Ascorbic acid (vitamin C) content
The ascorbic acid of the fruits in the control sample decreased from the beginning to 30 days of storage, presenting averages of 27.52 ± 3.32 mg.100 mL-1 and 18.15 ± 1.78 mg.100 mL-1, respectively (Figure 5). According to Coelho et al. (2010), the vitamin C content of immature yellow passion fruits is reduced during storage, decreasing from 30.97 ± 3.58 mg.100 mL-1 to 18.99 ± 1.97 mg.100 mL-1. However, the vitamin C content did not change when the fruits were harvested at an adequate maturity stage.
At 30 days of storage under refrigeration and controlled atmosphere, the ascorbic acid content decreased in fruits stored at 21% O2 and 0.03% CO2 and matched similar levels to the those of the control samples. For the atmosphere with 1% O2 and 0.03% CO2, it was only observed a tendency for decreasing the vitamin C content (Figure 5). This evidences the benefit effect of the lower oxygen level on the preservation of ascorbic acid content. However, the fruits stored at 5% O2 and 15% CO2 presented higher decrease in vitamin C compared to that of the control sample. Hence, the high concentration of CO2 promoted a small oxidative activity in the tissue during the fruit storage. According to Fennema (2000), the free oxygen promotes the ascorbic acid oxidation.
After the fruits removal from the atmospheres and storage during 9 days under refrigeration, the vitamin C content dropped in all atmosphere treatments, but this decrease was not significant when compared to that found in fruits in the control sample evaluated at 30 days of cold storage (Figure 5).