Physiological and Biochemical Changes During the Growth of Custard Apple (Annona squamosa L.) Fruit Cultivated in Vietnam

This study evaluated some physiological and biochemical changes that accompanied the growth stages of custard apple cultivated in Lang Son, Vietnam. Regarding the pigment content of the peel, the research results showed that the content of chlorophyll a, b, and total reached the highest value at week 13, then decreased rapidly when the fruit entered the ripening stage. Meanwhile, carotenoid content in the peel increased gradually from week 3 until complete ripening at week 16, from 0.014 to 0.063 mg·g⁻¹ fresh peel. Protein, lipid, and tannin content in the fruit flesh decreased gradually from week 3 to maturity. The vitamin C and reducing sugar content tended to reduce in week 3 to 7, then increased again until the fruit ripened. While the starch content varied quite complicatedly, it decreased from week 3 to 7, increased again from week 9 to 13, then decreased sharply as the fruit entered the ripening stage (down from 10.011% at week 13 to 1.795% at week 16). Regarding enzyme activity, α-amylase and peroxidase activity increased during the fruit development stages, corresponding to week 3 to 15 in this study. At week 16, the peroxidase activity continued to increase, while the α-amylase activity began to decrease. Unlike these two enzymes, catalase activity gradually increased from fruit formation to the 11th-week fruit stage, reaching 11.542 µM H₂O₂·g⁻¹·min⁻¹, and then decreased rapidly to 3.167 µM H₂O₂·g⁻¹·min⁻¹ in the 16th-week fruit stage.