Utilization of the waste aqueous phase from tea residue hydrothermal carbonization for preparing active food packaging films.

Hydrothermal carbonization (HTC) is an effective strategy for high-value utilization of tea residue (TR), and it was noticed the aqueous phase (AP) has not been extensively studied. This study aimed to investigate the chemical components and characteristics of the AP, and applied it in active food packaging films. The results showed that the total phenolic content of AP was 1.86 mg GAE/mL, and the main compounds in AP were organic acids, alcohols, and amino acids. The AP showed excellent antibacterial activity and antioxidant capacity. The active films were prepared using the casting method. The 4:7-AP/PVA film showed outstanding mechanical properties (tensile strength = 34.18 MPa, elongation at break = 458.67%), antioxidant ability (DPPH scavenging capacity 92.01%), antibacterial activity, water resistance and biocompatibility. The banana preservation test showed the AP/PVA films could successfully prolong the shelf-life of bananas and have the potential to be food packaging films.

Novel pH-responsive indicator films based on bromothymol blue-anchored chitin for shrimp freshness monitoring.

The cellulose nanofibers (CNFs) based pH-sensitive indicator films were developed by mixing guar gum (GG) with bromothymol blue-anchored chitin (BTB-Chitin) as an indicator to monitor shrimp freshness. The BTB-Chitin was prepared by grafting hydroxypropyltriethylamine groups (HPTA) to chitin first, then anchoring bromothymol blue (BTB) to prepare intelligent pH response BTB-Chitin. The 0.08 BTB-Chitin films had a good tensile strength of 11.76 MPa and the water contact angle values were 125°, which displayed obvious color response to pH buffers and acid base volatile gas. Besides, the homogeneous and flexible composite films showed good color stability and reversibility. The released amount of BTB was very low from the BTB-Chitin films in heptane and corn oil. The composite films had been degraded completely in 15 days in soil. The pH and volatile base nitrogen were measured to determine the degree decay of shrimp (Litopenaeus vannamei), and the prepared pH-sensitive films changed from yellow (fresh) to cyan (spoiled) with the freshness of shrimp decreased, indicating the BTB-Chitin films could detect the shrimp freshness in real-time and high visibility.

Characterization of high amylose corn starch-cinnamaldehyde inclusion films for food packaging.

The antibacterial films prepared from high amylose corn starch-cinnamaldehyde (HACS-CIN) inclusion complex were reported in this work and the different structural, mechanical, physicochemical and antibacterial properties of the films were investigated. The FT-IR results supported that the CIN was encapsulated in the helical structure of HACS by self-assembly. The encapsulation efficiency was as high as 39.19%, and the releasing rate results showed HACS-CIN inclusion films could slow down the volatilization of CIN. The films showed excellent mechanical properties with tensile strength of 14.77 MPa and elongation at break of 44.95%; and good transparency with visible light transmittance of 70%. UV transmittance test showed good UV-blocking property with UV light transmittance of 30%. Antibacterial test indicated an inhibitory effect on S. aureus and E. coli. Strawberry preservation experiment showed the films delayed the shelf life of strawberries. This work provides the HACS-CIN inclusion films are potential candidates for biodegradable food packaging.