Effect of AITC treatment on surface color and firmness of mulberry
fruit
Most mulberry fruit is bright red in color before full ripeness
and becomes purply-black when fully ripe due to the presence of
copious amounts of anthocyanins compounds, the majority as
identified in the fruit extract being cyanidin-3-glucoside and
cyanidin-3-rutinoside (Butkhup et al., 2011; Jiang et al., 2013). As
shown in Fig. 2A–C, the color parameters (L*, a* and b*) of fruit
decreased rapidly in the control group but gradually decreased in
the AITC treatment groups (5 and 15 mL L1). The control fruit had
the lowest a* value (11.90) and b* value (4.72) on day 15, namely,
decreases of 51.70% and 62.69% from the initial values of 24.70 and
12.60, respectively. The decrease in a* and b* value of AITC-treated
fruit was not significant during the storage. L* value tended to
decrease during storage (Fig. 2C), and it decreased severely in the
control while the brightness values were well-maintained in AITC
treated groups. Surface color is an important index to evaluate the
quality and ripening process of mulberry fruit (Oz and Ulukanli,
2014). In the present work, significant differences in the color
parameters (a* and b*) were observed between treatments and
control (P < 0.05) after 15 d of storage. The results indicate that
AITC treatment can slow down the ripening process of mulberry
fruit.
Firmness is one of the most common physical parameters used
to assess the quality of fruits (Luo et al., 2009). In the present work,
firmness decreased in the control and all AITC treated fruit during
the storage period. The firmness of control fruit softened rapidly in
the first three days and then decreased gradually to 1.30 N by day
15, namely, about 25.1% of the initial value on day 0 (Fig. 2D).
However, the firmness of fruit treated with AITC at 5 and 15 mL L1
was 4.07 N and 4.67 N on day 15, respectively. This indicated that