88C-32 |
Determination of shape parameters for asparagus spears by 3-D digitizing |
E. F. MORALES-BLANCAS1, R. C. Cárcamo1, and L. Cisneros-Zevallos2. (1) Instituto de Ciencia y Tecnología de los Alimentos (ICYTAL), Universidad Austral de Chile, Campus Isla Teja s/n., Casilla 47, Valdivia, Chile, (2) Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843-2117
Surface area and volume of horticultural crops are two important factors when calculating heat and mass transfer into or out of the produce during post-harvest processing. The use of more accurate methods for measuring surface area, volume and shape descriptors will allow more efficient processing and quality grading operations. The objective of this study was to determine three-dimensional (3-D) properties, surface area (AS) and volumen (V), and a shape descriptor for green asparagus spears. Eighty samples of green asparagus spears (UC-72) were evaluated. They had a gauge of 12 to 18 mm (10 cm from the tip) and a length of 16 cm . Due to the highly perishable nature of asparagus, plaster replicas were made using an alginate impression material and dental technology. A computarized system mounted with a NURBS (Non-Uniform Rational B-spline) modelling software (Rhinocerosâ , Robert McNeel&Associates, Seattle, WA) and a precision mechanical 3-D digitizer, accuracy of stylus tip 0.64 mm (Microscribe-3Dä , Immersion Co., San José, CA) was used first to capture 3-D points directly from the surface features of the plaster spear and then to mathematically represent 3-D irregular geometry. Afterwards, the 3-D properties (AS, V) were calculated. Results allowed to obtain a simple model of the following form: AS=aDa + bDb + cV (r2=0.997) where both Da (minor diameter) and Db (major diameter) were measured 10 cm from tip. Additionally, a shape descriptor defined as the ratio of the volume of the object compared with the volume for an infinite cylinder of the same surface area showed close correlation with asparagus spear mass. These results suggest that it is possible to accurately calculate 3-D properties of horticultural crops using the method proposed in this study. Reliable calculations of heat and mass transfer and index quality grading can be done more efficiently.
Session 88C, Food Engineering: Physical and Chemical Properties
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