Microperforation of Three Common Plastic Films by Laser and Their Enhanced Oxygen Transmission for Fresh Produce Packaging

Three different plastic films of biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET) and low‐density polyethylene (LDPE) were perforated using Nd‐YAG laser. Effects of laser pulse energy were examined by varying energies from 50 to 250 mJ where the pulse duration and pulse repetition were kept constant at 10 ns and 1 Hz, respectively. It was found that perforation diameters of all films increased with increasing pulse energies. Observed perforations were different among the three film types. Explanation was contributed to material inherent property and its interaction with laser. Incorporation of an inorganic filler (i.e. silica based anti‐blocking agent used in packaging film) of 0.5 wt% into the LDPE films (0.5Si‐LDPE) could improve perforation performance for LDPE. This was attributed to an increased thermal diffusivity of the 0.5Si‐LDPE film. Commercial BOPET and BOPP films containing 97 microholes/m² (hole diameter of ~100 µm) showed an improvement in oxygen transmission rates (OTR) of 18 and 5 times that of the neat films without perforation. In the case of perforated 0.5Si‐LDPE films having similar perforations of 97 microholes/m² and perforation diameter of 100 µm, a two‐fold increase of OTR was obtained. Gas transmission rates of the microperforated films were measured based on the static method. Measured OTR and CO₂TR values of the three films with varying perforation diameters in a range of ~40–300 µm were compared and discussed. Overall results clearly indicate that perforation by laser is an effective process in developing breathable films with tailored oxygen transmission property for fresh produce packaging. Copyright © 2014 John Wiley & Sons, Ltd.     

Inhibitory activity of Asian spices on heterocyclic amines formation in cooked beef patties

Heterocyclic amines (HCAs) are mutagenic compounds formed when foods are cooked at high temperatures. Numerous reports have shown that natural antioxidants from spices, fruits, chocolate, and tea can inhibit formation. In this study, we evaluated HCA formation in the presence of 5 of Asian spices: galangal (Alpinia galangal), fingerroot (Boesenbergia pandurata), turmeric (Curcuma longa), cumin (Cuminum cyminum), and coriander seeds (Coriandrum sativum). HCA levels were compared to patties containing rosemary (Rosmarinus officinalis), of which the inhibitory effect is well documented. Inhibition of HCA formation by the spices was evaluated in beef patties cooked at 204 °C (400 °F) for 10 min. All spices were mixed into patties at 0.2% before cooking, and HCAs levels were measured in the final product. All patties, including the control, contained 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl -6-phenylimidazo [4,5-b]pyridine (PhIP). The average HCA content of the control patties was 7 ng/g MeIQx and 6.53 ng/g PhIP. Turmeric (39.2% inhibition), fingerroot (33.5% inhibition), and galangal (18.4% inhibition) significantly decreased HCAs compared with the control. But, only turmeric and fingerroot were as effective as rosemary in preventing HCA formation. The HCA inhibition in patties containing spices was significantly correlated to the total phenolic content (R(2) = 0.80) and the scavenging activity (R(2) = 0.84) of the spices as measured by the 2,2-diphenyl-β-picrylhydrazyl assay. Results of this study suggest that addition of Asian spices can be an important factor in decreasing the levels of HCAs in fried beef patties.     

HS-SPME-GC-MS analysis of volatile aromatic compounds in alcohol related beverages made with mulberry fruits

Wine aroma is one of the most important parameters responsible for its quality, and hence for consumer acceptance. In order to obtain an appropriate technique to study volatile aroma compounds in mulberry wines, headspace-solid phase microextraction (HS-SPME) comb 40°C for 30 min with a 50/30 μm divinylbenzenecarboxen-polydimethylsiloxane (DVB-CAR-PDMS) fiber. Approximately 80 volatile compounds have been quantified in the mulberry wine, pertaining at several chemical groups, mainly higher alcohols, fatty acids, esters, and some volatile phenols whose concentration range from few to 138.36 mg/L. This work describes a novel methodology for the analysis of mulberry wines by HS-SPME coupled to GC-MS. HS-SPME using a 50/30 μm DVB-CAR-PDMS fiber is provided the higher extraction efficiency (p<0.05) for the volatiles including the most esters, higher alcohols, and fatty acids than by the other fibers.     

Effect of nanocalcium carbonate on the impact strength and accelerated weatherability of rigid poly(vinyl chloride)/acrylic impact modifier

Poly(vinyl chloride) (PVC) composites filled with nano‐ and micro‐CaCO₃ particles were prepared via a melt blending method. Transmission electron microscopy images revealed better dispersion of nano‐CaCO₃ than micro‐CaCO₃ in the PVC matrix. With more than 5 phr (parts per 100 parts of resin) of nano‐CaCO₃ content, both impact strength and heat stability were improved. Accelerated weathering tests were performed to investigate UV stability. The impact strength and white index obtained upon weathering exposure of PVC/(80 μm CaCO₃) nanocomposites showed a significant improvement upon incorporating nano‐CaCO₃. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Evaluation of bioactivities and phenolic contents of wild edible mushrooms from northeastern Thailand

Food Science and Biotechnology - Twenty-five wild edible mushrooms from Northeastern Thailand were analyzed for their antioxidant activities, proteins, sugars, β-glucan, and phenolic profiles....     

