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Valorization of freshwater crab shell residues to chitosan for postharvest quality of mango (Mangifera indica L.) by fruit coating
(2024-12-01)
Nimitkeatkai, Hataitip
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Apiwatanapiwat, Waraporn
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Janchai, Phornphimon
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Meelaksana, Jiraporn
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Vaithanomsat, Pilanee
Freshwater crab shells (Somanniathelphusa dugasti) are abundant in inland areas and rich in chitosan, which can be extracted and utilized. This study investigated the characteristics of chitosan from freshwater crab shells (FC-chitosan) and its impact on extending the shelf life of Nam Dok Mai mangoes (Mangifera indica L.). The FC-chitosan had a high degree of deacetylation (99.15 %), thereby enhancing solubility and reactivity for a uniform coating, and a low ash content (0.75 %), minimizing the interference effects on mechanical strength and transparency, both of which could contribute to its potential use as a well-adhering coating material. The FC-chitosan film exhibited superior properties as a coating film, with relatively higher transparency (25.09 % T/mm), tensile strength (21.57 MPa), and elongation (76.09 %) compared to commercially available marine crab chitosan. Mango fruits coated with 2.0 % (w/v) FC-chitosan demonstrated appropriate postharvest quality, with lower weight loss and maintained peel color, fruit firmness, titratable acidity, and ascorbic acid during storage at room temperature (30 ± 5 °C) for up to 11 days. The results suggest that FC-chitosan is effective as a coating material for delaying ripening and extending the shelf life of mangoes. The novelty of using chitosan derived from freshwater crab shells lies in its unique properties and its sustainable use of underutilized byproducts.
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Fabrication of hollow magnetic polyaniline particles via in-situ polymerization in one-pot for UV–Vis-NIR and EMI applications
(2024-01-01)
Promlok, Duangkamol
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Wichaita, Waraporn
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Phongtamrug, Suttinun
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Kaewsaneha, Chariya
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Sreearunothai, Paiboon
The concern on the adverse impacts of electromagnetic (EM) pollution has continuously increased. Instead of using heavy metal sheet, this work aims to develop magnetic polymeric particles, that can easily be incorporated in coatings, for EM/ultraviolet-visible-near infrared (UV–Vis-NIR) shielding. By carefully design structure and key components, hollow magnetic (HoM) polyaniline (PANI) particles possessing a void encircled with magnetic nanoparticles dispersed in PANI semi-conductive shell were fabricated via the oxidative polymerization in emulsion system. By using ethyl benzene as a soft template and different surfactive dopants, i.e., sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and poly(sodium 4-styrenesulfonate) (PSS), the HoM-PANI particles (0.5–2 μm) with well-defined hollow structure, high magnetic loading (17–21%wt), and superparamagnetic properties were obtained. The particle size distribution, and magnetic loading were slightly affected by the reaction temperature, whereas molecular weight (M<inf>w</inf>) of the localized dopant considerably influenced on the levels of interparticle connectivity, and hence, the conductivity could be tailored. The water dispersible HoM-PANI particles could form opaque coating, and free-standing film. PSS with M<inf>w</inf> of 70 K and 1 M yielded the larger HoM-PANI particles and more opaque films than small dopant molecules. Void size was the determining effect on excellent opacity of the coating containing HoM-PANI dispersed in poly(vinyl alcohol) matrix against UV–Vis-NIR, and EM radiation. The ability to tune their optical properties, and electrical conductivity accomplished by designing the particle nanostructure, and doping/de-doping by localized dopants enables them the promising candidates for functional paint, and film for irradiation protection.
