Impact of nano-CaCO3 -LDPE packaging on quality of fresh-cut sugarcane

Inorganic Fillers and Their Effects on the Properties of Flax/PLA Composites after UV Degradation

The present investigation seeks to assess the impact of fillers on the mechanical characteristics of entirely biodegradable composites, introducing an advanced solution to fulfil long-term durability demands within point-of-purchase (POP) industries. The inclusion of calcium carbonate (CaCO3) fillers on the various properties of the flax fibre-reinforced composites, after accelerated irradiation in an ultraviolet (UV) radiation exposure has been investigated in the present study. Different types of flax fibre-reinforced poly lactic acid (PLA) biocomposites (with and without filler) were fabricated. The mechanical (tensile and flexural), and physical properties of the specimens were assessed after 500 h of exposure to accelerated UV irradiation of 0.48 W/m2 at 50 °C and were compared with those of the unexposed specimens. The results indicate that the presence of the inorganic filler significantly improved the performance of the biocomposites compared to the unfilled biocomposites after UV exposure. After adding 20% of fillers, the tensile strength was increased by 2% after UV degradation, whereas the biocomposite without filler lost 18% of its strength after UV exposure. This can be attributed to the change in the photo-degradation of the PLA due to the presence of the CaCO3 filler, which acts as a safeguard against UV light penetration by creating a protective barrier. The scanning electron microscopy (SEM) images of the degraded specimen surface show substantial difference in the surface topography of the composites with and without fillers.

Nondestructive Detection of Weight Loss Rate, Surface Color, Vitamin C Content, and Firmness in Mini-Chinese Cabbage with Nanopackaging by Fourier Transform-Near Infrared Spectroscopy

A nondestructive optical method is described for the quality assessment of mini-Chinese cabbage with nanopackaging during its storage, using Fourier transform-near infrared (FT-NIR) spectroscopy. The sample quality attributes measured included weight loss rate, surface color index, vitamin C content, and firmness. The level of freshness of the mini-Chinese cabbage during storage was divided into three categories. Partial least squares regression (PLSR) and the least squares support vector machine were applied to spectral datasets in order to develop prediction models for each quality attribute. For a comparative analysis of performance, the five preprocessing methods applied were standard normal variable (SNV), first derivative (lst), second derivative (2nd), multiplicative scattering correction (MSC), and auto scale. The SNV-PLSR model exhibited the best prediction performance for weight loss rate (R_p² = 0.96, RMSEP = 1.432%). The 1st-PLSR model showed the best prediction performance for L* value (R_p² = 0.89, RMSEP = 3.25 mg/100 g), but also the lowest accuracy for firmness (R_p² = 0.60, RMSEP = 2.453). The best classification model was able to predict freshness levels with 88.8% accuracy in mini-Chinese cabbage by supported vector classification (SVC). This study illustrates that the spectral profile obtained by FT-NIR spectroscopy could potentially be implemented for integral assessments of the internal and external quality attributes of mini-Chinese cabbage with nanopacking during storage.

Mechanical and Antimicrobial Polyethylene Composites with CaO Nanoparticles

Low-density polyethylene composites containing different sizes of calcium oxide (CaO) nanoparticles were obtained by melt mixing. The CaO nanoparticles were synthesized by either the sol-gel or sonication methods, obtaining two different sizes: ca. 55 nm and 25 nm. These nanoparticles were used either as-synthesized or were modified organically on the surface with oleic acid (Mod-CaO), at concentrations of 3, 5, and 10 wt% in the polymer. The Mod-CaO nanoparticles of 25 nm can act as nucleating agents, increasing the polymer’s crystallinity. The Young’s Modulus increased with the Mod-CaO nanoparticles, rendering higher reinforcement effects with an increase as high as 36%. The reduction in Escherichia coli bacteria in the nanocomposites increased with the amount of CaO nanoparticles, the size reduction, and the surface modification. The highest antimicrobial behavior was found in the composites with a Mod-CaO of 25 nm, presenting a reduction of 99.99%. This strong antimicrobial effect can be associated with the release of the Ca²⁺ from the composites, as studied for the composite with 10 wt% nanoparticles. The ion release was dependent on the size of the nanoparticles and their surface modification. These findings show that CaO nanoparticles are an excellent alternative as an antimicrobial filler in polymer nanocomposites to be applied for food packaging or medical devices.

