The research, led by Jiraporn Sripinyowanich Jongyingcharoen of King Mongkut’s Institute of Technology Ladkrabang in Thailand together with Pattawee Wutthigarn, Suluh Pambudi, and Ekkapong Cheevitsopon, is the first to apply superheated steam fluidized bed drying to coconut press cake. The team compared this approach head-to-head with conventional hot air fluidized bed drying at three temperatures: 130, 145, and 160 degrees Celsius. The choice of technology matters because coconut press cake is a challenging material. Its small particle size and fibrous, lipid-rich structure make it prone to shrinkage, discoloration, and oil entrapment during drying, while its high moisture content demands aggressive moisture removal to reach a shelf-stable state. The researchers targeted a final moisture content of 0.03 grams of water per gram of dry matter, the level at which water activity drops to roughly 0.75, suitable for long-term storage.

Fluidized bed drying works by blowing a gas upward through a bed of particles fast enough that the particles become suspended and behave like a fluid. This ensures intimate contact between the drying medium and every particle, producing uniform, rapid moisture removal. The critical parameter is the minimum fluidization velocity, the gas speed at which the upward drag on the particles exactly balances their weight. In a clever twist, the team found that superheated steam actually made the cake easier to fluidize than hot air. At 130 degrees Celsius, the minimum fluidization velocity in steam was 3.70 meters per second, well below the 4.65 meters per second needed for hot air, because steam at that temperature is less dense and less viscous than air. As temperature rose, the viscosity of steam increased and its fluidization advantage narrowed, an effect the authors attribute to the competing influences of declining density and rising viscosity on the drag force.

The drying performance results were striking. Superheated steam fluidized bed drying consistently outpaced hot air, and the advantage was most dramatic at the lowest temperature tested. At 130 degrees Celsius, steam drying reached the target moisture in just 9 minutes, half the 18 minutes required with hot air, with a significantly higher average drying rate. Even at 160 degrees Celsius, the fastest condition overall, steam still edged out hot air, finishing in 5.5 minutes versus 6 minutes. The authors explain that superheated steam transfers heat more efficiently and creates an oxygen-limited environment that prevents the surface hardening and crust formation that can trap moisture inside particles. By comparison, conventional hot air oven drying of coconut press cake at 50 to 80 degrees Celsius has previously been reported to take anywhere from 70 to 565 minutes, highlighting the enormous throughput gains that high-temperature fluidization delivers.

Energy consumption told a similarly compelling story. The researchers measured the specific energy consumption, the electrical energy required per kilogram of moisture removed, using a power meter connected to the entire drying system during active drying. For both methods, energy consumption fell as temperature increased, because shorter drying times meant less cumulative energy input. But superheated steam was the clear winner at every temperature. The largest saving appeared at 130 degrees Celsius, where steam drying consumed 4.67 megajoules per kilogram of water removed compared with 8.25 megajoules per kilogram for hot air, a reduction of more than 40 percent. This advantage stems partly from the condensation of steam onto the cooler wet particles at the start of drying, which releases latent heat directly into the material and accelerates moisture transfer, and partly from the superior heat transfer coefficients of steam relative to air.

Quality attributes revealed a genuine trade-off between the two methods. Under the microscope, hot air dried samples showed a compact, dense, shrunken fibrous structure, driven by capillary forces that pull the cellulose-rich matrix together as water leaves. Steam dried samples, in contrast, retained a more open, expanded, porous morphology, apparently because rapid internal vapor generation partially counteracts structural collapse. This difference translated into color: steam dried cake was consistently and significantly whiter than hot air dried cake at every temperature, with the highest whiteness achieved at 160 degrees Celsius, where drying time was shortest. The oxygen-poor steam atmosphere limits oxidative discoloration, and reduced thermal exposure curbs non-enzymatic browning reactions such as the Maillard reaction and caramelization. Notably, steam dried samples also yielded significantly higher extractable oil content, peaking at 34.89 percent at 160 degrees Celsius, likely because their open structure allows better solvent penetration during analysis, whereas the dense hot-air-dried matrix physically traps oil inside.

