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Effect of Moisture Content on the Viscoelastic Properties of Individual Wheat Kernels Evaluated by the Uniaxial Compression Test Under Small Strain

¹Programa de Doctorado en Ciencias de los Alimentos, Departamento de Investigación y Posgrado en Alimentos, Universidad de Sonora, Blvd. Luis Donaldo Colosio esq. Reforma, Edif. 5P, Col. Centro, C.P. 83000, Hermosillo, Sonora, México. ²Corresponding author. Phone/Fax: +52 (662) 259 22 07. E-mail: bramirez@guaymas.uson.mx ³Centro de Investigación y de Estudios Avanzados (CINVESTAV-IPN), Libramiento Norponiente 2000, Fracc. Real de Juriquilla, Querétaro, C.P. 76230, Qro., México. ⁴Departamento de Biotecnología e Ingeniería de Alimentos, Centro de Biotecnología, Tecnológico de Monterrey, Av. Eugenio Garza Sada 2501 Sur, C.P. 64849, Monterrey, N.L., México.

Wheat product quality is related to its physicochemical properties and to the viscoelastic properties of the kernel. The aim of this work was to evaluate the viscoelastic properties of individual wheat kernels using the uniaxial compression test under small strain (3%) to create experimental conditions that allow the use of the elasticity theory to explain the wheat kernel viscoelasticity and its relationships to physicochemical characteristics, such as weight tests, size, and ash and protein contents. The following viscoelastic properties of the kernels of hard and soft wheat cultivars at two different moisture contents (original and tempered at 15%) were evaluated: total work (W_t), elastic work (W_e), plastic work (W_p), and modulus of elasticity (E). There was a significant decrease in W_t as the moisture content increased. In the soft wheat Saturno, W_t decreased 80% (from 0.217 to 0.044 N·mm) as the moisture content increased. Individual wheat kernels at their original moisture content showed higher W_e than under the tempered condition. W_p increased as the moisture content increased. E decreased as the moisture content increased. The soft wheat Saturno showed the highest decline (54.9%) in E (from 14.18 to 6.39 MPa) as the moisture content increased. There were significant negative relationships between the viscoelastic properties and the 1,000-kernel weight and kernel thickness. The uniaxial compression test under small strain can be applied to evaluate the viscoelastic properties of individual wheat kernels from different classes and cultivars.