The research team, led by Hee-Jin Kim and Hye-Seong Lee of Ewha Womans University in Seoul, took on a challenge that has long frustrated dairy scientists: commercial products differ not only in composition but also in raw material background, geographical origin, manufacturer, processing conditions, packaging, and storage history. Because these factors co-occur in real products rather than being independently manipulated in a laboratory, the team deliberately framed their work as an exploratory comparison of commercial product systems rather than a controlled experiment isolating the effect of any one ingredient. They selected eight market-available UHT milk products spanning skim, low-fat, and full-fat variants across three feeding-related product-system categories, identified as pasture-based/mixed-feeding, fermented-silage/mixed-feeding, and total mixed ration, or TMR, systems.

The analytical arsenal deployed was formidable. Physicochemical measurements captured basic composition with a MilkoScan FT2 instrument. Laser diffraction characterized the size distribution of fat droplets, which in milk, an oil-in-water emulsion, governs how light scatters and how the liquid flows. A spectrophotometer quantified color under standardized D65 illumination. A shear-rate-controlled rheometer measured apparent viscosity, and, in a particularly elegant touch, the same instrument was fitted with a ring-on-plate configuration lined with surgical tape to mimic the roughness of oral surfaces, allowing the researchers to measure friction coefficients at body temperature and generate Stribeck curves across boundary, mixed, and elastohydrodynamic lubrication regimes.

Complementing the physical measurements, electronic nose and electronic tongue systems generated instrumental fingerprints of aroma and taste variation. The electronic nose, equipped with fast gas chromatography columns, captured volatile profiles from the headspace of warmed samples, and a statistical screening procedure retained 24 peaks that were well represented by the major principal components. The electronic tongue, with its array of seven lipid-membrane and artificial-receptor sensors, distinguished the products with striking clarity: its first two principal components together explained nearly 94 percent of the variance in taste-related responses. The researchers were careful to note that these sensor systems do not directly measure human perception; they served as pattern-level evidence of product differentiation rather than as proxies for the tongue and nose of a drinker.

The human element came from two panels. Nine trained dairy panelists, each with more than three years of experience, rated the eight products on a battery of appearance, aroma, taste, flavor, mouthfeel, and aftertaste attributes using a nine-point intensity scale, following ISO 13299 guidelines with Williams Latin square presentation to balance order effects. Separately, 208 Korean adults aged 20 to 30, recruited at Ewha Womans University and screened for regular plain-milk consumption, rated overall liking on a nine-point hedonic scale under the same standardized room-temperature serving conditions, allowing direct alignment between expert perception and consumer preference.

The results painted a picture of coordinated, system-level differentiation. Within each product range, increasing fat content generally brought larger median particle diameters, greater lightness, higher apparent viscosity, lower friction in the mixed lubrication regime, and stronger perceived creaminess. Skim products had median droplet diameters around half a micrometer, while full-fat versions reached roughly 1.5 micrometers. Yet the pattern broke down in instructive ways. One full-fat product had a noticeably smaller particle size than its full-fat peers, and another showed lower friction despite comparable fat levels, evidence that lubrication behavior depends on particle-size distribution, interfacial composition, protein interactions, homogenization history, and heat treatment rather than fat alone. Color told a similar story: yellowness tracked the commercial product group more closely than fat level, with one product range appearing distinctly more yellow and another distinctly whiter.

Perhaps the most striking finding concerned creaminess itself. Among the three full-fat products, which differed significantly in particle size, viscosity, and friction, the trained panel detected no significant difference in perceived creaminess at all, with mean intensity scores clustering between 5.3 and 5.9. The authors interpret this as confirmation that creaminess is an integrated, emergent perception, one that the brain assembles from structural, rheological, tribological, and flavor cues rather than a direct readout of any single physical property. For product developers, this is a cautionary tale: engineering viscosity or droplet size in isolation may not deliver the mouthfeel consumers expect.

Consumer liking added another layer of nuance. The TMR full-fat product earned the highest liking score at 6.23, but a full-fat product from the pasture-based range remained among the least liked, scoring in the range of 3.59 to 4.14 for that product group. Fat content, in other words, did not uniformly buy favorability. A partial least squares regression model identified the sensory attributes driving preference: milky flavor, white color, and sweet taste were positively associated with liking, whereas hay-like flavor, yellow color, astringency, and salty taste pushed liking in the opposite direction. A follow-up model linking these liking-relevant sensory attributes to 34 instrumental predictors showed coordinated covariation across measurement domains, with whiteness and sweetness aligned with lightness, particle size, and viscosity, and hay-like, astringent, and salty notes oriented toward yellowness and selected electronic-sensor responses.

