Abstract This study investigates the application of NIR spectroscopy for real-time monitoring of process parameters in alcoholic fermentations. For this purpose, fermentation batches using Saccharomyces cerevisiae were carried out and monitored in situ by an immersed NIRS probe. Samples were collected throughout the fermentations, and concentrations of biomass, glucose, ethanol and glycerin were analyzed by reference methods and multivariate data analyses such as PCA and PLSR. PCA was used to investigate data variability and to select samples for calibration and for external validation sets. A PLSR model for biomass yielded R2 and RMSEP values of 0.99 and 0.276 g.L-1, respectively. For glucose, the carbon source, the PLSR model yielded an R2 of 0.95 and an RMSEP of 7.14 g.L-1. The PLSR model for ethanol was characterized by an R2 of 0.95 and an RMSEP of 0.06 g.L-1. For glycerin, a highly accurate PLSR model with an R2 of 0.98 and an RMSEP of 0.116 g.L-1 was obtained. These results indicate that an in situ NIRS probe is suitable for real-time monitoring of important parameters in alcoholic fermentations.

O cajá (Spondias mombin L. ) é utilizado na fabricação de sorvetes, geléias, polpas, produção de bebidas e consumo in natura. Um dos procedimentos mais importantes para a conservação de alimentos é a secagem, considerando que a maioria dos frutos frescos são constituídos de aproximadamente 80% de água. A secagem de alimentos é utilizada visando basicamente dois aspecto: o fator econômico do transporte e manuseio do produto; o material após seco e triturado é depois reidratado, em níveis desejáveis, para formulação de um novo produto como na fabricação de sorvetes, geléias, de iogurtes, de bebidas e também poderá ser adicionado em massa, biscoitos e outros produtos industrializados. O objetivo deste trabalho foi estudar a cinética de secagem do bagaço de cajá, em secador de bandejas com leito fixo, utilizando um planejamento fatorial composto central. Os fatores avaliados foram: temperatura (55; 65 e 75 ºC), velocidade do ar de entrada no secador (3,2; 4,6 e 6,0 m.s-¹) e espessura da torta na bandeja (0,8; 1,2 e 1,6 cm). A variável resposta considerada foi a umidade do bagaço (b.s). Os resultados mostraram que os efeitos principais e interações foram significativos ao nível de 95% de confiança. A melhor condição foi na temperatura 75 ºC, velocidade de 6,0 m.s-¹ e espessura de 0,8 cm.

The caja (Spondias mombin L.) is used in the manufacture of ice-cream, jams, pulps, beverages being also consumed in natura. One of the most important procedures in food conservation is drying, considering that most fresh fruits contain approximately 80% of water. Food drying is used to obtain two basic aspects: (1) the economic factor; in the shipping and handling of the product; (2) at the manipulation; once dried and grinded, the material is rehydrated, at desirable levels, to formulate a new product as in ice cream, jams, yoghurts and drinks and may also be added to pasta, biscuits and other industrialized products. The aim of this study was to investigate the kinetics of caja bagasse drying in a fixed-bed tray dryer, using central composite factorial planning. The following factors were evaluated: temperature (55, 65 and 75 ºC), dryer inlet air velocity (3.2, 4.6 and 6.0 m.s-1) and cake thickness (0.8, 1.2 and 1.6 cm) where the response of the considered variable was caja bagasse moisture content (b.s.) and the results showed that the main effects and their interactions were significant at a 95% confidence level being the best condition obtained at temperature of 75 ºC, velocity of 6.0 m.s-1 and cake thickness of 0.8 cm.