The problem nanoemulsions solve is deceptively simple to state and notoriously difficult to fix. Polyphenols, plant essential oils, lipophilic vitamins, and natural pigments carry impressive antioxidant and antibacterial credentials, yet their journey from laboratory bench to supermarket shelf is blocked by low water solubility, rapid thermal and photodegradation, and poor intestinal absorption. Traditional micron-scale emulsions fare little better, prone to aggregation and phase separation during long-term storage. Nanoemulsions, with droplet sizes typically below 500 nanometers, hold their ground through strong Brownian motion that counteracts gravitational separation, reinforced by electrostatic repulsion that depends on interfacial charge and solution conditions. The result is dramatically improved solubility and stability for hydrophobic bioactive compounds, along with enhanced bioavailability driven by the micellization efficiency of the lipid composition itself.

Crucially, the review insists on a rigorous definition: a food-grade nanoemulsion is a colloidal dispersion stabilized by a food-grade emulsifier in which every ingredient, from the oil phase and emulsifier to cosurfactants, solvents, polymers, and encapsulated bioactives, meets regulatory purity standards and falls within established acceptable daily intake limits. This is not an academic nicety. As nanoemulsions migrate from pharmaceutical contexts into edible products, the distinction between what works and what is legally and safely deployable becomes the central question of the field.

Because nanoemulsions are kinetically stable non-equilibrium colloids, they cannot form spontaneously from oil and water alone; they demand external energy or clever physicochemical manipulation. The review organizes fabrication strategies into two families. High-energy methods, including high-pressure homogenization, ultrasonic emulsification, microfluidization, and rotor-stator homogenization, use intense mechanical forces to shear, impact, and cavitate large droplets into nanoscale fragments, allowing emulsifiers to align in ordered fashion at the oil-water interface. Low-energy methods, including phase inversion temperature and composition techniques, self-emulsification, membrane emulsification, and solvent displacement, exploit spontaneous molecular interactions and interfacial energy minimization to assemble tiny droplets with minimal mechanical input.

Each technique carries a distinct industrial signature. High-pressure homogenization, the workhorse of large-scale production, pushes crude emulsions through narrow valves at 50 to 100 megapascals, routinely achieving droplets below 200 nanometers; researchers have used it to produce 125-nanometer pepper essential oil nanoemulsions with strengthened antibacterial activity and astaxanthin carriers with improved photostability and oral bioavailability. Its costs are equally clear: expensive equipment, high energy consumption, and shear and heat that can denature proteins, depolymerize polysaccharides, and oxidize lipids. Ultrasonic emulsification, by contrast, is cheap and simple, using cavitation bubble collapse to shatter droplets into the 50-to-150-nanometer range, but uneven acoustic energy distribution demands repeated cycles and risks localized overheating, confining it largely to laboratory research. Microfluidization, which collides pressurized fluid streams inside fixed-geometry interaction chambers, delivers precise size control and narrow distributions at 50 to 207 megapascals, yet hardware costs and microchannel blockage keep it at small scale. Rotor-stator homogenization, tolerant of viscous feedstocks and inexpensive to install, typically leaves droplets between 100 and 500 nanometers and requires supplementary homogenization to meet nanoemulsion specifications.

The low-energy family trades mechanical brutality for formulation finesse. The phase inversion temperature method exploits the temperature-dependent hydration of nonionic surfactants: as temperature rises toward the PIT, dehydration flips the surfactant’s affinity from water-loving to oil-loving, creating bicontinuous microemulsion intermediates with ultra-low interfacial tension, and rapid cooling then locks nanoscale droplets into place. The phase inversion composition method achieves the same kinetic trapping at constant temperature by systematically shifting oil, water, and surfactant ratios, yielding DHA and EPA carriers as small as 112 nanometers with narrow polydispersity. Self-emulsification, driven by chemical potential gradients when oil-surfactant mixtures contact water, offers ultra-low energy consumption and excellent scalability, with transparent sesame oil nanoemulsions around 67 nanometers demonstrating the approach’s precision. Membrane emulsification extrudes the dispersed phase through uniform nanoporous membranes to generate monodisperse droplets under mild conditions, preserving delicate bioactives, while solvent displacement dissolves lipophilic compounds in water-miscible organic solvents that diffuse away to trigger self-assembly, though residual solvent removal imposes regulatory and environmental burdens that limit food-grade scalability.

