Wet collections are the fluid-filled heart of natural history museums, housing millions of specimens preserved in ethanol or formalin. They preserve morphological, anatomical and molecular data that underpin research in biodiversity, taxonomy, pathology and anatomy, and they include irreplaceable type series and specimens of rare or extinct species. Increasingly, they also serve the public, offering visitors a visually compelling window on rare and endangered animals. But the choice of container, lid and seal is crucial: effective sealing prevents evaporation, maintains chemical stability and ensures long-term specimen preservation.

The CNHM team decided to reuse glass jars with ground-glass stoppers from the museum’s inventory, valuing their historical character and visually appealing appearance. Such jars, once standard in wet collections, are increasingly difficult and expensive to obtain, and older stocks often show substantial variability in stopper fit due to manufacturing inconsistencies or mismatched stoppers and jars mixed over time. Detailed guidance on sealing this type of container is limited and scattered across sources, so the researchers compiled a list of candidate sealants from the literature and colleagues’ recommendations and put them to the test.

Nine sealants were grouped into three categories. The first comprised silicone-based materials, including SIM-772, Liqui Moly and three viscosity variants of Korasilon paste. The second included wax-based solid sealants melted before application: yellow beeswax, white beeswax and a commercial beeswax–colophony mixture. The third category covered everything else: Vaseline, a jelly-like blend of paraffin wax and mineral oils; Alsirol, a high-viscosity silicone-free rotating joint grease; and Terostat-IX, a stretchy, self-adhesive artificial rubber sealant. Application methods varied by group, with wax-based sealants requiring stoppers preheated to 110 °C and melted sealant applied with a heat gun.

Evaluation focused on three criteria relevant to long-term exhibition use: aesthetic appearance, handling properties and sealing performance. An initial hands-on assessment examined texture, viscosity, ease of use and whether each sealant spread evenly, adhered to both stopper and jar rim, tended to drip and produced a clean, visually acceptable seal. For the evaporation test, each sealant was applied to triplicate jars filled with 70% ethanol and no specimens, alongside unsealed control jars, all stored in the dark at approximately 20 °C and 40–60% relative humidity. Ethanol levels were checked after two months and again after 1.5 years.

The results revealed clear trade-offs. Silicone-based SIM-772 and Liqui Moly were easy to apply but looked untidy, tended to leak into the preservative and sometimes allowed stoppers to push upwards after sealing. All three Korasilon variants were easy to apply and formed clean, transparent seals that were visually acceptable for exhibition purposes, performing best on jars with a perfect stopper-to-jar fit; where the fit was imperfect, higher-viscosity Korasilon was the better choice. Vaseline was easy to apply but visually unattractive, with stoppers prone to popping up. Alsirol was hard to apply and looked lumpy. Terostat-IX, with its thick rubbery consistency, filled irregularities well and proved effective for jars with poor-fitting stoppers, though its sticky, grey-rubber appearance was unappealing.

Wax-based sealants demanded more time, effort and manual skill. Yellow and white beeswax produced visually acceptable seals but, being less viscous when melted, readily leaked into the preservative, forming wax beads that sank to the bottom. The beeswax–colophony mixture, by contrast, rarely leaked, thanks to its higher viscosity, and filled imperfections in jar and stopper fit well. In the evaporation test, all sealants held ethanol over two months, but after 1.5 years failures emerged: one Vaseline-sealed jar lost roughly 30% of its ethanol, one medium-viscosity Korasilon jar lost 100%, and one Terostat-IX jar showed 10% loss. The researchers attributed these failures primarily to very poor stopper-to-jar fit rather than sealant failure, as the gaps were too wide for the sealing material to bridge.

