Changes in Consistency of Tomato Juice during Concentration

Processing tomatoes are typically harvested during a ten to twelve week season in California, and tomato juice is concentrated to stabilize the product for use during the remainder of the year. Manufacturers of value-added products formulated with concentrated tomato paste often note that there is a loss of consistency during the process and storage. To understand the reasons for this, samples of unconcentrated juice, processing intermediates, and concentrated paste were collected from an industrial processing plant during normal commercial production. All samples were diluted with water to 5 degrees Brix then analyzed for consistency and pectin content. Whole juice consistency, measured with a Bostwick consistometer, decreased through the course of juice concentration, with the largest change occurring early in the process, as the juice was concentrated from 5 to 10 degrees Brix. This decrease in consistency occurred during the production of paste from both hot- and cold-break juices. Total pectin content did not change as the juice was concentrated to paste but the proportion of the total pectin that was water soluble increased. The greatest increases in pectin solubility occurred during the hot- break and late in the process where the evaporator temperature was the highest.