INFLUENCE OF MICROWAVE DRYING ON THE CONTENT OF PHOTOSYNTHETIC PIGMENTS IN SPINACH

Abstract

Drying is the process of removing the moisture in the product up to certain threshold value by  evaporation.  In  this  way,  the  product  can  be  stored  for  a  long  period, since  the activities  of the microorganisms,  enzymes  or  ferments  in  the  material  are  suppressed  via  drying. Spinach  leaves (Spinacia oleracea) were dried using two different methods: hot air and microware drying. The aim of this  study  was  to  determine  the  effects  of  the  microwave  output  power  on  drying  time,  moisture content,  moisture  ratio  and  the  dried  product  quality  in terms  of  chlorophyll  content.  10  g  of  leaf samples were dried in an oven at 100 ^o C to asses their initial moisture content. Six different microwave output  powers  (120,  280,  340,  460,  600  and  700  W)  were  investigated  in  drying  experiments  at constant sample loading. Microwave drying period lasted between 3 and 10 minutes.  Increasing the microwave  output  power  resulted  in  a  considerable  decrease  in  drying  time.  The  content  of chlorophylls was colorimetrically determined by measuring absorbance in the absorbance maximum for these pigments. The chlorophylls were extracted using acetone which was proven to be one of the most  efficient  solvents.  Results  showed  that  the  optimum  microwave  power  for  drying  in  terms  of chlorophyll content is 340W.