Investigation On The Effects Of Various Drying Methods And Pretreatments On The Quality Attributes Of Dried Fruits And Vegetables

Nowadays fruits and vegetables dried chips had gained an increasing interest in the diet of the modern consumer due to a pleasant crispy mouthfeel.Usually,processed fruits and vegetable chips are the capable of increasing sector in the food industry.The several fruit and vegetable chips production techniques,instant controlled pressure drop(DIC)drying is an effective technology thru exceptional advantages.It pays to a porous structure characteristic and a pleasing crispy taste;those are important features of chips made from fruit and vegetable.Also,another promising characteristic of DIC is create in flavor,colour,rehydration and storage costs or production.The DIC technology also applied on many fruits and vegetables.Instant controlled pressure drop(DIC)is a novel dehydration method which follows a process in three-stage.The results revealed that blanching assisted with DIC(B+DIC)had a significant effect on fruits and vegetable chips as compared with DIC treated.The DIC dried mango chips were observed to have a low hardness(26.12 N),and maximum crispness(10.43)that were also observed in mango chips under B+DIC treated(14.66),exhibiting a puffy structure and crispy texture.The well-expanded structure which reflected by volume ratio(VR)was found in the mango(0.46 m L),change in colours(?E)were also obtained in the mango(30.40)and carrot(42.87)chips under B+DIC.The microstructures of the king oyster mushroom(KOM)(0.36 m L)chips under both treatments.The maximum total colour changes apple,carrot,KOM and potato chips products,which corresponded to its well-expanded appearances,showed a honeycomb-like pores structure,observed for DIC treated apple,fresh potato chips,and B+DIC dried KOM as well as in sweet potato.In addition,the B+DIC-treated carrot chips,pores size,increased the cell wall and expanded.Moreover,the mushroom chips mostly were shrunken after hot water blanching.The effects of selected pre-treatments combined with DIC drying on apple,pineapple,carrot,and king oyster mushroom(KOM)were investigated.The maximum water loss and solid gain were observed in the carrot and KOM chips under the combination of blanching,freezing,and osmotic dehydration associated with DIC(B+Fz+OD+DIC).The maximum change in total colour(?E)was recorded in the KOM chips when treated by freezing assisted with DIC(Fz+DIC).The maximum VR was observed in the osmotic dehydration assisted with DIC(OD+DIC)treated carrot chips.The highest sensory score,(i.e.,colour,flavour,and texture)were achieved in the case of B+Fz+OD+DIC treatment,and the DIC treated chips.The low hardness and high crispness were found in the pineapple chips under B+Fz+OD+DIC.The most desirable volume expansion was achieved for the chips treated with OD+DIC.Based on these results,the present study concluded that the combination of B+Fz+OD pre-treatments combined with DIC is the best solution to achieve the desired texture,microstructure,volume ratio,colour,and sensory evaluation for the four selected fruits and vegetable chips.Another part of this study drying kinetics of apple and peach dried chips during hot air drying(HAD)at(50?,60?,70?)and freeze drying(FD)were invistigated,drying characterestatics such as moisture ratio(MR),drying time,drying rate(DR),and moisture content(g/g db).In both drying methods drying process occurred essentially in the falling rate period respectively.On the other hand,in the both drying methods isotherm was investigated the sorption and desorption of apple and peach significantly increased.Moisture diffusivity(Deff)values of apple and peach fruit chips were different from 2.85×10-14 to 9.73×10-14 m2/s and 4.27×10-14 to 8.16×10-15 m2/s.Value of Deff increased gradually to the maximum value then declined as the decrease of moisture content(db),and in FD investigated the higher value of Deff;respectively.Similarly,in HAT was investigated the higher temperature resulted in the higher value of Deff.HAT-70? and FD were more-effective and promising drying method for apple and peach fruit chips.The last part of the present study,belongs to the nutritional and aromatic compounds of apple and peach chips dried with hot air treatment(HAT-50?,60? and 70?)and freeze-drying(FD).The results of present work shown that an increase in drying temperature caused degradation of total phenolic concerning corresponding content from apple and peach dried by hot air drying(HAD)and(FD)samples(p < 0.05).Similarly,trend founded in vitamin C(Vc),while apple chips dried by HAD and FD treatments,but peach dried chips had different from apple dried chips while the increased temperature also increased the Vc content.On the other hand,no differences in DPPH,ABTS and FRAP activity among the apple and peach dried chips samples dried by HAD and FZ,determined higher value in HAT-60? and followed by FD apple dried chips.The volatile profile or aromatic compound of apple and peach dried with HAD with(50?,60?,and 70?)and FD were characterized by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry(HS-SPME/GC–MS)and E-nose(electronic nose).GC–MS results showed that a total of 132 aroma compounds were identified in apple and peach dried chips,the maximum aroma compound was detected from 1,3-octanediol apple dried by all HAD treated apple chips were the main aroma components with contributions that over 75%.Differentiation of apple and peach chips dried with both treatments were conducted by cluster analysis of GC–MS data and principal component analysis of E-nose data.Both results showed that apple and peach dried chips could be mainly divided into two different groups:(A50,A60,A70,and AF)in the group(A)and(P50,P60,P70,and PF)selected in the group(B).There were significant differences in contents of alcohols,acids and aromatic compounds between group A and B.GC–MS combined with E-nose could be an accurate and fast method to detect the main flavour difference in different treatments in apple and peach dried chips.