Abstract Sulfiting agents are added to crustaceans products to prolong their shelf life. However, depending on the concentration, these agents can be toxic to consumers due to the presence of SO2. In this context, a colorimetric indicator label based on starch and iodine was developed to detect SO2 in shrimp, showing whether the product is safe or not for consumers. The incorporation of iodine into the starch matrix resulted in labels with a smooth and homogeneous surface, and reduced water solubility from 9.26% to around 0.12%. In both in vitro and shrimp paste test, a visual detection response was observed in the label containing 0.02% of iodine when evaluated in the presence of 100 to 160 ppm of SO2, with ΔE* values greater than 5 (can be identifiable by the human eye). Therefore, the elaborated label showed potential as an economical and simple method to detect SO2 concentration in shrimp-based foods.

ABSTRACT Background: During de-pulping of açai (Euterpe oleracea) for juice production in the Amazonia, large amounts of fibrous waste are daily discarded, a promising substrate for production of high-value cellulose nanofibrils. Therefore, this study sought to evaluate the modifications of açai surface fibers submitted to chemical pretreatment steps and compare the quality of nanostructured films produced with different cycles of mechanical nanofibrillation. Results: A 2-hour pretreatment (at 5% of NaOH) followed by two NaOH/H2O2 bleaching steps resulted in fibers with increased length and reduced diameter compared to raw fibers while preserving fiber integrity and cellulose I structure. The increase of fibers’ grinding cycles from 3 (minimum to gel point) to 21 (maximum suspension thickness) resulted in nanofibril films with higher crystallinity properties, uniform thickness, compacted morphology, and smoother surface. Nanofibril films formed after different numbers of passages exhibited similar mechanical strength, but distinct barrier properties. Conclusion: Açaí waste films produced with fibers submitted to 3 grinding cycles can be recommended for packaging applications that demand easily dissolving, such as instantaneous food. Oppositely, açaí fibers subjected to 21 cycles in grinder provide films suitable for water-resistant packaging, ideal for secondary coatings of papers and paperboards.

Thermoplastic starch properties depends of plastification process. The aim of this study was to analyze the effect of concentration of glycerol and water on plastification, glass transition temperature (Tg) and tensile properties of thermoplastic waxy starch (TPWS). Formulations were extruded in the following concentrations of starch/glycerol/water: 70/30/0 (TPWS 0%); 70/25/5 (TPWS 5%); 70/20/10 (TPWS 10%) weight percentage. Crystalline peaks in WAXS diagrams and native grains present in SEM micrographs showed that the TPWS 0% and 5% were not sufficient to promote total plastification of the waxy starch, and TPWS 10% showed the higher starch plastification. Tg measurements by DMTA were 30 ºC to TPWS 0%, 23 ºC to TPWS 5% and 40 ºC to TPWS 10%. These results showed that glycerol and water had effect plasticizer in TPWS 5% and antiplasticizer in TPWS 10%. Mechanical tensile results showed that higher tensile strength was observed in the systems with more effective starch plastification.