Study On Vaccum Freeze-dring Processing Technique Of Ficus Carica L.

Fig fruits are a kind of green food without pollution， pesticide residues andenvironmental disruption. It is soft and sweet in taste， fragrant in flavor， and has greatnutritive value and medicinal value. With soft texture and thin skin， fig fruits aresusceptible to mechanical injury and this made it difficult for storage and transportation.Thus developing new fig products of high quality is in demand. This will not only providea way of sustainable development for fig industry， but also improve the competitivestrength of fig products in the market both domestic and international and furthermoreopen up a new road for the fig export.At present，Figs were dried by traditional natural air drying or traditional cooked inmost of the areas．The poor drying technology and product quality can not meet consumerdemand．Therefore，in order to improve the drying techonoligy of figs and meet demandsof domestic and international market．In this study，Ficus carica L．from Weihai，Shandongwas choosed as the test materials，using vacuum freeze-drying technology for figs dryingdehydration，not only to keep the nutrients content of the figs in the greatest degree，butalso help transport and sales of figs，and increase its economic value．The test results showthat：1． This study used resistance detection method for eutectic point and melting point offig，the eutectic temperature is-28℃， the melting point is-24℃．Ultimately，Thepre-freezing temperature is-34^-38℃， pre-frozen time is2h before figs dring．2． This study choosed the rate of drying and freeze-drying energy consumption duringthe figs vacuum freeze-drying process as the test indicators，and slice thickness，dryingchamber pressure，heating plate temperature as the test influencing factors，the resultsshowed that the slice thickness of7to10mm，the drying chamber pressure of30to50Pa，the temperature of the heating plate at50to60°C by single-factor test．3． To further optimize the vacuum freeze-drying process of Ficus carica L byBox-Behnken experimental design，using Design Expert8.0.6software to analyze test dataand built the regression mathematical model of the main influential factors on the dryingrate and lyophilized energy consumption．Y1=-6.47972+0.25403X₁+0.19792X₂+0.015583X₃-1.16667×10^-3X₁X₂-3.33333×10^-4X₁X₃+2.0×10-4X₂X₃-9.30556X₁₂-1.75×10^-3X₂₂-3.125×10^-4X₃₂Y2=251.01972-5.71569X₁-7.47528X₂-0.036400X₃+0.047833X₁X₂-0.014200X₂X₃+0.17047X₁²+0.069370X₂²+9.96750×10^-3X₃² By response surface analysis，the optimal parameter conditons：material thickness9.43mm，heating plate temperature of55.34°C，drying chamber pressure38.40Pa，thepredictive value of drying rate and lyophilized energy consumption are0.51h-1and19.13kw h．According to the actual situation，this study choosed parameter conditons：materialthickness of10mm， the heating plate temperature of55°C，the drying chamber pressure40Pa，the actual measured drying rate is （0.52±0.01） h-1，lyophilized energy consumptionis （19.16±0．14） kw h．4． Vacuum freeze dried figs in the physical and chemical indicators，nutrients，sensoryindicators have shown a good advantage．During the lyophilized figs process，the Vcretention rate of95.09%，total sugar retention rate of96.89%，moisture content and wateractivity values were4.05%and0.612which inhibited the Microorganisms and relativeenzyme activity， the lyophilized figs can be achieved by safe storage，rehydration ratiowas6.16，the lyophilized figs had a good performance of rehydration．Amino acid contentretention rate of more than98%，essential amino acids accounted for32.09%of the totalamino acids．Fatty acid content retention rate of more than90%，unsaturated fatty acidcontent accounted for82.22%of the total fatty acids．the trace elements of Se had thehighest retention rate，up to96.76%，the retention rate of Cu was90.54%，Fe and Znretention rates were92.37%and91.28%．The L*and a*value of lyophilized figs wasincreased，it indicated that the brightness and the extent of red were increased．△E*difference value of the lyophilized before and afte was5.51，it indicated that the changedegree of colour reached to be identified by eye．Texture parameters of lasticity，adhesiveness，chewiness are lower，Brittleness was moderate，it indicated that thelyophilized figs were easy to chew，taste good， the hardness was not great，so thelyophilized figs shoud be used vacuum packaging to prevent its extrusion broken in thetransport．...