The science behind the beverage is a story of microbial cooperation. Kombucha is produced by fermenting sweetened substrate with a symbiotic culture of bacteria and yeast, known as a SCOBY. In the classic process, yeasts first convert sucrose into glucose and fructose while generating ethanol; acetic acid bacteria then transform glucose into gluconic acid and cellulose, and fructose into acetic acid, while lactic acid bacteria, when present, contribute lactic acid. The result is a two-phase product, a floating cellulose biofilm atop a sour, lightly carbonated liquid whose flavor can range from pleasantly fruity and sparkling to outright vinegar-like depending on how it is prepared. In the new work, the laboratory SCOBY was dominated by the bacterial genera Gluconoacetobacter, Gluconobacter and Komagataeibacter, together with the yeasts Brettanomyces and Schizosaccharomyces, a consortium maintained by regular back-slopping every two weeks.

What makes grape pomace an intriguing substrate is its chemistry. The residue is naturally acidic and loaded with polyphenols, the antioxidant compounds concentrated in grape skins, along with anthocyanins, the pigments responsible for red wine’s color. Earlier work by the same team had already shown that fermenting grape pomace with kombucha cultures significantly increases polyphenol and anthocyanin concentrations, and that in-vitro assays reveal enhanced antioxidant, anti-diabetic and anti-inflammatory activity. The authors are careful to stress that the present study assessed neither health effects nor superiority over other beverages; its goal was narrower and more commercial: to gauge consumer interest and measure how the drinks actually taste to real people.

To map the potential market, the researchers distributed a bilingual French and English questionnaire and collected roughly 400 responses, of which 388 to 392 valid answers were analyzed depending on the question. The panel skewed young and educated: 58.2 percent were aged 18 to 30, most held a master’s or doctoral degree, and the majority were Lebanese (69.9 percent) or French (23.5 percent). The survey probed eight sociodemographic variables alongside twenty questions covering juice and soda habits, awareness of functional foods, purchasing behavior and openness to novel products. Quality dominated shopping decisions, cited by 51 percent of respondents, while taste (58.2 percent) and nutrient content (23 percent) were the leading criteria for choosing a beverage. Notably, 57 percent of participants rarely drank soda, hinting at an appetite for alternatives perceived as healthier.

The kombucha-specific findings revealed a striking awareness gap. Sixty percent of respondents were unfamiliar with kombucha tea, and even among the 156 participants who knew the drink, 64.1 percent had never consumed it and only 41 percent were aware or very aware of its purported health benefits. Yet curiosity ran high: 82.4 percent said they would be interested or very interested in trying a novel kombucha knowing it had health advantages, 96.5 percent would try new products with health benefits, and 92.3 percent were drawn to eco-friendly novelties. The researchers ran 160 chi-square tests linking each survey item to each participant characteristic, adjusting for the false discovery rate with the Benjamini-Hochberg procedure. Ninety-two associations survived correction, though the effect sizes were uniformly modest, with a median Cramer’s V of 0.15, indicating weak but consistent patterns.

Physical activity emerged as the most broadly connected factor, associated with 17 of the 20 questionnaire items, followed by nationality (15 items), age (14), education and gender (11 each). To sharpen the picture, the team built a multivariable logistic regression model predicting interest in a novel healthy kombucha. Five characteristics retained independent associations. Women had nearly four times the odds of interest compared with men (adjusted odds ratio 3.99), Lebanese participants more than eight times the odds of French participants (AOR 8.05), and the self-employed nearly six times the odds of employees (AOR 5.74). Older respondents, aged 55 and above, showed markedly lower interest than the 18-to-30 group (AOR 0.24), and, counterintuitively, physically active participants were less interested than sedentary ones. Education and self-reported health issues dropped out of significance after adjustment, and income showed no association at all, suggesting that enthusiasm for the drink is not simply a function of purchasing power.

With the market signal established, the team turned to the harder question of palatability. Two pomace types were fermented: a Lebanese blend of Cabernet Sauvignon, Cabernet Franc, Syrah and Merlot, and a single-variety Négrette pomace from the Fronton region of France. Grape pomace at 100 grams per liter dry weight was infused in 80-degree-Celsius water for 20 minutes with either 20 or 30 grams per liter of sucrose, then inoculated with the SCOBY and fermented at 25 degrees Celsius for five or seven days. Seven formulations reached the tasting bench: three natural, three sweetened post-fermentation with a stevia-based sweetener at 5 grams per liter, and one flavored with natural raspberry aroma. Physicochemical analysis of the base fermentations showed pH values between 3.02 and 3.55, titratable acidity from 5.29 to 8.80 grams per liter as sulfuric acid, and residual sugars between 12.31 and 20.35 grams per liter.

