Effect of Simmering Time on the Physico-Chemical Properties and Shelf-Life Study of Ketchup Produced from Local Ingredients

Abstract Postharvest losses of tomatoes remain high throughout Cameroon (40–60%) and therefore require transformations. This study aimed at evaluating the effect of simmering time on the physicochemical analysis and shelf life of tomato ketchup produced from local ingredients. To achieve this, tomato (Solanum lycopersicum) and local seasoning were purchased as part of the recipe. Five different formulae were obtained at different simmering times (0min, 20mins, 30mins, 40mins and 50mins). To study the shelf life, for each simmering time, three samples were produced and stored at 4°C in a refrigerator in an air tight plastic packaging material to be used discontinuously for microbial and physicochemical antioxidant and phytochemicals analysis at week 0, week 2 and week 4. Commercial Ketchup was used as control. To evaluate the consumer preference of the products, a 9-scale hedonic test was conducted. The results revealed that pH ranged from 3.8 to 4.2 and decreased with simmering time. The degree of redness and titratable acidity also decreased with simmering time (15.3 to 10.57 and 1.8–10.4% respectively). Lycopene and vitamin C content depleted as well. The density of the ketchup (0.99-1.2g/ml) and the sugar concentration (1.2–3.2°brix) increased with simmering time. Nutritional evaluation showed that the ketchup samples were rich in carbohydrates (4.07%) and minerals (1.82%). Phytochemical analysis revealed that the spices brought several phytochemicals with flavonoid (1342.22mg/kg) and saponins (106.14mg/kg) been the highest. The microbial analysis revealed that the coliform, bacterial and fungi were within the WHO food standard acceptable limit during discontinuous storage. Sensory evaluation revealed that ST30 was the best accepted in term of overall acceptability, colour, taste and flavour. Transformation of tomatoes into paste can therefore help to prevent post-harvest losses and increase marketability.