Document Type : Articles
Authors
Department of Food Science, College of Agriculture and Forestry, Mosul University
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 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 .
Keywords
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