Relationship between Acid and Soluble Solid Content of Pineapple and Temperature

Pineapples (Ananas comosus (L.) Merr.) are harvested throughout the year, with acid and soluble solid contents varying with season. However, there is a lack of knowledge about the relationship between the acid and soluble solid content and climatic factors. To investigate these relationships, we analyzed the acid and soluble solid content records of a large number of fruit harvested over 15 years from three production areas in Japan. Over the warm period (June to September) pineapple acid content was low, while over the cool period (December to April) it was high, regardless of the cultivar. Soluble solid contents were highest in June and lowest between September and March. Acid content at harvest inversely correlated with the temperature immediately before harvest, and the relationship modelled linearly with the mean temperature over the 10 or 20 days before harvest as a variable. The acid content of ‘N67-10’ is highly dependent on temperature, while that of ‘Okinou P17’ is stable regardless of temperature. The soluble solid content was affected by temperature over longer periods than the acid content and was modelled using a quadratic equation with the mean temperature over the 70–120 days before harvest as a variable. The approximate curve of soluble solid content peaked around 23°C. The majority of ‘Okinou P17’ fruit yielded a soluble solid content of > 15 °Brix over a wide temperature range (≥ 19°C), while the temperature at which most ‘N67-10’ fruit had soluble solid of > 15 °Brix was limited to a narrow range (22–23°C). Although the coefficients of both model equations were significant for all cultivars, the R2 of soluble solid content was smaller than that of acid content. These results contribute to understanding the relationship between acid and soluble solid content and temperature.