38-12

T. HALEY, Food Science Department, Purdue University, 1160 Food Science Building, West Lafayette, IN 47907 and L. W. Clark, McNab, Incorporated, 20 North MacQuesten Parkway, Mt. Vernon, NY 10550.

The food industry uses a Bostwick standard for measurement of product viscosity and shear characteristics. Knowledgeable customers request and look for specific Bostwick numbers with their purchase. The Bostwick scale is a simple guillotine slide gate which, upon opening, allows the product to flow horizontally across a scale marked in centimeters. The Bostwick number is then the length of flow in a given time period (usually 30 seconds). Due to a product's non-Newtonian flow characteristics, attempts at correlating a Bostwick number with the analytical instrumentation of viscometer and refractometer proved unsuccessful. The in-line optical analyzer using the principle of light absorption for the count of suspended solids demonstrated a correlation to the Bostwick scale.

In September 1998, the Food Science Department of Purdue University conducted field trials with an optical analyzing system provided by McNab Inc. Data on tomato sauce showed a correlation between manual Bostwick measurements and the optical analyzer reading. A control loop back to the process was initiated where the optical analyzer was able to modulate a pump speed around a Bostwick setpoint.

Laboratory trials have broadened the database to tomato purees, pizza sauce, tomato paste dilution, ketchup and non-tomato products such as baby foods.

The theory of light absorption for suspended solids as related to the Bostwick will be addressed. Laboratory data, pilot plant data and commercial data will be presented showing trends and deviations with explanations. The market significance of this innovation is that for the first time there is an in-line, analytical measurement of Bostwick suitable for control loops and correlatable to the manual measurement.