Based on these results and the mixture’s established use in other wet collections, the team selected the beeswax–colophony mixture for sealing around 200 exhibition jars. The refined protocol builds on the manufacturer’s instructions and earlier published approaches. Stoppers are heated in an oven to approximately 110 °C, checked with an infrared thermometer, then fitted immediately to the jar. Softened strips of the mixture are applied along the stopper–jar edge and melted with a heat gun from above, with the jar continuously rotated during hardening to spot bubbles and cracks. A hair dryer set to cold air can accelerate hardening if the molten mixture begins to drip into the preservative. The preservative level must be kept at least 1 cm below the lower edge of the stopper to prevent capillary action of the fluid between jar and stopper during sealing — a problem that ruins bonding and requires the whole procedure to be repeated.

The workflow enabled sealing up to ten jars per hour when jars, stoppers, specimens and tools were prepared in advance. Several months after restoration, two jars had to be resealed due to ethanol loss; after one year, nearly all of the 200 restored jars remained airtight, with only two showing 10% ethanol loss, both caused by visibly poor stopper-to-jar fit. Notably, such seals failed early, within about a month, rather than gradually over time. The researchers caution that 1.5 years remains a short observation period in museum preservation, where sealing performance is expected over much longer timescales, and the exhibition set of 200 jars will continue to serve as a long-term test under display conditions. An interesting hybrid also emerged: applying Terostat-IX as a thicker underlying layer with the beeswax–colophony mixture over the top achieved excellent airtightness on problematic jars with large gaps.

The study offers practical guidance for curators and collection managers weighing sealant choices, emphasising that the beeswax–colophony mixture’s advantages align primarily with exhibition purposes, where visual appearance and long-term airtightness are prioritised. Its time-consuming application and need for trained staff make it impractical for large research collections requiring frequent access to specimens. For display contexts, however, the mixture delivers visually neat seals with a historical aesthetic that complements the traditional design of ground-glass jars — a low-tech solution that, refined through systematic comparison, keeps museum treasures safely submerged for visitors and scientists alike.

Subject of Research: Comparative evaluation of sealants for ground-glass-stopper jars in wet natural history collections

Article Title: Comparative evaluation of sealants for exhibition glass jars in wet natural history collections: application and protocol refinement

Article References: Lukić, M., Bućan, D., & Grbac, I. (2026). Comparative evaluation of sealants for exhibition glass jars in wet natural history collections: application and protocol refinement. Natural History Collections and Museomics, 3, Article e188287. https://doi.org/10.3897/nhcm.3.188287

Image Credits: AI Generated

DOI: 10.3897/nhcm.3.188287

Keywords: wet collections, sealants, beeswax, colophony, ground-glass stoppers, museum conservation, ethanol preservation, exhibition jars, Croatian Natural History Museum, collection management, Comparative, evaluation

The core problem the review addresses is well known: single-use plastic packaging remains one of the largest contributors to global waste streams, and while biopolymers have long been proposed as substitutes, they often fall short on performance. Pure starch films are brittle and hydrophilic, cellulose-based materials struggle with moisture, and protein films can lack mechanical robustness. The authors argue that bee-derived additives address several of these weaknesses simultaneously. Beeswax, a complex mixture of esters, fatty acids, and hydrocarbons secreted by worker bees, is highly hydrophobic and dramatically reduces water vapor permeability when incorporated into films or applied as a coating. Propolis, the resinous substance bees produce from plant resins to seal and sterilize their hives, is rich in phenolic compounds such as flavonoids and phenolic acids that confer potent antimicrobial and antioxidant activity.

Honey and royal jelly round out the bioactive toolkit. Honey’s high sugar content, low pH, and hydrogen peroxide-generating enzymes give it natural preservative power, while its humectant properties can modify film flexibility. Royal jelly, the nutrient-dense secretion fed to queen bees, contains proteins and fatty acids that contribute both bioactivity and structural function within a polymer network. When these substances are blended into biopolymer matrices, the review reports, the resulting composites show significant improvements in mechanical strength, water vapor and oxygen barrier performance, and thermal stability—three properties that have historically limited biodegradable packaging in real-world food applications.

