Progress in research on the safety of silicone rubber products in food processing.

Silicone rubber (SR) is widely used in the food processing industry due to its excellent physical and chemical properties. However, due to the differences in SR product production formulas and processes, the quality of commercially available SR products varies greatly, with chemical and biological hazard potentials. Residual chemicals in SR, such as siloxane oligomers and 2,4-dichlorobenzoic acid, are non-intentionally added substances, which may migrate into food during processing so the safe use of SR must be guaranteed. Simultaneously, SR in contact with food is susceptible to pathogenic bacteria growing and biofilm formation, like Cronobacter sakazakii, Staphylococcus aureus, Salmonella enteritidis, and Listeria monocytogenes, posing a food safety risk. Under severe usage scenarios such as high-temperature, high-pressure, microwave, and freezing environments with long-term use, SR products are more prone to aging, and their degradation products may pose potential food safety hazards. Based on the goal of ensuring food quality and safety to the greatest extent possible, this review suggests that enterprises need to prepare high-quality food-contact SR products by optimizing the manufacturing formula and production process, and developing products with antibacterial and antiaging properties. The government departments should establish quality standards for food-contact SR products and conduct effective supervision. Besides, the reusable SR products should be cleaned by consumers immediately after use, and the deteriorated products should be replaced as soon as possible.

Adopting the "Missile boats-Aircraft carrier" strategy via human-contact friendly oxidized starch to achieve rapid-sustainably antibacterial paperboards.

Polysaccharide-based antibacterial agents have received tremendous attention for the facile fabrication, low toxicity, and high compatibility with carbohydrate polymers. However, the antimicrobial mechanism, activity, and cytotoxicity for human-contact paperboards of oxidized starch (OST) with high carboxyl content, has not been explored. Herein, OST-27- 75 with 27- 75 wt% carboxyl contents were fabricated by H2O2 and coated on paperboards. Strikingly, OST-55 coating layer (16 g/m2) did not exfoliate from paperboard and possessed the rapid-sustainable antibacterial performance against Staphylococcus aureus and Escherichia coli. The soluble and insoluble components of OST-55 (OST55-S: OST55-IS mass ratio = 1: 2.1) presented different antimicrobial features and herein they were characterized by GC-MS, FT-IR, H-NMR, XRD, bacteriostatic activities, biofilm formation inhibition and intracellular constituent leakage to survey the antibacterial mechanism. The results revealed OST55-S displayed an amorphous structure and possessed superior antibacterial activity against S. aureus (MIC = 4 mg/mL) and E. coli (MIC = 8 mg/mL). Distinctively, OST55-S could rapidly ionize [H+] like "missile boats" from small molecule saccharides, while OST55-IS polyelectrolyte could continuously and slowly release for [H+] like an "aircraft carrier" to inhibit biofilm formation and disrupt cell structure. Eventually, the "Missile boats-Aircraft carrier" strategy provided a green methodology to fabricate polymeric antibacterial agents and expanded the use of cellulose-based materials.

Extrusion-blown oxidized starch/poly(butylene adipate-co-terephthalate) biodegradable active films with adequate material properties and antimicrobial activities for chilled pork preservation.

Food safety concerns from spoilage and non-degradable packaging risk human health. Progress made in biodegradable plastic films, but limited study on biomass composite films with favorable morphological, mechanical, and inherent antibacterial properties for fresh meat preservation. Herein, we present a versatile packaging film created through the extrusion blowing process, combining oxidized starch (OST) with poly(butylene adipate-co-terephthalate) (PBAT). SEM analysis revealed even distribution of spherical OST particles on film's surface. FTIR spectra revealed new intermolecular hydrogen bonds between OST and PBAT. While combining OST slightly reduced tensile properties, all composite films met the required strength of 16.5 ± 1.39 MPa. Notably, films with 40 % OST showed over 98 % antibacterial rate against Staphylococcus aureus within 2 h. pH wasn't the main cause of bacterial growth inhibition; OST hindered growth by interfering with nutrient absorption and metabolism due to its carboxyl groups. Additionally, OST disrupted bacterial membrane integrity and cytoplasmic membrane potential. Remarkably, the OST/PBAT film excellently preserved chilled fresh pork, maintaining TVB-N level at 12.6 mg/100 g on day 6, microbial count at 105 CFU/g within 6-10 days, and sensory properties for 8 days. It extended pork's shelf life by two days compared to polyethylene film, suggesting an alternative to a synthetic material.