Characterization, the review argues, is where many studies fall short. Droplet size distribution and the polydispersity index, measured primarily by dynamic light scattering and laser diffraction, form the structural foundation: optimal food applications typically require droplets below 200 nanometers, generating ultrahigh specific surface area and strong electrostatic repulsion that suppress creaming and sedimentation. A curcumin nanoemulsion averaging just 19.92 nanometers with a PDI of 0.17 exemplified exceptional stability and bioavailability. Zeta potential quantifies interdroplet electrostatic repulsion, with absolute values above 30 millivolts conventionally signaling good stability, though the review cautions that sterically stabilized systems using nonionic surfactants, proteins, or polysaccharides can remain stable at low charge, so zeta potential must be read alongside interfacial composition, ionic strength, and pH. Advanced tools round out the picture: pendant-drop and spinning-drop tensiometry for interfacial tension, Fourier-transform infrared spectroscopy for molecular interactions, differential scanning calorimetry for lipid phase transitions, nuclear magnetic resonance for diffusion behavior, and X-ray photoelectron spectroscopy for surface chemistry, each with artifacts that demand careful interpretation.

The applications emerging from this toolkit span three strategic sectors. In food quality improvement, essential oil nanoemulsions have kept probiotic viability above 8 log CFU per gram in yogurt over 28 days of refrigerated storage, extended apple juice shelf life from 7 to 21 days when combined with high-pressure homogenization, delayed potato sprouting by roughly 9 days through sustained methyl salicylate release, and stretched duck meat shelf life from 14 to 35 days using ginger essential oil carriers. In packaging, nanoemulsion-loaded biodegradable films are replacing conventional plastics, which accounted for about 36 percent of global plastic production in 2015 and dominate beach litter; cinnamon essential oil films for pork now double as freshness indicators, shifting color from bright brown to saddle brown as spoilage progresses, while anthocyanin-loaded chitosan and carrageenan systems respond to ammonia from deteriorating food. In functional foods, curcumin nanoemulsions replacing margarine improved bread’s antioxidant capacity, crumb elasticity, and pore uniformity, and basil seed hydrogel nanoemulsions fortified milk powder with vitamin D3 at 115.63 international units, nearly twenty times the level in unfortified spray-dried powder.

The review’s most sobering contribution is its evidence-level honesty. Bioaccessibility measured in simulated digestion, cellular uptake in Caco-2 models, pharmacokinetics in rats, and human trials represent a hierarchy of robustness, and the field remains heavily weighted toward the preliminary end. Encouraging signals exist: excipient nanoemulsions raised quercetin bioaccessibility 1.73-fold under the INFOGEST protocol and boosted rat bioavailability by 46.6 percent with systemic antioxidant capacity up 1.47-fold, while nanoencapsulated essential oils outperformed free oils against foodborne pathogens. Yet the authors flag a pronounced translational gap for lipophilic natural pigments such as astaxanthin, lycopene, and chlorophyll, where industrial-scale validation, long-term stability data, and systematic in vivo safety evaluation are still missing. Their prescription is a formulation-to-translation framework that weighs processing stability, gastrointestinal performance, sensory quality, safety, scalability, energy demand, and production feasibility collectively rather than treating droplet size or encapsulation efficiency as standalone proof of application potential. If the field heeds that call, the tiny droplets now confined to laboratory beakers may soon determine how the world’s food stays fresh, nutritious, and honestly labeled.

