EFFECTS OF CO-IMMOBILIZATION OF PECTINASE AND AMYLASE ON ULTRAFILTRATION OF APPLE JUICE SIMULATE

In view of its possible application in apple juice clarification, the potential of co‐immobilized pectinase/amylase by physical adsorption on a polysulfone ultrafiltration hollow fiber was examined. Solutions containing different concentrations of pectin and starch were used. The effect of various operational parameters on the production of reducing compounds, mainly galacturonic acid and maltose, was investigated. Results indicated that relative permeate flux, during ultrafiltration of starch‐pectin solutions, was up to 35% higher when commercial pectinase and amylase were co‐immobilized on a hollow fiber membrane. Although the concentration of reaction products increased up to 50% with the pectin concentration, the same was not verified when the starch content changed from 3.85 to 5.00 mg/mL. However, the reference permeate flux was improved when starch was added to substrate, independently of its concentration. Considering the size of an average starch granule, this increase in permeate flux was attributed to the removal of pectin gel by dragging. Permeate fluxes were comparable for both batch and permeate recycling operations.     

EFFECTS OF PECTINASE IMMOBILIZATION DURING HOLLOW FIBER ULTRAFILTRATION OF APPLE JUICE

The immobilization of commercial pectinases by physical adsorption on hollow fiber ultrafiltration (HFUF) membranes was studied in view of its possible application in fruit juice clarification. The optimal pH during immobilization and washing was investigated, as well as the effects of enzyme and pectin concentrations and retentate flow on the operation. Results indicated that permeate flux was not initially increased when pectin solution or apple juice was ultrafiltred through pectinase immobilized on HFUF membranes. However, enzyme immobilization greatly extended the membrane operation, by keeping permeate flux constant during prolonged periods at a reasonable yield.     

Effects of Irradiation and Storage on the Flavor of Garlic Bulbs cv "Red"

The effects of 50 Gy gamma irradiation 30 days after harvest on the flavor of garlic bulbs cv “Red” during storage at room temperature for 300 days were evaluated. The contents of sulfur compounds and enzymatic pyruvate (EP) were determined by GLC and spectrophotometry as a measure of flavor intensity. Upon comparison of irradiated and nonirradiated bulbs no differences were observed in the contents of EP, cyclic disulfide compounds 144-1 + 144-11 (GLC-induced rearrangment products of allicin, the chief flavor component), and diallyl disulfide (DADS). At the end of the storage both samples showed a significant reduction in 144-1 + 144-11 and EP. On the contrary, DADS underwent an increase in both treatments.