Chemical contaminants from food contact materials and articles made from or containing wood and bamboo - a review.

Due to recently introduced 'so-called' bio- and plant-based friendly food contact materials and articles (FCM/FCA), some neglected safety issues need to be raised. In this review, potential chemical contaminants from FCM/FCA made from or containing wood and bamboo are presented. Sources, migration, and analytical issues in determining contaminants including intentionally and non-intentionally added substances (IAS and NIAS, respectively) are reviewed. Most of the contaminants are components from melamine-formaldehyde-resin (MFR), paints and coatings, preservatives, and bleaching agents. Tableware made of MFR containing bamboo fibres as a filler are not always suitable for use as tableware since harmful amounts of melamine and formaldehyde can migrate from the tableware into food and even accelerate the degradation of certain polymers with which they are mixed. In addition, in the EU bamboo in plastic FCM is not authorized under Regulation (EU) 10/2011. Paints and coatings used to provide surface coverage for bamboo and wooden articles also pose a risk of migration of heavy metals. Limits on preservatives in wood FCM are covered by legislation in many countries, nevertheless their contamination should not be ignored. Some wood species are considered 'toxic' or contain 'toxic' constituents that should not be used in contact with food, which are worth considering for legislation. IAS analyses in bamboo and wooden FCM is generally not a problem, but has proven to be more challenging for NIAS. Due to a complex mixture of substances contained in plant-based materials, there is a need to improve databases for non-target screening of such chemicals.

HS-GC-IMS identification of volatile aromatic compounds of freshly-cooked rice packaged with different disposable lunchboxes.

The rapid development of online-to-offline food delivery service has necessitated the replacement of plastic lunchbox using biodegradable ones. In current study, a total number of fourteen panelists were firstly recruited and trained to investigate how different commercial disposable lunchboxes affect the freshly cooked rice sensory properties during heat preservation (60 °C, 60 min). The lunchboxes were made of pure polypropylene (PP), polypropylene-starch (PP-S), pure wheat-straw and sugarcane-straw (WS & SS) and Paper. The discrepancy of volatile aromatic substances was then analyzed using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) to study the possible mechanism beneath the variations of the influences of different lunchboxes on the aromatic properties of rice. Results showed that, compared with the textural attributes, the aroma was significantly and positively correlated with panelist's acceptability, among which, the aroma of starchy, sulfur and smoky are the most important ones. The moisture absorption plays an important role in affecting the aromatic characteristics of the packaged rice. While all lunchboxes have inhibitory effects on the production of volatile flavor substances including 2,6-Dimethylpyrazine, 2-Acetylpyrazine and γ-Octalactone, pure PP and PP-S lunchboxes generated undesirable flavor substances including 2-Ethyl-1-hexanl and Camphene, and thus reduced panelist's preferences. It was also found that the panelist liked the rice packaged by Paper lunchbox the best because of its better performance in maintaining the aroma of starchy and sulfur, the two substances that are associated with the higher concentration of ethereal and fruity volatile flavor substances. This study provides important information for manufacturers to understand how different disposable lunchboxes may impact the textural and aromatic properties of packaged foods.

Controlled moisture permeability of thermoplastic starch/polylactic acid/poly butylene adipate-co-terephthalate film for the autolysis of straw mushroom Volvariella volvacea.

Straw mushrooms are prone to autolyze, leading to a high requirement of environmental humidity. In this work, thermoplastic starch/polylactic acid/poly (butylene adipate-co-terephthalate) (TPS/PLA/PBAT) film was produced by extrusion. The moisture permeability of the film was controlled by adjusting the content of TPS, which could be expected to further control humidity of the microenvironment in the package. Results revealed that the water vapor transmission rate of the film linearly increased from 612.31 g/m2·24 h to 1082.50 g/m2·24 h with the increase in the TPS concentration. The TPS/PLA/PBAT film with 30 wt% TPS showed the strongest inhibition on the autolysis of straw mushrooms compared with other groups, effectively delaying the increase in the free water, soluble solid content, rate of weight loss, and polyphenol oxidase of straw mushrooms and extending the shelf life of straw mushrooms from 24 h to 72 h.