The technical logic behind these improvements is worth unpacking. In a typical biopolymer film, long-chain polysaccharides or proteins form a network held together by hydrogen bonds, which are easily disrupted by water molecules migrating from humid food or ambient air. Beeswax, when dispersed as microscopic droplets or layered lamellae within the matrix, creates tortuous pathways that slow both water vapor and oxygen diffusion. Propolis phenolics, meanwhile, can interact with polymer chains through hydrogen bonding and hydrophobic associations, reinforcing the network at the molecular scale while scavenging the free radicals that drive lipid oxidation in packaged foods. The dual action—physical reinforcement plus chemical protection—is what the authors describe as a synergistic approach to active packaging, meaning the material does more than passively contain food; it participates in preserving it.

Antimicrobial performance is perhaps the most commercially compelling claim. Food spoilage and foodborne illness are driven by microorganisms that grow on surfaces, so packaging that releases antimicrobial compounds at the food interface can extend shelf life without treating the food itself. Propolis has demonstrated activity against common spoilage and pathogenic bacteria as well as fungi, and films incorporating it have been shown in numerous studies to inhibit microbial growth on meat, cheese, fruits, and vegetables. The review emphasizes that this active function, combined with antioxidant scavenging of oxidative species, translates directly into longer shelf life and reduced food waste—a benefit with its own environmental accounting, since wasted food carries an embedded carbon footprint that often exceeds that of the packaging around it.

Safety and regulatory questions receive careful treatment in the review. Any material intended for food contact must demonstrate that its components do not migrate into food at harmful levels, and bee-derived substances occupy a favorable position here because many are already consumed directly as foods or traditional remedies. The authors evaluate migration behavior and biodegradability as part of their suitability assessment, noting that the natural origin of the additives eases some toxicological concerns, though they caution that standardization remains a serious hurdle. Propolis composition varies with geography, flora, and bee species, meaning that two batches of propolis extract can differ substantially in their phenolic profile and therefore in their antimicrobial potency. For an industry accustomed to precisely specified synthetic additives, that variability is not a trivial obstacle.

Cost and scalability present further challenges that the review does not shy away from. Beeswax and especially royal jelly are expensive relative to commodity plastics, and global supply is bounded by the capacity of managed and wild bee populations—a constraint that carries its own ecological weight given ongoing concerns about pollinator decline. The authors argue that valorizing apicultural by-products, such as wax cappings and propolis residues generated during honey harvesting, could improve the economics while fitting the materials into a circular bioeconomy framework, in which waste streams from one process become feedstock for another. Green processing technologies, including solvent-free extrusion and other low-impact fabrication methods, are highlighted as routes to keep the environmental ledger of the new packaging genuinely positive.

The review also situates these materials within the broader international policy landscape. Global agreements on plastic pollution, combined with national bans on single-use plastics and tightening food safety regulations, are creating market pressure for alternatives that perform comparably without the environmental debt. Biopolymer packaging reinforced with bee-derived bioactives, the authors contend, aligns with goals for food safety, waste reduction, and environmental sustainability simultaneously—a rare trifecta in packaging research, where improving one property often degrades another. The multifunctionality is the selling point: a single film that blocks moisture, repels oxygen, kills surface microbes, slows oxidation, and then decomposes harmlessly at end of life.

What would it take to move from laboratory films to supermarket shelves? The authors point to formulation optimization as the immediate next step—finding the right ratios of beeswax to propolis to polymer for each food type, since the demands of packaging fresh produce differ sharply from those of packaging fatty snacks or raw meat. Standardized extraction and characterization protocols for propolis would help manufacturers specify materials reliably, and regulatory approval pathways would need to be navigated jurisdiction by jurisdiction. The review’s authors, who thank IIT Kharagpur and Woxsen University for research assistance, frame these as solvable engineering and policy problems rather than fundamental barriers, and the open-access publication is clearly intended to accelerate collaboration across the food science, materials science, and apiculture communities.

