ORIGINAL PAPER Viscometric Behavior of Reconstituted Tomato Concentrate Chockry Barbana & AbdelFattah El-Omri Received: 18 May 2009 / Accepted: 9 September 2009 / Published online: 25 September 2009 # Springer Science + Business Media, LLC 2009 Abstract The rheological properties of tomato concen- trates produced by hot and cold break have been exten- sively studied by many authors. Only a few studies, however, focus specifically with the rheology of reconsti- tuted concentrates from tomato powders. In this study, the rheological properties of reconstituted tomato concentrate from lyophilized freeze-dried tomato juice were evaluated using rotational viscometer at temperatures 20°C, 30°C, 40°C, 50°C, and 60°C and at concentrations of 9.7%, 12.9%, 20.5%, and 26.8% total soluble solids. Using power law model, both flow behavior index (n) and consistency coefficient (k) were determined. The calculated values of flow behavior index (n) were less than unity (0.03–0.28) at all temperatures and concentrations indicating the shear- thinning characteristic of the concentrate. The effect of temperature and concentration on the consistency coeffi- cient (k) was studied. Positive correlation between k in the range of 1.57 and 38.33 Pa s n and inverse absolute temperature (1/T) has been shown by Arrhenius model. Additionally, linear correlation between consistency coeffi- cient (k) and concentration (C) was determined. The activation energies were found in the range of 3.63 and 7.36 kJ/mol K depending on concentration. The results of this study might be useful to improve the design of processing operations dealing with tomato powder reconstitution. Keywords Reconstituted tomato concentrate . Rheology . Power law model . Consistency coefficient . Flow behavior index . Activation energy Introduction Tomatoes represent an essential product of human diet and provide a good nutritional resource rich in vitamin C, potassium, and antioxidant mainly lycopene. Dietary intake of tomato products has been shown to be associated with a decreased risk of chronic diseases, such as cancer and cardiovascular disease (Lazarus et al. 2004; Toor and Savage 2005). Generally, tomatoes are processed as tomato concentrate and manufactured to a wide variety of products including soups and ketchups. However, tomato powder represents an important market due to many advantages as ease of packing, transportation, and mixing. In addition, tomato powder is a basic ingredient for dehydrated soup manufac- ture and other tomato products (Abu-Jdayil et al. 2004; Jaya and Das 2009). Likewise, recently, tomato pulp powder was used successfully as a thickening agent in the formulation of commercial tomato ketchup at different levels (1%, 2%, 5%, 7%, and 10% w/w) (Farahnaky et al. 2008). The knowledge of the rheological behavior of recon- stituted tomato concentrate from tomato powder is essential C. Barbana (*) Tecnología de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, C/ Miguel Servet, 177, 50013 Zaragoza, Spain e-mail: barbana@unizar.es A. El-Omri Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan Food Bioprocess Technol (2012) 5:209–215 DOI 10.1007/s11947-009-0270-3