Study On The Freeze Concentration Technology Of Apricot Juice

In recent years, the characteristics of its low temperature and effective protection to thenutritional quality of the concentrated materials, freeze concentration process has been paidwidely attentions. In this paper, taking apricot juice as experimental material, the weight of icecrystals, purity as test targets, through single factor test, researched the influence of crystal weightand purity by refrigerant temperature, juice concentration, taking ice time,with Box-behnkenresponse surface design method. According to the relationship between the degree of apricotjuice’s concentration and the state of ice crystal’s growth, developed and improved the multi-levelfreeze concentration for apricot juice, systematically elaborated the various factors that influencedapricot juice frozen concentrated consequent in the light of changes in nutrients before and afterconcentration. Specific studies and results are as follows:(1) On the basis of single factor experiments, used response surface software, according to theexperimental requirements of the two corresponding values that ice strength, ice crystal puritywere taken maximum and minimum, and drew the best crafts for apricot juice freeze concentration:refrigerant temperature-15.00℃, juice concentration14°Brix, taking ice time1.3h. The validationtests showed that the average ice strength148.21g, purity1.0°Brix on this process.(2) According to the relationship between the apricot juice soluble solids content and freezingtemperatures can be concluded that: Soluble solids content and freezing temperatures werenegatively related to the relationship, the greater the solid content, the lower the freezing point, theregression equation: Y=-0.0063x2+0.1175x-1.7862(R2=0.9992). According to this equation,you can quickly calculate the freezing temperature. When detector shows this temperature, adjustthe power to reduce the cooling capacity of the refrigeration compressor unit. Taking this methodcan effectively reduce ice entrained solute content, reduce losses and reduce energy consumption.(3) After multistage frozen concentrated treatment, the soluble solids content of apricot juiceincreased from13°Brix to49.8°Brix. It is about3.8times the original concentration of apricotjuice. Drawing regression equation about concentrated juice soluble solids content andconcentrated series: TSSc=0.058x3－2.3214x2＋18.627x＋13.074（R2=0.9997）;regressionequation about icing fluid soluble solids content and concentrated series: TSSi=0.125x3－0.3857x2＋1.8679x－0.0814（R2=0.9913）.(4) Concentrated apricot juice was diluted by distilled water to the the original concentration ofapricot juice, and then determined the pH, protein, total phenols, flavonoids, reducing sugars, total sugars, total acid, vitamin C and other indicators. The experimental results showed that: In theinitial concentration, nutrients have varying degrees of loss. With the increase concentrated series,the downward trend is leveling off, but the retention of vitamin C decreases significantly. VitaminC retention rate was70%after three concentrations. Compared to the traditional hotconcentrations, freeze concentration obvious advantages.