No abstract

This work reports the production of fatty acid methyl esters (FAMEs) and fatty acid ethyl esters (FAEEs) by means of waste fried oil (WFO) transesterification using methanol and ethanol at supercritical conditions, in a continuous catalyst-free process. Transesterification experiments were performed from 573 to 623 K, at 10, 15, and 20 MPa, with oil/alcohol molar ratios of 1:20, 1:30, and 1:40 and water addition to alcohol of 0, 5, and 10 wt %. The extent of the reaction was explored using a novel parameter, convertibility, which corresponds to the maximum ester content attainable from the feedstock (92.1%). The highest FAME and FAEE contents achieved were 81.7 and 82.2%, respectively. Results show that transesterification of WFO in methanol was more efficient than that in ethanol, the temperature had the strongest influence, and the addition of water considerably improved the ester yield.

No abstract

Vigilância Sanitária (Anvisa) recommendations, the oxidized oil in this study should be discarded after 5.5 h at 180°C.

Pectin methylesterase (PME) hydrolyzes methyl ester groups in pectin chains to form carboxylic groups, releasing methanol and H 3 O + . The aim of this study was to determine PME activity in samples of pectinases by UV-VIS spectroscopy, to measure the acid and methanol produced in the reaction of pectin with pectinase and to verify the thermal inactivation of exogenous PME in mango juice. The activity of PME in samples of pectinase was determined by potentiometry, UV-VIS spectroscopy, and by the action of alcohol oxidase. The reaction showed greater activity at pH 4.0 to 4.5 and at a temperature of 45° C. PME activity determined by UV-VIS spectroscopy with bromophenol blue indicator showed a good correlation with the activity determined by potentiometry and with alcohol oxidase. The results showed that bromophenol blue indicators can be used to determine PME activity in samples of pectinases where the optimum pH is located in the acidic range. The thermal inactivation of exogenous PME in mango juice occurred at 75° C for 20 min of exposure.Index terms: Pectin metilesterase, activity, thermal inactivation, mango juice. RESUMOA PME hidrolisa os grupos metil éster na cadeia da pectina, formando grupos carboxílicos, liberando metanol e H 3 O + . Objetivou-se, com o presente estudo, determinar a atividade da PME em amostras de pectinases por espectroscopia Uv-vis para quantificar o ácido e o metanol produzido na reação da pectina com as pectinases e verificar a inativação térmica da PME exógena no suco de manga. A atividade da PME nas três amostras de pectinases foi determinada por potenciometria, espectroscopia Uv-Vis, e pela ação da álcool oxidase. A reação mostrou uma maior atividade em H de 4,0 a 4,5 e a temperatura de 45º C. A atividade da PME, determinada por UV-Vis com o indicador azul de bromofenol apresentou uma boa correlação com a atividade determinada por potenciometria e com a álcool oxidase. Os resultados mostraram que o indicador azul de bromofenol pode ser utilizado para determinar a atividade da PME em amostras de pectinases em que o pH ótimo situa-se na faixa ácida. A inativação térmica da PME no suco de manga ocorreu na temperatura de 75º C, por 20 min de exposição.Termos para indexação: Pectina metilesterase, atividade, inativação térmica, suco de manga.