Hollow tube covalent organic framework for syringe filter-based extraction of ultraviolet stabilizer in food contact materials.

In this work, a novel hollow tube covalent organic framework constructed by cyclotricatechylene and tetrafluoroterephthalonitrile (CTC-TFPN-COF) with polyether bond was synthesized, and it was coated on filter membrane for extraction of ultraviolet stabilizer in migration from food contact materials. Since the monomers of the polymer were linked by polyether bond, the CTC-TFPN-COF exhibited strong chemical stability in severe conditions such as acid, alkali and various organic solvent. The excellent features of high porosity and robust structure endowed the CTC-TFPN-COF good candidate as adsorbent for extraction of ultraviolet stabilizer. Moreover, the CTC-TFPN-COF coated membranes were immobilized on syringe filter and coupled with multiple channel injection pump to realize high throughput sample pretreatment strategy. Subsequently, a sensitive analytical method for ultraviolet stabilizer was established followed by ultra-high performance liquid chromatography-tandem mass spectrometry. The flow rate of extraction and desorption, elution solvent and the volume of desorption solvent were optimized. The method was assessed, which showed wide linear ranges with R2 greater than 0.99, low limits of detection (0.9-91 ng L-1) and low limits of quantification (3-300 ng L-1). The developed method was successfully applied to determine trace ultraviolet stabilizer in the migration of food contact materials with different simulated solution, which demonstrated its promising potential in practical analysis.

Influence of cooking conditions on the migration of silicone oligomers from silicone rubber baking molds to food simulants.

The stability, surface micromorphology, and volatile organic compounds (VOCs) of silicone rubber baking molds (SRBMs) were tested while using the molds under severe conditions: baking at 175 °C, microwaving at 800 W, and freezing at -18 °C. Moreover, migration tests of SRBMs to food simulants (isooctane, 95% ethanol, and Tenax®) at 70 °C for 2 h (accelerated conditions) were performed. The initial total VOCs concentration was 2.53% higher than that recommended by BfR Recommendations on Food Contact Materials. Therefore, the SRBM samples were considered as badly tempered materials, and 18 different types of silicone oligomers were identified during the migration tests. The following percentage of silicone oligomers with a molecular weight lower than 1000 Da in isooctane, 95% ethanol, and Tenax® were detected: 70.7%, 91.8%, and 97.2%, respectively. It has been proven that previous baking treatments effectively reduced the content of silicone oligomers migrating from SRBMs.

Molecular dynamics simulation of three plastic additives' diffusion in polyethylene terephthalate.

Accurate diffusion coefficient data of additives in a polymer are of paramount importance for estimating the migration of the additives over time. This paper shows how this diffusion coefficient can be estimated for three plastic additives [2-(2'-hydroxy-5'-methylphenyl) (UV-P), 2,6-di-tert-butyl-4-methylphenol (BHT) and di-(2-ethylhexyl) phthalate (DEHP)] in polyethylene terephthalate (PET) using the molecular dynamics (MD) simulation method. MD simulations were performed at temperatures of 293-433 K. The diffusion coefficient was calculated through the Einstein relationship connecting the data of mean-square displacement at different times. Comparison of the diffusion coefficients simulated by the MD simulation technique, predicted by the Piringer model and experiments, showed that, except for a few samples, the MD-simulated values were in agreement with the experimental values within one order of magnitude. Furthermore, the diffusion process for additives is discussed in detail, and four factors - the interaction energy between additive molecules and PET, fractional free volume, molecular shape and size, and self-diffusion of the polymer - are proposed to illustrate the microscopic diffusion mechanism. The movement trajectories of additives in PET cell models suggested that the additive molecules oscillate slowly rather than hopping for a long time. Occasionally, when a sufficiently large hole was created adjacently, the molecule could undergo spatial motion by jumping into the free-volume hole and consequently start a continuous oscillation and hop. The results indicate that MD simulation is a useful approach for predicting the microstructure and diffusion coefficient of plastic additives, and help to estimate the migration level of additives from PET packaging.

