Oxalate and ascorbic acid in kiwifruit during growth and storage

Changes in the oxalate and ascorbic acid content of berries of kiwifruit (A ctinidia deliciosa) cv Hayward were studied during growth on the plant and during storage. During growth the location of oxalate crystals and ascorbic acid in the fruit was determined using polarised light microscopy and hist ochemical procedures. Oxalate crystals were observed as raphides in idiobla st cells, principally in the fruit's inner pericarp. The number of idioblas t cells and the number of raphides per idioblast increased greatly during f ruit growth. Histochemical analysis further showed increasing levels of asc orbic acid during fruit growth, particularly in the inner pericarp. During storage, chemical analysis carried out with enzymatic kits showed that inso luble oxalate was a waste product, and that soluble oxalate and ascorbic ac id levels decreased significantly over time. Oxalic acid was not formed by catabolism of L-ascorbic acid during storage.