Yoonjee Chang

Development of polylactic acid nanocomposite films reinforced with cellulose nanocrystals derived from coffee silverskin

Bio-nanocomposite films based on polylactic acid (PLA) matrix reinforced with cellulose nanocrystals (CNCs) were developed using a twin-screw extruder. The CNCs were extracted from coffee silverskin (CS), which is a by-product of the coffee roasting process. They were extracted by alkali treatment followed by sulfuric acid hydrolysis. They were used as reinforcing agents to obtain PLA/CNC nanocomposites by addition at different concentrations (1%, 3%, and 5% CNCs). Morphological, tensile, and barrier properties of the bio-nanocomposites were analyzed. The tensile strength and Youngs modulus increased with both 1% and 3% CNCs. The water vapor permeability decreased gradually with increasing addition of CNCs up to 3% and good oxygen barrier properties were found for all nanocomposites. These results suggest that CNCs from CS can improve the physical properties of PLA-based biopolymer film. The developed PLA/CNC bio-nanocomposite films can potentially be used for biopolymer materials with enhanced barrier and mechanical properties.

Ascorbic Acid-Based Oxygen Scavenger in Active Food Packaging System for Raw Meatloaf: An ascorbic acid-based oxygen scavenger…

A nonferrous oxygen scavenger (NFOS) comprising activated carbon and sodium l-ascorbate was developed to enhance the preservative efficacy of raw meatloaves. To determine the optimum formulation of activated carbon and sodium l-ascorbate, NFOSs with varying ratios of components (1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, and 1:2, w/w) were prepared and their oxygen-scavenging volumes were measured over 4 d at 25 °C. Assays of oxygen-scavenging capacities indicated that the optimum NFOS formulation of activated carbon and sodium l-ascorbate was achieved at a ratio of 1:1.6 (w/w). Finally, the optimal NFOS sachet was applied to packaging of raw meatloaves and its oxygen-scavenging capacity was periodically analyzed. Moreover, microbiological changes (including total aerobic bacteria, lactic acid bacteria, and yeasts and molds) and an effect on lipid oxidation during the storage were examined at 4 °C for 4 d. The meatloaves packaged with NFOS sachet had lower thiobarbituric acid reactive substances and microbiological changes than control meatloaves, indicating the practical utility in the food packaging industry. PRACTICAL APPLICATION Oxygen-scavenging sachets containing iron powder have been generally used although those have several problems. Therefore, to solve them, an ascorbic acid-based oxygen scavenger composed of activated carbon and sodium l-ascorbate was newly developed. It did not only inhibit lipid oxidation but also reduce microbial growth in meatloaves. It could be used as a promising packaging material to protect meat products from lipid oxidation and microbial contamination.

Development of Biopolymer Composite Films Using a Microfluidization Technique for Carboxymethylcellulose and Apple Skin Particles

Biopolymer films based on apple skin powder (ASP) and carboxymethylcellulose (CMC) were developed with the addition of apple skin extract (ASE) and tartaric acid (TA). ASP/CMC composite films were prepared by mixing CMC with ASP solution using a microfluidization technique to reduce particle size. Then, various concentrations of ASE and TA were incorporated into the film solution as an antioxidant and an antimicrobial agent, respectively. Fourier transform infrared (FTIR), optical, mechanical, water barrier, and solubility properties of the developed films were then evaluated to determine the effects of ASE and TA on physicochemical properties. The films were also analyzed for antioxidant effect on 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and antimicrobial activities against Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica, and Shigella flexneri. From the results, the ASP/CMC film containing ASE and TA was revealed to enhance the mechanical, water barrier, and solubility properties. Moreover, it showed the additional antioxidant and antimicrobial properties for application as an active packaging film.