The vision that emerges from the paper is striking in its simplicity: packaging that borrows chemistry bees have refined over millions of years of hive-keeping. Bees evolved propolis to sterilize their colonies and wax to seal out moisture, and those same molecular strategies, transferred into starch, cellulose, chitosan, and protein films, could help solve a problem the bees never faced. As the review concludes, bee-derived bioactive-reinforced biopolymer packaging represents a sustainable, multifunctional, and viable alternative to traditional petroleum-based plastics. Whether it scales affordably will depend on the coming years of formulation work, supply-chain development, and regulatory engagement—but the hive, it turns out, has been running the relevant experiments all along.

Subject of Research: Bee-derived bioactives incorporated into biopolymer matrices for sustainable active food packaging

Article Title: Sustainable food packaging reinforced by bee-derived bioactives and biopolymers

Article References: Singh, D., Gupta, R. K., Mandal, S., Gupta, P., Gupta, A., & Asfaw, W. A. (2026). Sustainable food packaging reinforced by bee-derived bioactives and biopolymers. Discover Sustainability. https://doi.org/10.1007/s43621-026-04875-2

Image Credits: AI Generated

DOI: 10.1007/s43621-026-04875-2

Keywords: beeswax, propolis, honey, royal jelly, biopolymers, food packaging, antimicrobial, antioxidant, biodegradability, sustainability, circular bioeconomy, food preservation

The central challenge in biopolymer packaging has always been performance. Films made from pectin, starch or other natural polysaccharides are renewable and compostable, but they typically fall short of petroleum-based plastics in the properties that matter most: resistance to water, barrier function against gases and mechanical strength. Multilayer designs help, because each layer can be optimized for a different function, yet bonding dissimilar biopolymer layers together without synthetic adhesives remains difficult. The Algerian team approached this problem at the molecular level, using a mild pectinase enzyme treatment to remodel the interface between the film’s two layers rather than relying on chemical crosslinkers.

The film architecture is deliberately asymmetric. The inner layer is made of pectin extracted from orange peel waste, and it is here that the researchers embedded microcapsules derived from Saccharomyces cerevisiae, common baker’s yeast. These yeast cells were plasmolyzed, a process that shrinks the cytoplasm away from the cell wall and creates internal voids that can be loaded with bioactive molecules. When the team introduced orange peel phenolic extracts into these plasmolyzed cells, they achieved an encapsulation efficiency of 85.4 plus or minus 2.1 percent, a remarkably high figure that means most of the valuable antioxidant cargo was successfully locked inside the yeast shells rather than lost during processing.

The outer layer of the film is a composite of carrageenan, chitosan and beeswax, a combination chosen for its hydrophobic character and film-forming ability. Beeswax in particular is known to boost water vapor resistance, while chitosan contributes antimicrobial activity and carrageenan provides a negatively charged polysaccharide network that can interact electrostatically with the positively charged chitosan. The result is a natural, food-contact-compatible barrier layer that shields the inner pectin matrix and its encapsulated antioxidants from the humid outside world.

The enzymatic step is where the design becomes genuinely synergistic. Before casting the outer layer, the researchers treated the pectin surface with a mild dose of pectinase, an enzyme that cleaves the chains of galacturonic acid that make up pectin. Rather than degrading the film, this controlled micro-hydrolysis created new chain ends and exposed reactive groups precisely at the interface. The team quantified this effect by measuring reducing sugars, which rose to 8.63 plus or minus 0.47 milligrams of glucose equivalents per gram, and galacturonic acid, which reached 4.86 plus or minus 0.28 milligrams per gram. These newly generated carboxyl groups formed stronger hydrogen bonds and ionic interactions with the carrageenan-chitosan layer, dramatically improving interlayer cohesion without any synthetic chemistry.

