The physico-mechanical properties of 3 films composed by carvacrol, grape seed extract (GSE) and chitosan in different proportions were studied. The films, prepared by solvent casting technique with the following compositions of the casting solutions in carvacrol, GSE and chitosan: film-1: 9.6 ppm-684 ppm-1.25% w/v, film-2: 60 ppm-400 ppm-1.2% w/v and film-3: 90 ppm-160 ppm-1.24% w/v and were compared to a control (1.25% w/v chitosan) film. Mechanical, structural, barrier and colour properties of the films were evaluated. Film-3 presented the lowest water vapour and carbon dioxide permeabilities (WVP and CO 2 P) and tensile strength (TS) values and the highest oxygen permeability (O 2 P), whereas film-1 presented the highest water content and the lowest crystallinity, CO 2 P, TS and luminosity. These results suggest that in the range studied, carvacrol and GSE affect the film structure and its mechanical properties due to hydrophilic (GSE) and hydrophobic (carvacrol) compounds. This work will help the development of edible films, based on physico-mechanical properties, contributing to food preservation and shelf-life extension.
The effect of heat and the combined heat/ultrasound (thermosonication) treatment on the inactivation kinetics of peroxidase in watercress (Nasturtium officinale) was studied in the temperature range of 40-92.5°C. In the heat blanching processes, the enzyme kinetics showed a first-order biphasic inactivation model. The activation energies and the rates of the reaction at a reference temperature for both the heat-labile and heat-resistant fractions were, respectively, E a1 = 421 ± 115 kJ mol À1 and E a2 = 352 ± 81 kJ mol À1 , k 1 84:6 C ¼ 18 AE 14min À1 and k 2 84:6 C ¼ 0:24 AE 0:14min À1 . The initial relative specific activity for both isoenzyme fractions were also estimated, being C 01 = 0.5 ± 0.08 lmol min À1 mg protein À1 and C 02 = 0.5 ± 0.06 lmol min À1 mg protein À1 , respectively. The application of thermosonication was studied to enable less severe thermal treatments and, therefore, improving the quality of the blanched product. In this treatment the enzyme kinetics showed a first-order model. The activation energy, the rate of reaction at a reference temperature and the initial relative specific activity were, respectively, E a3 = 496 ± 65 kJ mol À1 , k 3 87:5 C ¼ 10 AE 2min À1 and C 03 = 1 ± 0.05 lmol min À1 mg protein À1 , proving that the enzyme became more heat labile. The present findings will help to design the blanching conditions for the production of a new and healthy frozen product, watercress (Nasturtium officinale), with minimized colour or flavour changes along its shelf life.
The thermal degradation kinetics of both components of vitamin C, ascorbic acid (AA) and dehydroascorbic acid (DHAA), were determined in a nectar of Cupuac ßu (Theobroma grandi¯orum) with 25% of pulp and 15% of sugar in water. AA was assayed by HPLC and the results showed that AA degraded into DHAA. A reversible ®rst order model described well the AA degradation data, with an activation energy of 74 AE 5 kJ/mol and k 80 C 0X032 AE 0X003 min À1 . DHAA kinetic behavior suggested a consecutive ®rst order reaction where DHAA was the intermediate product of AA degradation. A mechanistic model was derived to predict DHAA concentration. Rate constants were replaced by the Arrhenius equation in the model to evaluate the temperature dependence and the kinetic parameters for AA degradation, previously determined, were used. An activation energy of 65 AE 9 kJ/mol and a k 80 C of 0X013 AE 0X003 min À1 were estimated. The present ®ndings will help to predict the best Cupuac ßu nectar processing conditions that minimize degradation of an important quality factor such as vitamin C.
The use of ultrasound in food processing creates novel and interesting methodologies, which are often complementary to classical techniques. In this work, the effect of heat and the combined treatment heat/ultrasound (thermosonication) on the thermal degradation kinetics of vitamin C in watercress (Nasturtium officinale) was studied in the temperature range of 82.5 to 92.5°C. First order reaction kinetics adequately described the vitamin C losses during both blanching processes.The activation energies and the reaction rates at 87.5°C for heat (H) and thermosonication (Ts) treatments were, respectively, E a vitC H = 150.47 ± 42.81 kJ mol − 1 and E a vitC Ts = 136.20 ± 60.97 kJ mol − 1 , and k 87.5°CvitC H = 0.75 ± 0.10 min − 1 and k 87.5°CvitC Ts = 0.58 ± 0.11 min − 1 . No significant differences (P N 0.05) were detected between both treatments. The thermosonication treatment was found to be a better blanching process, since it inactivates watercress peroxidase at less severe blanching conditions and consequently retains vitamin C content at higher levels. The present findings will help to optimise the blanching conditions for the production of a new and healthy frozen product, watercress, with heat and a new blanching process methodology.Industrial relevance: Thermosonication blanching can be useful since it reduces processing times, and consequently minimizes the adverse effects of heating on watercress quality. This new application will provide good material, in terms of vitamin C, for further processes, and can be an excellent alternative to the traditional heat treatment.
A B S T R A C TChitosan films with grape seed extract and carvacrol microcapsules (CMF) were prepared and their physicochemical properties and effect on physico-chemical and microbiological parameters in refrigerated salmon were tested. CMF showed higher values of thickness (0.41 ± 0.04 mm), moisture content (13 ± 1 g water/100 g film), a (11 ± 3), b (12 ± 3), opacity (20 ± 1%), water vapor permeability (WVP) (4.4 ± 0.4) × 10 −10 gPa −1 s −1 m −1 , oxygen permeability (O 2 P) (1.3 ± 0.3) × 10 −12 gPa −1 s −1 m −1 and carbon dioxide permeability (CO 2 P) (1.3 ± 0.3) × 10 −12 gPa −1 s −1 m −1 as compared to those of the chitosan control film (CCF). CMF showed lower values of L (66 ± 5) and water solubility (17 ± 1%).The salmon packed into CMF presented on the 7th day of storage a lower value of TVB-N (37 ± 4 mg N/ 100 g fish) as compared to the CCF (42 ± 3 mg N/100 g fish) and control samples (CS; 66 ± 7 mg N/100 g fish). The CMF showed lower values of pH and lightness after 7 days of storage as compared to CS and CCF. The CMF showed also lower values of mesophilic and psychrophilic bacteria and Pseudomonas spp, reaching the maximum limit allowed for the first two only on the 7th day of storage.CMF increases the shelf-life of refrigerated salmon to 4-7 days of storage due to the antimicrobial effect of the natural agents.
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