Bostwick consistometer

Chapter HI relates to measurement of flow properties of foods that are primarily fluid in nature, unithi.i surveys the nature of viscosity and its relationship to foods. An overview of the various flow behaviors found in different fluid foods is presented. The concept of non-Newtonian foods is developed, along with methods for measurement of the complete flow curve. The quantitative or fundamental measurement of apparent shear viscosity of fluid foods with rotational viscometers or rheometers is described, unithi.2 describes two protocols for the measurement of non-Newtonian fluids. The first is for time-independent fluids, and the second is for time-dependent fluids. Both protocols use rotational rheometers, unit hi.3 describes a protocol for simple Newtonian fluids, which include aqueous solutions or oils. As rotational rheometers are new and expensive, many evaluations of fluid foods have been made with empirical methods. Such methods yield data that are not fundamental but are useful in comparing variations in consistency or texture of a food product, unit hi.4 describes a popular empirical method, the Bostwick Consistometer, which has been used to measure the consistency of tomato paste. It is a well-known method in the food industry and has also been used to evaluate other fruit pastes and juices as well. 

Close the gate of a Bostwick consistometer and adjust leveling screws until the leveling bubble indicates that the consistometer is level. 

McCarthy, K.L. and Seymour, J.D. 1994. Gravity current analysis of the Bostwick consistometer for power law foods. J. Texture Stud. 25 207-220. 

Concentrated compositions that increase in viscosity when diluted are described in U.S. Patent 6,150,320. A Bostwick consistometer is used for all viscosity measurements and equivalence is offered to Brookfield measurements using Spindle no. 1, at 60 r/min, and the Zahn viscometer, no. 1 cup. A low-viscosity hard surface cleaning emulsion, approximately 12 mPa s, is described in U.S. Patent 5,934,375 that increases in viscosity upon dilution with water to 800 to 1200 mPas. 

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