Evaluation of nanocomposite packaging containing Ag and ZnO on shelf life of fresh orange juice

Nanocomposite LDPE films containing Ag and ZnO nanoparticles were prepared by melt mixing in a twin-screw extruder. Packages prepared from the films were then filled with fresh orange juice and stored at 4 °C. Microbial stability, ascorbic acid (AA) content, browning index, color value, and sensory attributes of them were evaluated after 7, 28, and 56 days of storage. Packages containing the nanomaterials, expect 1% nano-ZnO, kept the microbial load of fresh juice below the limit of microbial shelf life (6 log cfu/ml) up to 28 days The least degradation of AA (80.50 mg/100 g), development of brown pigments (OD = 0.23) and losing of color (∆E = 6.0) were observed in pouches containing 0.25% nano-ZnO, after the same time. Sensory attributes were also ranked highest for the juice thus packed in the recent packages after 28 days (p < 0.05). Packages containing nanosilver increased shelf life of fresh juice although part of its sensory attributes were lost.

Industrial relevance

Compared with pure packaging materials, antimicrobial nanocomposite packages containing Ag and ZnO as an alternative non-thermal technology can extend the shelf life of fresh orange juice up to 28 days. However, a certain concentration of nano-ZnO in the packages showed less adverse effects on sensory characteristics.     

Effect of nanocomposite packaging containing Ag and ZnO on inactivation of Lactobacillus plantarum in orange juice

Nanocomposite LDPE films containing Ag and ZnO nanoparticles were prepared by melt mixing in a twin-screw extruder. Orange juice was sterilized and was inoculated with 8.5 log cfu/mL of lactobacillus plantarum. Packages prepared from nanocomposite films were then filled with this orange juice and then stored at 4 °C. Microbial stability of the juice was evaluated after 7, 28, 56, 84, and 112 days of storage. The results showed that microbial growth rate significantly reduced as a result of using this nanocomposite packaging material. Reduced numbers of L. plantarum were observed (p < 0.05) in nanocomposite packages of orange juice containing nanosilver and nano-ZnO. Moreover, packaging made from nanocomposite film containing nanosilver showed a more pronounced antimicrobial effects, as compared with nano-ZnO during 112 days storage of inoculated orange juice. However, LDPE + 5% P105 packages, showed a significant antimicrobial activity compared with others.     

Effect of salep‐based edible coating enriched with grape seed extract on postharvest shelf life of fresh strawberries

Effects of novel edible coatings based on salep solution (SS) enriched with grape seed extract (GSE) (1.5% SS, 1.5% SS + 0.5% GSE, 1.5% SS + 1.5% GSE, 1.5% SS + 3% GSE) on the quality characteristics of fresh strawberries were monitored after 0, 4, 8, 12, 16, and 20 days of storage (1°C, 95% RH). The lowest growth of microorganisms, weight loss, softening and ascorbic acid, phenol and anthocyanin degradation was measured in strawberries coated with 1.5% SS + 3% GSE. The highest superoxide dismutase activity and the lowest peroxidase activity were determined in strawberries coated with 1.5% SS + 3% GSE. Moreover, they received the highest ranked sensory attributes. Incorporating GSE into the SS coating formulation as a new hurdle increased its antimicrobial properties and extended the shelf life of coated strawberries compared to uncoated by up to 20 days.     

Microstructural evolution and mechanical properties of AlCrFeNiCoC high entropy alloy produced via spark plasma sintering

AlCrFeCoC high entropy alloy was synthesised through mechanical alloying and spark plasma sintering. The milling time had a strong influence on the particles shape and structure and consequently on microstructural and mechanical evolution of the material after sintering. The material's microstructure after spark plasma sintering contained FCC and BCC phases as well as ordered BCC and C₂₃C₆ carbide. The material's strength increased with increasing the milling time because of the finer microstructure and phases formation evolution.