Twenty untrained panelists, 13 women and 7 men aged 24 to 60, rated all seven drinks on the nine-point hedonic scale in an ISO-compliant sensory laboratory, with randomized serving orders, palate cleansers and five-minute intervals between samples. The researchers acknowledge the panel falls short of the sample sizes recommended by the AFNOR NF ISO 11136 standard for consumer testing, a constraint imposed by pandemic-era logistics, so the results are explicitly exploratory. Still, the statistics were emphatic. Repeated-measures ANOVA found a significant formulation effect for all seven attributes, with the formulation explaining 82 percent of the variance in overall acceptance. The raspberry-flavored sample topped the table with a mean liking score of 6.75, statistically tied with the sweetened Négrette formulation at 6.15, and was chosen as the favorite by 65 percent of panelists. Sweetening reliably lifted scores for sweetness, sourness, fruity taste and overall liking across every base formulation, while the raspberry aroma delivered its clearest advantage on smell, scoring 7.05 against 4.30 for its unsweetened counterpart.

The chemistry helped explain the preferences. The least-liked natural formulation, the seven-day Lebanese fermentation, carried the highest titratable acidity and the lowest residual sugar, while better-accepted drinks balanced lower acidity against more remaining sweetness. Interestingly, acetic acid concentration alone did not predict acceptance; the Négrette base contained the most acetic acid yet outperformed the more acidic Lebanese blend, pointing to the overall sweet-sour balance rather than any single parameter as the sensory key. One caveat deserves attention: residual ethanol was detected in all base fermentations, ranging from 3.84 to 7.93 grams per liter, a natural byproduct of yeast activity over the short five-to-seven-day fermentations. The authors caution that these experimental formulations therefore cannot be considered strictly non-alcoholic, and that process optimization would be needed to meet regulatory thresholds for non-alcoholic beverages.

Taken together, the study sketches a plausible path from winery waste to supermarket shelf, while remaining candid about its limits. The convenience sample, the modest sensory panel and the confounding of grape variety with sucrose concentration and fermentation parameters all mean the findings are preliminary rather than proof of market readiness. Open questions include willingness to pay, the optimal branding strategy, and whether promoting the drink as a wine-industry by-product would help or hinder acceptance, since prior research suggests informed consumers respond positively to upcycled foods but education was not independently linked to interest here. What the study does establish is a concrete signal: a young, sustainability-minded public is willing to try a kombucha made from discarded grape skins, and with the right balance of sweetness and fruit aroma, that willingness could translate into genuine liking. For an industry drowning in pomace, that may be the most valuable fermentation of all.

Subject of Research: Consumer acceptance and sensory evaluation of kombucha fermented from wine-industry grape pomace

Article Title: Grape pomace kombucha: consumer interest and sensory characteristics

Article References: Barakat, N., Julien, S. G., Bouajila, J., Beaufort, S., Rizk, Z., Taillandier, P., & El Rayess, Y. (2026). Grape pomace kombucha: consumer interest and sensory characteristics. Heliyon, 12(15), Article e45527. https://doi.org/10.1016/j.heliyon.2026.e45527

Image Credits: AI Generated

DOI: 10.1016/j.heliyon.2026.e45527

Keywords: grape pomace, kombucha, SCOBY, fermentation, functional beverages, sensory analysis, consumer survey, food waste valorization, polyphenols, wine by-products, circular economy, hedonic testing

The importance of molecular weight is not trivial. The bioactivity of collagen and elastin peptides, their absorption in the gut, and ultimately their claimed effects on skin hydration, elasticity and photoaging all depend heavily on the size of the peptide fractions. Smaller peptides, particularly those below 1 kilodalton, are generally considered the most bioavailable and biologically active. Previous work by the same research group had already shown that a collagen peptide beverage maintained a stable distribution during three months of accelerated storage, with more than 65 percent of peptides below 1 kDa and antioxidant activity, measured by ABTS radical scavenging, preserved at 80 to 90 percent. But existing national and industry standards for molecular weight determination were written for simple peptide powders, not for multi-ingredient beverages.

Leading the study, researchers from China compared three mainstream gel permeation chromatography methods drawn from Chinese national and enterprise standards, designated Methods A, B and C, each using a different acetonitrile-water-trifluoroacetic acid mobile phase composition. All three relied on the same TSK-GEL G2000 SWXL size-exclusion column, UV detection at 220 nanometers, and calibration with a suite of peptide standards ranging from cytochrome C at 12,384 daltons down to glycylglycylglycine at just 189 daltons. The team tested the methods on a pure collagen and elastin peptide powder and on two commercial beverages, one fortified with vitamin C and one with epigallocatechin gallate, both made from the same production batches of peptide raw material, allowing a rigorous like-for-like comparison.

The first major finding concerned calibration curve fitting, a detail with outsized consequences. Gel permeation chromatography estimates molecular weight from retention time via a calibration curve, and the researchers showed that the relationship between the logarithm of molecular weight and retention time is inherently sigmoidal rather than linear, consistent with established theory in size-exclusion chromatography. Linear fits produced coefficients of determination between 0.9898 and 0.9925 but left systematic U-shaped residual patterns, revealing hidden bias. Refitting with cubic polynomials raised the R-squared values to between 0.9970 and 0.9999 and slashed the root mean square error, with Method B achieving an extraordinary R-squared of 0.9999 and residuals within ±0.01. In short, the mathematical model used to process the data mattered as much as the chromatography itself.

