17D-13 |
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H. H. CHONG and B. L. Reuhs. Dept. of Food Science, Purdue Univ., 745 Agriculture Mall Drive, West Lafayette, IN 47907 Two methods are used commercially to produce tomato products depending on the desired properties of the finished products. Hot break involves a processing temperature of approximately 90°C or higher, which causes inactivation of enzymes important to viscosity, particularly pectinmethylesterase and endopolygalacturonase. These two enzymes contribute to the break down of pectins, which are complex polysaccharides found in the primary cell walls and intercellular regions of higher plants. The hot break method is used to produce the majority of tomato products that have high viscosity, such as paste. Conversely, the cold break method involves a processing temperature below 70°C, which allows enzyme activity and results a less viscous product, such as juice. The advantage of cold break over hot break is that it produces a more natural color and a fresher flavor. The objective of the current research is to determine the correlation between the physical and chemical properties of hot and cold break preparations. The physical properties of the preparations were evaluated for color, soluble solids, pH, moisture content, microstructure and viscosity. The carbohydrate content and the degree of pectin polymerization of the preparations were evaluated using gas chromatography, colorimetric assays and high performance liquid chromatography. As predicted, the pectin isolated from the cold break preparation was degraded to a significantly greater extent than the pectin from the hot break preparation. However, our findings did not show a direct correlation between the degree of polymerization of pectin and the viscosity and other properties of the tomato preparations. These observations are significant to the food processing industry because they suggest that other factors must be taken into considerations when determining the viscosity of the preparation.
Session 17D, Food Chemistry: Chemical effects of food processing and preservation
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