Reliability and validity of a new colour-changing test food with an acid-base reaction for the clinical assessment of masticatory performance.

The aim of this study was to determine the reliability and validity of a new test food for the clinical assessment of masticatory performance. The test food had two overlapping acidic/basic halves. Ten dentate subjects chewed one unit for 10-100 cycles. One subject chewed ten units for the same number of cycles. Differences in the L*, a* and b* colour axes were determined before and after chewing by ANOVA. Colour guides were created based on the values of these axes and matched with the number of cycles. The reliability of the guides was evaluated using 30 images, where three examiners indicated the number of cycles in which the colour closest to that of a chewed material was found. The data were contrasted with the real values of the guides to determine the validity (Kappa coefficients). The equivalence of the guides with the median particle size (X50) was determined using equidimensional curves. The test food progressively changed from green to pink during chewing. As the number of cycles increased, the a* values increased and the b* values decreased (p < 0.05). Overall, the guides showed a Kappa value >0.8 for the intra-examiner and inter-examiner reliability and the validity comparisons. The a* and X50 values were inversely proportional to each other, and the b* values showed a direct relationship with the X50 values. The L* values did not show correspondence. The new test food showed high reliability and validity for the assessment of masticatory performance through clinical colour guides matched with the number of cycles and X50.

Ferrous ions reused as catalysts in Fenton-like reactions for remediation of agro-food industrial wastewater.

Cassava is the most important tuberous root in tropical and subtropical regions of the world, being the third largest source of carbohydrates. The root processing is related to the production of starch, an important industrial input, which releases a highly toxic liquid wastewater due to its complex composition, which inhibits high performances of conventional effluent treatments. This study aims to evaluate Fenton-like and photo-Fenton-like reactions for treatment of cassava wastewater, reusing ferrous ions from the preliminary coagulation stage. Pre-treated cassava wastewater was submitted to oxidation in three variations of hydrogen peroxide concentrations, with more relevant analytical responses verified in color, turbidity, COD (Chemical Oxygen Demand), and acute toxicity in Artemia salina, besides the action of radicals during Fenton-like reactions. At higher peroxide concentrations, a decrease of 68% in turbidity and 70% in COD on the photo-Fenton-like system was observed, even at slow reaction rates (fastest rate constant k = 2 × 10-4 min-1). Inclusion of UV increases the viability of the Fenton-like reactions by supplementing the reaction medium with hydroxyl radicals, verified by the tert-butanol tests. The oxidation process leads to high EC50 values in 24 h of incubation in Fenton-like reactions and 48 h in photo-Fenton-like reactions. Final COD and turbidity suggests that the reuse of iron, which remains in the preliminary treatment step shows a great potential as a catalyst for Fenton-like advanced oxidation processes. Tertiary treatment can be less expensive and harmful to the environment, reducing production of residual sludge and metal content in the final effluent, which reduces polluting potential of the effluent regarding solid waste.