Efecto del proceso de acidificación sobre el color de queso cottage

The objective of this study was to evaluate the color change of cottage cheese made with different processes of acidification (enzymatic and chemical) over time. The research was conducted at Universidad del Valle (Cali, Colombia) laboratories, between 2014 and 2015. Microbial rennet and lactic culture (CC) were used for enzymatic coagulation method (control cheese), and solutions of citric acid (CA) and phosphoric acid (PA) were used for the chemical method. The physicochemical properties were determined, and color behavior was analyzed over nine days of storage. Significant differences in acidity and moisture for the three coagulants were found. In the color plane, it was observed that the final and initial points of the coordinates a * and b * are close together; changes in color were mostly due to changes in brightness. The speed at which brightness decreased in the three cheeses matches kinetics order to zero and one. The first order kinetics displayed in higher values of linear correlation coefficients (R), AC: 0.8410 ± 0.0533; AF: 0.8390 ± 0.0847, and CC: 0.8717 ± 0.0256. The kinetics of change in color also adjusted correctly to zero and the first order kinetic model; that is, no significant difference (p <0.05) between these results. However, the speed of color change for the three cheeses had a slightly higher setting for zero order kinetics, as evidenced by the linear correlation coefficient (R) results, AC: 0.8800 ± 0.0205; AF: 0.8543 ± 0.0099, and CC: 0.7982 ± 0.0605.

KINETIKA REAKSI TRANSESTERIFIKASI MINYAK GORENG BEKAS DENGAN KATALIS HETEROGEN CaO DARI CANGKANG KERANG DARAH (Andara granosa)

Biodiesel (Fatty Acid Methyl Ester / FAMEs) is an alternative fuel replacing crud oil (petroleum) which is more friendly to environmen, unsmelling and containing no sulfur. Biodiesel is produced by reacting vegetable oil with alcohol using a base as a catalyst. The transesterification has carried out used waste frying oil with CaO catalyst from blood mussel shells (Anadara granosa) that calcined at a temperature of 800oC for 10 hours as heterogeneous base catalyst. The reaction of transesterification produce products that is optimalized by varying the temperature of the reaction time, and determined by the reaction order. The reaction follows first kinetics order with an activation energy (Ea) which is 93.5 kJ / mol and the frequency factor (A) which is 8,16x 1010min-1. The biodiesel Characterization fuel is measured according to ASTM D 6751. The blood mussel shell (Anadara granosa) is a new source for production of heterogeneous base catalysts that can be used for synthesis biodiesel with high purity.

Calculation of parameters for the model of an ideal phosphor

Equations for the calculation of kinetic parameters of thermoluminescent processes are theoretically derived for a model of an ideal phosphor. The values used in the calculation are obtained from glow curves and the function that describes the normalized glow curve generated. On the basis of this function, the equations for activation energy, frequency factor, and retrapping factor, were derived. All expressions are valid for a general case, when the filling factor of traps is f0?1. The concept of kinetics order was used for the calculation of parameters and the parameter of kinetics order was defined by means of real physical parameters. Results obtained by the analysis of synthetic curves and experimental glow curves of phosphor materials provide a deeper understanding of thermoluminescent kinetics.

AN INDEPENDENT METHOD FOR OBTAINING THE ACTIVATION ENERGY OF THERMOLUMINESCENCE GLOW PEAKS

The activation energy E (eV) of the first-order thermoluminescence (TL) glow peak is currently obtained using a two heating rates method. However, this method having the common drawback, that it assumes the first-order kinetics in the luminescence process. In the present work, an equation is suggested to determine the activation energy E (eV) of any glow peak, independent on the kinetics order of the process. To apply this method, three heating rates (β1,β2,β3), the corresponding peak temperatures (T1,T2,T3) and intensities (I1,I2,I3) of the isolated glow peaks are required. The applicability of the suggested method is demonstrated here by taking some numerically computed first-, second- and general-order TL glow peaks.