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Hollow natural rubber latex particles as bio-based alternative white pigment for coating applications
(2022-11-15)
Promlok, Duangkamol
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Sonongbua, Kritayakorn
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Wilepsuwan, Mutita
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Suteewong, Teeraporn
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Tangboriboonrat, Pramuan
Due to the broad particle size distribution as well as non-spherical shape of natural rubber (NR) latex particles, the non-collapse hollow NR latex particles (HL-NRPs) with well-defined void structure were developed aiming to use as an eco-friendly white pigment/additive for coatings. These hybrid HL-NRPs were prepared via the seeded emulsion polymerization of methyl methacrylate/divinylbenzene/acrylic acid (MMA/DVB/AA) monomers on NR core particles in one-pot. Using cumene hydroperoxide (CHP)/tetraethylene pentamine (TEPA) as a redox initiator, the copolymerization occurred at the particle/water interface. Without seed removal, a single void inside NRP was in situ formed by the phase separation process. Hydrophobic and elastic NR became the inner wall which strengthened the HL particles. Whereas its indigenous stabilizers, i.e., proteins-lipids, allowed the osmosis from the aqueous medium to further expand the void. The proposed mechanism was illustrated using oleic acid (OA) as a model fatty acid for non-rubber substances. Since the multiple light scattering inside the hollow structure could enhance their refractive index, the optical performance of HL-NRPs as a low-density opacifying agent in poly(vinyl alcohol) matrix, was examined using UV-Vis spectroscopy. Results showed that the HL-NRPs-based films exhibited high blocking ability over UV and visible regions. Moreover, the HL-NRPs coated with chitosan (CS) enabled these nanocomposites to adsorb the formaldehyde vapor. For sustainable development, HL-NRPs/CS could potentially be a green alternative white pigment/additive for coatings.
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Dip- and Spray-coating of Schanz pin with PLA and PLA nanosphere for prolonged antibacterial activity
(2021-10-01)
Chinavinijkul, Panarin
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Riansuwan, Kongkhet
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Kiratisin, Pattarachai
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Srisang, Siriwan
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Nasongkla, Norased
In this study, variation of coating parameters was performed to determine a suitable condition for a vancomycin-coated Schanz pins in poly(lactic acid) (PLA) for prolonged antibacterial activity. Herein, the solvent used to dissolve the polymer (DCM vs. CHCl<inf>3</inf>), the concentration of the polymer in the solvent (2 vs. 5% w/v), the vertical withdrawing speed of the implant from the solution (0.4 vs. 2.4 cm/s), and the number of dip-coating cycles denoted in layers (1 L vs. 3 L) were investigated for its drug loading. Results showed that the optimal parameters were at 2% w/v PLA in DCM at 0.4 cm/s withdrawing speed and at 3 cycles for a high vancomycin loading with low deviation in result. Another experiment was performed by varying the concentration (1, 2, 4% w/v) and number of dip-coating cycles (10 L, 20 L, 30 L) which finalized 2% w/v PLA at 10 cycles as the optimal drug loading at 2.04 ± 0.09 mg. When observing the drug-release profile, the prior formulation released 2.21 ± 0.01 mg or 92.88 ± 0.44% of drug in one week. To reduce the amount of drug release in the first week, the method was further improved by spray-coating with PLA nanospheres (PLA-NS) for multiple cycles (10-, 20-, and 30-NS) to prolong drug release. After one, two, and three weeks, the drug-release were around 76%, 80%, and 88%, respectively. However, more drugs were lost as the number of cycles increases which suggests that lower (10-NS) coating cycle is better. Therefore, the final process was selected to be 2% PLA dip-coated for 10 cycles then spray-coated with PLA nanosphere for 10 cycles. Results showed that this method can help prolong release for at least 24 days. A short-term bacterial and cytotoxicity tests were done for 3 days with no S.aureus formed nor cytotoxicity. These results supported that the coating was successful in inhibiting the growth of S.aureus.
