Fresh apple juice treated with ultrasound (for 0, 30, 60 and 90 min, at 20 °C, 25 kHz frequency) was evaluated for different physico-chemical, Hunter color values, cloud value, antioxidant capacity, scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical, ascorbic acid, total phenolics, flavonoids, flavonols and microbial characteristics. No significant effect of sonication was observed on pH, total soluble solids (°Brix) and titratable acidity of apple juice. Sonication significantly improved ascorbic acid, cloud value, phenolic compounds, antioxidant capacity, DPPH free radical scavenging activity and differences in Hunter color values. Moreover, significant reduction in microbial population was observed. Findings of the present study suggested that sonication treatment could improve the quality of apple juice. It may successfully be employed for the processing of apple juice with improved quality and safety from consumer's health point of view.

This work investigated the polyanion-initiated gelation process in fabricating chitosan-tripolyphosphate (CS-TPP) nanoparticles intended to be used as carriers for delivering tea catechins. The results demonstrated that the particle size and surface charge of CS-TPP nanoparticles could be controlled by fabrication conditions. For preparation of CS-TPP nanoparticles loaded with tea catechins, the effects of modulating conditions including contact time between CS and tea catechins, CS molecular mass, CS concentration, CS-TPP mass ratio, initial pH value of CS solution, and concentration of tea catechins on encapsulation efficiency and the release profile of tea catechins in vitro were examined systematically. The study found that the encapsulation efficiency of tea catechins in CS-TPP nanoparticles ranged from 24 to 53%. In addition, FT-IR analysis showed that the covalent bonding and hydrogen bonding between tea catechins and CS occurred during the formation of CS-TPP nanoparticles loaded with tea catechins. Furthermore, studies on the release profile of tea catechins in vitro demonstrated that the controlled release of tea catechins using CS-TPP nanoparticles was achievable.

Enzymatic browning and microbial growth lead to quality losses in apple products. In the present study, fresh apple juice was thermosonicated using ultrasound in-bath (25 kHz, 30 min, 0.06 W cm(-3)) and ultrasound with-probe sonicator (20 kHz, 5 and 10 min, 0.30 W cm(-3)) at 20, 40 and 60°C for inactivation of enzymes (polyphenolase, peroxidase and pectinmethylesterase) and microflora (total plate count, yeast and mold). Additionally, ascorbic acid, total phenolics, flavonoids, flavonols, pH, titratable acidity, (°)Brix and color values influenced by thermosonication were investigated. The highest inactivation of enzymes was obtained in ultrasound with-probe at 60°C for 10 min, and the microbial population was completely inactivated at 60°C. The retention of ascorbic acid, total phenolics, flavonoids and flavonols were significantly higher in ultrasound with-probe than ultrasound in-bath at 60°C. These results indicated the usefulness of thermosonication for apple juice processing at low temperature, for enhanced inactivation of enzymes and microorganisms.

Adaptable hydrogel networks with reversible connectivity have emerged as a promising platform for biomedical applications. Synthetic copolymers and low-molecular-weight gelators (LMWG) have been shown to form reversible hydrogels through self-assembly of the molecules driven by self-complementary hydrophobic interaction and hydrogen bonding. Here, inspired by the adhesive proteins secreted by mussels, we found that simply adding natural polyphenols, such as epigallocatechin gallate (EGCG) to amyloid fibrils present in the nematic phase, successfully drives the formation of hydrogels through self-assembly of the hybrid supramolecules. The hydrogels show birefringence under polarized light, indicating that the nematic orientation is preserved in the gel phase. Gel stiffness enhances with incubation time and with an increase in molecular ratios between polyphenol and fibrils, fibril concentration, and pH. The hydrogels are shear thinning and thermostable from 25 to 90 °C without any phase transition. The integrity of the trihydroxyl groups, the gallate ester moiety in EGCG, and the hydrophobicity of the polyphenols govern the interactions with the amyloid fibrils and thus the properties of the ensuing hydrogels. The EGCG-binding amyloid fibrils, produced from lysozyme and peptidoglycans, retain the main binding functions of the enzyme, inducing bacterial agglomeration and immobilization on both Gram-positive and Gram-negative bacteria. Furthermore, the antibacterial mechanism of the lysozyme amyloid fibril hydrogels is initiated by membrane disintegration. In combination with the lack of cytotoxicity to human colonic epithelial cells demonstrated for these hybrid supramolecules, a potential role in combating multidrug-resistant bacteria in biomedical applications is suggested, such as in targeting diseases related to infection of the small intestine.