Acoustic impedance of some fruits and vegetables from the region of Zacatecas, Mexico: An approach to the quality of agricultural products

Food quality focuses on specific parameters such as physical, chemical, sensory, and microbiological properties. In the case of physical properties, appearance, texture and condition are the factors that are tested using various technological aids. One of these is low-intensity ultrasound, which is used to examine the internal structure of food by means of acoustic impedance testing, i.e., the resistance food to the acoustic wave propagating through it in the ultrasound spectrum. This paper presents a study to determine the acoustic impedance of various agricultural products from the Zacatecas region of Mexico. The products were purchased from a local store. The fruit and vegetables analysed were peach (Prunus persica), grape (Vitis vinifiera), guava (Psidium guajava), apple (Malus domestica) and quince (Cydonia oblonda); onion (Allium cepa), prickly pear (Opuntia ficus-indica), tomato (Solanum lycopersicum), carrot (Daucus carota), beans (Phaseolus vulgaris), and maize (Zea mayz). The acoustic phase velocity of the products was measured using the transmission technique. Bulk density was also determined. The acoustic impedance of the individual products was determined indirectly. This resulted in the following values: peach, Z ≈ 1.53 MRayls; grape, Z ≈ 1.17 MRayls; guava, Z ≈ 0.655 MRayls; apple, Z ≈ 0.90 MRayls; and quince, Z ≈ 22.54 MRayls; onion, Z ≈ 1.062 MRayls; prickly pear, Z ≈ 1.311 MRayls; tomato, Z ≈ 1.035 MRayls; carrot, Z ≈ 0.719 MRayls; bean, Z ≈ 4.144 MRayls; and maize, Z ≈ 3.6 MRayls. We hope to further explore the acoustic properties of agricultural products in order to correlate them with optical, rheological, and textural properties.