Lisiane de Marsillac Terra

Evaluation of activity of a commercial amylase under ultrasound-assisted irradiation

The main objective of this work was to evaluate the effects of ultrasound irradiation on the activity of a commercial amylase. A central composite design was carried out to assess the effects of temperature and pH on the enzyme activity in the presence and absence of ultrasound irradiation. The activation energy, the influence of treatment time as well as the substrate concentration on enzyme activity were also determined in the presence and absence of ultrasound irradiation. The results demonstrated that the effect of temperature was less pronounced in the presence of ultrasound, resulting in a decreasing of about 80% in the activation energy in comparison with the value obtained in the absence. The enzyme showed activities about 3 times higher for temperatures up to 40 °C in the presence of ultrasound. The pH negatively affected the activity in the presence of ultrasound, whereas in the absence a positive effect was verified. The ultrasound irradiation is a promising technology to be used in enzymatic reaction due to its positive effects on enzyme activity.

A comparison among stochastic optimization algorithms for parameter estimation of biochemical kinetic models

Mathematical models in biochemical engineering field are usually composed by nonlinear kinetic equations, where the number of parameters that must be estimated from a set of experimental measurements is usually very high. In these cases, the estimation of the model parameters comprises numerical iterative methods for minimization of the objective function. Classical methods for minimization of the objective function, like the Newton method, requires a good initial guess for all parameters and differentiation of the objective function and/or model equations with respect to the model parameters. Besides, the use of stochastic optimization methods for parameter estimation has gained attention, since these methods do not require a good initial guesses of all model parameters and neither the evaluation of derivatives. In this work, some stochastic optimization methods (Artificial Bee Colony, Differential Evolution, Particle Swarm Optimization and Simulated Annealing) were used in the estimation of kinetic parameters of a biochemical model for an alcoholic fermentation of cassava hydrolyzed. The results indicated that Differential Evolution provides better results among the stochastic optimization methods evaluated.

Optimization of enzymatic hydrolysis of cassava to obtain fermentable sugars

This work evaluates the enzymatic hydrolysis of starch from cassava using pectinase, α-amylase, and amyloglucosidase. A central composite rotational design (CCRD) was carried out to evaluate the effects of amyloglucosidase, pectinase, reaction time, and solid to liquid ratio. All the experiments were carried out in a bioreactor with working volume of 2 L. Approximately 98% efficiency hydrolysis was obtained, resulting in a concentration of total reducing sugar released of 160 g/L. It was concluded that pectinase improved the hydrolysis of starch from cassava. Reaction time was found to be significant until 7 h of reaction. A solid to liquid ratio of 1.0 was considered suitable for hydrolysis of starch from cassava. Amyloglucosidase was a significant variable in the process: after its addition to the reaction media, a 30%–50% increase in the amount of total reducing sugar released was observed. At optimal conditions the maximum productivity obtained was 22.9 g/(L·h).

Colorimetric and sensory characteristics of fermented cured sausage with Brazilian ostrich meat addition

The aim of this study was to determine the colorimetric and sensory characteristics of a fermented cured sausage containing ostrich meat (Struthio camelus) and pork meat. Four treatments were performed: one with no ostrich meat (TC) and the others containing 19.08 (T1), 38.34 (T2), and 57.60% (T3) of ostrich meat and pork meat. Colorimetric analyses were measuring L*, a*, b*, C*, and ho. Sensory analysis was conducted assessing color, aroma, flavor, and texture at the end of the sausages’ processing. The sausages containing ostrich meat were statistically different from the control in the instrumental colorimetric analysis. In the sensory analysis, no significant differences were observed between the treatments for aroma, flavor, and texture. However, significant differences were found in the color of the sausages due to the high myoglobin content present in the ostrich meat, which resulted in a very dark color in the treatment with the highest percentage of this type of meat.

Green technologies for the extraction of bioactive compounds in fruits and vegetables

ABSTRACT Bioactive compounds are extracted from natural sources and they have beneficial effects on human health. Fruits and vegetables are rich in carotenoids, phenolic compounds, Vitamin C, among others. Extraction processes for these compounds depend on several factors such as the technique that is used, the raw material, and the organic solvent. Conventional techniques generally require large amounts of organic solvents, high energy expenditure, and are time consuming, which has generated interest in new technologies that are referred to as clean or green technologies. These can reduce or eliminate the use of toxic solvents, and thus preserve the natural environment and its resources. The aim of this review is to discuss recent techniques used to extract bioactive compounds from natural sources, in order to reduce the economic and ecological impact of these processes.