Optimization of pectinase-assisted extraction of Annona muricata L. juice and the effect of liquefaction on its pectin structure.

BACKGROUND: Soursop (Annona muricata L.) is an underutilized tropical and subtropical fruit with high nutritional and therapeutic benefits. This fruit is faced with enormous post-harvest losses due to its high perishability. This work was aimed to optimize the pectinase-assisted extraction conditions of soursop juice using Doehlert design and to study the effect of pectinase on its pectin structure. RESULTS: The predicted models were validated for all the responses studied and the regression coefficients ranged from 0.905 to 0.987 (P ≤ 0.05). An incubation time of 172 min, enzyme concentration of 0.04% (w/w) and incubation temperature at 42.9 °C were found to be the optimal conditions for soursop juice extraction, which resulted in 75.20%, 3.74, 7.35 °Brix, 87.06%T, and 0.44% MAE for soursop juice yield (%), pH, total soluble solids (TSS) (°Brix), clarity (%T) and titratable acidity (% malic acid equivalent, MAE), respectively. Morphologically, untreated soursop pulp presented a non-uniform spherical surface; enzyme hydrolyzed soursop exhibited ruptured and wrinkled surface; meanwhile for the different pectin obtained, untreated soursop pectin depicted porous surface and enzyme hydrolyzed soursop pectin showed whirling rough surface. Fourier-transform infrared (FTIR) confirmed the presence of similar chemical group stretching and vibrations in commercial pectin and soursop pectin. CONCLUSION: Under the optimum conditions, the numerical predictions were similar to the experimental data obtained, thus confirming the validity of the models. Application of enzyme treatment caused the breakdown of pectin structure as illustrated by scanning electron microscopy (SEM) and FTIR analyses.

White-flesh guava juice clarification by a fixed-angle conical rotor centrifuge laboratory and characterization of continuous disk stack centrifuges.

The two objectives of this paper were to determine the effect of centrifugation parameters on guava juice physicochemical characteristics and to identify operational characteristics of continuous disc-stack centrifuges based on the performance of a laboratory centrifuge. Effects of g-force (149 g-3731 g) and centrifugation time (10-40 min) on juice physicochemical characteristics (protein, pectin, galacturonic acid, dry matter, total soluble sugars contents; pH; electrical conductivity, clarity and particle size distribution) were assessed. Laboratory centrifuge performance was evaluated for 1343 g, 2388 g and 3731 g. At 1343 g, separation limits (x max ), feed flow-rates of disc-stack centrifuges and cut-off sizes (x 50 ) were determined for corresponding laboratory centrifuge operation times. Significant decrease in average particle size, protein and pectin contents was observed, contrary to juice clarity. Similar clarification efficiency was obtained for g-forces ≥ 1343 g. x max were 2669 nm, 2200 nm and 1783 nm, with corresponding x 50 for continuous centrifuges, 1887 nm, 1556 nm, 1261 nm, for 20 min, 30 min and 40 min, respectively.

Pectinase hydrolysis of guava pulp: effect on the physicochemical characteristics of its juice.

The objective of this research is to assess the effect of enzymatic treatment of guava puree on the physicochemical parameters of the juice. Pectinases from Aspergillus niger were applied to the puree at 43 ± 3 °C under constant stirring. Enzyme concentrations used were: 0.033 % (w/w), 0.055% (w/w), 0.078 % (w/w) and 0.1 % (w/w). For each enzyme concentration, the treatment times were varied from 3 - 90 min. Physicochemical parameters of raw puree and enzymatically treated juice were determined. These were: viscosity, pH, electric conductivity, protein and polyphenol content, galacturonic acid content, color, TSS, and antioxidant capacity. Particle distribution, homogeneity of raw puree and juice samples dried extracts were assessed using a Field Emission Scanning Electron Microscopy (FESEM). A 91% viscosity decrease was recorded for each enzyme concentration after 3 min of enzyme reaction. That drecrase was accompanied by an increase in galacturonic acid content with increasing depectinization factors. Enzyme treatment of guava puree led to a decrease in pH, protein and polyphenol contents and an increase in conductivity and color. Analysis of FESEM images of guava samples bestowed a decrease in particle size, a scattering of particles in the medium, an increase in continuous phase proportion and an improvement of sample homogeneity with increasing values of processing parameters, due to the breaking-down of bigger particles and the solubilization during depectinization.

Extraction and purification of beta-amylase from stems of Abrus precatorius by three phase partitioning.

The stems of Abrus precatorius were used to extract a beta-amylase enriched fraction. A three phase partitioning method and a Doehlert design with 3 variables (ratio of crude extract/t-butanol, the ammonium sulphate saturation and pH) were used. The data was fitted in a second-order polynomial model and the parameters were optimized to enrich beta-amylase. Experimental responses for the modulation were recovery of activity and the purification factor. The optimal conditions were: a ratio of crude extract/t-butanol of 0.87 (v/v), saturation in ammonium sulphate of 49.46% (w/v) and a pH of 5.2. An activity recovery of 156.2% and a purification factor of 10.17 were found. The enriched enzyme was identified as a beta-amylase and its molecular weight was 60.1kDa. Km and Vmax values were 79.37mg/ml and 5.13U/ml, respectively and the highest activity was registered at a temperature of 70°C and a pH between 6 and 6.5. A significant stabilization of the beta-amylase was observed up to 65°C.

Optimisation of low temperature extraction of banana juice using commercial pectinase.

The objective of this work was to develop a process with optimum conditions for banana juice. The procedure involves hydrolyzing the banana pulp by commercial pectinase followed by cloth filtration. Response surface methodology with Doehlert design was utilised to optimize the process parameters. The temperature of incubation (30-60 °C), time of reaction (20-120 min) and concentration of pectinase (0.01-0.05% v/w) were the independent variables and viscosity, clarity, alcohol insoluble solids (AIS), total polyphenol and protein concentration were the responses. Total soluble sugar, pH, conductivity, calcium, sodium and potassium concentration in the juice were also evaluated. The results showed reduction of AIS and viscosity with reaction time and pectinase concentration and reduction of polyphenol and protein concentration with temperature. Using numerical optimization, the optimum conditions for the enzymatic extraction of banana juice were estimated. Depectinization kinetics was also studied at optimum temperature and variation of kinetic constants with enzyme dose was evaluated.