Structural changes and triacetin migration of starch acetate film contacting with distilled water as food simulant

Development of cinnamon essential oil-loaded PBAT/thermoplastic starch active packaging films with different release behavior and antimicrobial activity

The poly (butylene adipate-co-terephthalate)/thermoplastic starch (PBAT/TPS) active packaging films containing cinnamon essential oil (CEO) were fabricated by melting blending and extrusion casting method. The effects of TPS content (0 %, 10 %, 20 %, 30 %, 40 % and 50 %) on the properties of the films and their application in largemouth bass preservation were studied. As TPS content increased from 0 % to 50 %, the water vapor permeability increased from 7.923 × 10-13 (g•cm/(cm2•s•Pa)) to 23.967 × 10-13 (g•cm/(cm2•s•Pa)), the oxygen permeability decreased from 8.642 × 10-11 (cm3•m/(m2•s•Pa)) to 3.644 × 10-11 (cm3•m/(m2•s•Pa)), the retention of CEO in the films increased. The release rate of CEO from the films into food simulant (10 % ethanol) accelerated with increasing TPS. The films exhibited different antibacterial activity against E. coli, S. aureus, and S. putrefaciens. It was closely related with the release behavior of the CEO. The films containing CEO could efficiently inhibit the decomposition of protein and the growth of microorganisms in largemouth bass. It showed that the higher TPS in the films, the better inhibitory effect. This study provided a new idea for developing PBAT/TPS active films with different release behavior of active agents and different antibacterial activity for food packaging.

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.

Controlling plasticizer migration based on crystal structure and micromorphology in propionylated starch-based food packaging nanocomposites

Migration of additives is an important issue for proper application in food packaging. In this work, propionylated waxy and normal starch-based nanocomposites (PW-N and PN-N) with two different amylopectin content were immersed in distilled water, and structural changes and migration mechanism of plasticizer (triacetin) were discussed in detail. Results showed that when immersion time was prolonged to 150 h, small crystals of PN-N disappeared, and amorphous structures formed gradually in PW-N and PN-N. Exfoliated structures still remained in PW-N with prolonged immersion time, while exfoliated structures gradually formed from intercalated ones in PN-N, and the peak representing d001 (d-spacing) at q = 1.70 nm^-1 faded. The migration mechanism of triacetin obeyed the first-order kinetic model and Fick's law; furthermore, in comparison with PW-N, PN-N showed a larger diffusion coefficient (D₂ = 12.13 μm²·h^-1). These results contributed to expanding the application of starch-based nanocomposites in future environmentally friendly food packaging.

Preparation and characterization of native and autoclaving-cooling treated Pinellia ternate starch and its impact on gut microbiota

The aim of this study was to investigate and compare the structural and physicochemical properties of native Banxia starch (BXS) and autoclaving-cooling treated Banxia starch (CTBXS) and its related impacts on production of short chain fatty acids (SCFAs) and human gut microbiota by in vitro fecal fermentation. BXS had semicircle to spherical granules, whereas CTBXS exhibited block-shape. According to XRD and TGA, BXS had a C-type crystalline pattern, while CTBXS had a B-type crystalline pattern. CTBXS had better thermal stability than BXS. In addition, BXS exhibited significantly higher solubility and swelling power than CTBXS, and CTBXS had higher content of SDS than BXS. Moreover, BXS and CTBXS could change the composition and abundance of gut microbiota, could also promote the production of SCFAs. This study is beneficial to well understand the in vitro digestion and fecal fermentation behaviors of BXS and CTBXS, and can be developed as a potential functional food with the aim of improving colonic health.

Migration kinetic of silver from polylactic acid nanocomposite film into acidic food simulant after different high-pressure food processing

The migration study of nano-Ag migration from polylactic acid (PLA) films was studied. Samples treated by high-pressure food processing (0, 100, 200, 300, and 400 MPa pressure) were soaked in acetic acid solution and incubated at 20 °C for 90 days. At the end of storage, nano-Ag particles (AgNPs) migration from the PLA/AgNPs composite film treated under 200 MPa high pressure was the lowest. However, AgNPs migration was accelerated under 400 MPa high pressure. High-pressure processing (200 MPa) could cause denser structure and higher crystallinity degree in films than other treatments. Lower amount of AgNPs induced a decline in the intensity of specific characteristic peaks. The diffraction peak intensity of α-crystal for the film sample treated with 400 MPa was the lowest on day 60. The crystallization index of the PLA matrix changed with different high-pressure processing. The result indicated that appropriate high-pressure food processing could effectively suppress AgNPs migration from PLA-based film while contacting with acidic acid food simulant. PRACTICAL APPLICATION: The release of nanoparticles from food packaging material is a very important matter when the migration is concerned with regulatory and toxicity issues. The study described the migration kinetic of AgNPs from PLA nanocomposite film into acidic food simulant after different high-pressure food processing. The results indicated that the PLA/AgNPs nanocomposite film was safe for acidic food after high-pressure treatment.

Diffusion Mechanism of Cinnamon Essential Oils Release from Calcium Alginate Based Controlled Release Films in Contact with Food Simulating Solvent

Calcium alginate based controlled release films with moderate mechanical properties were fabricated in this paper. The diffusion mechanism of these films contacting food simulating solvent (FSS) was explored in some detail. With the increase of glycerol content, the diffusion coefficient (D) values of cinnamon essential oils (CEOs) diffusing to ethanol first increased slowly (0.3–0.6 mL), then vigorously (0.6–0.9 mL), and then mildly (0.9–1.2 mL). The D values of the CEOs diffused to water are all in the order of magnitude of 10⁻¹⁰ cm²/s. The D values of CEOs diffused from films EG3 and EGC1 to aqueous ethanol altered enormously at a small moisture percentage (w = 0.3), then continuously varied vigorously, and at last altered mildly in the range of w = 0.3–1. All the results above indicate that, considering the FSS, the diffusion ability of molecules is jointly determined by the size and distribution of free volume in the system (polymer + diffusive substance + solvents), the intermolecular interaction, and the partition coefficient of the solvents. In addition, several pairs of D values, such as D_EG and D_GA, are very close to each other, indicating that different kinds of interactions between different groups may have the same effect on the diffusion ability of molecules. The correlation between D₁ and D₂ indicates that polymeric emulsifier chains also exist in the polymer-rich layer. All the findings and analysis could provide the theoretical basis and data support for further molecular dynamic simulation and could guide the design of controlled release food packaging for food protection.