Preparation Of Clarified Hami Melon Juice And The Application Of Membrane Technology In The Sterilization

Hami melon has rich nutrition and excellent taste, but it is perishable. An effective way to avoid putridness is to manufacture juice. Hami melon juice is a kind of typical heat-sensitive juice, the change of aroma constituents and its off-odors formation that caused by thermal processing could not being avoided. Membrane filtration is a kind of nonthermal processing technology. Membrane filtration can filtrate the bacteria effectivly and preserve flavors and nutrients of hami melon juice well.This paper were studied systematically on the membrane technology process and pretreatment process in order to provide foundational theoretical gists and reference for this process industralization. The main results were presented as followed:Sensory qualities, nutrimental compositions and juice yield of five kinds of hami melon were analysed. Boxiekexin (cassaba) is the best selection because of its full-bodied fragrance, rich nutrition and supernal juice yield.The color preserving technology was studied in order to avoid browning during the processing of hami melon juice.The effect of good color protection could be obtained by appending 0.25% citric acid and 0.2% Vc.The effect on Hami melon juice clarification was studied by using pectinase. Both single factor test and orthogonal test were carried out. The results showed that the influence order of each factor on clarifying hami melon juice was juice pH>dosage of pectinase>reaction time>reaction temperature. The best clatification conditions were amount of pectinase 0.02%, temperature 30℃, the time 1.0h and pH4.0. The transmittance of the juice treated was up to 97%, the soluble solid content(SSC) was increased appreciably, the pectin was disposed about 97.5%, the protein was disposed about 92%. There was inapparent difference in total sugar content, total acidity and vitamin C content between the clarified juice and raw juice. The emzyme was effective for the removal of pectin from Hami melon juice. The result was satisfactory.Filtrating bacteria by organic membrane was studied. The optimal operation conditions were pressure of 0.05Mpa and temperature of 25℃using 0.2μm PTFE membrane.The application of ceramic membrane in filtrating bacteria of hami melon juice was studied. Hami melon juice was filtrated by ceramic membrane with 0.10μm, 0.20μm, 0.50μm pore size. The physical, chemical and sensory properties, nutritional components, microorganisms idexes and permeation in the same conditons were investigated. The optimal technology wer pressure of 0.20Mpa, feed in flux of 8L/min and temperature 25℃with 0.20μm ceramic membrane. Compared to the organic membrane, ceramic membrane was disassembled easily, its ability of standing against heat,acid, microbial corrosion was better, can provide high efficiency. Because of the high mechanical strength, difficult to damage, ceramic membrane was more suitable for industrial application.