Biological and Agricultural Engineering

May 27 – Exit Seminar: Improved Methods of Standardization for Color Measurements of Processed Tomatoes

Wednesday, May 27, 2015
2:00 PM

2045 Bainer Hall



Improved Methods of Standardization for Color Measurements of Processed Tomatoes



Anupriya Chetal  



The project presents and develops a shelf stable color reference standard material for use in color hitch standardization in the California Processing Tomato Inspection Program. It stimulates the specular and light scattering properties of tomato products better than the opaque red tiles being used currently. 8.5 % NTSS was prepared and various optical properties of this concentration were studied. A hyperspectral camera was used with a visible light source to measure the reflectance of the tomato juice and determine the scatter coefficient using diffuse reflectance equation. The instrumental setup was created with a bright small diameter spot of light applied to the tomato juice sample and the hyperspectral camera viewing it from a small offset to allow scatter measurements. The collected data was analyzed by nonlinear regression to get the scatter coefficient.

Along with this the hunter colorimeter was used to measure the minimum paste sample “diffuse thickness” corresponding to optical infinity and Microtrac particle size analyzer was used to measure the particle size of the tomato paste. Different samples were used to study the variations and effects of screen sizes and hot break, cold break variations. Six readings were taken from each bag of tomato paste within a week of the bag being opened. The screen sizes studied were 0.020”, 0.033”, 0.045”, 0.060”, 0.090”, 0.150”, 0.250” with varieties of hot break and cold break paste.

Analyzing the reflectance values and scatter coefficients of the samples, a 3-D Scattering reference standard was developed. It is made with three parts: a fog 3 filter on the top, a red glass filter in the center and a white Teflon disc at the bottom. The reflectance values of this reference standard were similar to that of the 8.5% NTSS paste, and mimicked the properties better than the Hunter red tile.

2045 Bainer Hall University of California Davis

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