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In order to obtain pumpkin chips, hot air drying (HAD), freeze-drying (FD), combinations of hot air drying + explosive puffing drying (HAD + EPD) and freeze-drying + explosive puffing drying (FD + EPD) were studied and, the impacts of various methods and conditions (temperature, vacuum pressure and decreased the moisture content level after pre-drying) on the physical, antioxidant and textural properties of pumpkin slices have been examined.The best texture attributes, the highest rehydration ratio (RR), the highest volumetric expansion (VE), and the lowest bulk density were obtained from FD + EPD products. Otherwise, when FD samples were compared with FD + EPD ones, it was clearly seen that higher retention of total phenolic content, antioxidant capacity, total carotenoids and a better color quality were obtained. However, the combination of FD + EPD allows drying at a slightly shorter processing time that is compared to a single FD. FD + EPD products provided the highest crispness when it is compared with HAD + EPD. This fact indicated that the pre-drying method (FD) and the reduction of moisture level had a major impact on textural properties. Consequently, the FD + EPD combination proved that it is a more promising process when it was compared to other drying techniques in order to produce nutritious pumpkin chips., Scientific Research Projects of Ege UniversityEge University [BAP FLP-2018-20443], This research was supported by the Scientific Research Projects of Ege University (BAP FLP-2018-20443). The authors thank to the students Deniz Arc, Huseyin Tuncer and Ahmet Gurhan Akcan for lab support.

Adsorption isotherms, at 4, 25 and 60 °C for microencapsulated extra virgin olive oil powder (MEVOP) prepared by rotor–stator homogenization (RSH) and ultrasonic homogenization (UH) methods before spray drying, were obtained using standard static gravimetric method. The sorption isotherms exhibited type III (J shape) behaviour. The sorption isotherms of MEVOP depended on temperature, chemical composition of particle surface and particle size of samples. The equilibrium moisture contents (EMC) decreased with increasing temperature. The sorption isotherm of MEVOP obtained with UH shifted up compared to that obtained with RSH because of the smaller particle size of MEVOP obtained with UH. The Guggenheim–Anderson–de Boer (GAB) model was the best fitting the experimental sorption data. Monolayer moisture contents of MEVOP were in the range of 0.036–0.079 kg H2O per kg d.s. All K values of MEVOP were higher than 0.89. C values of MEVOP obtained with RSH and UH method varied in range of 7.17–13.86 and 8.42–27.76, respectively. Net isosteric heat of sorption was evaluated using the Clausius–Clapeyron equation and differential entropy decreased with increasing moisture content. Gibbs-free energy decreased with increasing equilibrium moisture content. The spreading pressure increased with the rise in water activity for all temperatures.

In this study, physical and chemical properties of microencapsulated extra virgin olive oil powder (MEVOP) produced through spray drying were investigated during storage under different temperatures (4, 25 and 60 °C). The effect of homogenization methods in terms of rotor–stator (RSH) and ultrasonic (UH) were also examined on MEVOP along storage period. The physical and chemical properties of MEVOP obtained either RSH or UH showed that water activity, tapped density, Carr index (flowability), caking degree, surface oil content, peroxide value (PV) and free fatty acid (FFA) significantly increased, while bulk density, microencapsulation efficiency (ME), total phenolic content and antioxidant capacity significantly decreased during storage at 4, 25 and 60 °C. However, as the particle size of MEVOPs stored at 4 °C decreased along storage time, particle size of samples stored at 25 and 60 °C increased due to increase in surface oil content and particle–particle cohesion. The MEVOPs stored 4 and 25 °C had higher particle density compared to the sample stored at 60 °C during storage. Rapid changes in antioxidant capacity and total phenolic content of MEVOP were also determined during storage with increased storage temperature. There was a significant effect of homogenization method on particle size, for this reason physical and chemical properties of powder changed. When all quality characteristics and oxidative stability were evaluated, MEVOP should be stored at ambient or lower temperature in order to increase its shelf life.