Osmotic Dehydration of Apples Under Reduced Pressure Conditions
Abstract The aim of the study was to determine the effect of reduced pressure on the osmotic dehydration of apples. Tests were performed under vacuum of 8 kPa, 67 kPa, 80 kPa and under the atmospheric pressure (100 kPa). The samples were dehydrated in a sucrose solution with a concentration of 30°Bx, 50°Bx and 70°Bx. It has been shown that the effect of low pressure application depends significantly to the concentration of the osmotic solution. It has been found that the overall weight change significantly depend on the concentration of the solution, and after 3 hours of dehydration at a pressure of 80 kPa at solutions of 30°Bx, 50°Bx and 70°Bx total weight loss increased by 65%, 12% and 25% respectively, when compared to samples dehydrated at atmospheric pressure. From the studied variants of reduced pressure, the pressure of 80 kPa seems to be the optimal one, as evidenced by the lowest values of weight gain to water loss ratios for apples dehydrated in solutions of 50°Bx and 70°Bx.
Analiza procesu suszenia papryki czerwonej w złożu fontannowym z nagrzewaniem mikrofalowym
. The purpose of the study was to determine the applicability of spouted dryer heated by microwave material and obtain information about the process and the kinetics of water loss and of the effect of the drying process on antioxidant activity and polyphenol content of red pepper. During drying red peppers was found that with the increase of the microwave power is increased content of polyphenolic compounds and antioxidant activity. The results indicate that fountain-microwave drying ovens allows for drought of good quality and improving the quality of dried peppers over traditional convection drying.
Cutting test application to general assessment of vegetable texture changes caused by freezing
Cutting test is extensively applied to assess quality of vegetables subjected to the freezing treatment. Particularly, the changes of tissue structures are evaluated on the grounds of maximum cutting force of material. The vegetable material was air frozen by two methods, i.e. at natural convection and by impingement fluidization. The cutting test performed on Brookfield materials testing machine was used to evaluate the influence of freezing method on product texture. The scanning electron microscopic images of tissue were included into the supportive analysis of freezing-mediated damages. It was found that a change in maximum cutting force can not be considered as a fully reliable indicator of material quality evaluation owing to the force value dependence on a mass change of material during its treatment. A complementary attribute that depicts freezing damage size proves to be appropriately defined material elasticity.