Effect of nano-SiO2 packing on postharvest quality and antioxidant capacity of loquat fruit under ambient temperature storage

Effect of nano-SiO₂ packing on postharvest quality and antioxidant capacity of two different loquat cultivars (white-flesh 'Qingzhong' and red-flesh 'Dawuxing') were determined. Results showed that nano-SiO₂ packing significantly inhibited internal browning, retarded the decline of total soluble solids, titratable acidity, ascorbic acid content and extractable juice in both cultivars. Decay index of nano-SiO₂ packing in 'Dawuxing' and 'Qingzhong' was 53.25% and 42.84% lower than control after the day 12, respectively. Meanwhile, nano-SiO₂ packing enhanced the contents of individual phenolic compounds and soluble sugar compounds, induced higher superoxide dismutase and catalase activities, which contributed to improving 1,1-diphenyl-2-picrylhydrazyl and hydroxyl radical scavenging capacity. Furthermore, the contents of total soluble solids, ascorbic acid and soluble sugar were higher in 'Qingzhong' than those in 'Dawuxing', which dedicated to better quality. These results indicated that nano-SiO₂ packing was a promising approach in inhibiting decay, maintaining quality and expanding shelf life of loquats.

Effect of carbon dots with chitosan coating on microorganisms and storage quality of modified-atmosphere-packaged fresh-cut cucumber

BACKGROUND

In order to inhibit microorganisms and improve storage quality of fresh-cut cucumber, fresh-cut cucumber was treated by carbon dots (CDs) from kelp/chitosan (CH) coating solution with CD concentrations of 0%, 1.5%, 3% and 4.5% and then packaged as well as stored at 4 °C for 15 days. The effect of CDs/CH coating on microorganisms and the quality of modified-atmosphere-packaged fresh-cut cucumber during storage were investigated.

RESULTS

The CDs was monodispersed spherical morphology with size distribution of 0.54-0.83 nm. Interaction of CDs and CH had the generation of strong hydrogen bond. Inhibition zone diameters of CDs/CH coating against Staphylococcus aureus and Escherichia coli were enhanced with the increase of CD concentrations. Moreover, CDs/CH coating inhibited the growth of total number of colonies, mold, and yeast in modified-atmosphere-packaged fresh-cut cucumber during storage. A coating of 4.5% CDs/CH effectively reduced the losses of weight, firmness, and total soluble solids, the degradation of ascorbic acid content and flavor, and inhibited peroxidases activity, as well as decreased water mobility in fresh-cut cucumber during storage.

CONCLUSION

The results indicated that a CDs/CH coating was helpful for inhibiting microorganisms and improving storage quality, and could be an effective method to prolong shelf life of fresh-cut cucumber. © 2019 Society of Chemical Industry.

Effect of CaCO₃ Nanoparticles on the Mechanical and Photo-Degradation Properties of LDPE

CaCO₃ nanoparticles of around 60 nm were obtained by a co-precipitation method and used as filler to prepare low-density polyethylene (LDPE) composites by melt blending. The nanoparticles were also organically modified with oleic acid (O-CaCO₃) in order to improve their interaction with the LDPE matrix. By adding 3 and 5 wt% of nanofillers, the mechanical properties under tensile conditions of the polymer matrix improved around 29%. The pure LDPE sample and the nanocomposites with 5 wt% CaCO₃ were photoaged by ultraviolet (UV) irradiation during 35 days and the carbonyl index (CI), degree of crystallinity (χ_c), and Young’s modulus were measured at different times. After photoaging, the LDPE/CaCO₃ nanocomposites increased the percent crystallinity (χ_c), the CI, and Young’s modulus as compared to the pure polymer. Moreover, the viscosity of the photoaged nanocomposite was lower than that of photoaged pure LDPE, while scanning electron microscopy (SEM) analysis showed that after photoaging the nanocomposites presented cavities around the nanoparticles. These difference showed that the presence of CaCO₃ nanoparticles accelerate the photo-degradation of the polymer matrix. Our results show that the addition of CaCO₃ nanoparticles into an LDPE polymer matrix allows future developments of more sustainable polyethylene materials that could be applied as films in agriculture. These LDPE-CaCO₃ nanocomposites open the opportunity to improve the low degradation of the LDPE without sacrificing the polymer’s behavior, allowing future development of novel eco-friendly polymers.

Responses of Fresh-Cut Strawberries to Ethanol Vapor Pretreatment: Improved Quality Maintenance and Associated Antioxidant Metabolism in Gene Expression and Enzyme Activity Levels

Strawberries were treated with different concentrations of ethanol vapor and then cut into four wedges and stored at 4 °C for 1 week. It was found that 4 mL/kg of ethanol was the optimal concentration to reduce the decrease of firmness and weight loss. Total phenolics content, total flavonoid and anthocyanin contents, antioxidant enzyme activities, and gene expression related to the antioxidant were elevated using the ethanol treatment. Ethanol vapor also suppressed microbial growth and promoted free radical (hydroxyl and DPPH) scavenging capacities and four kinds of esters and bioactive components in strawberry wedges. Moreover, ethanol enhanced antioxidant enzyme activities including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) by activating related gene expression. The results of our research indicate that ethanol vapor has potential application in preserving quality and improving antioxidant capacity of fresh-cut strawberries.