Control of tomato juice consistency with pectinmethylesterase, calcium(II)ion and sodium ion
Abstract
Model systems containing pectin, protein, NaCl and CaCl$\sb2$, and later hot-broken tomato juice containing supplemental NaCl and CaCl$\sb2$, were reacted with pectinmethylesterase (PME) at both alkaline and acidic pH. The effects of pH, Ca$\sp{++}$, Na$\sp+$, and protein on tomato PME activation, deactivation, and consistency-controlling ability were elaborated. Much more deesterification occurred in pH 8.0 systems than in pH 4.3 systems. Supplemented Ca$\sp{++}$ and Na$\sp+$ salts greatly increased PME activity at pH 4.3 but decreased PME activity at pH 8.0. Protein dramatically altered the viscosity of pectin systems. NaCl was used to slow or weaken the strength of gels or prevent gelation in highly deesterified pectin systems. A new method for calculating the effect of pectin-protein interactions on consistency was proposed. Component fractional viscosities were subtracted from the gross viscosity to obtain the non-measurable viscosity fraction caused by the interaction of pectin and protein. Reduced viscosity values suggest larger, less compact pectin-protein complexes in the pH 8.0 reacted system than in the pH 4.3 system. PME treatment greatly increased gross viscosity and precipitate weight ratio values but greatly decreased serum viscosity of tomato juice. PME treatment of hot-broken tomato juice resulted in a high viscosity, high PPT, but low serum viscosity product. Tomato juice consistency varied with selective addition of Ca$\sp{++}$ and Na$\sp+$ salts in the presence of PME. Moreover, it was suggested that tomato product yield could be increased by optimization of Ca$\sp{++}$ and Na$\sp+$ salt concentrations in the presence of highly deesterified pectin. Schematics were proposed for the pectin-pectin, pectin-protein, and protein-protein interactions that may be responsible for the stable, high viscosity purees obtained with both model systems and tomato juice.
Degree
Ph.D.
Advisors
Nelson, Purdue University.
Subject Area
Food science
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