Fabrication and characterization of kidney bean (Phaseolus vulgaris L.) protein isolate–chitosan composite films at acidic pH

Modelling and assessment of plasticizer migration and structure changes in hydrophobic starch-based films

The structures of starch and starch-based materials determine additives migration from material matrix. Propionylated starch derived from waxy, normal, G50 and G80 starch were selected as the matrix, the amylose effect on plasticizer (triacetin) migration as well as structural changes in hydrophobic starch-based films were discussed. The constant (k₁) of first-order rate and initial release rate (V₀) of triacetin migration were consistent with the increment of amylose content. Meanwhile, diffusion model disclosed that Fick's second law was apposite to characterize the short-term migration of triacetin, and larger diffusion coefficient (D) values of short- and long-term migration were also found in films with higher amylose content, indicating that amylose-formed structures were in favor of triacetin migration. In comparison of propionylated amylopectin, Van der Waals's interactions between propionylated amylose and triacetin were easier to be weakened with the migration of triacetin, which promoted the decrease of wavenumber of C-O-C, and enlarged the inter-planner spacing of crystalline structures, promoting the formation of amorphous structures and wrinkles and embossments in films with higher amylose content. This work confirmed that regulating the structures of starch were effective to control the migration behavior of additives from starch-based films.

Cellulose Nanocrystals to Improve Stability and Functional Properties of Emulsified Film Based on Chitosan Nanoparticles and Beeswax

The framework of this work was to develop an emulsion-based edible film based on a chitosan nanoparticle matrix with cellulose nanocrystals (CNCs) as a stabilizer and reinforcement filler. The chitosan nanoparticles were synthesized based on ionic cross-linking with sodium tripolyphosphate and glycerol as a plasticizer. The emulsified film was prepared through a combination system of Pickering emulsification and water evaporation. The oil-in-water emulsion was prepared by dispersing beeswax into an aqueous colloidal suspension of chitosan nanoparticles using high-speed homogenizer at room temperature. Various properties were characterized, including surface morphology, stability, water vapor barrier, mechanical properties, compatibility, and thermal behaviour. Experimental results established that CNCs and glycerol improve the homogeneity and stability of the beeswax dispersed droplets in the emulsion system which promotes the water-resistant properties but deteriorates the film strength at the same time. When incorporating 2.5% w/w CNCs, the tensile strength of the composite film reached the maximum value, 74.9 MPa, which was 32.5% higher than that of the pure chitosan film, while the optimum one was at 62.5 MPa, and was obtained by the addition of 25% w/w beeswax. All film characterizations demonstrated that the interaction between CNCs and chitosan molecules improved their physical and thermal properties.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Enhancing the Viability of Lactobacillus plantarum as Probiotics through Encapsulation with High Internal Phase Emulsions Stabilized with Whey Protein Isolate Microgels

Probiotics with positive physiological effects on intestinal microflora populations of the host are popular in functional foods. Low relative humidity (RH) and temperature are beneficial for probiotic survival. In the present study, freeze-dried Lactobacillus plantarum powder, representative of probiotics, was encapsulated in the high internal phase emulsions (HIPEs) stabilized with whey protein isolate (WPI) microgels, to avoid the contact of water. Homogeneously dispersed WPI microgels with particle sizes around 300 nm were formed through thermal treatment of WPI solution. The particle size of the microgels decreased with the elevation of protein concentrations as well as the departure of pH values from the isoelectric point of the protein. When internal oil phase volume fractions were higher than 80% (w/w), WPI microgels with concentrations higher than 4.0 wt %, prepared at pH 4.0, 6.0, and 7.0 conditions, could stabilize the oil to form homogeneous HIPEs with tilting stability. The HIPEs thus formed had a cellular and tunable pore structure that could resist mechanical perturbation. Encapsulation of L. plantarum within HIPEs successfully increased the cell viability after pasteurization processing. The protective effect was even improved with the elevation of the oil volume fraction and increase of WPI microgel concentrations. Under different pH conditions, the strongest protective effect appeared at pH 4.0, when the WPI microgels accumulated on the oil droplet surface. When the large amount of oil and the protein microgel layer on the oil-water interface were combined as two specialties, the HIPEs were demonstrated to have high potential for enhancing the viability of probiotics during food thermal processing.