Interestingly, hot air drying claimed one quality victory of its own. Cake dried with hot air at 160 degrees Celsius exhibited the highest swelling capacity, at 12.37 milliliters per gram of dry matter, and the highest water holding capacity, at 9.74 grams of water per gram of dry matter. The authors suggest that intense thermal exposure under hot air may modify the protein matrix surrounding starch granules and disrupt cell walls, enhancing the material’s ability to absorb and retain water. Water retention capacity, however, showed no significant differences across any treatment, indicating that neither the drying medium nor temperature substantially altered the capillary retention mechanisms within the fibrous matrix. Overall, the hydration properties of the dried press cake matched or exceeded those of commercial dietary fiber sources such as apple, oat, wheat, and pea bran in several respects, underscoring its potential as a functional fiber ingredient.

The microbiological findings may be the most consequential for food safety. Fresh coconut press cake carried an aerobic plate count of 123,000 colony-forming units per gram, along with measurable coliforms, E. coli, and yeasts and molds. Both drying methods dramatically reduced microbial loads, but steam was consistently more lethal at equivalent temperatures. At 160 degrees Celsius, steam drying brought the aerobic plate count down to 2,950 CFU per gram, compared with 10,500 for hot air, and reduced yeast and mold counts to below the detection limit of 25 CFU per gram. Critically, only steam fluidized bed drying at 160 degrees Celsius satisfied every microbiological criterion of the Philippine National Standard for coconut flour, the benchmark the team selected because it explicitly covers coconut residue. E. coli and Salmonella were not detected in any dried sample, though the authors caution that without inoculated challenge tests these results cannot be read as validated pathogen elimination. Prior research lends mechanistic support: microbial death rates in superheated steam can be dramatically faster than in hot air, with documented D-values for E. coli of under 0.10 minutes in steam at 300 degrees Celsius versus 1.12 minutes in air.

To tie the whole dataset together, the researchers ran an exploratory principal component analysis across fourteen process, quality, and safety variables. The analysis revealed that longer drying times and higher energy consumption clustered with higher residual microbial counts, while the steam treatments grouped toward lower microbial loads, greater whiteness, and higher extractable oil content. Hot air drying at 160 degrees Celsius stood apart, aligned with the superior hydration properties. The authors are careful to acknowledge limitations, including the absence of sensors to measure oxygen and steam concentrations in the drying chamber and the lack of direct lipid oxidation measurements, and they frame the multivariate results as descriptive rather than causal. Still, the practical conclusion is clear. For producers seeking maximum water binding in the dried cake, hot air at 160 degrees Celsius remains a defensible choice. But for a combination of speed, energy efficiency, whiteness, oil availability, and regulatory-grade microbial safety, superheated steam fluidized bed drying at 160 degrees Celsius emerged as the standout process, offering tropical coconut industries a credible route to transform a perishable waste stream into a safe, high-value functional food ingredient within minutes rather than hours.

Subject of Research: Comparative evaluation of superheated steam versus hot air fluidized bed drying of coconut press cake for energy efficiency, quality, and microbial safety

Article Title: Integrated evaluation of superheated steam and hot air fluidized bed drying of coconut press cake: Impacts on energy efficiency, product quality, and microbial safety

Article References: Jongyingcharoen, J. S., Wutthigarn, P., Pambudi, S., & Cheevitsopon, E. (2026). Integrated evaluation of superheated steam and hot air fluidized bed drying of coconut press cake: Impacts on energy efficiency, product quality, and microbial safety. Journal of Agriculture and Food Research, 31, Article 103307. https://doi.org/10.1016/j.jafr.2026.103307

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103307

Keywords: coconut press cake, superheated steam drying, fluidized bed drying, food safety, energy efficiency, functional foods, dietary fiber, microbial inactivation, food processing, agro-industrial waste, drying technology, sustainable food

The core premise of nutrigenomics is deceptively simple. Nutrients do not merely fuel a fish; they act as chemical signals that switch genes on and off, reshaping metabolism, immunity, and growth at the molecular level. The field emerged in the late 1990s at the intersection of nutritional science and genomics, and it has since migrated from human medicine into livestock and, more recently, into aquaculture. Farmed fish are an especially attractive target because their diets are entirely controlled by producers. If researchers can identify which genes respond to which dietary ingredients, they can in principle design feeds that maximize feed conversion efficiency, strengthen disease resistance, and even alter the nutritional profile of the fillet that reaches the consumer’s plate. The retracted review argued that this approach could transform aquaculture into a precision discipline, where rations are tailored to the genome of each species rather than formulated by trial and error.

