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.     

Antimicrobial Activity of Cinnamaldehyde and Eugenol and Their Activity after Incorporation into Cellulose‐based Packaging Films

Cinnamaldehyde and eugenol were investigated for their antimicrobial activity against 10 pathogenic and spoilage bacteria and three strains of yeast, using an agar‐well diffusion assay. The minimum inhibitory concentrations (MICs) of these compounds were determined using an agar dilution method. Finally, cinnamaldehyde‐incorporated and eugenol‐incorporated methyl cellulose films were prepared to obtain active antimicrobial packaging materials. These antimicrobial cellulose‐based packaging films were investigated for antimicrobial activity against target microorganisms using both an agar‐disc diffusion technique and a vapour diffusion technique. At a concentration of 50 µl/ml, cinnamaldehyde and eugenol revealed antimicrobial activity against all test strains. They showed zones of inhibition, ranging from 8.7 to 30.1 mm in diameter. Eugenol and cinnamaldehyde possessed ‘moderate?strong inhibitory’ and ‘strong?highly strong inhibitory’ characteristics, respectively. With MICs of 0.78?50 µl/ml, cinnamaldehyde and eugenol also inhibited the growth of all test microorganisms. Among the test microorganisms, Aeromonas hydrophila and Enterococcus faecalis were the most sensitive to cinnamaldehyde and eugenol. Cinnamaldehyde showed lower MICs against all test strains than those of eugenol. In an agar‐disc diffusion assay, cellulose‐based film containing cinnamaldehyde or eugenol totally failed to exhibit a clear inhibitory zone. However, it showed positive activity against all selected test strains in terms of size and enumeration of microbial colonies in a vapour diffusion assay. This study shows the potential use of cinnamaldehyde and eugenol for application in antimicrobial packaging film or coating. Copyright © 2011 John Wiley & Sons, Ltd.     

Packaging performance comparison for distribution and export of papaya fruit

This paper presents the development and testing procedures for new packaging systems for papaya fruit. Papaya is a nutritious tropical fruit, consumed both in its fresh form and as a processed product worldwide. Thailand is a major exporter of fresh and processed papayas from Asia. Major quality indices for papayas include colour, size, firmness and freedom from defects and decay. A high percentage of post‐harvest losses of papaya fruits have been reported as exports have increased. Mechanical damage is one of the major causes of the quality loss of papaya fruits, therefore, proper packaging is demanded for better protection. In addition, other criteria are important to meet consumer acceptance. New packaging systems for papayas were compared with the existing systems currently used for local markets. The packaging systems were evaluated in terms of physical protection, heat transfer characteristics for rapid cooling and maintaining optimum temperature and relative humidity during post‐harvest, quality maintenance, and marketing issues. Two cushioning systems, foam nets and paper‐based wrap materials, were also compared. Actual shipment and vibration tests were performed and the effect on quality was determined. The new packaging systems tested showed better protective performance and improved quality parameters, as compared to existing systems. Minimized mechanical injuries resulted in a decreased susceptibility to decay and bruising. Paper‐based cushions showed similar protection to plastic foam nets materials but offered a better ripening response for papayas. The data were compared to seek an optimum packaging system for papayas based on the various criteria. Copyright © 2005 John Wiley & Sons, Ltd.     

Measurement and Analysis of Vehicle Vibration for Delivering Packages in Small‐Sized and Medium‐Sized Trucks and Automobiles

In distribution, packaged products are subjected to the variation in vibration levels from transport vehicles that vary in frequency and acceleration while moving to their destinations. This vibration may negatively affect the product or packaging. This study measured and analysed vibration levels in vehicles commonly used to transport packages in the last leg of the package delivery service that is used by single‐parcel carriers. Using data recorders, we monitored vertical, lateral and longitudinal vibrations over 75 h of travel time in five different types of small and medium package delivery vehicles. The study presents these data as power density (PD) spectra and compares it with previously measured PD vibration levels in commercial long‐haul interstate tractor‐trailer truck shipments. Data were collected in the USA and Thailand. Copyright © 2011 John Wiley & Sons, Ltd.     

Life cycle inventory and analysis of re‐usable plastic containers and display‐ready corrugated containers used for packaging fresh fruits and vegetables

Today's demanding distribution challenges require engineers to choose from various types of materials, design and construction methods, to develop containers that can deliver goods with minimal damage. The challenge is even greater when packing and shipping goods which are perishable and sensitive to both physical and climatic changes in environment. In recent years the type of packaging material used to design and construct containers has undergone more scrutiny than ever, due to environmental challenges. This study focuses on two types of containers that have been designed and are being used to pack and ship fresh fruits and vegetables. The study compares the re‐usable plastic containers to single‐use display‐ready paper corrugated trays. Results show that, based on the scope of this study and comparing 10 different produce items, such as apples, carrots, grapes, oranges, onions, tomatoes, strawberries, etc., the re‐usable plastic containers require 39% less total energy, produce 95% less total solid waste and generate 29% less total greenhouse gas emissions. This study focused on the North American market. Major European nations have been using a large number of re‐usable plastic containers for these types of fresh produce for the past three decades. This study was initiated by the Franklin Associates, an independent consulting firm for allowing an in‐depth review of all data and results from a two year study titled: Life Cycle Inventory of Reusable Plastic Containers and Display‐Ready Corrugated Containers Used for Fresh Produce Applications. Copyright © 2006 John Wiley & Sons, Ltd.     