The performance gains measured in the composite films are striking. Compared with a control film lacking the microcapsules, water solubility dropped from 39.0 percent to 19.0 percent, meaning the film is far more stable when exposed to moisture. The water vapor transmission rate fell from 6.49 to 3.10 times ten to the minus six grams per square millimeter per hour, roughly a halving of moisture permeability. Oxygen permeability fell even more dramatically, from 8.9 to 3.8 times ten to the minus seven grams per square meter per hour, a critical improvement for packaging that must protect oxidation-sensitive foods such as oils, nuts and meats. Perhaps most impressively, Young’s modulus, a measure of stiffness, increased more than eightfold, from 1.20 to 9.96 megapascals, indicating that the yeast capsules and the engineered interface act as reinforcing elements within the polymer matrix.

Structural analyses confirmed what the mechanical tests suggested. Fourier-transform infrared spectroscopy revealed enhanced intermolecular interactions, particularly hydrogen bonding between the polysaccharide chains and the phenolic cargo. Scanning electron microscopy showed a more homogeneous matrix with the yeast microcapsules well dispersed rather than clumped. X-ray diffraction preserved the characteristic crystalline peaks of the base polymers but showed the crystallinity index falling from 12.40 percent in the control to 7.06 percent in the capsule-loaded film, a partial amorphization that improves flexibility and guest-molecule dispersion without destroying the underlying crystalline phase. Thermal analysis added further reassurance, demonstrating improved stability at elevated temperatures, an important consideration for processing and storage.

One of the most commercially relevant findings concerns how the encapsulated antioxidants behave over time. Free phenolic extracts incorporated directly into films tend to burst out quickly, providing a short-lived antioxidant effect. In contrast, the yeast-encapsulated phenolics diffused out slowly in a pH-dependent manner, sustaining antioxidant activity for much longer. This controlled-release behavior means the packaging could actively protect food throughout its shelf life, scavenging the free radicals that drive rancidity and oxidative spoilage. Because the release rate depends on pH, the film could even be tuned to respond to the chemical environment of the packaged product, a step toward intelligent, responsive packaging systems.

The broader significance of the work lies in its circular economy logic. Orange peels supply both the pectin matrix and the antioxidant payload, yeast provides a cheap, food-grade and biodegradable capsule material, and beeswax and carrageenan complete the barrier layer, all from renewable or byproduct streams. The enzyme treatment replaces petrochemical adhesives with a biological process that operates under mild conditions. The authors report that the study received no external funding and declare no competing interests, and they acknowledge support from the Institute of Materials Science of Barcelona, ICMAB-CSIC, where scanning electron microscopy and thermal analysis experiments were carried out during a short research stay.

Scaling such systems from the laboratory to industrial production will require optimization of extraction yields, enzyme dosing and film casting at larger formats, along with food-safety validation and lifecycle assessment. But the conceptual advance is clear: by treating waste as a design feedstock and using enzymes and living cells as fabrication tools, packaging can be made stronger, more protective and functionally active simultaneously. If such multifunctional biodegradable films reach commercial maturity, the orange peel thrown away after breakfast juice could one day wrap the food on the shelf, protecting it with the very antioxidants the fruit itself produced.

Subject of Research: Development of bilayer biopolymer packaging films from orange peel waste using enzymatic interfacial engineering and yeast microencapsulation of polyphenols

Article Title: Synergistic Enzymatic Interfacial Engineering and Yeast Microencapsulation of Orange Peel Polyphenols for the Valorization in Advanced Bilayer Biopolymer Films

Article References: Laib, I., Laib, D. E., & Chenchouni, H. (2026). Synergistic Enzymatic Interfacial Engineering and Yeast Microencapsulation of Orange Peel Polyphenols for the Valorization in Advanced Bilayer Biopolymer Films. Waste and Biomass Valorization. https://doi.org/10.1007/s12649-026-03781-y

Image Credits: AI Generated

DOI: 10.1007/s12649-026-03781-y

Keywords: orange peel waste, biopolymer films, yeast microencapsulation, pectinase, polyphenols, active packaging, carrageenan, chitosan, beeswax, antioxidant release, food packaging, waste valorization