The technological engine behind this vision is a battery of omics tools. Whole genome sequencing has supplied reference assemblies for major farmed species, while RNA sequencing, or transcriptomics, allows scientists to measure which genes are active in fish fed different diets, exposing the molecular fingerprints of each ration. Proteomics extends the analysis to the proteins those genes produce, and metabolomics captures the biochemical end products of metabolism, closing the loop between gene and physiology. Perhaps the most disruptive entry is CRISPR gene editing, which enables researchers to deliberately disable or modify genes suspected of governing feed efficiency, fatty acid synthesis, or stress tolerance, then observe the consequences. The review highlighted these tools as the foundation for identifying the genetic pathways that control how fish digest proteins, metabolize lipids, and mount immune responses, turning what was once an opaque black box into an experimentally tractable system.

Among the nutritional pathways receiving the most attention, lipid metabolism stands out. Lipids are a principal energy source for many fish, and the genes governing fatty acid synthesis, elongation, and desaturation determine whether a farmed fish can build health-promoting omega-3 fatty acids such as EPA and DHA from plant-based feed ingredients. The review cited work on hybrid grouper showing that high-lipid diets cause hepatic fat accumulation and that bile acids modulate this process. Carbohydrate metabolism presents a parallel puzzle: carnivorous fish express low levels of amylase and glucokinase and therefore handle starch poorly. A single-nuclei RNA sequencing study of largemouth bass fed high-carbohydrate diets revealed disturbed hepatic energy metabolism and activation of oxidative stress and liver fibrosis pathways, while whole genome resequencing combined with RNA sequencing linked genes such as fabp6, lpcat2, pla2g1b, and pentose phosphate pathway genes to growth performance under carbohydrate-rich, thermally fluctuating conditions.

Species-specific findings form the empirical backbone of the field. In Atlantic salmon, research has concentrated on lipid metabolism and immune function, including the identification of genes involved in omega-3 biosynthesis and pathogen resistance. One frequently cited study replaced fish oil with vegetable oil in salmon diets and used liver transcriptomics to track the consequences: genes for fatty acid biosynthesis, inflammation, and oxidative stress, including fasn, cox2, and pparα, shifted expression, signaling a fundamental rewiring of lipid handling. Tilapia has served as a model for testing plant-based alternative feeds on nutrient utilization and growth, while catfish studies have uncovered nutrigenomic pathways tied to hypoxia tolerance and feed efficiency, informing breeding programs for hardier strains. Carp, with their natural talent for carbohydrate metabolism, are being studied as candidates for sustainable plant-based feeding, a trait that could ease pressure on wild-capture fisheries that supply fishmeal.

The larval stage of farmed fish has emerged as a particularly sensitive window where nutrition leaves lasting genomic marks. Larvae are typically reared on live feeds such as rotifers and artemia, enriched with phospholipids, fatty acids, and micronutrients that support growth, survival, and disease resistance. Researchers formulating a microdiet of 22 percent lipid and 52 percent protein for pike silverside larvae found differential gene expression and overexpression of apoptotic, DNA damage repair, and oxidative stress genes, which correlated with suboptimal growth and survival, prompting a recommendation to reduce lipid content. De novo transcriptomic sequencing of tropical gar embryos and larvae identified nutrigenomic markers spanning cell cycle, digestion, muscle development, and behavioral genes. In Atlantic cod larvae, RNA sequencing and qPCR revealed that fast-moving copepod prey stimulated swimming activity, boosting glycolysis and oxidative phosphorylation in muscle cells but also elevating reactive oxygen species, a burden that prey nutritional quality must counterbalance. Adding alpha lipoic acid to pike silverside microdiets improved larval survival and feed efficiency by modulating mitochondrial biogenesis and DNA repair.

