3.1.2. Mechanical properties
Freezing/thawing of berries produced a smooth surface layer with several waxy regions. No fissures or microcracks were observed on the surface of raw and frozen/thawed berries (Fig. 1a and b). Despite the above, freezing/thawing decreased the mechanical strength of the skin (Table 1). In comparison with raw fruits, freezing and subsequent thawing of fruits produced berries characterised by significantly lower maximum force (66 ± 5%) and work (73 ± 4%) required to puncture the skin. The maximum puncture force was 4.1 ± 0.7 and 1.4 ± 0.4 N for raw and frozen/thawed blueberries, respectively. The work required to puncture the skin of raw and frozen/thawed blueberries was 11 ± 2 and 3 ± 1 J, respectively (Table 1).