Design, fabrication and evaluation of a Bobloon vacuum Dryer

Abstract

The bobloon vacuum, a device that employs a deflating and inflating bobloon to create vacuum inside a drying chamber was fabricated according to the design shown in Figure 1. To evaluate the performance of the device, samples arranged in a basket, were introduced into the drying / vacuum chamber before the chamber was made air tight by means of a screw cap. The magnitude of vacuum is read off the vacuum meter (operation pressure -1.5kp), while an incooperated industrial thermometer helped to ensure a working temperature of 50⁰C. The samples (10g each) of carrot, hot pepper and guava after eight hours of vacuum drying reported new weights of 3.7, 4.3 and 5.5g respectively. Equal weights of same produce (samples), dried under the sun (inside a glass covered cabinet dryer) for 8 hours had the following weights respectively: 1.8, 2.2 and 2.8g. Results showed that Vitamin A in the carrot samples reduced from 213µg/100g in fresh sample to 146µg/100g in vacuum dried and 16.5µg/100g for sun dried samples respectively. The sensory evaluation (color comparison) between fresh, vacuum dried and sundried carrot, showed no significant difference between the fresh and vacuum dried samples (p≤0.05).