INFLUENCES OF SOME POST-HARVEST DIPPING TREATMENTS ON GUAVA (Psidium guajava L.) FRUIT QUALITY AND THE INCIDENCE OF SKIN BROWNING DURING SHELF LIFE

During 2002 and 2003 seasons the influences of post-harvest dipping
treatments of 500 ppm boron (boric acid), 4.0% calcium chloride, 0.25% zinc sulfate,
10 mM sodium benzoate, 2.0 mM salicylic acid, 2.0 mM acetyl salicylic acid, 200 ppm
ABG-3168 (ReTain), 0.5% plantacur-E (25.0% alpha-tocopherol) and 3.0% corn
starch for 3 min on mature seedy "Balady" guava fruit quality and the incidence of
skin browning during 4-days of shelf life at 25°C±3 and 50-60% RH were studied. The
results showed that most fruit quality parameters were significantly influenced by the
applied treatments. Except the ABG treatment, all the other treatments significantly
decreased the incidence of skin browning compared with the control. In this respect,
the most effective treatment was sodium benzoate followed by acetyl salicylic acid,
s.Jicylic acid, and boron treatments. Except the plantacur-E treatment, all the other
treatments significantly decreased the weight loss of fruit compared with the control.
Acetyl salicylic acid, sodium benzoate, boron, and calcium chloride treated fruits were
significantly firmer than the control. The concentration of fruit acidity was greatly
increased in all the treatments during 4-days of shelf life compared to the initial
concentration. Acetyl salicylic acid treated fruit contained the highest acidity
concentration followed by zinc sulfate and that was significantly higher than all other
treatments. Calcium chloride treated fruit contained a significant higher concentration
of TSS than all other treatments. There were clear decreases in the concentration of
vitamin C (about 24% in the control) during 4-days of shelf life in all the treatments
compared to the initial concentration. Boron, calcium chloride, acetyl salicylic acid,
zinc sulfate, sodium benzoate, corn, and plantacur-E treated fruit showed Significant
higher concentrations of vitamin C than the control. However, salicylic acid and ABG
treatments significantly decreased the concentration of vitamin C compared with the
control. Surprisingly, there was almost no response of guava fruit to ABG application
despite, it is a climacteric fruit type. The results concluded that some of the used
compounds (especially sodium benzoate, acetyl salicylic acid, salicylic acid, boron,
and zinc sulfate) showed clear effects on maintaining quality and decreasing the
incidence of browning. However, non of these compounds, at the used
concentrations, could completely eliminate the incidence of browning during shelf life.
Applying higher concentrations of these compounds might further inhibit browning and
better maintain quality of guava fruit during shelf life.