The back extrusion analysis of jam berries is shown in
Table 3. The firmness of berries from line Apel 23, estimated
as the initial gradient of force, compression force
or compression area, was significantly higher than control.
Peak drop off, a measure of sample heterogeneity, was also
significantly higher than control in berries from this line. A
representative curve of back extrusion test in control and
Apel 23 line can be observed in Fig. 2. In the case of jam
made from Apel 14 fruits, firmness and drop off were
higher than control, although the differences were not statistically
significant. The area of tension curve after compression,
reported as adhesiveness, was also measured as
an estimation of sample viscosity. Adhesiveness correlates
positively with firmness of berries; line Apel 23 which
showed the highest firmness also displayed the highest
adhesiveness value.