Novel Robust, Reusable, Microbial‐Resistant, and Compostable Protein‐Based Cooling Media

Abstract

Novel environment-friendly heat-storage materials with efficient cooling capacity are in high demand by the food, pharmaceutical, and related industries and supply chains. Better control and prevention of cross-contamination caused by meltwater from traditional ice have become critical to ensure the safety and quality of food and other commodities. Here is reported a microbial-resistant, reusable, and compostable novel stationary cooling medium, "Jelly Ice Cubes" (JICs), based on gelatin-menadione sodium bisulfite (MSB) hydrogels (Gel/MSB-JICs) with cooling efficiency comparable with traditional ice. For the first time, the photo-crosslinking reactions induced by MSB are proposed and validated theoretically and experimentally. Photo-tuning is used collectively with rapid-freeze-slow-thaw treatment to construct robust hydrogel frameworks against the functional and structural damages caused by the phase transition of water during repeated uses. Exceptionally stable cooling efficiency and robust mechanical strength are observed across ten application cycles, with stable antimicrobial functions against bacteria, fungi, and yeast. At the end of the lifecycle of JICs, they can be composted or used as a soil treatment to promote plant growth. The novel JICs are competent as promising, safer, and more eco-friendly substitutes for traditional ice and ice packs.

Mechanisms and Performances of Physically and Chemically Crosslinked Gelatin-Based Hydrogels as Advanced Sustainable and Reusable “Jelly Ice Cube” Coolants

“…Initially, multiple tests were conducted to confirm the formation of gelatin microcrystalline domains induced by rapid-freezing-slow-thawing treatments, demonstrating the macro- and microstructural changes of Gel/MSB hydrogels according to the previously used protocols. − As shown in Figure a, the opacity of the Gel/MSB hydrogels increased with a higher number of FFTCs, indicating the formation of gelatin microcrystalline domains before photoirradiation, consistent with previous studies. , X-ray diffraction (XRD) spectra shown in Figure b reveal similar crystalline structures of Gel/MSB after repeated FFTCs, providing evidence of the presence of gelatin microcrystalline domains and locally concentrated MSB molecules after FFTCs. , On the one hand, after repeated FFTCs, there was a slight intensification in the gelatin characteristic peak at 2θ = 15–30° from F0 A0 to F1 A0 and F10 A0, indicating the increase in the degree of crystallinity in gelatin domains. The changing tendency of the gelatin characteristic peak supports the proposed physical and chemical crosslinking of gelatin molecules under the rapid freezing condition and photo-crosslinking reaction.…”

“…Proper photoirradiation excites ground state MSB to its singlet excited state, which spontaneously transits to the triplet excited state via internal conversion and intersystem crossing. , The generated triplet MSB then initiates a series of photoreactions through either hydrogen/electron transfer (type I) or energy transfer (type II). The type I reaction was found to be essential in the gelatin crosslinking reaction as hydrogens attached to α-carbons of various amino acids and specific side groups in the gelatin chain serve as primary hydrogen donors . Considering the short lifetime of radical species, photo-crosslinking reactions necessitate a close distance between coupling points. , The reduced intermolecular distance increases the possibility of an effective photo-crosslinking reaction.…”

“…Food and pharmaceutical industries are facing significant waste and economic challenges due to quality loss and microbial cross-contamination resulting from temperature abuse. − Conventional cold chain temperature control methods rely on ice and encapsulated ice packs as heat storage materials. − However, these approaches are unsustainable due to excessive water and plastic consumption. In addition, ice can also lead to meltwater-induced microbial cross-contamination, compromising the quality of adjacent products.…”

“…Furthermore, combining the rapid-freezing-slow-thawing treatment with the photo-crosslinking induced by menadione sodium bisulfite (MSB) significantly enhanced JICs’ mechanical and heat-absorbing stability, suggesting a synergistic physical and chemical crosslinking effect on the gelatin hydrogel structure . MSB, a water-soluble vitamin K derivative, is a photosensitizer with low toxicity, low cost, and pale color, found effective in crosslinking protein-based materials. , …”

Design and Development of Robust, Daylight-Activated, and Rechargeable Biocidal Polymeric Films as Promising Active Food Packaging Materials

“…The activity of a photosensitizer (PS) in a film is dependent on its potential to produce ROS and photostability under daylight or UVA irradiation, common lighting conditions in stores or residence . The PS will be excited to its singlet state ( 1 PS) and then intersystem crossing to its triplet state ( 3 PS), which is the key transient intermediate for the generation of ROS . To demonstrate the ability of generating ROS by EVA/VK 3 films under daylight illumination, a series of measurements of singlet oxygen ( 1 O 2 ), hydroxyl radical ( · OH) and hydrogen peroxide (H 2 O 2 ) were conducted, and Figure a,b presents the results under two different daylight illumination intensity conditions (lux 25 K and 15 K).…”