Cloning and protein expression of the sn-1(3) regioselective lipase from Cordyceps militaris

In this study, the gene of a novel lipase with sn-1(3) regioselectivity (i.e., sn-1 or sn-3 specific) from Cordyceps militaris was successfully expressed by a heterologous expression system. Total RNA was extracted from C. militaris and then single-stranded cDNA was synthesized. The resulting C. militaris lipase (CML) gene was inserted in Escherichia coli expression plasmids [pET-29b(+), pET-26b, and pColdIII] to construct plasmids encoding CML, which were then transformed to E. coli strains BL21 (DE3), C43 (DE), C41 (DE3), and Origami (DE3) for protein expression. Although the recombinant CML expression level was high, it was overproduced in the form of inclusion bodies. Under a specific condition, the soluble form of the recombinant CML was detected using Western blot analysis; however, no enzyme activity was observed. To overcome the lack of post-translational modifications in recombinant CML, a baculovirus-insect expression system was introduced for eukaryotic lipase expression. pDualBac was used as the transfer vector, and the CML gene was fused under the control of the polyhedrin promoter. After generating the recombinant baculovirus, the active form of CML was successfully produced and its kinetic parameters were determined.

Analytical Survey on the Package Source, Components, and Various Characteristics of Processed Foods in Korea

This study was conducted to investigate the packaging characteristics including pack sources and pack components of processed foods in Korea. For the survey, 704 food package samples were selected based on the consumption of top 10 brackets in each food item. They were consisted of 1,245 packaging components. Seven specific items were firstly investigated including product name, capacity of the food, package component, package source, food contact area, food contact ratio, and package thickness. The processed foods in Korea can be classified into 16 pack sources and 21 pack components, respectively. By using this information, the data were analyzed specifically. The collected data were analyzed in 8 major categories: frequency of use by pack components and pack sources, pack components by the products, pack sources by the products and pack components, pack thickness/food contact ratio by the products, food contact ratio by pack components and pack sources. Consequently, this survey will provide various information of the packaging characteristics of processed foods in Korea.

Protection of Grain Products from Sitophilus oryzae (L.) Contamination by Anti‐Insect Pest Repellent Sachet Containing Allyl Mercaptan Microcapsule

The purpose of this study was to develop an anti-insect pest repellent sachet to prevent Sitophilus oryzae (L.) (Coleoptera: Curculionidae) contamination in grain packaging. The anti-insect pest activities of essential oils (EOs) from garlic (Allium Sativum), ginger (Zingiber Officinalis), black pepper (Piper nigrum), onion (Allium cepa), and fennel (Foeniculum vulgare) as well as major compounds (allyl disulfide, AD; allyl mercaptan, AM) isolated from of garlic and onion (AD and AM) were measured against S. oryzae. The results revealed that garlic EO, onion EO, AD, and AM showed strong fumigant insecticidal activities. Among these, AM showed the highest acetylcholinesterase (AChE) inhibition rate, indicating that the fumigation insecticidal efficacy of AM is related with its AChE inhibition ability. Subsequently, the microcapsules were produced with a high efficiency (80.02%) by using AM as a core material and rice flour as a wall material. Finally, sachet composed of rice flour microcapsule containing 2% AM (RAM) was produced. Repellent assay was performed to measure anti-insect pest ability of the RAM sachet, showed remarkable repelling effect within 48 h both in the presence or absence of attractant. In a release profile of RAM sachet, it was expected to last over 20 mo during the distribution period of brown rice. Moreover, RAM sachet showed no undesirable changes to the sensory properties of the rice both before and after cooking. Taken together, these results suggest that the newly developed RAM sachet could be used as a packaging material to protect grain products from S. oryzae contamination. PRACTICAL APPLICATION The rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), causes damages to stored products and its contamination in grain products has become a major problem in cereal market. To preserve brown rice, an anti-insect pest repellent sachet containing 2% allyl mercaptan was newly developed and it showed remarkable repellent abilities against S. oryzae. It could be used as an active food packaging system to protect grain products from insect pest contamination.