No abstract

This work evaluates the effect of temperature and soluble solids on the degradation rate of phenolic compounds, and antioxidant activity of extracts from Bixa orellana L. leaves. The temperatures were studied in the range of typical food processes (70-90 °C) and food storage (−20-37 °C). The results showed that the thermal degradation of the phenolic compounds follows first-order kinetics, in which the degradation rate depends on the temperature, the amount of soluble solids, and the pH. The loss of antioxidant activity also follows first-order kinetics. Under different storage conditions, the half-life times of the total phenols were in the range 40.72-202.47 days, while for the antioxidant activity, the half-times were from 55.87-68.83 days for the ABTS and from 57.85-107.03 days for the FRAP method. The antioxidant activity of the extracts follows the same pattern of thermal degradation as the phenolic compounds. Therefore, we conclude that antioxidant activity is due to its phenolic compounds.

Viscera of tilapia (Oreochromis spp.) were used for the production of a protein hydrolysate, which was characterized in terms of proximate composition, molecular weight distribution, amino acid composition and antioxidant activity (ABTS radical scavenging capacity, ferric ion reducing power (FRAP) and ion chelating activity). Liposomes from soy lecithin (SL), rapeseed lecithin (RL), and soy-rapeseed (SRL) lecithin blend (1:1, w/w) were prepared, showing average particle sizes of 153, 218 and 193 nm, respectively, and similar ζ potential of -46 mV. Rapeseed lecithin liposomes presented much higher antioxidant activity than with SL. Liposomes made of SRL, having intermediate hydrodynamic and antioxidant properties than the other two, were selected to encapsulate the tilapia hydrolysate at different concentrations (5, 10 and 20 g/100 g, with respect to lecithin). Liposomes loaded with 20 g/100 g of hydrolysate (SRLH20) had smaller particle size and higher ABTS values and iron chelating activity, while liposomes loaded with 5 g/100 g (SRLH5) had higher electronegative ζ potential and entrapment efficiency, which was calculated as a function of total protein content, antioxidant capacity and individual amino acid residues. Charged amino acid residues and alanine were highly entrapped in both SRLH5 and SRLH20. No clear preference for encapsulating hydrophobic or hydrophilic amino acids was observed.

Background: Fish is an essential source of nutrients for human nutrition due to the composition of proteins, vitamins, minerals, among other nutrients. Enzymatic hydrolysis represents an alternative for the use of by-products of the aquaculture industry. Objective: We propose to evaluate the effect of stirring speed, temperature, and initial protein concentration on the degree of hydrolysis of proteins and antioxidant activity of red tilapia (Oreochromis spp.) viscera hydrolysates. Methods: The effect of stirring speed, temperature, and initial protein concentration on the degree of hydrolysis of proteins and antioxidant activity was evaluated using an experimental design that was adjusted to a polynomial equation. The hydrolysate was fractioned to determine the antioxidant activity of the fractions, and functional properties were also measured. Results: Stirring speed, protein concentration, presented a statistically significant effect (p <0.05) on all the response variables. However, the temperature did not present a statistically significant effect on the degree of hydrolysis. The best conditions of hydrolysis were stirring speed of 51.44 rpm, a temperature of 59.15 °C, and the protein concentration of 10 g L-1 . The solubility of the hydrolysate protein was high at different pH, and the hydrolysate fraction with the highest antioxidant activity has a molecular weight <1 kDa. Conclusions: The degree of hydrolysis and the biological activity of red tilapia viscera hydrolysates (Oreochromis spp.) are affected by temperature, substrate concentration, and stirring speed. The optimal conditions of hydrolysis allowed to obtain a hydrolysate with antioxidant activity that is due to the peptides with low molecular weight.

El objetivo del presente trabajo fue evaluar el efecto de la temperatura, el pH y el contenido en sólidos solubles, sobre la velocidad de reacción, en la degradación térmica de los fenoles totales del extracto etanólico de semillas de Bixa orellana L. Se determina también la estabilidad de fenoles totales y su actividad antioxidante durante 91 días a condiciones de almacenamiento de-20, 8, 23 y 37 °C. Los resultados mostraron que la degradación de fenoles totales, se ve afectada por la temperatura y los sólidos solubles, siguiendo una cinética de primer orden, tanto en condiciones de procesamiento como de almacenamiento. Por su parte, la actividad antioxidante (ABTS y FRAP), se ve afectada por la temperatura de almacenamiento. Los tiempos de vida media estuvieron entre 27.74-38.25; 27.99-36.51 y 22.18-35.98 días-1 , para compuestos fenólicos, ABTS y FRAP, respectivamente. Mientras que la energía de activación fue 4.08, 3.24 y 5.52 KJ.mol-1 para fenoles totales, ABTS y FRAP, respectivamente. Se concluye que la actividad antioxidante de estos extractos depende de su contenido de compuestos fenólicos los cuales son afectados por la temperatura y por el contenido de sólidos solubles.