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Mango seeds from agro‐industry represents an environmental problem due to the amounts of by‐products produced. Conversely, poly (lactic acid) (PLA) is a potential green alternative to conventional plastics. The goal of this study aimed to develop a biocomposite based on PLA and mango’s by‐product for rigid packaging. Six biocomposites are obtained by extrusion/injection processing using formulations with PLA as a matrix and up to 20% by weight of mango seed’s by‐products. The materials are characterized by chemical and physical analysis; scanning electron microscopy/energy dispersive X‐ray, X‐ray diffraction; Fourier transform infrared spectroscopy (FTIR); thermal gravimetric analysis/differential thermogravimetry; differential scanning calorimetry (DSC), and mechanical analysis. FTIR bands and DSC transitions related to starch are higher in the kernel, while more cellulose bands are found in the integument. Kernel presented thermal degradation in the biocomposites, the sample PLA+20 wt% kernel. For the other compositions, it is possible to observe that they could keep their morphology. Significant improvements in both mechanical and barrier properties are found in the formulation with 20 wt% integument (up to 38% in elastic modulus). Therefore, this study suggests that biocomposites developed from PLA / Integument / Kernel have potential as a new biomaterial for rigid food packaging systems.

The processing to which a material is subjected can affect its physical or chemical structures, resulting in products with different hygroscopic behaviours. The present work studied the water adsorption properties of sorghum subjected to different types of processing: raw flour (produced by milling whole grain), extrudates (obtained using a double screw extruder) and extruded flour (obtained by milling the extrudates). The isotherms were obtained using an automated instrumental method. The tests were run in duplicate at 25 °C with relative humidity values ranging between 11 and 84%. The water adsorption data fitted the GAB model well, showing high coefficients of determination. The estimated water contents of the adsorption monolayer ranged from 5.3 to 6.9 g of water per 100 g of dry material. The sorption isotherms were affected by the type of processing, extrusion cooking resulting in products with less water in the monolayer (less hygroscopic). The milling process yielded high water contents in the monolayer, probably due to the breakdown of some polymer-polymer interactions, which exposed the binding sites. To ensure microbiological stability, the water contents in the materials should not exceed 6.9 g of water per 100 g of dry material for raw sorghum flour, 5.3 g of water per 100 g for sorghum extrudates and 6.7 g of water per 100 g for extruded sorghum flour. Keywords: Extruded flour; Extrudates; Raw flour; Sorghum bicolor L.; Sorption isotherms. ResumoO processamento ao qual um material é submetido pode afetar sua estrutura física ou química, resultando em produtos com diferentes comportamentos higroscópicos. No presente trabalho, objetivou-se estudar as propriedades de adsorção de água do sorgo em diferentes formas de processamento: farinha crua (produzida pela moagem de grãos inteiros), extrusados (produzidos em extrusora de duplo parafuso) e farinha extrusada (obtida pela moagem dos extrudados). As isotermas foram obtidas usando o método instrumental automatizado. Os testes foram realizados em duplicata, a 25 °C, com valores de umidade relativa variando entre 11 e 84%. Os dados de adsorção de água foram bem ajustados ao modelo de GAB, mostrando altos coeficientes de determinação. O teor estimado de água da monocamada variou de 5,3 a 6,9 g de água por 100 g de material seco. As isotermas de sorção foram afetadas pelo tipo de processamento, sendo que o cozimento por extrusão resultou em produtos com menor valor de monocamada (menos higroscópico). O processo de moagem produziu valores de monocamada elevados, provavelmente devidos à degradação de algumas interações polímero-polímero, que expuseram sítios de ligação. Para garantir a estabilidade microbiológica, o teor de água nos materiais não deve ser superior a 6,9 g de água por 100 g de material seco para a farinha crua de sorgo; 5,3 g de água por 100 g para os extrusados de sorgo, e 6,7 g de água por 100 g para a farinha extrusada. Palavras