Abstract:
The objective of this work was to delay the browning in fresh-cut mangosteen (Garcinia mangostana L.) stored at 8±2 °C, 85%RH. Three sets of antibrowning agents were tested. They were 1% (w/v) citric acid (CA), 1% (w/v) citric acid plus 0.5% (w/v) ascorbic acid (CA+AA) and 1% (w/v) citric acid plus 0.5% (w/v) sodium erythorbate (CA+SE). Fresh-cut mangosteen without antibrowning agents was set as a control. The results showed that the use of antibrowning agents retarded the color change at the cut of mangosteen rind. The L* values of mangosteen rind treated with CA was the highest (p≤0.05). The a* values of this treatment was lower than the control (p≤0.05) while chroma was higher than the control. Sensory analysis showed that the score of browning index on the cut surface treated with CA was close to the ideal score. The above results pointed that CA was the most effective antibrowning agent to delay browning in fresh-cut mangosteen. Citric acid was then selected to incorporate into edible coating. Five conditions were tested. They were 1% (w/v) citric acid without coating (CA-n-Alg), without citric acid but coating with 2% (w/v) sodium alginate followed by either 1.0 or 1.5% (w/v) calcium chloride (n-CA-Alg-Ca1.0, n-CA-Alg-Ca1.5), and 1% (w/v) citric acid and coated with 2% (w/v) sodium alginate followed by either 1.0 or 1.5% (w/v) calcium chloride (CA-Alg-Ca1.0, CA-Alg-Ca1.5). The results showed that the L* values at the cut surface of mangosteen rind in treatment CA-Alg-Ca1.0 was the highest (p≤0.05). The a* values of this treatment was lower than other treatments. Among five treatments, the score of browning index on the cut surface of mangosteen rind in treatment CA-Alg-Ca1.0 was close to the ideal score. The acceptance and the preference score of CA-Alg-Ca1.0 was the highest throughout 9-day of storage (p≤0.05). The coating also lowered browning score on the aril of mangosteen (p≤0.05). Water loss in samples coated with alginate was lower than the uncoated (p≤0.05). During 9-day of storage, the fresh-cut mangosteen with coating appeared to be similar to the fresh one. The microbiological shelflife of fresh-cut mangosteen at 8±2 °C, 85%RH was 9 days. The properties of crude polyphenol oxidase (PPO) from an extract mangosteen rind were also studied. The optimum pH and temperature of crude PPO was 6.0 and 40°C. This finding supported the use of antibrowning agents to delay browning reaction via reducing pH on the cut surface of mangosteen rind. The increasing incubation time of crude PPO with antibrowning agents increased the effectiveness of inhibition.