Fractal image analysis and bruise damage evaluation of impact damage in guava

Impact bruise damage and quality of ‘Gim Ju’ guava were investigated for different drop heights and number of drops using fractal image analysis. For the impact test, a stainless-steel metal ball (250 g) was dropped on fruit from three drop heights (0, 0.3, 0.6 m) either once or five times. Fruit quality was evaluated for impact energy, bruise area (BA), bruise volume (BV), bruise susceptibility, bruise score and pulp color (L*, a*, b* and C values). The fractal dimension (FD) value using fractal image analysis was analyzed at the bruise region. Results showed that five drops (0.3 m) with a high impact energy (3 678.75 J) and a single drop (0.6 m) with a low impact energy (1 471.50 J) exhibited no significant in BA, BV, bruise score as well as all color values (L*, a*, b* and C). While the FD value of a single drop from 0.6 m had a higher FD value than that of five drops from 0.3 m. It is indicated that FD exhibited a better performance to classify impact bruising level of guava than BA, BV and color parameters. The FD value gradually decreased with increase of storage time and bruise severity. The correlation coefficient (r) values of FD (r =  − 0.794 and − 0.745) between BA and BV were more significant than those L* (r =  − 0.660 and − 0.615) and a* (r = 0.579 and 0.473). The coefficient of determination (R²) of the polynomial equation in bruised fruit (R² = 0.85 to 0.99) was greater than the control (no bruise) (R² = 0.80). A higher R²_val (0.88 and 0.92) was exhibited at five drops. Interestingly, FD analysis showed greater potential than color measurement to assess bruise impact damage in guava.