Film-forming ability of collagen hydrolysate extracted from leather solid wastes with chitosan

Discharges of huge quantities of leather solid wastes by leather industries and the increased use of synthetic packaging films have raised serious concerns on account of their environmental impacts. The paper focuses on the development and characterization of potential environmentally friendly composite films using collagen hydrolysate (CH) extracted from leather solid wastes and chitosan (C) to assess the feasibility of producing polymeric materials suitable for applications in packaging and wrapping purposes. Solid collagen-based protein hydrolysate was extracted from chromium-tanned leather wastes and analyzed to determine its chemical properties. With the goal of improving the physico-chemical performance of CH, three types of composite films (CH75/C25, CH50/C50, CH25/C75) were prepared with increasing concentrations of C, and some of their physical and functional properties were characterized. The results indicated that the addition of C caused increase (p < 0.05) in the thickness, tensile strength (TS), elasticity modulus (EM), and water vapor permeability (WVP), leading to stronger films as compared with CH film, but significantly (p < 0.05) decreased the elongation at break (EAB) and solubility of films (p < 0.05). The light barrier measurements present low values of transparency at 600 nm of the CH/C films, indicating that the films are very transparent and they have excellent barrier properties against UV light. The structural properties investigated by FTIR and DSC showed total miscibility between both polymers. Scanning electron micrographs revealed that CH/C composite films showed a compact homogeneous structure. These results demonstrate the potential application of CH/C composite films in packaging industry.

Emerging Chitosan-Based Films for Food Packaging Applications

Recent years have witnessed great developments in biobased polymer packaging films for the serious environmental problems caused by the petroleum-based nonbiodegradable packaging materials. Chitosan is one of the most abundant biopolymers after cellulose. Chitosan-based materials have been widely applied in various fields for their biological and physical properties of biocompatibility, biodegradability, antimicrobial ability, and easy film forming ability. Different chitosan-based films have been fabricated and applied in the field of food packaging. Most of the review papers related to chitosan-based films are focusing on antibacterial food packaging films. Along with the advances in the nanotechnology and polymer science, numerous strategies, for instance direct casting, coating, dipping, layer-by-layer assembly, and extrusion, have been employed to prepare chitosan-based films with multiple functionalities. The emerging food packaging applications of chitosan-based films as antibacterial films, barrier films, and sensing films have achieved great developments. This article comprehensively reviews recent advances in the preparation and application of engineered chitosan-based films in food packaging fields.

Effect of glycosylation with xylose on the mechanical properties and water solubility of peanut protein films

This study aimed at improving the mechanical properties and water solubility of peanut protein isolate (PPI) films by glycosylating with xylose (X). The modification process of glycosylation was optimized by using response surface methodology (RSM). The effects of pH, temperature and time on degrees of glycosylation (DG), tensile strength (TS), elongation (E), solubility and microstructure of xylose glycosylated PPI films (PPI-XF) were determined. The changes of DG in different conditions indicated that crosslinking should occur between PPI and xylose during the modification. Optimum glycosylation conditions were found to be pH 9.5, 91.5 °C and 95 min. Under these conditions, TS and E values of PPI-XF were 10.37 MPa and 96.47 %, respectively. Due to glycosylation, solubility of PPI-XF decreased from 96.64 to 35.94 % and these films remained intact in water for 24 h. The microstructure of PPI-XF was denser and more compact than the unmodified PPI films. These results suggest that the xylose glycosylated PPI films have potentiality of being used as biodegradable films in food packaging application.

Fabrication and characterization of antioxidant pickering emulsions stabilized by zein/chitosan complex particles (ZCPs)

Lipid peroxidation in oil-in-water (o/w) emulsions leads to rancidity and carcinogen formation. This work attempted to protect lipid droplets of emulsions from peroxidation via manipulation of the emulsions' interface framework using dual-function zein/CH complex particles (ZCPs). ZCP with intermediate wettability was fabricated via a simple antisolvent approach. Pickering emulsions were produced via a simple and inexpensive shear-induced emulsification technique. ZCP was irreversibly anchored at the oil-water interface to form particle-based network architecture therein, producing ultrastable o/w Pickering emulsions (ZCPEs). ZCPE was not labile to lipid oxidation, evidenced by low lipid hydroperoxides and malondialdehyde levels in the emulsions after thermally accelerated storage. The targeted accumulation of curcumin, a model antioxidant, at the interface was achieved using the ZCP as interfacial vehicle, forming antioxidant shells around dispersed droplets. The oxidative stability of ZCPEs was further improved. Interestingly, no detectable hexanal peak appeared in headspace gas chromatography of the Pickering emulsions. The novel interfacial architecture via the combination of steric hindrance from ZCP-based membrane and interfacial cargo of curcumin endowed the emulsions with favorable oxidative stability. This study opens a promising pathway for producing antioxidant emulsions via the combination of Pickering stabilization mechanism and interfacial delivery of antioxidant.

