ABSTRACT
Ultrasonication (US)-assisted Fenton-system (US-Fenton) with different US time was developed for synthesizing chitosan (CS)-ferulic acid (FA) conjugates. The optimal US-Fenton for a suitable time was selected for preparing a film with CS-FA conjugate and its structural, functional, rheological, and physical properties were also investigated. Compared with Fenton-system, US-Fenton enhanced the grafting ratio of the conjugates, which increased firstly and then decreased as US time. The conjugate obtained by US-Fenton for 1 min (FUS1) possessed the highest grafting ratio (121.28 mg FA/g) and its grafting time was also shortened from 12 h to 1 min contrasted with Fenton grafted method. Structural characterization results showed that FA was conjugated on CS via ester and amide bonds with decreased crystallinity. Scanning electron microscopy and molecular weight analysis indicated that the degradation degree of CS-FA conjugates increased with US time. The DPPH and ABTS radical-scavenging activities of FUS1 were the closest to ascorbic acid, and it also showed the best antibacterial effect among the test conjugates. Accordingly, FUS1 was selected to obtain the film for contrasting with CS film. FUS1 film solution exhibited a decreased viscosity. In comparison to CS film, UV transmittance of FUS1 film approached zero, and its moisture, oxygen, and carbon dioxide permeabilities significantly decreased (P < 0.05). Moreover, its water solubility and tensile strength increased by 58.09% and 25.72% than those of CS film, respectively. Therefore, US-Fenton for 1 min could be a promising method for efficiently preparing active food package materials and FUS1 film possessed broad application prospects.
Subject(s)
Chitosan , Chitosan/chemistry , Antioxidants/chemistry , Ascorbic Acid/chemistry , Coumaric Acids/chemistryABSTRACT
The eco-friendly polyelectrolyte bilayer films were prepared by layer-by-layer (LBL) casting method using chitosan (CS) and four types of edible citrus pectin as film substrates. The results showed that the polyelectrolyte bilayer films exhibited excellent comprehensive properties. Furthermore, the interaction between CS and pectin was closely related to the degree of methyl-esterification (DM), molecular weight (Mw), and zeta potential of pectin. The low DM, Mw, and high zeta potential of the low methyl-esterified pectin (LM) resulted in a denser internal structure of the bilayer film, stronger UV shielding performance, and stronger gas barrier ability. The high DM and Mw of the high methyl-esterified pectin (HM) endow the bilayer film with stronger mechanical properties, thermal stability, and antifogging property. The microstructural and spectroscopic analysis showed that there are hydrogen bonds and electrostatic interactions between the layers. Overall, the developed CS-pectin polyelectrolyte bilayer films provided potential applications for food bioactive packaging.
ABSTRACT
Pullulan-based composite films incorporated with bacterial cellulose (BC) and ferulic acid (FA) were prepared by solution casting method. The rheological, morphological, barrier, optical, anti-fogging, and antioxidant properties of pullulan-based composite films doped with BC and FA were investigated. The rheological results showed that all film-forming solution was pseudoplastic fluid and its viscosity increased with the increase of BC content. An appropriate BC (2 %) and FA were uniformly dispersed in pullulan to form uniform and dense composite films. With the increase of BC content, the roughness and opacity of composite films increased while their UV-vis barrier performance was improved by incorporating BC and FA. Fourier transform infrared spectrometer analysis demonstrated that hydrogen bond interactions among pullulan, BC, and FA were found, and incorporating BC could increase the crystallinity of the composite films, thus enhancing their mechanical, barrier, hydrophobic, and thermal stability properties. Pullulan-based composite films incorporated with 2 % BC and FA (P-BC2-FA) showed better mechanical properties, water, oxygen, and carbon dioxide barrier performances, and its water contact angle value also increased compared with control, respectively. P-BC2-FA film showed superior anti-fogging and antioxidant activities. These results indicate that the P-BC2-FA film are expected to be a potential target of bioactive packaging.
Subject(s)
Antioxidants , Cellulose , Carbon Dioxide , Cellulose/chemistry , Coumaric Acids , Food Packaging/methods , Glucans , Oxygen , Permeability , WaterABSTRACT
Based on finite time thermodynamics, an irreversible combined thermal Brownian heat engine model is established in this paper. The model consists of two thermal Brownian heat engines which are operating in tandem with thermal contact with three heat reservoirs. The rates of heat transfer are finite between the heat engine and the reservoir. Considering the heat leakage and the losses caused by kinetic energy change of particles, the formulas of steady current, power output and efficiency are derived. The power output and efficiency of combined heat engine are smaller than that of single heat engine operating between reservoirs with same temperatures. When the potential filed is free from external load, the effects of asymmetry of the potential, barrier height and heat leakage on the performance of the combined heat engine are analyzed. When the potential field is free from external load, the effects of basic design parameters on the performance of the combined heat engine are analyzed. The optimal power and efficiency are obtained by optimizing the barrier heights of two heat engines. The optimal working regions are obtained. There is optimal temperature ratio which maximize the overall power output or efficiency. When the potential filed is subjected to external load, effect of external load is analyzed. The steady current decreases versus external load; the power output and efficiency are monotonically increasing versus external load.