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Facile control of structured ZnO polymeric nanoparticles through miniemulsion polymerization: Kinetic and UV shielding effects
(2021-08-01)
Sudjaipraparat, Narissara
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Suteewong, Teeraporn
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Tangboriboonrat, Pramuan
Zinc oxide polymeric nanoparticles (ZPPs) of poly (styrene-co-acrylic acid) P(St/AA), containing oleic acid modified zinc oxide nanoparticles (OA-ZnO NPs), were synthesized via miniemul-sion polymerization. By simply adjusting the quantity of reactants, i.e., sodium dodecyl sulfate (SDS) surfactant, potassium persulfate (KPS) initiator, and divinyl benzene (DVB) crosslinking agent, the location of ZnO NPs were altered from the inner (core) to the outer (shell), leading to core-shell and Pickering-like morphologies, respectively. The Pickering-like ZPPs were obtained when using SDS at below or equal to the critical micelle concentration (CMC). At above the CMC, the complete en-capsulation of OA-ZnO NPs within the ZPPs depicted a kinetically controlled morphology. The transition to Pickering-like ZPPs also occurred when reducing the KPS from 2 to 0.5–1%. Whereas the DVB accelerated the polymerization rate and viscosity in the growing monomer-swollen nanodroplets and, hence, contributed to kinetic parameters on particle morphology, i.e., an increase in the DVB content increased the rate of polymerization. A hollow structure was obtained by replacing styrene with the more hydrophilic monomer, i.e., methyl methacrylate. All ZPPs-incorporated poly (vinyl alcohol) (PVA) films greatly improved shielding performance over the UV region and were relatively transparent on a white paper background. Due to the large number of ZnO NPs in the central region and, hence, the ease of electron transfer, composite films containing core-shell ZPPs possessed the highest UV blocking ability. ZnO NPs in the outer part of the hollow and Pickering-like ZPPs, on the other hand, facilitated the multiple light scattering according to the difference of refractive in-dices between the inorganic shell and organic/air core. These results confirm the advantage of structured ZPPs and their potential use as transparent UV shielding fillers.
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Effect of silver particle-longkong peel extract coating on postharvest decay and browning in longkong fruit
(2020-01-01)
Lichanporn, Intira
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Techavuthiporn, Chairat
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Wongs-Aree, Chalermchai
We aimed to assess the effect of longkong peel extract (LPE)-silver particle-alginate coating on the postharvest decay and browning of longkong fruit during storage at 13°C and 90–95% relative humidity (RH). Longkong was coated with 0, 0.45 or 0.90 mg·L−1 LPE in silver particle-alginate solution and then stored at 13°C and 90–95% RH for nine days. In the mixture consisting of the longkong peel extract and silver solution, the silver particle size was modified to yield fine particles. Electron micrography showed the presence of silver particle sizes ranging in size from approximately 71–625 nm. Fruit coated without LPE exhibited severe browning, weight loss and decay incidence during storage. Coating with 0.45 and 0.90 mg·L−1 LPE significantly inhibited the increase in fruit browning by mainly reducing peroxidase (POD) and polyphenol oxidase (PPO) activities. LPE coating effectively reduced the longkong weight loss and decay incidence. No fruit treatment showed a significant titratable acidity change or increased soluble solids at the end of storage. These results indicate that coating with LPE is a promising approach to inhibit decay and browning and to maintain the quality of longkong during low-temperature storage.
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Formulation of chitosan-oleic acid coating for Kiew Wan tangerine by response surface methodology
(2010-05-01)
Puttongsiri, Tongchai
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Haruenkit, Ratiporn
The coating formulation is an essential factor in maintaining the postharvest quality of tangerines. A common problem found in coated tangerines is off-flavor due to improper coating. The aim of this study was to use chitosan and oleic acid to formulate the most suitable coating for tangerines displayed at room temperature (30±2°C). In order to optimize the formulation, response surface methodology (RSM) with a central composite design was applied. The response effect of chitosan (1-2%) and oleic acid (1-4%) on weight loss, ethanol in juice, and carbon dioxide and oxygen in fruit were investigated. A second order model was used to explain the effect of the dependent variables (weight loss, O<inf>2</inf>, CO<inf>2</inf>, ethanol), which were highly significant and produced R<sup>2</sup> values in the range from 77 to 92%. The optimum coating formulation for tangerine was found to be 1% chitosan (v/v) and 2.5% oleic acid (v/v), which was based on a composite desirability value of 0.80.

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