Development of new active packaging film made from a soluble soybean polysaccharide incorporated Zataria multiflora Boiss and Mentha pulegium essential oils

An active edible film from soluble soybean polysaccharide (SSPS) incorporated with different concentrations of Zataria multiflora Boiss (ZEO) and Mentha pulegium (MEO) essential oils was developed, and the film's optical, wettability, thermal, total phenol and antioxidant characteristics were investigated, along with their antimicrobial effectiveness against Staphylococcus aureus, Bacillus cereus, Escherichia coli O157:H7, Pseudomonas aeruginosa and Salmonella typhimurium. The film's colour became darker and more yellowish and had a lower gloss as the levels of ZEO or MEO were increased. Antioxidant activity of the films was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric-reducing antioxidant power assays. DPPH was reduced in the range of 19.84-74.12% depending on the essential oil type and concentration. Film incorporated with 3% (v/v) ZEO showed the highest DPPH radical scavenging activity and ferric reducing antioxidant power (IC50=4188.60±21.73mg/l and EC50=8.86±0.09mg/ml, respectively), compared with the control and MEO added film. Films containing ZEO were more effective against the tested bacteria than those containing MEO. S. aureus was found to be the most sensitive bacterium to both ZEO or MEO, followed by B. cereus and E. coli. A highest inhibition zone of 387.05mm(2) was observed for S. aureus around the films incorporated with 3% (v/v) ZEO. The total inhibitory zone of 3% (v/v) MEO formulated films was 21.98 for S. typhimurium and 10.15mm(2) for P. aeruginosa. Differential scanning calorimetry (DSC) analysis revealed a single glass transition temperature (Tg) between 16 and 31°C. The contact angle increased up to 175% and 38% as 3% (v/v) of ZEO or MEO used: it clearly shows that films with ZEO were more hydrophobic than those with MEO. The results showed that these two essential oils could be incorporated into SSPS films for food packaging.

Development of novel zein-sodium caseinate nanoparticle (ZP)-stabilized emulsion films for improved water barrier properties via emulsion/solvent evaporation

This work attempted to develop novel high barrier zein/SC nanoparticle (ZP)-stabilized emulsion films through microfluidic emulsification (ZPE films) or in combination with solvent (ethyl acetate) evaporation techniques (ZPE-EA films). Some physical properties, including tensile and optical properties, water vapor permeability (WVP), and surface hydrophobicity, as well as the microstructure of ZP-stabilized emulsion films were evaluated and compared with SC emulsion (SCE) films. The emulsion/solvent evaporation approach reduced lipid droplets of ZP-stabilized emulsions, and lipid droplets of ZP-stabilized emulsions were similar to or slightly lower than that of SC emulsions. However, ZP- and SC-stabilized emulsion films exhibited a completely different microstructure, nanoscalar lipid droplets were homogeneously distributed in the ZPE film matrix and interpenetrating protein-oil complex networks occurred within ZPE-EA films, whereas SCE films presented a heterogeneous microstructure. The different stabilization mechanisms against creaming or coalescence during film formation accounted for the preceding discrepancy of the microstructures between ZP-and SC-stabilized emulsion films. Interestingly, ZP-stabilized emulsion films exhibited a better water barrier efficiency, and the WVP values were only 40-50% of SCE films. A schematic representation for the formation of ZP-stabilized emulsion films was proposed to relate the physical performance of the films with their microstructure and to elucidate the possible forming mechanism of the films.

Characterization of soluble soybean polysaccharide film incorporated essential oil intended for food packaging

This study examines the development of new bio-active polysaccharide-based bioplastics through casting and solvent-evaporation. Soluble soybean polysaccharide (SSPS) films incorporated with Zataria multiflora Boiss (ZEO) or Mentha pulegium (MEO) at various concentrations were prepared and characterized. The presence of ZEO and MEO improved polysaccharide interactions, reducing the films' water solubility and water vapor barrier properties, but did not markedly modify their moisture content or thickness. Differing amounts of ZEO or MEO had no significant effect on mechanical behavior, with the exception of 3% oil concentration, which decreased tensile strength and significantly increased elongation at break. DMTA curves revealed a single Tg, which may indicate the compatibility of essential oil and SSPS. The electron scanning micrograph for the composite film was homogeneous, without signs of phase separation between the components. These results suggest that ZEO and MEO can potentially be directly incorporated into SSPS to prepare active biodegradable films for food-packaging applications.