Subject of Research: Fabrication, characterization, and food industry applications of food-grade nanoemulsions

Article Title: Food-related nanoemulsions: Fabrication approaches, characterization methods, and emerging applications

Article References: Zhang, Z.-H., Zhang, K., Li, X., Qin, Y., Yan, J., & Gao, X. (2026). Food-related nanoemulsions: Fabrication approaches, characterization methods, and emerging applications. Current Research in Food Science, Article 101591. https://doi.org/10.1016/j.crfs.2026.101591

Image Credits: AI Generated

DOI: Not provided

Keywords: nanoemulsions, food science, bioactive compounds, essential oils, high-pressure homogenization, phase inversion, bioavailability, food packaging, intelligent packaging, natural pigments, colloidal stability, functional foods

The research, published in the open-access journal MicrobiologyOpen, is notable for being the first comprehensive characterization of the pigment chemistry of M. terreus, a species only described in 2010 and rarely studied since. While its better-known relative M. luteus has been investigated extensively for biotechnologically useful pigments such as beta-carotene and zeaxanthin, the chemical composition and biological activities of M. terreus pigments had remained essentially unexplored. The new study set out to close three gaps at once: establishing what pigments the bacterium actually makes, testing those pigments against cancer types not previously examined, and probing the molecular mechanisms behind any anticancer effects using computational tools.

The identification of the isolate began conventionally. Soil samples from poplar forests, pine forests, potting soil, and agricultural fields were diluted, plated on tryptic soy agar, and incubated at several temperatures. Colonies showing distinct yellow, red, or pink pigmentation were purified, and fifteen distinct isolates were screened quantitatively for pigment production in liquid culture. SK34, recovered from pine forest soil, produced the highest total pigment content. Sequencing of its 16S ribosomal RNA gene and comparison with GenBank records placed it firmly within the Micrococcus group, with its closest relative being M. terreus DSM 28110. The sequence has been deposited in GenBank under accession number PX765938.

The chemical heart of the study came from liquid chromatography coupled to quadrupole time-of-flight mass spectrometry, a technique that separates compounds and measures their accurate masses to within five parts per million. Because carotenoids are easily degraded by light and heat, all analyses were performed under low-light conditions at controlled temperatures. The analysis revealed eight distinct carotenoids in the extract. Phytoene dominated at nearly 31 percent of the total, followed by zeaxanthin at 17.1 percent, beta-cryptoxanthin at 13.7 percent, and beta-carotene at 10.4 percent, with smaller amounts of astaxanthin, alpha-carotene, lycopene, and sarcinaxanthin. Since phytoene is colorless, the researchers concluded that the abundant yellow zeaxanthin is the main contributor to the bacterium’s vivid pigmentation.

Biological testing showed the extract was active against all five cancer lines examined: liver (HepG2), lung (A549), neuroblastoma (SH-SY5Y), breast (MCF-7), and cervical (HeLa) cells, with effects that increased in a dose-dependent manner. The concentration needed to halve cell viability after 24 hours was lowest for SH-SY5Y cells at 61.91 micrograms per milliliter, followed by MCF-7 at 82.08, A549 at 97.60, HeLa at 153.74, and HepG2 at 243.76 micrograms per milliliter. Crucially, healthy human dermal fibroblasts retained more than 90 percent viability even at the highest concentration tested, 1000 micrograms per milliliter. Because no inhibitory concentration could be established for the healthy cells within that range, the researchers reported minimum selectivity indices, which exceeded 16 for SH-SY5Y, 12 for MCF-7, and 10 for A549. Values above 2 are generally considered indicative of selective cytotoxicity, and values above 10 reflect high selectivity, placing this extract in promising territory.

To understand how the extract kills cancer cells, the team turned to the two cellular self-destruction programs most relevant to cancer biology: apoptosis, or programmed cell death, and autophagy, the cellular recycling process that can tip into lethal overdrive under stress. Apoptosis is governed by a delicate balance between pro-death signals such as p53, Bax, and the caspase enzymes, and anti-death proteins such as Bcl-2 and Akt1. Cancer cells frequently disable these death circuits, so therapies that restore them are a major research focus. The researchers treated SH-SY5Y cells at the extract’s inhibitory concentration and measured gene expression by quantitative real-time PCR.

The gene expression results were unambiguous. Expression of p53, Bax, caspase-3, caspase-8, and caspase-9 all rose significantly, while the antiapoptotic genes Bcl-2 and Akt1 were suppressed. The ratio of Bax to Bcl-2, a widely used molecular indicator of apoptotic commitment, increased markedly in treated cells. Notably, caspase-9, the initiator caspase of the intrinsic or mitochondrial pathway, showed the largest change, suggesting the extract primarily activates the internal suicide program rather than the external death-receptor route, although the concurrent rise in caspase-8 hints that both pathways may be engaged. Autophagy genes Beclin-1 and mTOR shifted only slightly and not significantly, indicating that apoptosis, not autophagy, is the dominant mechanism.

