Exopolysaccharide riclin and anthocyanin-based composite colorimetric indicator film for food freshness monitoring.

Food freshness monitoring is vital to ensure food safety. Recently, packaging materials incorporating pH-sensitive films have been employed to monitor the freshness of food products in real time. The film-forming matrix of the pH-sensitive film is essential to maintain the desired physicochemical functions of the packaging. Conventional film-forming matrices, such as polyvinyl alcohol (PVA), have drawbacks of low water resistance, poor mechanical properties, and weak antioxidant ability. In this study, we successfully synthesise PVA/riclin (P/R) biodegradable polymer films to overcome these limitations. The films feature riclin, an agrobacterium-derived exopolysaccharide. The uniformly dispersed riclin conferred outstanding antioxidant activity to the PVA film and significantly improved its tensile strength and barrier properties by forming hydrogen bonds. Purple sweet potato anthocyanin (PSPA) was used as a pH indicator. The intelligent film with added PSPA provided robust surveillance of volatile ammonia and changed its color within 30 s in the pH range of 2-12. This multifunctional colorimetric film also engendered discernible color changes when the quality of shrimp deteriorated, demonstrating its great potential as an intelligent packaging material to monitor food freshness.

Intelligent films of marine polysaccharides and purple cauliflower extract for food packaging and spoilage monitoring.

In this study, metalloanthocyanin-inspired, biodegradable packaging films were developed by incorporating purple cauliflower extracted (PCE) anthocyanins into alginate (AL)/carboxymethyl chitosan (CCS) hybrid polymer matrices based on complexation of metal ions with these marine polysaccharides and anthocyanins. PCE anthocyanins-incorporated AL/CCS films were further modified with fucoidan (FD) because this sulfated polysaccharide can form strong interactions with anthocyanins. Metals-involved complexation (Ca2+ and Zn2+-crosslinked films) improved the mechanical strength and water vapor permeability but reduced the swelling degree of the films. Zn2+-cross-linked films exhibited significantly higher antibacterial activity than did pristine (non-crosslinked) and Ca2+-cross-linked films. The metal ion/polysaccharide-involved complexation with anthocyanin reduced the release rate of anthocyanins, increased the storage stability and antioxidant capability, and improved the sensitivity of the colorimetric response of the indicator films for monitoring the freshness of shrimp. The anthocyanin-metal-polysaccharide complex film showed great potential as active and intelligent packaging of food products.

Valorization of Berries' Agro-Industrial Waste in the Development of Biodegradable Pectin-Based Films for Fresh Salmon (Salmo salar) Shelf-Life Monitoring.

The healthy properties of berries are known; however, red fruits are very perishable, generating large losses in production and marketing. Nonetheless, these wastes can be revalued and used. The main objective of this study was the development of biodegradable pectin films with berry agro-industrial waste extracts to monitor salmon shelf-life. The obtained extracts from blueberries, blackberries, and raspberries wastes were evaluated in terms of flavonols, phenols and anthocyanins contents, and antioxidant capacity. Then, pectin films with the extracts of different berries were developed and characterized. The results showed that the blueberry extract film was thicker (0.248 mm), darker (L* = 61.42), and opaquer (17.71%), while the highest density (1.477 g/cm3) was shown by the raspberry films. The results also showed that blueberries were the best for further application due to their composition in bioactive compounds, antioxidant capacity, and color change at different pHs. The salmon samples wrapped in blueberry films showed lower values of pH and deterioration of fish during storage compared to the control and pectin samples. This study contributes to the valorization of berries agro-industrial waste by the development of eco-friendly films that can be used in the future as intelligent food packaging materials contributing to the extension of food shelf-life as a sustainable packaging alternative.

The Applications of Sensors and Biosensors in Investigating Drugs, Foods, and Nutraceuticals.

The present Special Issue is focused on developing and applying several sensors, biosensor devices, and actuators for the analysis of drugs, foods, and nutraceuticals. Some applications concern classical topics, such as clostridium determination in dairy products, flavouring material in foods like ethylvanillin, or the antioxidant properties of fruit juices, while other applications are more innovative, such as food safety analysis, artificial human senses (electronic nose, or tongue) development, or ethanol determination in pharmaceutical drugs, or forensic purposes using catalytic fuel cell; and lastly, new studies devoted to intelligent food packaging. Therefore, this Special Issue should interest both specialists in the sector and readers who are simply curious, or are simply interested in innovations in the field of food and drug analysis.

Natural Biomaterial-Based Edible and pH-Sensitive Films Combined with Electrochemical Writing for Intelligent Food Packaging.

An edible and pH-sensitive film combined with electrochemical writing was developed by using gelatin, gellan gum, and red radish anthocyanins extract for intelligent food packaging. The composite film showed an orange red-to-yellow color change in the pH range of 2-12. The tensile strength, ductility, and barrier abilities to ultraviolet (UV) light and oxygen of the films were improved as the concentration of red radish anthocyanins increased. Multicolor patterns were successfully drawn on the films by using the electrochemical writing method. The composite films, which acted as gas sensors, presented visible color changes in the presence of milk and fish spoilage, while the written patterns were well-preserved. Accordingly, this composite film with written patterns could be an easy-to-use indicator with great potential for monitoring food spoilage as a part of an intelligent packaging system.