Practical Approach in Developing Desirable Peel–Seal and Clear Lidding Films Based on Poly(Lactic Acid) and Poly(Butylene Adipate‐Co‐Terephthalate) Blends

In this research, poly(lactic acid) (PLA) blend with poly(butylene adipate‐co‐terephthalate) (PBAT) were selected to fabricate peelable lidding films. In general, blending PLA with PBAT results in hazy films; however, desirable low haze films (<10%) could be achieved in this study by designing proper blend composition and cast film process under optimum conditions. Based on various blends containing PBAT ranging from 15 to 30% by weight, it could be seen that a PBAT/PLA blend of 20/80 showed desired optical and peel–seal property, which had a haze of <10% and low peel strength in an easy‐peel characteristic. It was also observed that not only the blend composition but also the film thickness could influence both optical and peel–seal behaviours because the bulk morphology and surface irregularities of the films could vary by changing films' thicknesses. Thus, cast extruded pristine and PBAT/PLA (20/80) blend films of three different thicknesses (20, 35 and 50 μm) were studied. Peel–seal behaviour and optical properties of these films were examined. An I‐peel test (180°) of films sealed on PLA sheet (thickness of ~350 μm) with different interfacial sealing temperature illustrated failure mechanism of four types, i.e. tearing, partial tearing, cohesive and adhesive failure. Based on this study, the PBAT/PLA of 20/80 wt% films with thickness of 20 μm can be used as easy‐peel lidding film sealed with PLA container. Such PBAT/PLA blend films possess a low haze of ~4% and a low peel strength of 8–10 N/15 mm at a broad range of interfacial sealing temperature of 76–105°C. Copyright © 2017 John Wiley & Sons, Ltd.     

Flexible and Tough Poly(lactic acid) Films for Packaging Applications: Property and Processability Improvement by Effective Reactive Blending

This study demonstrates a practical means to overcome inherent brittleness problem of poly(lactic acid) (PLA) and make PLA feasible as packaging material. PLA with suitable processability is utterly required for package manufacturers, where flexible, tough PLA film is essential for packers and end users. Highly flexible PLA films with 60‐fold increase in elongation at break (Eb) over that of the neat PLA were successfully produced by integrating effective reactive blending and economical film blowing process. The ‘two‐step’ blending was used to prepare PLA compound; poly(butylene adipate‐co‐terephthalate) (PBAT – another biodegradable polymer) was first blended with 0.5–1% chain extender (epoxy‐functionalized styrene acrylic copolymer) (ESA), followed by subsequent blending with PLA in twin‐screw extruder. Blown films of reactive blend of PLA/PBAT/ESA (80/20/1) showed impressively high Eb of 250% versus a very low Eb of 4% for the neat PLA. Resulting blown films still possessed high modulus of 2 GPa, yield stress of 50–60 MPa and good toughness of ~100 MPa. Significant enhancement in the film's ductility was attributed to homogeneous blend with developed fine strand‐like structure as a result of effective in situ compatibilization and good interfacial adhesion between the PLA and PBAT. PLA/PBAT/ESA blend also offered improved processability. Resulting films had acceptable haze of ~10% for common packaging, and clearer film close to PLA (≤2%) could be obtained by designing PLA skin layers in multilayer structure. Films of PLA/PBAT/1%ESA exhibit potential as packaging material; their mechanical and optical properties are comparable with or even exceed some existing films used in the market. Copyright © 2015 John Wiley & Sons, Ltd.     

Quality and biochemical changes of longan (Dimocarpus longan Lour cv. Daw) fruit under different controlled atmosphere conditions

Sulphur dioxide has been used to control pericarp browning in longan fruit. However, due to health and regulatory concerns, alternative treatments should be tested. The objective of this study was to find the tolerance levels of longan fruit to low O₂ (2%, 5%, 10% and 15%) and elevated CO₂ (5%, 10%, 15% and 20%) at 2 °C. According to the tolerance study, controlled atmospheres (CA) of 5% O₂ + 5% CO₂, 5% O₂ + 10% CO₂ and 5% O₂ + 15% CO₂ were compared with normal air (control) at 2 °C. Pericarp browning and decay incidence of longan were significantly (P ≤ 0.05) higher in control than all the CA treatments. CA storage reduced polyphenol oxidase (PPO) activity, maintained L* value and slowed down a decrease in total phenolic contents (TPC). Pericarp browning was highly correlated with PPO, L* and TPC.     

Microstructural Analyses of Biaxially Oriented Polylactide/Modified Thermoplastic Starch Film with Drastic Improvement in Toughness

This study presents microstructural regularization of biaxially oriented polylactide blended with a silane‐modified thermoplastic starch (BO‐PLA/mTPS) film, traced by X‐ray diffraction and scattering, and differential scanning calorimetry techniques. Interfacial adhesion improvement of mTPS favors PLA crystallization, and produces a large δ‐crystal (100–150 nm) with isotropic orientation when combining with BO stretching. High draw ratio (5 × 5), and BO stretching rate (75 mm s^?1) lead to tight packing of PLA lamellae in both BO‐PLA/TPS and BO‐PLA/mTPS films, resulting in drastic toughness improvement (i.e., fivefold increases of Young's modulus and tensile strength, and threefold increase of elongation, as compared to those of the films without the BO process) with significantly decreased water absorption. However, the effect of reactive compatibility by mTPS on mechanical and water barrier properties is hindered by the BO process in which the V_H‐type patterns of TPS and mTPS are unclearly present, overlapped with (203) diffraction plane of PLA crystal, especially applying fast stretching.