Effects of Input Variables on the Conversion of 5 Ton/h Processed Tomato Juice in a Triple-Effect Evaporator

Tomato is grown in many regions of the world; and processed tomato products account for 80% of total tomato consumption. A worldwide tomato processing industry has since evolved with a range of technologies which are able to convert tomatoes into products such as paste, sauces and ketchup. Tomato concentrate production can be classified as either Hot Break (HB) process or Cold Break (CB) process. CB process involves chopping the fresh tomato suitable for processing at lower temperatures, ranging from 65 to 75°C, resulting in a less viscous, but slightly better flavoured paste which is mainly used for triple concentrate paste, packed for domestic use. The heated tomato pulp is then conveyed via a special pump to an extraction unit. Two products, the refined juice for concentrate and the waste for disposal come out of the extraction unit. The yield from extractor (about 95%) varies according to the variety of tomatoes treated, pulp’s temperature, type of sieve fitted, the rotation speed, and shape of the rotor on each operating stations. The refined juice is collected and constantly feed to an evaporator from where it passes through different effect(s) where its concentration level is gradually increased until the required concentration is obtained.

This study is aimed at using Matrix Laboratory (MATLAB®) to model a triple-effect evaporator for a 5 ton/h processed tomato juice initially at 5% concentration to 35% tomato paste concentration. The steam economy (SE) was reduced from 3.7 at an interval of 0.4 to study its effect on the outlet tomato paste concentration. Based on some thermodynamic assumptions, the effect of varying some input variables on the output parameters was studied. Other values of SE were later assumed and the process repeated until the desired 35% tomato paste concentration was obtained. The desired concentration was obtained in the third effect when a steam economy of 2.1 was used. With this SE of 2.1, the concentration of tomato paste obtained in first effect is 11%; second effect is 7% while the target concentration of 35% is obtained in the third effect. It was concluded that most of the output parameters, such as tomato paste concentration; water removed; volumetric flow rate; and area decrease with increasing SE; only mass of flow rate increases with increasing SE. Also, the tomato paste concentration increases as the number of effect increases; with a tomato paste concentration of 35% obtained in the third effect. The choice of SE and the number of effects should be properly considered before the design of tomato paste production facility.