Efecto de la adición de ácido ascórbico en la degradación de nitratos y nitritos en mortadela / Effect of addition of ascorbic acid in the degradation of nitrate and nitrite in mortadella

El objetivo de la presente investigación fue evaluar  el efecto de la adición de ácido ascórbico (Vitamina C) para reducir la concentración de nitritos y nitratos adicionada a la mortadela como conservante. Se realizaron tres formulaciones de mortadela a las cuales se añadió tres concentraciones diferentes de ácido ascórbico (F1: 0,25 g/kg, F2: 0,50 g/kg y F3: 0,75 g/kg) y un testigo, mediante espectrofotometría UV-Visibles se cuantificó la concentración inicial y la final para comprobar la reducción de nitratos y nitritos y la formación de color y  el ácido ascórbico residual se lo cuantificó mediante voltametría. El análisis de varianza aplicado al experimento nos indicó  que si existió diferencia significativa (p˂0,05) eentre los tres  tratamientos estudiados,  se alcanzó reducciones de nitratos del 30,78 %  en la F1, 50 % en la F2 y 76 % en la F3, en este caso la reducción de nitratos y valores de nitrito formado de 0,41 mg/kg en la F1, 0,24 mg/Kg en la F2 y 0,04 mg/Kg en la F3, en la formación de nitritos. La F3 presentó el mayor % de reducción de nitratos y la menor cantidad de formación de nitritos. En conclusión la adición de ácido ascórbico a la mortadela reduce la concentración residual de nitratos al cabo de tres días, donde ya no se presentó reducción significativa de este conservante. ABSTRACTThe aim of this research was to evaluate the effect of the addition of ascorbic acid to reduce the concentration of nitrites and nitrates in mortadella. Three formulations of mortadella were tested to which three different concentrations of ascorbic acid (0.25 g / kg, F2: 0.50 g / kg and 0.75 g F3 / kg F1) were added. Through UV-visible spectrophotometry it was quantified the initial and final concentration of nitrates and nitrites and color formation, and the residual ascorbic acid was quantified by voltammetry. The analysis of variance indicated that there was significant difference (p˂0,05) among the three treatments. Nitrate reduction of 30.78% in F1, F2 50% at 76% and the values of F3 and formed nitrite 0.41 mg / kg in F1 0.24 mg / kg was achieved in F2 and 0.04 mg / kg in F3, in the formation of nitrite. F3 showed the highest percentage reduction of nitrates and the least amount of formation of nitrite. In conclusion, the addition of ascorbic acid to mortadella reduces the residual nitrate concentration after three days, where no longer significant reduction of this preservative was presented

Reliability analysis of structures by a three-stage sequential sampling based adaptive support vector regression model

A three-stage adaptive support vector regression (SVR) based metamodel is built by sampling training data sequentially close to a limit state function (LSF). The approach alleviates the difficulty of scarcity of samples in the reduced space for reliability evaluation of a structure involving implicit LSF. Specifically, importance sampling is proposed to ensure a sufficient number of simulation points near the approximated failure plane. A design of experiment is initially constructed by a space-filling design over the entire domain. The optimum choices of the hyper-parameters of the SVR model are then determined by minimizing the generalized root mean square error (GRMSE). A subset of Monte Carlo simulation samples with magnitude of approximated LSF less than the noted GRMSE values are selected. Subsequently, the data points are added sequentially from the subset, based on the maximin criterion. Finally, the SVR model is iteratively updated to improve the reliability estimation by adding more data from the latest subset until convergence. An improved stopping condition is proposed to avoid false convergence. The effectiveness of the proposed approach along with estimation of very small probability of failure is elucidated through three numerical examples