Tomato product viscosity is determined by the physical properties of the pulp
Abstract
In tomato product manufacturing, the initial "break" stage is critical to the quality attributes of the final product. Hot-break (HB) products (break above 90 °C) maintain higher viscosity at the cost of degraded color and flavor as compared to the cold-break (CB) products. It is believed that the relatively low viscosity of CB tomato product results from the break-down of pectin and release of water-soluble pectic oligomers by the pectolytic enzymes, whereas HB solubilizes more intact pectic polymers. In the present study, the chemistry and viscosity of tomato products were analyzed. The carbohydrate composition of tomato sera was analyzed by GC (gas chromatography), HPAEC (high performance anion exchange chromatography) and Proton NMR (proton nuclear magnetic resonance spectroscopy). The GC and HPAEC results showed that free glucose and fructose are the major carbohydrate components of tomato sera. Pectin was also detected and further analyzed by HPSEC (high performance size exclusion chromatography), and it was demonstrated that the molecular size and quantity of pectin is responsible for the viscosity difference of HB and CB tomato serum. Nevertheless, the amount of pectin in sera is too low to play a major role in the gross viscosity of HB and CB tomato products. Tomato pulp suspension was prepared for shear-flow measurements, which showed that the pulp suspension has comparable viscosity to that of tomato products, and hot-break pulp suspension is more viscous than the cold-break. An oscillatory frequency sweep test on the HB and CB tomato pulps showed that there is an evident difference in the viscoelastic behaviors of the tomato pulps produced by these two breaking methods. Therefore, we demonstrated that instead of pectin, distinct rheological properties of tomato pulps have a major contribution to the overall viscosity difference of tomato products.
Degree
M.S.
Advisors
Reuhs, Purdue University.
Subject Area
Food Science
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