Survey of counterfeit melamine tableware available on the market in Thailand, and its migration

A simple measurement of sample density by adopting the principles of buoyancy could help screen counterfeit melamine ware if the density was below 1.50 g cm?3. However, samples with a density exceeding 1.50 g cm?3 were not necessarily made from melamine formaldehyde. FTIR analysis showed that all counterfeit products were made of urea formaldehyde and coated on the food-contact side with melamine formaldehyde, a tactic probably intended to cover up the true product features. The overall migration of real and counterfeit melamine samples complied with both European Union and Thai regulations, as the exposure layers in both cases were melamine formaldehyde. Formaldehyde migration failed to comply with Thai standards, but this was not the case for European Union standards. However, the results showed a significant inconsistency between individual items of the same brand and between individual exposures of the same test specimen. This indicated the inherent inhomogeneity between individual items, which mainly resulted from the manufacturing process: for instance, insufficient temperature and time to obtain complete polycondensation of monomers. Therefore, it is recommended that constant surveillance be conducted on melamine articles available in the marketplace in terms of quality and safety.     

Preharvest bagging with wavelength-selective materials enhances development and quality of mango (Mangifera indica L.) cv. Nam Dok Mai #4

BACKGROUND: Preharvest bagging has been shown to improve development and quality of fruits. Different light transmittance bags showed different effects on fruit quality. This study presents the benefits of using newly developed plastic bagging materials with different wavelength‐selective characteristics for mangoes (cv. Nam Dok Mai #4). Mangoes were bagged at 45 days after full bloom (DAFB) and randomly harvested at 65, 75, 85, 95, and 105 DAFB. The bags were removed on the harvest days. The wavelength‐selective bags (no pigment, yellow, red, blue/violet, blue) were compared with the Kraft paper bag with black paper liner, which is currently used commercially for several fruits, and with non‐bagging as a control. RESULTS: Bagging significantly (p?0.05) reduced diseases and blemishes. Mango weight at 95 DAFB was increased approximately 15% by VM and V plastic bagging, as compared to paper bagging and control. Plastic bagging accelerated mango ripening as well as growth. Plastic‐bagged mangoes reached maturity stage at 95 DAFB, while non‐bagged mangoes reached maturity stage at 105 DAFB. Paper bagging resulted in a pale‐yellow peel beginning at 65 DAFB, while plastic bagging improved peel glossiness. CONCLUSION: Preharvest bagging with different wavelength‐selective materials affected mango development and quality. Bagging mangoes with VM and V materials could reduce peel defects and diseases, increase weight, size, and sphericity, improve peel appearance, and shorten the development periods of mangoes. The results suggest a favorable practice using the newly developed VM and V plastic bags in the production of mangoes, and possibly other fruits as well. Copyright © 2010 Society of Chemical Industry     

Starch hydrolysis kinetics of Bacillus licheniformis α-amylase

The reaction kinetics for thermostable Bacillus licheniformis α-amylase was determined under two sets of conditions: an initial rate study over a range of low starch concentrations (1–8%, w/w) in a batch reactor, and a continuous rate study at a high starch concentration of 40% during which a twin-screw extruder was used as a bioreactor for the first 600 s and the reaction was continued to equilibrium in a batch reactor. The Michaelis–Menten model was found to be sufficient for describing the kinetics at low starch concentrations; however, a modified first-order model was required at high concentration. There was no evidence of substrate inhibition at the high starch concentration. The rate of product formation, calculated in terms of dextrose equivalent (DE) values, was found to be proportional to the square root of the rate of starch consumption.     

Comparison of reusable and single‐use plastic and paper shipping containers for distribution of fresh pineapples

This paper presents the effects of different packaging systems and fruit orientation on bruising and pre‐cooling time of pineapples during distribution. The package types studied were reusable plastic containers, single‐use paper corrugated containers and plastic foam containers (FCs). Simulated vibration tests were performed to evaluate the shipping containers on their protective performances. After the vibration tests, pineapples were evaluated for bruise damage and decay during storage for 5 days. Pineapple fleshes were also evaluated for bruise volume and changes in colour, firmness, total soluble solids content (TSS) and titratable acidity (TA) after storage of 5 days. Bruise damage was more intense as the storage time increased. Package types had significant effects (p ≤ 0.05) on bruise damage of pineapples. The corrugated containers showed the best protective performance for pineapples, while the FCs showed the worst. The corrugated containers with paperboard partitions showed the lowest damage levels as compared to other package types studied. Foam‐net cushion reduced bruise damage of pineapples. L values and firmness of pineapple flesh were highly associated with degree of bruising. The results suggested that slight bruising on the skin may signify severe bruising on the flesh and bruising accelerated decay in pineapples. Orientation did not show a significant effect (p ≤ 0.05) on bruising. The highest pre‐cooling rates were observed in the reusable plastic containers, while the slowest rates were observed in the single‐use paper containers. The results indicated that careful handling in the proper packaging with optimum cushion can minimize bruise damage and decay of pineapples after shipments. Copyright © 2007 John Wiley & Sons, Ltd.