Ascorbic acid degradation in aqueous solution during UV-Vis irradiation.

This work studied the effect of multi-wavelength UV processing on the ascorbic acid content of aqueous solutions, at different pH values (3, 4, and 5). The source of radiation was a mid-pressure mercury lamp (460 W), emitting between 250 and 740 nm. The samples were treated for 60 min, at 25 °C and 45 °C, with the lamp on and with the lamp off.

Kinetic and thermodynamic study of the photochemical degradation of patulin.

In a previous work, the UV photodegradation of patulin was concluded to follow a first-order kinetic and to be faster at acidic pH. In this case, the UV photodegradation of aqueous patulin solutions was studied at acidic pH values (3-6) similar to the values of apple juices where patulin has been found, obtaining that the first-order kinetic constant increased when the acidity of the reaction media was also increased (pH decreased). From the parameters obtained by fitting the experimental data to both the Arrhenius and Van't Hoff equations, the existence of kinetic and thermodynamic compensations was studied.

Kinetic and thermodynamic compensation. A current and practical review for foods.

Kinetic and thermodynamic compensations have been reported in many chemical, physical, biological and food processes. Kinetic compensation can be found for any process and when it takes place, it gives information about the reaction mechanism and whether the reaction is controlled by enthalpy or entropy. It consists of the linear relationship between the logarithm of the frequency factor (lnk) and the activation energy (E), both previously obtained from the Arrhenius equation for different values of an environmental variable (e.

Ascorbic acid stability in fruit juices during thermosonication.

Thermosonication is an emerging technology useful for inactivating microorganisms and enzymes in fruit juices. However, the effect of the ultrasound processing on the ascorbic acid content is not clear and the results reported in the literature are contradictory. In this work, the impact of sonication and thermosonication on the ascorbic acid content was first evaluated in model systems.

Peroxidase (POD) and polyphenol oxidase (PPO) photo-inactivation in a coconut water model solution using ultraviolet (UV).

The interest in coconut water as a beverage is increasing due, not only to its sensory properties, but also to its nutritional characteristics. Even so, several challenges limit its processing, the inactivation of the polyphenol oxidase (PPO) and peroxidase (POD) enzymes being the most important. Although the inactivation of these enzymes has been extensively studied in coconut water, both by conventional and emerging technologies, the technologies evaluated so far are either not effective in the inactivation of these enzymes and/or result in undesirable changes.

Toxic effect of melanoidins from glucose-asparagine on trypsin activity.

In this work the effect of the presence of the melanoidins from glucose-asparagine on the enzymatic activity of trypsin is studied. It was observed that an excess of N alpha-benzoyl-L-arginine ethyl ester (BAEE) has an inhibiting effect on this enzyme activity. The maximum reaction rate was obtained for a 0.