RESUMO
Carboxymethyl chitosan (CMCS) was synthesized by alkylation of chitosan using monochloroacetic acid and characterized by FTIR and (1)H-NMR spectroscopies. Different molecular weights (Mws) of CMCS were prepared by radiation degradation of CMCS in the solution form at different irradiation doses. The structural changes and Mw of degraded CMCS were confirmed by UV-Vis, FTIR and GPC. The antioxidant activity of CMCS was evaluated using scavenging effect on DPPH radicals, reducing power and ferrous ion chelating activity assays. The antioxidant activity of CMCS enhanced with decreasing CMCS Mw. The possible practical use of CMCS as preservative coating for peach fruit by dipping treatment after 10 days of storage at ambient temperature was investigated. The CMCS with lower Mw had a good effect on delaying spoilage and decreasing malondialdehyde (MDA) content of peach fruits suggesting their possible use as antioxidant and preservative coating.
Assuntos
Anti-Infecciosos/química , Antioxidantes/química , Quitosana/análogos & derivados , Conservantes de Alimentos/química , Raios gama , Anti-Infecciosos/farmacologia , Anti-Infecciosos/efeitos da radiação , Antioxidantes/farmacologia , Antioxidantes/efeitos da radiação , Aspergillus nidulans/efeitos dos fármacos , Candida albicans/efeitos dos fármacos , Quitosana/química , Quitosana/farmacologia , Quitosana/efeitos da radiação , Escherichia coli/efeitos dos fármacos , Conservação de Alimentos , Conservantes de Alimentos/farmacologia , Conservantes de Alimentos/efeitos da radiação , Frutas/efeitos dos fármacos , Prunus/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacosRESUMO
The pH effect on the oxidative stability of ascorbic acid in the presence of food colorant FD&C Red Nr 3 during storage with or without light was investigated. The quenching mechanism and kinetics of ascorbic acid on the FD&C Red Nr 3 photosensitized oxidation in an aqueous system at 25 degrees C were also studied by measuring the degradation of ascorbic acid or depletion of headspace oxygen. Red Nr 3 had no influence on the oxidation of ascorbic acid under dark storage, but accelerated its oxidation rate under light storage. The oxidative stability of ascorbic acid decreased as the pH increased from 4 to 7 under light without FD&C Red Nr 3. The quenching rates of ascorbic acid on the singlet oxygen by measuring the degradation of ascorbic acid in the presence of Red Nr 3 under light storage were 1.53 +/- 0.15 x 10(8), 1.86 +/- 0.25 x 10(8), and 1.19 +/- 0.12 x 10(8) M(-1)S(-1) at pH 4, 5.6, and 7, respectively.