Protein-level measurements corroborated the transcript data. Enzyme-linked immunosorbent assays showed significantly elevated Bax protein, reduced Bcl-2, a sharply increased Bax/Bcl-2 ratio, and higher levels of cleaved caspase-3 and cleaved caspase-9, with a smaller but significant rise in cleaved caspase-8. Flow cytometry using Annexin V and propidium iodide staining provided the final piece of evidence: in untreated cultures, 92.32 percent of SH-SY5Y cells were viable, but after extract treatment the viable fraction fell to 71.45 percent, while early apoptotic cells rose to 14.13 percent and late apoptotic cells to 10.99 percent, for a total apoptosis rate of 25.12 percent. This orderly progression from early to late apoptosis is exactly the pattern desired of a candidate anticancer agent.

Computational docking added a mechanistic hypothesis about which individual carotenoids matter most. The five major compounds were docked against three apoptosis-related proteins: Akt1, p53, and Bcl-2. Against Akt1, beta-carotene bound most strongly at minus 9.0 kilocalories per mole, outperforming even the reference drug capivasertib. Against Bcl-2, zeaxanthin led at minus 9.1, with astaxanthin close behind. Against p53, astaxanthin achieved minus 7.8 kilocalories per mole. As expected for long, lipophilic polyene chains, the carotenoids relied overwhelmingly on hydrophobic and van der Waals contacts within the binding pockets, engaging conserved residues such as phenylalanine, tyrosine, and valine. The authors caution that docking predicts thermodynamic feasibility of binding rather than functional activation, and that molecular dynamics simulations would be needed to confirm stability. Still, the combined evidence suggests the extract’s components may simultaneously inhibit cell-survival proteins such as Bcl-2 and Akt1 while supporting pro-apoptotic signaling through p53 and the caspase cascade.

Perhaps the most intriguing implication is that no single carotenoid can claim credit. The researchers argue that the coexistence of eight carotenoids may generate additive or synergistic effects, since mixtures can modulate multiple molecular targets at once, an advantage in cancer therapy where coordinated pathway modulation generally outperforms single-target approaches. The team also acknowledges limitations: the mechanistic analyses used the inhibitory concentration, so some observed changes may be downstream consequences of apoptosis rather than its earliest triggers, and time-course studies at lower doses will help disentangle cause from effect. In vivo validation remains the essential next step before any clinical relevance can be claimed. Nevertheless, the work transforms an obscure soil bacterium into a credible source of bioactive pigments and illustrates how integrated metabolomics, cell biology, and computational chemistry can accelerate the search for natural anticancer compounds hiding in ordinary dirt.

Subject of Research: Anticancer activity of a carotenoid-rich pigment extract from Micrococcus terreus SK34 against human cancer cell lines

Article Title: Carotenoid‐Rich Pigment Extract From Micrococcus terreus SK34 Induces Apoptosis in SH‐SY5Y Neuroblastoma Cells: Integrated Metabolomic, Molecular Docking, and Experimental Validation

Article References: Karaagac, S. I., Albayrak, S., ShadiDizaji, A., Kiziler, M. E., Eroglu, E., Arslan, N. P., & Taskin, M. (2026). Carotenoid‐Rich Pigment Extract From Micrococcus terreus SK34 Induces Apoptosis in SH‐SY5Y Neuroblastoma Cells: Integrated Metabolomic, Molecular Docking, and Experimental Validation. MicrobiologyOpen, 15(5), Article e70382. https://doi.org/10.1002/mbo3.70382

Image Credits: AI Generated

DOI: 10.1002/mbo3.70382

Keywords: carotenoids, Micrococcus terreus, neuroblastoma, apoptosis, SH-SY5Y, molecular docking, LC-Q-TOF-MS, natural pigments, anticancer, zeaxanthin, Bcl-2, soil bacteria