Beyond growth, nutrigenomics is being deployed to armor fish against disease through diet rather than drugs. Functional feeds enriched with probiotics, prebiotics, or plant-derived bioactive compounds have been shown to reshape the expression of immune-related genes. In rainbow trout, dietary supplementation with the probiotic Lactobacillus rhamnosus upregulated genes governing gut barrier function, including mucins and tight junction proteins, alongside immune genes such as cytokines and toll-like receptors. In Pacific white shrimp, vitamin C supplementation upregulated antioxidant defenses, including sod and cat, and immune genes including toll-like receptors and penaeidins, increasing resistance to the pathogenic bacterium Vibrio parahaemolyticus. Selenium studies in rainbow trout demonstrated that organic selenomethionine significantly upregulated antioxidant genes such as gpx1 and sod2, reducing markers of oxidative stress, while laminarin, a bioactive polysaccharide from brown algae, altered immune gene expression in abalone. Microalgal diets rich in Isochrysis galbana upregulated energy metabolism genes in Pacific oysters, and vitamin C-enriched diets in tilapia boosted SOD and CAT expression while dialing down the stress marker HSP70.

The human-health dimension of this research extends to biofortification and contaminant control. Because omega-3 fatty acids reduce cardiovascular risk and support cognitive function, researchers are pursuing fish strains genetically optimized for EPA and DHA production, including transgenic strategies that stimulate desaturase gene expression. Nutrigenomic approaches may also identify genes governing the metabolism and detoxification of heavy metals and pesticides, opening a route to fish lines that accumulate fewer contaminants and meet stricter food safety standards. The review even sketched a vision of regionally tailored products, fish engineered or selectively bred to carry more selenium or vitamin A precursors, addressing specific nutrient deficiencies in particular populations. By contrast, plant protein substitution is not without molecular cost: in zebrafish fed soybean meal, transcriptomics revealed altered lipid homeostasis through genes such as ppara, fabp2, mttp, and cyp7a1, along with mild intestinal inflammation marked by elevated pro-inflammatory cytokines.

The retraction of this particular review does not settle any of these scientific questions, but it does underscore the scrutiny that fast-moving fields attract, and it coincides with a candid discussion of the field’s unresolved problems. The review itself acknowledged that RNA sequencing and CRISPR remain expensive, that bioinformatics capacity is a bottleneck for many aquaculture facilities, and that genetically modified fish raise public acceptance concerns, biodiversity risks, and ecological hazards if transgenic animals escape and interbreed with wild populations. Looking forward, it pointed to artificial intelligence and machine learning for predicting gene-nutrient interactions and optimizing feed formulas, multi-omics integration for holistic views of fish biology, and cross-sector partnerships to build affordable technologies and responsible regulatory frameworks. Readers should consult the publisher’s retraction notice before relying on any claim from the withdrawn article, but the underlying research program it surveyed, from copepod-fed cod larvae to CRISPR-edited salmon, continues to advance in the peer-reviewed literature, carrying the promise of seafood that is healthier for people and gentler on the planet.

Subject of Research: Fish nutrigenomics and its application to sustainable aquaculture nutrition

Article Title: RETRACTED ARTICLE: Fish nutrigenomics: unravelling the genetic code for sustainable aquaculture and improved nutritional benefits

Article References: Iqbal, G., Wani, M. N., Piyushbhai, M. K., Dar, S. A., & Sharma, A. (2025). RETRACTED ARTICLE: Fish nutrigenomics: unravelling the genetic code for sustainable aquaculture and improved nutritional benefits. Blue Biotechnology, 2(1), Article 19. https://doi.org/10.1186/s44315-025-00043-9

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00043-9

Keywords: nutrigenomics, aquaculture, fish nutrition, genomics, CRISPR, RNA sequencing, omega-3 fatty acids, feed efficiency, disease resistance, transcriptomics, sustainable food, retraction