The statistical centerpiece of the study was a multiple factor analysis that integrated ten active data blocks comprising 59 variables, from sensory ratings and particle-size measures to color, rheology, tribology, and the electronic nose and tongue fingerprints. The first two dimensions of this integrated quality space accounted for over 82 percent of total variance and revealed two overlapping directions of differentiation: one a coordinated structural and mouthfeel axis linking droplet size, lightness, viscosity, creaminess, and oral coating, and a second flavor-appearance axis pitting hay-like, yellow, salty, and astringent notes against milky, white, and sweet ones. Because many variables loaded on both dimensions, the authors stress these represent overlapping system-level patterns, not independent causal pathways.

The team is candid about the limitations. Fat content, feeding system, origin, manufacturer, and processing history were confounded by design, so no single factor can be credited with the observed differences. Fatty acid analysis, which showed one pasture-range full-fat product with the highest omega-3 content and lowest omega-6 to omega-3 ratio, covered only the three full-fat products. The consumer panel was limited to younger Korean adults with an unequal sex distribution, and all samples were served at 24 degrees Celsius rather than refrigerator temperatures. Even so, the message for the dairy industry is clear and actionable: benchmarking and developing UHT milk demands integrated management of flavor, appearance, and oral-processing properties as a single quality system. In a global market where shelf-stable milk is a staple, the difference between a product consumers love and one they tolerate may hinge not on fat percentage printed on the label, but on the harmonious choreography of droplets, light, friction, and flavor reaching the mouth with every sip.

Subject of Research: Sensory, physical, and consumer-response quality differentiation of commercial ultra-high-temperature milk

Article Title: Integrated quality differentiation of commercial ultra-high-temperature milk: relationships among physical, sensory, and consumer-response characteristics

Article References: Integrated quality differentiation of commercial ultra-high-temperature milk: relationships among physical, sensory, and consumer-response characteristics. (n.d.). https://doi.org/10.1007/s10068-026-02311-9

Image Credits: AI Generated

DOI: 10.1007/s10068-026-02311-9

Keywords: UHT milk, sensory analysis, creaminess, tribology, rheology, consumer liking, electronic nose, electronic tongue, multiple factor analysis, dairy science, food emulsions, mouthfeel

The team focused on three iconic Korean fermented soybean products: cheonggukjang, doenjang, and meju. Although all three begin with boiled soybeans, they diverge dramatically in their fermentation conditions, microbial communities, and resulting chemistry. Cheonggukjang is fermented briefly and with little salt, allowing Bacillus species to dominate. Doenjang undergoes prolonged maturation in a high-salt environment that reshapes its microbial ecology. Meju, the fermented soybean brick that serves as the foundation for both doenjang and soy sauce, is dominated by fungi such as Aspergillus species and is rich in the enzymes and metabolites those microbes generate. Because these pastes are known to contain bioactive compounds with antioxidant, anti-inflammatory, and immunomodulatory properties, the researchers reasoned that their extracts might act as functional starter ingredients rather than mere flavorings.

To test the idea, the scientists prepared extract solutions from commercially purchased cheonggukjang, doenjang, and meju by diluting each paste 1:100 in distilled water, then centrifuging and filtering the mixture. Each extract was inoculated at 0.5 percent by volume into 400 milliliters of milk cream. A control butter was fermented with a commercial starter containing Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. All creams were fermented at 37 degrees Celsius for 24 hours, aged at 4 degrees Celsius for 12 hours, and then churned at 280 revolutions per minute for 15 minutes. The resulting butters were subjected to a battery of analyses covering pH, color, viscosity, moisture and fat content, microbial counts, electronic nose and electronic tongue profiling, and a sensory evaluation by a sixteen-member trained panel.

The pH results immediately revealed a fundamental biochemical divide. Butters fermented with the soy paste extracts had significantly higher pH values than the control, with the cheonggukjang sample highest of all. The explanation lies in the contrasting metabolisms of the microbial communities involved. Commercial lactic acid starter cultures flood the cream with lactic acid early in fermentation, driving pH down. The mixed communities drawn from traditional pastes, by contrast, include fungi and Bacillus species that decompose proteins and deaminate amino acids, releasing ammonia and other alkaline metabolites that push pH upward. The authors suggest this milder acidity may actually benefit the product, reducing sourness while allowing flavor-producing microbes to remain metabolically active, potentially enhancing both flavor quality and the delivery of probiotic organisms.

