2.9. Mechanical resistance: cutting force
Analysis of
firmness of green bean samples during storage at
refrigerated conditions was carried out through the determination
of the cutting force. The cutting force of the green beans was
measured using an Instron texture analyzer (mod. 5865, ITW Test
and Measurement Italia S.r.l., Italy). The analysis was conducted
with a light-knife probe (contact area: 103m
5.0
102 m) and
a load cell of 1 kg. The crosshead speed was set to 1.67
104 m/s
and the total distance through the sample was set at 3
103 m. A
selected 2.0
102 kg sample (made of 6 green beans) was loaded
onto the bottom plate of texture analyzer, centered under the knife
probe, with the main axis of the green beans of the sample
perpendicular to the probe. The values of the force as a function
of the distance was measured in each experiment and the
maximum force achieved during cutting cycle was calculated as
the cutting force.
Cutting force was determined on three independent samples
(for a total of 18 green beans), with duplicate measurements for
each independent samples. In order to take into account the effect
of the biological variability of the samples on the analysis of the
results, the statistical significance of the observed differences was
evaluated through ANOVA.