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Cardboard packaging is a good example of sustainable material use, yet even more sustainable solutions are available, such as replacing wood fibers with those from alternative sources like agricultural waste. In our research, we produced paperboard from fibers obtained from waste tomato stems using a pilot paper machine, and its basic, surface, and mechanical properties were then determined. Additionally, we produced corrugated cardboard from the tomato fiber-based paperboard and analyzed its performance under different environmental conditions. A comparative analysis was made with commercial corrugated cardboard to determine the differences in mechanical properties and the quality of the prints made using the flexographic printing technique. The results indicated that the properties of tomato fiber-based paperboard and corrugated cardboard are sufficient for many packaging applications. Analyses showed that the mechanical properties of both commercial and corrugated cardboard produced from tomato stems were affected by the environmental conditions, while the change in print quality was minor. Exposure to high humidity had a much greater effect than exposure to low temperature. High humidity lowered the tensile and bursting strength and resistance to compression, resulting in decreased strength and stiffness, while low temperature had a less severe effect. Nevertheless, corrugated cardboard made from tomato-based paperboard can be used for storage of fresh produce locally, as well as for transport packaging, provided the transport box is designed to address its poor stacking strength. The print quality of this cardboard is also suitable for transport packaging, and the readability of the UHF RFID tags remains satisfactory. The findings of this study have significant implications for the development of sustainable materials. The successful use of tomato stems, a waste product from agriculture, in the production of corrugated cardboard supports the circular economy by turning waste into a valuable resource. [ABSTRACT FROM AUTHOR]

Starch-based pH-sensing films with bacterial nanocellulose (BNC) and red cabbage anthocyanins (RCA) as active components were investigated in this research. Their structural, physical, surface and colorimetric properties were analyzed, mainly as a function of BNC concentration. The aim of the research was to relate the changes in the intermolecular interactions between the components of the films (starch, anthocyanins and BNC) to the physical, surface and colorimetric properties that are important for the primary intended application of the produced films as pH indicators in smart packaging. The results showed that maize starch (MS) was more suitable as a matrix for the stabilization of anthocyanins compared to potato starch (PS). PS-based films showed a lower value of water contact angle than MS-based films, indicating stronger hydrophilicity. The swelling behavior results indicate that the concentrations of BNC in MS-based films (cca 10%) and the concentration of about 50% BNC in PS-based films are required if satisfactory properties of the indicator in terms of stability in a wet environment are to be achieved. The surface free energy results of PS-based films with BNC were between 62 and 68 mJ/m2 and with BNC and RCA between 64 and 68 mJ/m2; for MS-based films, the value was about 65 mJ/m2 for all samples with BNC and about 68 mJ/m2 for all samples with BNC and RCA. The visual color changes after immersion in different buffer solutions (pH 2.0–10.5) showed a gradual transition from red/pink to purple, blue and green for the observed samples. Films immersed in different buffers showed lower values of 2 to 10 lightness points (CIE L*) for PS-based films and 10 to 30 lightness points for MS-based films after the addition of BNC. The results of this research can make an important contribution to defining the influence of intermolecular interactions and structural changes on the physical, surface and colorimetric properties of bio-based pH indicators used in smart packaging applications. [ABSTRACT FROM AUTHOR]

Simple, low-cost methods for sensing volatile organic compounds that leave no trace and do not have a detrimental effect on the environment are able to protect communities from the impacts of contaminants in water supplies. This paper reports the development of a portable, autonomous, Internet of Things (IoT) electrochemical sensor for detecting formaldehyde in tap water. The sensor is assembled from electronics, i.e., a custom-designed sensor platform and developed HCHO detection system based on Ni(OH)2–Ni nanowires (NWs) and synthetic-paper-based, screen-printed electrodes (pSPEs). The sensor platform, consisting of the IoT technology, a Wi-Fi communication system, and a miniaturized potentiostat can be easily connected to the Ni(OH)2–Ni NWs and pSPEs via a three-terminal electrode. The custom-made sensor, which has a detection capability of 0.8 µM/24 ppb, was tested for an amperometric determination of the HCHO in deionized (DI) and tap-water-based alkaline electrolytes. This promising concept of an electrochemical IoT sensor that is easy to operate, rapid, and affordable (it is considerably cheaper than any lab-grade potentiostat) could lead to the straightforward detection of HCHO in tap water. [ABSTRACT FROM AUTHOR]