Oday Al-Jammaas; Salih Sultan; Waleed Mahmood
Volume 19, Issue 2 , June 2019, , Pages 66-74
Abstract
The present study was undertaken to evaluate the characteristics of pectin methylesterase produced from Aspergillus niger. The enzyme had a molecular weight of 59.668 kDa. The enzyme exhibited maximum activity at 45°C. The enzyme lost most of its initial activity after 20 min of incubation at 75°C. ...
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The present study was undertaken to evaluate the characteristics of pectin methylesterase produced from Aspergillus niger. The enzyme had a molecular weight of 59.668 kDa. The enzyme exhibited maximum activity at 45°C. The enzyme lost most of its initial activity after 20 min of incubation at 75°C. Optimal activity and stability of the enzyme occurred at pH 4, with more than 90 % of retained activity after 10 min at pH 5. Michaelis constant (Km) was found equal to (1) mg/ml, whereas, maximum velocity (Vmax) was (1000) μmol/min. The catalyzed reaction by pectin methylesterase had activation energy equal to 9.66 Kcal/mol. The enzyme lost 24% and 13% of its initial activity during two months of storage at4°C and -20 °C, respectively. The enzyme was activated by NaCl, KCl and CaCl2 at concentration of 25 mM and inhibited by MgSO4, polygalacturonic acid, methanol, IAA and EDTA.
Oday Al-Jammaas; Salih Sultan; Waleed Mahmood
Volume 19, Issue 1 , March 2019, , Pages 84-92
Abstract
Effect of treatment of hot break single strength tomato juice (SSTJ) with different concentrations of exogenous pectin methylesterase (0, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 U/ 100 ml tomato juice) (PME) produced by Aspergillus niger under optimum conditions (45°C and pH= 4 for 10 min ...
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Effect of treatment of hot break single strength tomato juice (SSTJ) with different concentrations of exogenous pectin methylesterase (0, 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 U/ 100 ml tomato juice) (PME) produced by Aspergillus niger under optimum conditions (45°C and pH= 4 for 10 min in a water bath) selected based on a preliminary experiment was investigated in this study. The maximum viscosity value (342 cP) for tomato juice was obtained when pectin methylesterase concentration was added as (25 U/ 100 ml juice). The changes in some properties of (SSTJ) were evaluated after pasteurization and bottling in amber glass bottles and during storage at 4 and 22°C for 6 weeks. It was found that there was a significant increasing in viscosity for enzymatic treated (SSTJ) samples after pasteurization, comparatively to the viscosity value of enzymatic untreated SSTJ (control), storage for 6 weeks at two respective temperatures, caused an insignificant decreasing in the viscosity of enzymatic treated (SSTJ) samples. A significant increasing in GalA for WSP was observed in juices after their pasteurization and storage at 4 and 22°C for 6 weeks. The results indicated that there were significant decreasing in GalA for CSP whereas, the decreasing of GalA for NSP was insignificant for enzymatic treated tomato juices as compared with untreated tomato juices. The DM for WSP and CSP in treated samples were significantly lower than that for untreated samples after pasteurization and bottling and during storage for 6 weeks at 4 and 22°C. The DM of NSP could not be assaying due to the saponification of methylesters during the alkali extraction of this fraction .
