The effect of postharvest air-heat treatment of the Satsuma mandarin fruit (cv. 'Kawano Wase'), was studied in order to obtain a suitable sugar-acid ratio. Fruit were collected on two harvest dates (50% and 75% of surface turned yellow) and and heated for 3 and 5 days at 30° C. One sample was control (absence of pre-treatment). Fruit were stored at room temperature for 6 days. The results showed no significant difference in the weight loss between the control and treatment. Soluble solids content substance was increased in both treatments and control, while the titratable acidity significantly decreased in both treatments. Larger changes in colour were observed in fruits harvested when 50% of surface turned yellow colour than in fruit harvested when 75% of fruit surface turned yellow, and the differences among treatments are singnificant.