Physical measurement of firmness of banana fruit pulp: determination of optimum conditions for measurement

Abstract

Stress-relaxation curves were obtained by plunging a conical probe into the pulp of green and yellow banana fruits [Musa (AAA group, Cavendish subgroup) ‘Giant Cavendish’]. Three stress-relaxation parameters, minimum stress-relaxation time (T0), relaxation rate (R), and maximum stress-relaxation time (Tm), were calculated from the stress-relaxation curve. Plunging depth and plunging speed varied the parameters. When parameters were fixed, with a plunging speed of 0.5 mm/s and the plunging depth of 0.6 mm, the yellow bananas showed significantly lower T0 and Tm than green bananas. The lower, T0 and Tm can predict the degradation of polymers responsible for the pulp texture. Measurements of stress-relaxation parameters in different parts of banana pulp revealed that the physical properties were not uniform within the same fruit.