Repeatability was another pillar of validation. Standard samples re-injected before and after each batch showed retention time relative standard deviations below 0.1 percent, and theoretical plate numbers for the smallest standard exceeded system suitability requirements across all methods, confirming that the column remained in good condition. When the researchers calculated the distribution across five molecular weight ranges and three average molecular weight parameters, the RSD values for all samples stayed below 3 percent under both fitting models, demonstrating that each of the three methods is internally precise and suitable for the comparative analysis that followed.

The most commercially significant breakthrough, however, was the solution to matrix interference. In principle, any peak eluting after the smallest peptide standard, around 20.5 minutes, must represent compounds smaller than 189 daltons. The team hypothesized that this late-eluting region might instead contain aromatic beverage excipients absorbing UV light. Testing pure vitamin C and EGCG under identical conditions confirmed it: both additives eluted after the 20.5-minute cutoff, and the apparent sub-189 dalton fraction swelled to as much as 20 percent of the total distribution in the beverages. By simply excluding peaks after 20.5 minutes, the researchers eliminated the interference entirely. After the cutoff was applied, chromatographic profiles of powder and beverages overlapped almost perfectly, all relative deviations fell below 10 percent, and chromatographic fingerprint similarity analysis using the system recommended by the Chinese Pharmacopeia Commission returned correlation coefficients above 0.99 between each beverage and the pure peptide reference.

With interference removed, the study turned to the question of whether different laboratories using different official methods could ever agree on a number. Under linear fitting, significant differences appeared among the methods, particularly in the high molecular weight range above 3 kDa and in key parameters such as the weight-average molecular weight, whose ranking even flipped depending on the fitting model. Under cubic fitting, those systematic discrepancies largely vanished. In the critical sub-1 kDa region, where bioactive small peptides concentrate, all three methods became statistically consistent, with inter-method RSD values below 5 percent. The authors propose that if the industry adopts cubic polynomial fitting as a shared data-processing convention, results from different platforms become directly comparable; failing that, Method A, which proved most robust across both fitting modes, could serve as an interim reference method.

Perhaps the most reassuring result for product developers is that formulation freedom and analytical rigor can coexist. The two beverages deliberately contained ingredients chosen to adjust pH, viscosity, flavor and stability, including sodium hyaluronate, chitosan oligosaccharide and broccoli seed extract in the EGCG formulation. Electronic nose and electronic tongue profiling confirmed that the drinks delivered noticeably richer, more balanced flavor profiles than the plain peptide powder, with more harmonious distributions of umami, saltiness, sweetness and sourness. Crucially, none of this sensory engineering disturbed the measured molecular weight profile of the peptides. Manufacturers can therefore optimize taste, mouthfeel and shelf life without compromising the verifiable quality of the functional ingredient, provided the 20.5-minute exclusion rule and appropriate fitting model are applied.

The authors are candid about limitations. All experiments ran on a single HPLC platform, so cross-instrument validation remains to be done, and the exclusion rule has so far been tested only in these two matrices, with spiking recovery or blank matrix runs recommended for unknown formulations. The TSK-GEL G2000 SWXL column also has limited resolution below 500 daltons, where a difference of one or two amino acid residues barely changes hydrodynamic volume; the authors suggest LC-MS/MS or dedicated small-molecule columns such as Superdex 30 Increase for fine characterization in that range, and point toward future work linking precise peptide spectra to in vitro bioactivity and clinical endpoints. Even so, the framework delivers three concrete contributions: a validated chromatographic cutoff to strip away non-peptide interference, clear evidence that cubic fitting slashes inter-method variability, and demonstration that the approach survives contact with real, commercially formulated products. For an industry racing to capitalize on collagen’s popularity, that combination of rigor and practicality may prove as valuable as the peptides themselves.

Subject of Research: Molecular weight analysis of fish-derived collagen peptides in beverages by comparative gel permeation chromatography

Article Title: Developing an Analytical Framework for the Molecular Weight Analysis of Fish‐Derived Collagen Peptides in Beverages: A Multi‐Method Comparative Study

Article References: Feng, M., Li, Y., Luo, Y., Jiang, Y., & Zhao, C. (2026). Developing an Analytical Framework for the Molecular Weight Analysis of Fish‐Derived Collagen Peptides in Beverages: A Multi‐Method Comparative Study. Food Science & Nutrition, 14(9), Article e72386. https://doi.org/10.1002/fsn3.72386

Image Credits: AI Generated

DOI: 10.1002/fsn3.72386

Keywords: collagen peptides, gel permeation chromatography, molecular weight distribution, functional beverages, fish-derived peptides, matrix interference, calibration curve fitting, quality control, elastin peptides, food analysis, skin health, HPLC