ABSTRACT
This work evaluated the synergic effect of carvacrol essential oil (EO) and montmorillonite (MMT) (named hybrid compound), incorporated in thermoplastic starch (TPS) films in different contents (4.5, 9, and 15 wt%). TPS films were characterized by FTIR, FT-Raman, DSC, XRD, and antimicrobial assay. FTIR and FT-Raman indicated new hydrogen bonds between hybrid and starch, altering the thermal properties and requiring more energy to destroy the TPS-hybrid bonds. XRD analysis showed slight crystallinity changes, and TPS-15 hybrid showed an amorphous structure that allows the diffusion of EO thought the films. TPS-hybrid films showed antimicrobial behavior against E. coli due to the synergistic effect of MMT and EO, which resulted in strong antimicrobial effects due to the destabilization and partial destruction of the bacteria cell membrane. The hybrid probably changed the E. coli cell permeability, respiration, and electron transport. TPS-15 hybrid sample presented the lowest crystallinity, facilitating the film's oil diffusion, maximizing the bacterium inhibitory effect, and acting as a biocidal agent. The results demonstrated that a hybrid compound is a good option for starch antimicrobial films for fresh food, such as fruits and vegetables.
Subject(s)
Bentonite/pharmacology , Cymenes/pharmacology , Anti-Bacterial Agents/pharmacology , Anti-Infective Agents/metabolism , Anti-Infective Agents/pharmacology , Bentonite/metabolism , Cymenes/metabolism , Drug Synergism , Escherichia coli/drug effects , Monoterpenes/pharmacology , Nanocomposites/chemistry , Oils, Volatile/pharmacology , Permeability , Starch/chemistry , Tensile StrengthABSTRACT
The aim of this work was to synthesize pinus residue/pectin-based composite hydrogels for the immobilization of ß-D-galactosidase. These hydrogels were synthesized via chemical crosslinking, and characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, thermal analysis, mechanical assays, X-ray diffraction, and swelling kinetics. The water absorption mechanism in the hydrogel networks occurs by non-Fickian transport. The ß-D-galactosidase immobilization capacities of the hydrogels containing 0, 5 and 10% of pinus residue were respectively 242.08 ± 0.36, 181.27 ± 0.50 and 182.71 ± 0.36 mg enzyme per g dried hydrogel, at pH 4.0 and after 600 min. These values were 182.99 ± 0.41, 219.99 ± 0.47 and 218.56 ± 0.39 mg g-1, respectively, at pH 5.6. Pectin-based hydrogels demonstrated to be excellent solid supports for the immobilization of enzymes. ß-D-Galactosidase immobilized in pectin-based hydrogels could be applied in the hydrolysis of lactose contained in either dairy foods or lactose-intolerant individuals.