Physical properties told a reassuring story for manufacturers. Viscosity showed no significant differences among any of the butters, treated or control. Butter’s high-fat water-in-oil matrix provides substantial emulsification stability, and the small quantities of microbial metabolites generated during fermentation were simply not enough to alter its flow behavior. This means soy paste extracts can be incorporated without compromising the texture consumers expect. Color, however, did change: the meju and cheonggukjang butters were significantly more yellow than the control and the doenjang butter. Bacillus species abundant in these pastes produce peptides, free amino acids, and Maillard reaction products during fermentation, while molds and yeasts can promote browning reactions between reducing sugars and amino acids. The yellowness matters commercially, because previous research has shown that consumers associate a deeper golden hue in butter with higher purchase intention.

Microbial counts exposed the most striking differences. Total plate counts were significantly higher in all three extract-fermented butters than in the control, with cheonggukjang butter highest, reflecting its Bacillus-rich, low-salt, short-fermentation origin. Lactic acid bacteria counts were also elevated in all treated samples, but here meju butter took the lead. The researchers attribute this to Aspergillus oryzae, the fungus central to meju fermentation, whose powerful enzymes break proteins and carbohydrates into low-molecular-weight compounds that effectively feed lactic acid bacteria. Meju-derived communities also showed greater tolerance and adaptability to environmental stress than freeze-dried commercial strains. The doenjang-derived bacteria, adapted to high-salt conditions, grew more slowly in butter’s low-salt, high-fat environment, while cheonggukjang organisms, adapted to high water activity, were similarly constrained in the low-moisture product.

The flavor chemistry was mapped with an electronic nose, which identified elevated levels of volatile compounds including trimethylamine, ethanethiol, ethyl acetate, 2-methylbutanal, 3-methyl-1-butanol, and propyl acetate in the extract-fermented butters. Ethyl acetate, associated with buttery and fermented notes, was markedly higher in the meju butter. Principal component analysis of the aroma data achieved a discrimination index of 88, with the first principal component alone explaining 97.4 percent of the variance, cleanly separating the control from the treated samples and distinguishing the treated samples from one another. Notably, the sulfurous, rancid, and beany flavors often associated with fermented soybean products were not detected in the finished butter, suggesting the extracts can contribute desirable fermented aromas without importing off-flavors.

The electronic tongue added a taste dimension. Extract-fermented butters scored higher than the control in sourness, saltiness, and umami. The elevated sourness tracked with lactic acid bacteria counts, since more bacteria meant more organic acids. Saltiness was highest in the doenjang butter, consistent with residual salts carried over from its brine-fermented origin. Umami, measured against a monosodium glutamate reference, was highest in the meju butter, reflecting its greater content of glutamic acid, small peptides, and nucleotides released by the proteolytic activity of Aspergillus and Bacillus enzymes. Interestingly, the taste-based principal component analysis showed minimal differences among the three treated butters, indicating that despite their different origins, the pastes share overlapping microbial communities and metabolite profiles that converge in the finished dairy matrix.

The sensory panel delivered the verdict that matters most to consumers. The meju butter scored highest in flavor, taste, absence of off-flavor, and overall acceptability, and together with the cheonggukjang butter earned the top appearance scores, mirroring the color measurements. Panelists rated all extract-fermented butters higher than the control for texture attributes, likely because metabolites such as melanoidins, polyphenols, and peptides disperse within the fat matrix and moderate greasiness. The authors caution that their extracts contained both microorganisms and metabolites, so the observed effects reflect their combined action, and further microbiological work will be needed to separate the two. Still, the conclusion is clear: meju extract in particular can meaningfully improve the quality, microbial profile, and sensory appeal of fermented butter. As demand grows for dairy products that offer health benefits beyond basic nutrition, this study suggests that centuries-old Korean fermentation wisdom may have a place on the modern breakfast table, one golden, umami-rich pat at a time.

Subject of Research: Use of Korean traditional fermented soy paste extracts as starter ingredients to improve the quality and sensory properties of fermented butter

Article Title: Quality properties of fermented butter using extract solution from Korean traditional fermented pastes

Article References: Jeong, Y.-S., Yong, H. I., & Park, S.-Y. (2026). Quality properties of fermented butter using extract solution from Korean traditional fermented pastes. Food Science of Animal Resources, 46(1), Article 92. https://doi.org/10.1007/s44463-026-00089-2

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00089-2

Keywords: fermented butter, Korean fermented soy paste, meju, doenjang, cheonggukjang, lactic acid bacteria, electronic nose, electronic tongue, sensory evaluation, food fermentation, dairy quality, umami