Mathematical modelling of the volumetric contraction of cupuaçu seeds during the drying process

Cupuaçu (Theobroma grandiflorum Schum) is a tropical Amazonian fruit that has gained a significant share of the global tropical fruit pulp market. The state of Pará stands out as the largest national producer, with the municipalities of Acará, Tomé-Açu, and Moju being the main production centres. Cupulate®, a product similar to chocolate, is derived from cupuaçu seeds and was developed and patented by Embrapa Amazônia Oriental, located in Pará, in the 1980s. However, the processing of cupuaçu seeds involves several stages, with drying considered the most crucial step as it reduces the moisture content in the seeds, making them less prone to microbiological activity that can lead to spoilage. The aim of this study was to evaluate the volumetric contraction of cupuaçu seeds during the drying process and to fit different mathematical models to the experimental values concerning moisture content. Cupuaçu seeds with an initial average moisture content of 1.5 (decimal d.b.) were used. The seeds were subjected to drying in a prototype vertical fixed-bed drying silo with forced air at temperatures of 55, 65, and 75°C. The volume reduction was analysed as a function of moisture content through different mathematical models fitted to the experimental data, considering the magnitude of error in the estimation of volumetric contraction. The modified Bala and Woods and Polynomial models showed the best fits to the experimental data of apparent volumetric contraction, We recommend that producers employ the Polynomial model to optimise the drying process of cupuaçu seeds at 75°C to achieve improved prod.