Relationship between In‐line Viscosity and Bostwick Measurement during Ketchup Production

Abstract

The Bostwick consistometer remains an integral part of assessing the consistency of tomato products in the factory. This work addresses the blending of tomato pastes, packed at different Bostwick readings, for use in tomato ketchup production. The objective of this study was to correlate in-line viscosity measurements of 12 degrees Bx tomato concentrates to final product quality. Five blends of tomato concentrate were prepared by blending 2 pastes and diluting the mixture to a soluble solids level of 12 degrees Bx. In-line viscometry measurements at process temperature were made using magnetic resonance viscometry. The resulting Herschel-Bulkley parameters were used to evaluate an apparent viscosity at a characteristic shear rate. The apparent viscosity and Bostwick measurement for the blends were correlated based on a gravity current flow analysis, yielding a coefficient of determination of over 0.99. Ketchup was made from the tomato concentrate blends at 3 levels of natural tomato soluble solids (NTSS). The ketchup Bostwick measurement was then correlated to the ratio of (eta/rho)(-1/5) of the 12 degrees Bx tomato concentrate yielding coefficients of determination of 0.97, 0.97, and 0.91 for NTSS levels of 6%, 7%, and 7.8%, respectively. This study demonstrates that final product quality can be predicted from in-line viscosity measurements of an intermediate product.

Correlation between in-line measurements of tomato ketchup shear viscosity and extensional viscosity

“…The Bostwick consistometer allows only a punctual estimate of the apparent viscosity at one specific shear rate. According to the predictions using the model from McCarthy et al (McCarthy and McCarthy, 2009), the estimate is of the same order of magnitude but still 20% far off that measured using the rotational rheometer ARES-G2. The accuracy may be improved by performing a calibration for the specific brand of tomato ketchup and calculating its own "c" coefficient to insert in Equation 5.…”

“…Where c is a constant that for the measurements in (McCarthy and McCarthy, 2009) corresponded to 0.0861,  the apparent viscosity at the shear rate given by Equation 4, and  the fluid density.…”

“…In-line viscometry of tomato ketchup was developed to overcome these limitations, though at higher price. In-line ketchup viscosity measurements were performed by means of magnetic resonance (McCarthy and McCarthy, 2009), pressure differential (Barringer et al, 1998), in-line absorption photometry (Haley and Smith, 2003), and ultrasonic Doppler velocimetry (Jin Choi et al, 2006). Shear flow was characterized with these methods and it was assumed that this type of deformation was representative to the flow in the pipes during processing.…”

The Emptying Behaviour of Highly Viscous Liquids. Part II: Development of Test Methods and Evaluation of Untreated and Coated Films

“…The device is used to measure the distance which is covered by a viscous liquid in a unique rectangular tube during a certain time. Although this traditional method, which does not give quantitative physical properties, is mainly used for the validation of processing parameters in a production environment, it has inspired several studies in order to correlate the results obtained to exact measurements [82][83][84].…”

Individual and sequential effects of stirring, smoothing, and cooling on the rheological properties of nonfat yogurts stirred with a technical scale unit

“…Consistency was determined with a Bostwick consistometer (CSC Scientific Co., Fisher Scientific, Nepean, ON, Canada) to evaluate resistance to flow of the yogurts by the ASTM standard method (ASTM, 2013;Standard F1080-93). Flow on an inclined plane is caused by the effect of the gravitational force on the product (McCarthy and McCarthy, 2009). The flow distance depends on the viscosity but also on the elastic properties and adherence of the product to the surface of the consistometer (Monnet et al, 2008).…”