Non-destructive detection of granulation in stored 'Magallanes' pummelo [Citrus maxima (Burm. Ex Rumph.) Merr.] fruit

Granulation is a common physiological disorder found in citrus fruit. It is characterized by discolored, dry and hardened juice vesicles. It lowers the overall quality of the fruit. This study assessed two non-destructive methods, flotation and a capacitance-based technique, for determining granulation. This research included the degree of granulation, along with some physico-chemical characteristics of small, medium, and large 'Magallanes' pummelo fruit. The two non-destructive methods tested did not correctly determine granulation in 'Magallanes' pummelo and therefore cannot be used to detect granulation. The entire pummelo fruit did not float, nor sink in water or in 10% salt solution. The distance between conducting plates in the capacitance measurement and the thick pummelo rind could have prevented this technique in differentiating the granulated from the non-granulated fruit. Granulation was evident in a few fruit even at harvest, as well as during storage with large fruit presenting greater granulation than small fruit. Though degree of granulation did not differ, the percentage of granulation was greater in large fruit (91.48%) at nine weeks of storage in ambient conditions. Granulation developed further with storage. Granulation was slight at three weeks of storage. At six weeks of storage, medium and large fruit had lower hue and TSS. Large fruit had lower TA while chroma, visual quality and pH did not vary among the three fruit sizes. Fruit size may be used as a factor in determining granulation in ambient-stored 'Magallanes' fruit, wherein large fruit were more granulated.