show that hot air drying method at 60 degrees C drying temperature and, halving of fruits before drying can be proposed for drying of strawberry tree fruits in respect of drying kinetics, color and HMF values.