An apparatus to study compression stress in fruits and vegetables

Abstract

An adjustable and continuous multiple force applicator was developed, to study compression stress related to the transporte and storage of fruits and vegetables, using a cylinder-embolus system of a 10 ml syringe, a two-stage pressure controlling valve, air distributor device and a compressed air tank. The equipment is a modular one with 12 force applicator units (regularly spaced of 8.5 cm) connected to the pressure regulator through the air distributor. To apply the compression force, a 3,35 cm (od) acrylic ring was glued to the embolus. The test of the equipment showed an excellent correlation (R²- = .9996) between the adjusted pressure and the applied force. During a real case study, mature-green 'Kada' tomato fruits were stored at a temperature of 20 ± 3^oC under forces of 0, 2.25, 4.50 and 9.21 N that caused increasing levels of deformation, delayed the color development and reduced the CO₂ evolution as a function of the compression force, differently from what happens in the case of impact and vibration stresses.