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This thesis is divided into four aspects for experimentation: fruit growth survey and harvest maturity of ‘Yilan red’ guava (Psidium guajava L.), the impact of harvest maturity on the fruit quality and storability of ‘Yilan red’ guava, the impact of harvest maturity and storage temperature on the peel color and fruit respiration rate and ethylene production of ‘Yilan red’ guava, and the impact of postharvest 1-Methylcyclopropene treatment on the ripening and quality changes of ‘Yilan red’ guava.
The fruit growth survey and harvest maturity research covers investigation of growth and development, changes on weight, firmness, peel color, total soluble solids, titratable acidity, TSS/TA ratio, and ascorbic acid in different development stages. The cumulative growth curve of longitudinal and transverse diameters can be clearly divided into three stages: The first stage is before 42 days after anthesis in 2013, in this stage, the longitudinal and transverse diameters significantly increased; the second stage is 42-77 days after anthesis, in this stage, the fruit longitudinal and transverse diameters showed little change, almost stagnant; the third stage is 77 days after anthesis, in this stage, the longitudinal and transverse diameters increased significantly until the fruit reached maturity. The first stage of 2014 is before 49 days after anthesis; the second stage is 49 days to 70 days after anthesis; the third stage is 70 days after anthesis until fruit reached maturity. Results show that ‘Yilan red’ guava is a fruit with double-sigmoid curve. The results on harvest maturity show that in the third stage, the flesh firmness was the firmest 63 and 77 days after anthesis, and it was the softest 98 and 105 days after anthesis. The L and b* values of the peel color after anthesis gradually increased, with 35-77 and 91-105 days reaching significant differences; the a* value first increased and then decreased, without significant differences. The total soluble solids were higher 91 and 98 days after anthesis, reaching significant differences at 105 days. The titratable acid showed significant differences for 91 and 98 days after anthesis, but 105 days after anthesis showed no significant differences. The TSS/TA ratio was the highest 98 days after anthesis, reaching significant differences at 91 days. The ascorbic acid content was the highest for 91 days after anthesis, reaching significant differences with 98 and 105 days after anthesis.
As for the impact of harvest maturity (105, 112, and 119 days after anthesis) on fruit quality and storability, the survey covered fruit weight, peel color, fruit firmness, total soluble solid content, titratable acid content, TSS/TA ratio, and ascorbic acid content. For the storability part, the decay rate and weight loss rate were also surveyed. The results on quality show that between days 105 and 112, besides the total soluble solid content, the other quality items did not reach significant differences. However, both of them (105 and 112 days after anthesis) reached significant differences in the quality items compared to 119 days after anthesis; the fruit of 119 days after anthesis had the highest fruit weight, L, a*, and b* values of peel color, and TSS/TA ratio; however, it had the lowest fruit firmness, titratable acid, and ascorbic acid content. The total soluble solid content was the highest in the fruit 112 days after anthesis and the lowest 105 days after anthesis, reaching significant differences. The recommended harvest maturity for the ‘Yilan red’ guava is 112 days.
The survey of the impact of harvest maturity (105, 112, and 119 days after anthesis) and storage temperature (25, 20, 10, and 5℃) on ‘Yilan red’ guava covered the impact of decay rate, L, a*, and b* values, respiration rate, and ethylene production. Results show that ‘Yilan red’ guava should be a climacteric fruit. The decay rate of the fruit 105 days after anthesis began to increase only on day 10; the fruit 112 days after anthesis began to increase on day5; the fruit 119 days after anthesis began to increase on day 4. By day 112 and 119 after anthesis, the rate increased simultaneously to 100%. The fruit harvested on day 105 stored under 20℃ after anthesis achieved maximum peel color L value on day 10; the fruit 112 and 119 days after anthesis and stored under 20℃ reached the maximum value by day 5. The peel color a* value of 105, 112, and 119 days after anthesis began to increase after storing for 5 days, 2 days, and 1 day, and the value continued to increase until the end of the experiment. The peel color b* value for days 105, 112, and 119 after anthesis began to increase after 4 days, 2 days, and 1 day, reaching the maximum value by day 10, 5, and 4. The respiration rate of the fruit of 105 days after anthesis began to increase on day 5, reaching the peak by day 9. The ethylene production of the fruit 105 days after anthesis gradually increased after storage, reaching the peak by day 10. The fruit 112 days after anthesis reached the peak on the fourth day, but it slightly declined on day 5 and increased once again the following day, reaching the second peak by day 7. The fruit 119 days after anthesis reached the peak on day 5. The storage temperature results indicate that the decay rate showed a significant increase on day 6 and day 10. On day 6, it was mainly 25℃ and 20℃; on day 10, it was the result of temperature restoration from 10℃ and 5℃. As for the peel color L, a*, and b* value of fruit flesh, it was observed that the fruit of 25℃ increased first, followed by the fruit of 20℃. The fruit stored under 10℃ and 5℃ increased after temperature restoration, but the L and b* value of the fruit of 10℃ failed to show normal increases. The respiration rate of fruit stored increased first in the fruit stored under 25℃, followed by 20℃. The temperatures of 10℃ and 5℃ showed significant increases only after the temperature restoration. For the ethylene production, the fruit of 25℃ and 20℃ also increased first, while the fruit of 10℃ and 5℃ clearly and intensely increased after temperature restoration, the maximum value exceeding the fruit stored under 25℃ and 20℃. Since the storage temperature of 10℃ causes fruit climacteric anomalies and fruit peel browning more serious than those of fruit stored under 5℃, which is the most suitable storage temperature for ‘Yilan red’ guava.
The discussion on the 1-MCP experiment covers the impact of three concentrations of 1-MCP treatment (0, 300, 600 nl l-1 ) on the decay rate, weight loss, L, a*, b* value, firmness, total soluble solids, titratable acid, TSS/TA ratio, ascorbic acid, respiration rate, and ethylene production during the ‘Yilan red’ guava fruit storage period. Most of the physiological and biochemical changes during ripening were affected by 1-MCP. However, the results of 2013 and 2014 revealed differed results. In the 2-year experiment, 1-MCP treatment showed significant results in delaying loss of green (increased a* values), delaying loss of firmness, and delaying increases in ethylene production. In the 2013 results, 1-MCP had a significant impact on delaying the a* and b* value increasing, delaying loss of firmness, and delaying increases in ethylene production. However, it had no significant impact on decay rate, weight loss, L value, total soluble solids, titratable acid, and respiration rate. In the 2014 results, 1-MCP showed significant effects on delaying weight loss, L value and a* value increases, delaying loss of firmness, decreases in total soluble solids, and delaying increases in ethylene production. It had less effect on delaying decay rates, increasing b* values, and respiration rates decreasing, without causing a significant impact on titratable acid. The recommended concentration in this experiment is 600 nl l−1.
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