The quality of ketchups from the Czech Republic's market in terms of their physico-chemical properties
Keywords:tomatoes, ketchup, PCA, chemical analysis, rheology
Ketchup is a tomato-based condiment with a tang contributed by vinegar, sugar, salt and spices. Physical and chemical quality requirements for ketchup are regulated in the Czech Republic by Decree No. 157/2003 as amended. The main monitored parameters determining the quality of ketchups are total tomato content, total soluble solids, total organic acids and total salt content. In this work the following parameters were monitored in a total of eight ketchups from the commercial markets in the Czech Republic: pH, total solids, total soluble solids, citric acid content, acetic acid content, lycopene content, fructose, glucose and sucrose content and content of Ca, K, Mg and Na. In addition to chemical analyses, rheological measurements were performed and dynamic viscosity and yield stress were determined. The results obtained were statistically processed and the hypothesis i) whether the sales price of ketchups is related to the quality of ketchups expressed in chemical composition and ii) whether the chemical composition affects the rheological properties of ketchups has been verified. The Pearson correlation matrix showed very good correlation between the total solids and tomato content in the ketchup (R = 0.8464) as well as between the total soluble solids and tomato content in the ketchup (R = 0.8583). Another significant correlation was found between total soluble solids and total saccharides content in ketchup (R = 0.7309) as well as between potassium content and and tomato content in the ketchup (R = 0.8864). The chemical composition of ketchups did not significantly affect the dynamic viscosity of ketchups, however strong correlation between tomato content in ketchup and between yield stresses was found (R = 0.8436). No correlation was found between the ketchup price and chemical composition of ketchup, however cheaper ketchups contained more salt.
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