This laboratory experiment was carried out at the Department
of Agricultural Technology, Mahasarakham University, Northeast Thailand
during July and August 2008. The experiment aimed to determine an effective
natural organic acid that would delay the unattractive skin browning of
santol fruit, while at the same time not damaging the quality of the fruit.
The experiment included a study of the fruit’s polyphenol oxidase
(PPO) activity, phenolic content and quinone content, as they relate to
colour and a study of total soluble solid content, pH, titratable acidity
and vitamin C content as they relate to fruit quality. A Completely Randomized
Design (CRD) with four replications was used. Each replication consisted
of 10 fruits. Santol fruit was harvested at 145 days after full bloom
and dipped for 30 min in aqueous solutions of two organic acids that were
used as treatments, i.e., 0% for T1 (control), 5% citric acid
for T2, 5% ascorbic acid for T3, 10% citric acid
for T4 and 10% ascorbic acid for T5 and stored at
room temperature (28°C, 90% R.H.) to investigate the effect of the
acid on fruit weight, skin colour, PPO activity and other internal parameters.
The results showed that the most appropriate anti-browning agent for santol
fruit was found with T2. It gave the highest mean values, 57.37
and 55.95, of brightness (L*) at 4 and 10 Days After Storage (DAS), respectively.
In addition, PPO activity of flesh tissue was lowest for T2
with mean values of 0.0078 to 0.0092 by 0 and 300 S, respectively. The
phenolic content in the flesh tissue significantly increased with an increase
in numbers of DAS, whereas the reverse was found with the pH level in
the fruits. They were lowest for T2, with mean values of 6.00,
by 10 DAS. There were no significant differences among the treatments
in any of the measured Total Soluble Solids (TSS), Titratable Acidity
(TA) and vitamin C content.