The study, published in Food Chemistry: X, explores what happens when low-density polyethylene (LDPE), the soft, flexible plastic commonly used for produce bags, is blended with raw diatomite, alkaline-activated diatomite, potassium permanganate, and potassium permanganate impregnated into activated diatomite. Diatomite, also known as diatomaceous earth, is an amorphous silica material formed from the fossilized cell walls of microscopic aquatic algae. It is remarkably porous, with voids making up roughly 80 to 90 percent of its volume, chemically inert, and inexpensive, which makes it attractive as a low-cost adsorbent. Its surface carries silicon hydroxyl groups that can attract organic molecules such as ethylene, but in its natural state the density of these groups is often too low to be highly effective.

To unlock diatomite’s full adsorption potential, the researchers activated it with a strong alkaline treatment. Purified diatomite powder was milled through a 200-mesh sieve, washed, and then immersed in 5 molar sodium hydroxide solution at 85 degrees Celsius for one hour. This harsh chemical bath dissolves impurities that clog the mineral’s natural pores and induces partial dissolution and rearrangement of its structural ions, increasing the specific surface area and optimizing the distribution of surface functional groups. The activated material was then impregnated with potassium permanganate by soaking it in a 2 normal KMnO4 solution at low temperature, yielding particles with a manganese oxide content of roughly 18.5 percent and a permanganate uptake of about 2.82 grams per 100 grams of diatomite, a loading comparable to commercial ethylene-scavenging sachets.

The treated and untreated particles were then compounded into LDPE using industrial melt processing. The team first prepared 10 percent masterbatches in a twin-screw extruder and then diluted them into blown films containing 1, 3, and 5 weight percent of each filler, producing films 30 to 40 micrometers thick. This manufacturing route matters because it uses the same equipment that produces commercial packaging, meaning the concept could, in principle, be scaled without exotic new machinery. Spectroscopic analysis confirmed that the polymer matrix remained chemically intact and that the permanganate was retained in an active form within the films, while thermal analysis showed that diatomite slightly raised the onset of thermal degradation from 447 to about 459 degrees Celsius, thanks to the mineral’s insulating character.

The ethylene removal results revealed a striking and somewhat counterintuitive pattern. In powder form, the alkaline-activated, permanganate-impregnated diatomite was the star performer, removing about 909 microliters of ethylene per gram within 24 hours, far outpacing neat potassium permanganate powder, whose limited gas-accessible surface and tendency to agglomerate hampered its performance. Once embedded in LDPE films, however, the picture changed. The best-performing films were those containing just 1 weight percent of the impregnated particles, which removed 373 microliters of ethylene per gram over 48 hours, and 1 weight percent of plain diatomite, which removed 297 microliters per gram. Surprisingly, raising the loading to 3 or 5 percent actually reduced ethylene removal. Scanning electron microscopy explained why: at higher loadings, the polar mineral particles clump into large agglomerates within the non-polar polymer, burying active sites and blocking gas transport, while at 1 percent the particles disperse relatively uniformly.

The study also delivered a sobering lesson about gas barriers. Contrary to what has been reported for some other mineral-polymer systems, adding diatomite did not improve the films’ resistance to gas diffusion. The oxygen transmission rate of the 1 percent diatomite film actually increased by about 132 percent compared with neat LDPE, and water vapor transmission rose slightly as well. The researchers attribute this to a fundamental mismatch: hydrophilic diatomite, covered in silanol groups, bonds poorly with hydrophobic polyethylene, creating microscopic voids at the interface through which gases pass more easily. Mechanical properties told a similar story, with tensile strength and elongation declining as filler content increased, although films with 1 percent alkaline-activated diatomite retained strength values between 15 and 19 megapascals, comparable to commercial LDPE films used for fresh produce. Optical clarity, meanwhile, was essentially preserved at 1 percent loading, an important consideration for shoppers who want to see the fruit they are buying.

The decisive test came with real bananas. Mature green bananas harvested in Ratchaburi Province, Thailand, were packed individually in bags made from neat LDPE, 1 percent diatomite LDPE, or 1 percent permanganate-impregnated activated diatomite LDPE, then stored for 10 days at 25 degrees Celsius alongside an unpacked control group. The results were dramatic. Unpacked bananas lost nearly 18 percent of their weight and developed dark spots and dried peel by day 6, while all packaged fruits stayed within 2 to 3 percent weight loss. But the packaging types diverged sharply in how well they slowed ripening itself. Bananas in the 1 percent diatomite film kept their green peel through the entire 10-day storage period, showed only a slight decline in firmness, and reached a total soluble solids level of just 6.97 degrees Brix by day 10, compared with 16.63 degrees Brix for bananas in plain LDPE and 9.80 degrees Brix for the unpacked control.

Perhaps the most intriguing finding is that the film with the highest measured ethylene removal was not the best at preserving the fruit. The permanganate-impregnated film removed more ethylene in closed-vial tests, yet the plain diatomite film delivered superior banana quality. The authors suggest that postharvest performance is governed not by ethylene scavenging alone but by the balance among ethylene removal, gas permeability, and moisture regulation. The higher oxygen transmission of the diatomite film may have helped maintain healthy aerobic respiration, while its higher water vapor permeability prevented condensation on the fruit surface, avoiding the peel softening and lenticel damage associated with saturated humidity. The researchers are careful to note that their closed-vial measurements do not directly represent the dynamic atmosphere inside a package containing respiring fruit, and that simultaneous monitoring of ethylene, oxygen, and carbon dioxide in actual packages will be needed to disentangle these effects.

The team is equally candid about the limits of the work. The films remain a laboratory-scale proof of concept: long-term stability of the polymer matrix, potential migration of permanganate or manganese into food, and overall food-contact safety were not evaluated, so the materials cannot yet be considered suitable for direct commercial use. Still, the study opens a genuinely novel direction. Diatomite had never before been investigated as an ethylene adsorbent embedded in a polymer matrix for fruit packaging, and the finding that a simple, cheap, unmodified mineral at just 1 percent loading can outperform more elaborate chemically treated formulations is the kind of result that could reshape how the packaging industry thinks about active films. If subsequent safety and scale-up studies succeed, the fossilized shells of ancient algae, one of nature’s most abundant porous materials, could soon be quietly working inside the plastic bags at the grocery store, buying bananas and other climacteric fruits an extra week of freshness and keeping a little more of the global harvest out of the bin.

Subject of Research: Ethylene-scavenging LDPE composite films with diatomite and potassium permanganate for extending banana shelf life

Article Title: Effect of diatomite and KMnO 4 -impregnated diatomite in LDPE films on ethylene removal and postharvest quality of bananas

Article References: Yann, T., Winotapun, C., Yos, P., Voon, L. H., Wong, Y. H., Ngamchuachit, P., & Boondamnoen, O. (2026). Effect of diatomite and KMnO4-impregnated diatomite in LDPE films on ethylene removal and postharvest quality of bananas. Food Chemistry: X, 39, Article 104499. https://doi.org/10.1016/j.fochx.2026.104499

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104499

Keywords: ethylene scavenger, diatomite, potassium permanganate, LDPE film, active packaging, banana shelf life, postharvest quality, food packaging, blown film extrusion, climacteric fruit, alkaline activation, Food Chemistry: X