A microwave based system was developed for drying of apple slices while on-line controlling their temperatures. An infrared thermography assisted control system allowed to realize temperature control by detecting the instantaneous maximum temperature among the samples under test instead of a chosen slice. The effectiveness of the system at hand in realizing temperature control both in space and in time was proven for three temperatures: 55, 65 and 75 C. Temperature fluctuations became larger both with time increasing and with rising temperature levels thus causing a negative impact on dried fruit quality. In fact apples slices dried at 75 C by microwave showed L⁄ (lightness) and white index (WI) values significantly lower (p < 0.05), when compared to the fresh samples and to the apples dried by hot air. To overcome such behaviour a mode stirrer was introduced resulting in halving the temperature spatial oscillations of sample slices.
|Digital Object Identifier (DOI):||dx.doi.org/10.1016/j.jfoodeng.2012.05.003|
|Codice identificativo ISI:||WOS:000306779400010|
|Codice identificativo Scopus:||2-s2.0-84862687361|
|Appare nelle tipologie:||1.1 Articolo in rivista|