تاثير آبگيري اسمزي بر دماي گذار شيشه اي و شاخص هاي كيفي ميوه توت فرنگي با هدف توليد دم نوش توت فرنگي

چكيده انگليسي :

76 Efficacy of Osmotic Dehydration on Glass Transition Temperatureand Quality Attributes of Strawberry in Order to Produce Strawberry Tea Mohammad Zarean mohammad zarean@ag iut ac ir July 14 2015 Department of Agricultural Machinery Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiMorteza Sadeghi sadeghimor@cc iut ac ir AbstractStrawberry is an aromatic fruit with high nutritional value and moisture content The respiration intensityof this fruit is high compared with other fruits This makes it a perishable product susceptible tomechanical damage which cannot be stored for a long time Therefore drying of strawberry is of greatimportance for improving its shelf life Applying osmotic dehydration process when combined with otherdrying methods could be led to some advantages firstly the final product will have better quality incomparison with normal drying techniques and secondly helps saving energy Osmotic dehydrationprocess can be used for having products with intermediate moisture content or as a pretreatment forprocesses such as drying and freezing In this research osmotic dehydration of strawberry var Selva slices with the initial moisture content of 92 w b and thickness of 5 mm and diameter of 2 5 0 9 cmwas carried out The samples were soaked in osmotic solution of glucose at concentrations of 30 40 and50 Brix temperatures of 25 40 and 50 C and durations of 30 60 and 120 min The kinetics of masstransfer during osmotic dehydration including the amount of water loss WL solid gain SG and weightreduction WR as well as the kinetics of color indices L a and b chroma index and E were studied Moreover the glass transition temperature Tg of the control sample and those soaked in the osmoticsolution for 1 and 2 h was measured by a DSC apparatus Then the samples were dried in an oven at 95 C for 12 h until they reached to a constant weight and their shrinkage and color indices were determined The strawberry tea drink was prepared from the dried samples The drinks were compared in terms oftaste and color using sensory evaluation Analysis of variance showed that the effect of temperature andinteraction effect of solution concentration and temperature on WL was significant Also the effect oftemperature on SG and the effects of concentration and temperature on WR were significant The Tg of thesamples decreased with increase in temperature and concentration due to the moisture loss and weightreduction The effect of temperature and interaction effect of concentration and temperature on shrinkagewere significant After drying the shrinkage in osmotic dehydrated samples reduced 13 compared withthe untreated samples With decrease in moisture content during osmotic dehydration the lightness L and the redness a decreased but the yellowness b increased Applying osmotic pretreatment led tosignificant increase in L and b values for oven dried treatments in comparison with the correspondingvalues for the control treatment Also applying osmotic pretreatment caused improvements in E andChroma index The results obtained by sensory evaluation revealed an enhancement in taste and color forpretreated samples The drink prepared from the dried sample pretreated at concentration of 40 Brix andtemperature of 40 C had the best quality in terms of color and taste Keywords Chroma index glass transition temperature mass transfer kinetics osmoticdehydration strawberry total color difference

زارعان آدرمنابادي، محمد

تاثير آبگيري اسمزي بر دماي گذار شيشه اي و شاخص هاي كيفي ميوه توت فرنگي با هدف توليد دم نوش توت فرنگي

اختلاف رنگ كل , سينتيك انتقال جرم , شاخص كروما