Effects of temperature and different thickeners on rheological properties of ketchup

Tomato is a high value food which is consumed with its unique taste and flavor. Ketchup produced from tomatoes is a popular product which is consumed with pleasure today especially by young population. Especially in recent years, more and more ketchup are being produced and consumed using tomato paste and tomato juice. Ketchup is usually not consumed alone, generally it is consumed with fried potatoes, pasta and fast food products. Sensory quality is an important quality criterion in terms of consumption of tomato ketchup.Consumers expect that the ketchup products to have good taste, odor and color characteristics . In addition to these properties, the rheological properties of the product also affect the sensory properties of the product. For example, liquidity for liquid foods, consistency for semi-solid foods and textural properties for solid foods are important. In heterogeneous and semi-solid products such as ketchup, depending on the processing methods, there are differences in consistency in ketchup depending on the quality of the raw materials used in production. For this reason, ketchup formulations may be supplemented with various thickening additives so that the desired consistency and continuity of the ketchup consistency can be maintained. Hydrocolloids as thickening additives, are polymers that hydrate when multiple water molecules are bound by hydrogen bonds when dispersed in water. The substance firstly retains the water necessary for itself and then limits the movement of the remaining water by forming a three dimensional network of intermolecular and spaces. Therefore this makes the system stable. In this study, three different (guar gum, xanthan gum and modified corn starch) hydrocolloids were added to the ketchup formulation prepared in the laboratory. The rheological behavior of ketchup samples added with hydrocolloid was investigated using a rheometer at 1-100 s-1 shear rate intervals and at a wide temperature range (10-50 °C). The results obtained are modeled using the software program of the rheometer. As a result of the preliminary studies, it has been determined that addition of 1% thickening agent (for guar gum and xanthan gum) is suitable for providing the ideal consistency value when ketchup is made from tomato paste. It had also been observed that 1% addition of modified corn starch does not provide structural integrity and continuity. It has been determined that the best effect on the rheological properties of ketchup was provided by the guar gum. The guar gum can be preferred because the price is lower than other thickeners. Studies on modified corn starch, which is one of the most preferred thickening agents in the market, should be enhanced by appropriate prob and plate processing. These results are important for determining production conditions and standardization in ketchup production. Keywords: Rheology, ketchup, thickener, guar gum, xanthan gum, modified corn starch.