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Ketchup flow properties were investigated with a concentric cylinder viscometer in the temperature range .from 30°C to 80°C. A partial characterization of the product viscoelastic behavior at 30°C was also made by "Strain test" and "Frequency test. " The Harper and El Sahrigi equation (7" = acJ eEdRT), as well as the equation that links the apparent viscosity of ketchups to the serum viscosity and to the pulp content (% = qserum +A(%PJB), do not describe adequately the ketchup flow behavior that we found to be highly affected by the production technology and by the raw materials used.

The dissolution of iron and tin from tinplate cans filled with tomato purée (pH 4.34) and dioctyl sebacate oil (DOS), essential onion oil (EOO) or potassium nitrate was studied using atomic absorption spectroscopy (AAS), while nitrate was determined using high-performance liquid chromatography (HPLC). The maximum values found in cans were up to 284 mg kg(-1) for tin and 513 mg kg(-1) for iron at elevated storage temperature. Results indicated that the addition of EOO to tomato purée prevents the corrosion process in the case of tin, where concentrations were lowered from 223 to 28 mg kg(-1) for cans with DOS oil and EOO at 20 degrees C, respectively (inhibition rate of 87%). On the other hand, the presence of EOO enhanced the corrosion process for iron increasing the concentration from 15 to 46 mg kg(-1) during 7 months of storage, although this value did not exceed maximum permitted value (50 mg kg(-1)). In cans with tomato purée and potassium nitrate, dissolution of tin started after 30 (36 degrees C) and 60 (20 degrees C) days of storage as a consequence of nitrate action, which act as a corrosion accelerator. Since the addition of EOO improves the taste of canned tomato purée, its potential use as a corrosion inhibitor would be of interest.

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A continuous process to improve the consistency of diced tomatoes based on product immersion in calcifying solutions was developed. The process efficacy was evaluated by a pilot plant built for this purpose. The diced tomatoes were immersed in a saline solution containing tomato serum, sodium, and calcium chloride. The pH of the calcifying solution was held constant through the process to a value close to neutrality by a device for the automatic addition of sodium hydroxide to the calcifying solution. The results showed a substantial consistency increase in the product obtained by immersion with respect to the product obtained by direct calcium addition. Moreover, the immersion product, consistency being equal, shows lower calcium content. This new technology was also employed for the preparation of diced tomatoes packaged aseptically. The results showed that the consistency increment was about 200% more with respect to the product obtained with the traditional technology of aseptic packaging, whereas the other analytical parameters were very similar. Keywords: Tomato; diced tomatoes; calcification; firmness