Study of the Migration of Stabilizer and Plasticizer from Polyethylene Terephthalate into Food Simulants.

This study investigates the determination and migration of stabilizers and plasticizers from polyethylene terephthalate (PET). Two methods [ultrasonic extraction with dichloromethane or methanol and total dissolution with phenol/tetrachloroethane (m:m/1:1)] for pre-concentration of additives in PET material were performed. The diffusion of these additives from PET was evaluated by immersing in deionized water, acetic acid 3% (w/v), ethanol 20% (v/v), ethanol 50% (v/v) and isooctane at 20, 40, 55 and 70°C, respectively. The amount of additives in PET and food simulants was quantified by high-performance liquid chromatography-photodiode array detector (HPLC-PDA). The optimized HPLC method showed high correlation coefficients (R ≥ 0.9993), good precision, accuracy and reproducibility. Experimental diffusion coefficients (DP) were calculated according to a mathematical model based on Fick's second law, and the DP values of considered compounds ranged from 9.8 × 10(-15) to 1.4 × 10(-8) cm(2) s(-1) The experimental DP values were also compared with that predicted by currently used diffusion models. In addition, the effect of temperature on the diffusion rate was assessed. The effect of temperature on the diffusion coefficients followed an Arrhenius-type model with active energies ranged from 40.4 to 113.8 kJ mol(-1) for the target compounds.

Migration of copper from nanocopper/LDPE composite films.

Three nanocopper/low-density polyethylene (LDPE) composite films were tested in food simulants (3% acetic acid and 10% ethanol) and real food matrices (rice vinegar, bottled water and Chinese liquor) to explore the behaviours of copper migration using ICP-OES and GFAAS. The effects of exposure time, temperature, nanocopper concentration and contact media on the release of copper from nanocopper/LDPE composite films were studied. It was shown that the migration of copper into 10% ethanol was much less than that into 3% acetic acid at the same conditions. With the increase of nanocopper concentration, exposure time and temperature, the release of copper increased. Copper migration does not appear to be significant in the case of bottled water and Chinese liquor compared with rice vinegar with a maximum value of 0.54 µg mL-1 for the CF-0.25# bags at 70°C for 2 h. The presence and morphology of copper nanoparticles in the films and the topographical changes of the films were confirmed by field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM). In this manner, copper nanoparticles of different morphologies, sizes and distribution were found, and samples with higher nanocopper concentration had a more irregular topography. In the case of Fourier transform infrared spectroscopy (FTIR), no chemical bonds formed between copper nanoparticles and LDPE. Copper nanoparticles were just as physically dispersed in LDPE.

Determination of Polymer Additives-Antioxidants, Ultraviolet Stabilizers, Plasticizers and Photoinitiators in Plastic Food Package by Accelerated Solvent Extraction Coupled with High-Performance Liquid Chromatography.

An analytical method for the quantitative determination of 4 antioxidants, 9 ultraviolet (UV) stabilizers, 12 phthalate plasticizers and 2 photoinitiators in plastic food package using accelerated solvent extraction (ASE) coupled with high-performance liquid chromatography-photodiode array detector (HPLC-PDA) has been developed. Parameters affecting the efficiency in the process such as extraction and chromatographic conditions were studied in order to determine operating conditions. The analytical method of ASE-HPLC showed good linearity with good correlation coefficients (R ≥ 0.9833). The limits of detection and quantification were between 0.03 and 0.30 µg mL(-1) and between 0.10 and 1.00 µg mL(-1) for 27 analytes. Average spiked recoveries for most analytes in samples were >70.4% at 10, 20 and 40 µg g(-1) spiked levels, except UV-9 and Irganox 1010 (58.6 and 64.0% spiked at 10 µg g(-1), respectively), the relative standard deviations were in the range from 0.4 to 15.4%. The methodology has been proposed for the analysis of 27 polymer additives in plastic food package.