Résumé
Fungi are among the main responsible for damage and loss in stored grains, its control has been done through synthetic substances, which are harmful to man and the environment. Brazil, one of the leading countries in agriculture, has optimal environmental conditions for the development of mycotoxigenic fungi. Most of the synthetic chemicals used as preservatives have often been realized to be toxic to humans and also cause adverse environmental effects. Thus, it is necessary to search for alternative methods of controlling. In this study the aimed was to evaluate the efficacy of lemongrass essential oil in the control of the Aspergillus brasiliensis. In vitro and serial microdilution tests were carried out at different concentrations of essential oil and citral, which corresponds to 72% of the total oil composition. Inhibition of fungal growth on contaminated wheat grain was evaluated. The in vitro test results showed that the essential oil has fungicidal potential at concentrations from 0.6 956;L mL-1, the minimum inhibitory concentration was determined at 0.8 956;L mL-1. The tests with citral showed fungal control at concentrations from 0.6 956;L mL-1 onwards. For wheat grain, fungal growth inhibition was obtained at the concentration of 1.6 956;L mL-1. The essential oil of Cymbopogon flexuosus showed fungicidal activity against the fungus Aspergillus brasiliensis.
Sujets)
Antifongiques , Aspergillus , Poaceae/composition chimique , Triticum/microbiologie , Huile essentielle/analyseRésumé
Studies on the drying kinetics of medicinal, aromatic and spice plants are a necessary step towards establishing the combination of drying parameters that would not qualitatively and quantitatively alter the quality of the fresh product. The purpose of this study was to investigate the drying kinetics of Brazilian peppertree (Schinus terebinthifolius) leaves and to verify whether the theoretical diffusion and the semi-empirical Lewis drying models were capable of accurately predicting the drying curves of the product at 35, 40, and 45°C, with a dry air mass flow rate of 0.731 kg s-1 m-2. Leaves were collected at 0800 h, 1200 h and 1700 h. The goodness of fit between experimental and predicted values was based on the correlation coefficient, root mean square error, mean absolute percentage error, mean bias error, and fit index. Residual plot analysis was also considered in the selection of the most effective drying model. Temperature had a pronounced effect on mass transfer and drying rate decreased continuously during the course of drying. Leaf collection time had little influence on the drying kinetics. Effective moisture diffusivity was found to increase with temperature. The results indicated that the Lewis model was considered a better predictor of the thin-layer drying behaviour of Brazilian peppertree leaves than the theoretical model based on Fick's second law of diffusion.
Estudos sobre a cinética da secagem de plantas medicinais, aromáticas e condimentares são necessários para o estabelecimento de parâmetros operacionais de secagem de forma a não alterar significativamente a qualidade e o perfil fitoquímico dessas plantas. O objetivo do presente trabalho foi investigar a cinética da secagem das folhas da aroeira-vermelha (Schinus terebinthifolius), além de verificar se o modelo teórico de difusão e o modelo semi-empírico de Lewis são capazes de predizer com acurácia as curvas de secagem do produto a 35, 40 e 45°C, com fluxo de ar seco de 0,731 kg s-1 m-2. As folhas foram coletadas às 8:00, 12:00 e 17:00 h. O grau de adequação dos valores obtidos pelas curvas de secagem àqueles obtidos experimentalmente foi avaliado empregando-se o coeficiente de determinação, a raiz do erro quadrático médio, o erro percentual absoluto médio, o viés médio e o índice de ajuste. A análise da dispersão dos resíduos também foi utilizada na escolha do modelo de predição mais efetivo. Observou-se que a temperatura tem efeito significativo na transferência de massa e a taxa de secagem diminuiu continuamente ao longo da secagem. O horário de coleta das folhas não teve influência significativa sobre a cinética da secagem. A difusividade efetiva da água aumentou com o aumento da temperatura. Os resultados evidenciaram que o modelo de Lewis descreve com maior grau de acurácia a secagem de folhas de aroeira-vermelha que o modelo teórico baseado na Segunda Lei de Difusão de Fick.
Sujets)
Plantes médicinales , Anacardiaceae , CinétiqueRésumé
This research describes the drying kinetics and compares the convective drying rates of in natura and osmodehydrated pineapple slices in inverted sugar. The effective moisture diffusivity during air drying was estimated using Fick's second law of diffusion. The suitability of a theoretical liquid-diffusion model and seven semi-theoretical mathematical models for use in describing the experimental drying curves was also evaluated. Goodness of fit between experimental and predicted values was based on the root mean square error, mean absolute percentage error, mean bias error, agreement index, residual plot analysis and the principle of parsimony. Osmotic dehydration was conducted in 155, 310, and 465 mL L-1 osmotic solutions, at 40 and 50 ºC for 2 h at 60 rpm. Convective drying was performed in a tray cabinet dryer using heated ambient air at 60 ºC and 1.15 m s-1. Osmotic pretreatment facilitated water removal during the first hours of drying, a trend that was reversed towards the end of the process for samples osmodehydrated at the highest solution concentration. The effect of the osmotic pretreatments on drying rate was negligible at 40 ï°C, but at 50 ï°C the rate of moisture removal was more intense for samples in natura and osmodehydrated at the lowest solution concentration. Effective moisture diffusivity increased with temperature and solution concentration. The single-exponential, three-parameter semi-theoretical drying model gave the best predictions of the drying curves of pineapple slices both in natura and pre-osmodehydrated in inverted sugar.
O trabalho descreve a cinética de secagem e compara as taxas de secagem por convecção de fatias de abacaxi in natura e pré-desidratadas osmoticamente em açúcar invertido. A difusividade efetiva da água no interior do produto durante a secagem foi calculada empregando-se a Segunda Lei de Fick. Avalia, também, o grau de adequação de um modelo teórico de difusão de liquido e de sete modelos semi-teóricos na descrição das curvas experimentais de secagem. A desidratação osmótica foi realizada empregando-se soluções a 155, 310 e 465 mL L-1, a 40 e 50 ºC, sob agitação a 60 rpm e tempo de imersão de 2 h. A secagem por convecção foi feita em secador do tipo gabinete com bandejas, com ar à 60 ºC e 1,15 m s-1. O grau de ajuste dos modelos foi avaliado por meio da raiz do erro quadrático médio, do erro percentual absoluto médio, do viés médio, do índice de ajuste, pela análise da dispersão de resíduos e aplicando-se o princípio da parcimônia. O pré-tratamento osmótico facilitou a remoção de água durante as primeiras horas de secagem, comportamento que se reverteu ao final do processo para amostras desidratadas na solução mais concentrada. O efeito do pré-tratamento osmótico sobre a taxa de secagem foi desprezível a 40 ºC, no entanto, a 50 ºC, a taxa de remoção de água foi mais intensa para amostras in natura e pré-desidratadas nas soluções de menor concentração. A difusividade efetiva aumentou em função de aumentos na temperatura e na concentração da solução. O modelo exponencial simples de três parâmetros foi o que melhor descreveu as curvas de secagem por convecção de fatias de abacaxi in natura e pré-desidratadas osmoticamente em açúcar invertido