Yeasts isolated from fermented foods have attracted increasing attention for their probiotic potential; however, studies on yeast-derived postbiotics remain limited. In this study, endogenous yeast strains belonging to Kluyveromyces marxianus (n = 3), Yarrowia lipolytica (n = 3), Pichia fermentans (n = 3), and Debaryomyces hansenii (n = 3) were evaluated for their in vitro probiotic properties. A multi-criteria decision-making analysis using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) identified K. marxianus ETP12, P. fermentans SJ2023, and Y. lipolytica ARTP9.2 as the most promising strains for postbiotic production. Among them, K. marxianus ETP12 exhibited the highest functional potential and was subjected to comprehensive postbiotic characterization. The postbiotic of K. marxianus ETP12 was further characterized for total phenolic content, antioxidant capacity (DPPH and ABTS scavenging activities), phenolic compound profile, biofilm inhibition capacity, free amino acid composition, and fatty acid profile. The results revealed a diverse phenolic composition, primarily consisting of fumaric acid, quercetin, gallic acid, and quinic acid. A total of 29 essential, non-essential, and bioactive amino acids were identified, with lysine, leucine, and glycine as the predominant components. Fatty acid profiling indicated the predominance of palmitic and stearic acids, accompanied by medium-chain fatty acids. Notably, it exhibited strong biofilm-inhibition activity against S. aureus ATCC 25923 and C. sakazakii ATCC 29544. Overall, these findings demonstrate that K. marxianus ETP12 represents a valuable source of multifunctional postbiotics with potential applications in the development of functional foods and nutraceuticals.

Probiotic yeasts are increasingly proposed as adjuncts in fermented dairy products, but their behavior in kefir is still poorly described. This proof-of-concept study examined the effect of Saccharomyces boulardii CNCM I-745 supplementation on kefir produced with two traditional grain cultures and two industrial direct-vat-inoculation cultures during 21 days of cold storage at 4 °C. Microbiological, physicochemical, and sensory parameters were monitored on days 1, 7, 14, and 21. The starter culture type was the main source of variation, with traditional grain kefirs showing higher microbial counts and better sensory scores than industrial cultures. S. boulardii did not change pH, titratable acidity, Lactococcus spp., or total mesophilic aerobic bacteria, indicating that it can be added without disturbing the established kefir microbiota or its acidification pattern. The probiotic yeast increased the total yeast count, slightly modulated Lactobacillus spp., and gave a small improvement in taste–aroma scores. In the yeast-free industrial culture, S. boulardii maintained viable counts above 6 log CFU/g throughout storage, showing that it can act as the sole yeast source in kefir matrices that lack indigenous yeast. Traditional grain kefirs kept a more stable overall sensory quality across 21 days than industrial cultures. The multivariate analysis confirmed two largely independent quality dimensions, one related to lactic acid bacteria and acidity and another to sensory perception. The study supports the use of S. boulardii as a probiotic adjunct in kefir and provides preliminary effect-size information for future, adequately replicated trials.

The growing consumer demand for minimally processed, “clean-label” foods is increasing interest in innovative technologies that maintain quality while ensuring microbial safety. This study sheds light on how the protein:lipid ratio in meat-like model matrices modulates the effectiveness of combined high-intensity ultrasound (20 kHz) and carvacrol treatments applied against Escherichia coli ATCC 25922. Three emulsified systems with geometrically spaced protein:lipid ratios (0.33, 1.0, 3.0) were subjected to combinations of ultrasound and carvacrol (0–1200 ppm) at $30\pm 2$ °C. To address the rheological non-linearity, the matrix index was log-transformed, and the process was modeled using both Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). While both models achieved high predictive accuracy ($R^2>0.96$), lack-of-fit analysis revealed that the reduced polynomial RSM model provided a more robust and statistically valid representation of the process compared to the ANN, which exhibited significant overfitting to experimental noise ($p<{10}^{-9}$). The results highlighted a distinct matrix dependency: ultrasound alone provided the fastest inactivation in the high-lipid matrix, while the high-protein matrix exhibited much slower kinetics due to viscous damping. Consequently, the explicit mathematical relationships derived from the RSM model are proposed as the preferred, transparent kernel for future digital twins and autonomous process-control systems in smart food-processing lines.

Kefir is a self-carbonated fermented milk produced with kefir grains which is valued for its complex symbiotic microbiota and probiotic potential. Flavouring kefir is a recognised strategy to broaden consumer appeal, yet the moment at which a flavouring ingredient is introduced—before or after fermentation—may differentially affect the product. The present study evaluated the effect of the timing of instant coffee addition on the physicochemical, microbiological and sensory properties of kefir during 14 days of refrigerated storage (4 ± 1 °C). Three kefir samples were produced from UHT cow’s milk (3% fat) inoculated with 3% (w/v) kefir grains: a control without coffee (K), kefir with 0.5% (w/v) instant coffee added before fermentation (PreF_CK) and kefir with 0.5% (w/v) instant coffee added after fermentation and maturation (PostF_CK). Samples were analysed on days 1, 7 and 14. The coffee addition significantly increased the total dry matter (K = 10.72%; PreF_CK = 11.04%; PostF_CK = 11.00%; p < 0.01) and slightly modified the titratable acidity and pH (p < 0.05), whereas the ash content (expressed in terms of dry matter) did not differ among samples (p > 0.05). The titratable acidity increased and the pH decreased with storage in all samples (p < 0.05). Crucially, the coffee addition—irrespective of the timing—did not impair the viability of the kefir microbiota; the total mesophilic aerobic bacteria, Lactobacillus spp., mesophilic lactic cocci and yeast counts did not differ significantly among the samples (p > 0.05) and remained high throughout storage (lactic acid bacteria ≥8 log CFU/g; yeast ≥5.7 log CFU/g), exceeding the minimum thresholds of the standards for fermented milk products. Sensory evaluation showed that the control achieved the highest odour and taste scores (p < 0.001), while among the coffee-containing samples, the post-fermentation addition (PostF_CK) was generally scored at least as high as the pre-fermentation addition (PreF_CK); overall acceptability did not differ significantly among the samples (p > 0.05). These findings demonstrate that 0.5% instant coffee can be incorporated into kefir without compromising its characteristic microbiota or storage stability and that post-fermentation addition is a viable route for producing an acceptable coffee-flavoured kefir.

Citrus peel is examined here as a naturally evolved protective surface, with the goal of developing a transferable quantitative framework for extracting engineering-relevant descriptors from biological protective surfaces and using them as design templates for biomimetic counterparts. A single-specimen-per-species design is adopted to map intra-fruit geometric variation across regions and magnifications; absolute descriptor values are therefore reported as ordinal indicators of inter-species ranking rather than as population means. Five citrus species (lemon, orange, mandarin, grapefruit, and bitter orange) were characterised by mechanical testing (cutting, puncture, and compression; five replicates per fruit), gravimetric peel density and thickness, and scanning electron microscopy (SEM) at 100×–10,000×. The 135-image SEM dataset was processed with an automatic-calibration pipeline performing per-image scale-bar detection, multilevel-Otsu segmentation of albedo air space, cell-bounded surface segment (CBSS) and oil-gland segmentation on flavedo, and grey-level co-occurrence matrix (GLCM) texture analysis with a directional anisotropy index $A_F$. Calibration was consistent across all images (FoV × magnification $=\mathrm{403,273}\pm 410$ $\mathsf{\mu }$m$·\times$, $\pm 0.10\%$). Principal component analysis separated flavedo and albedo at every magnification (PC1 + PC2 = 84–92%). Within this dataset, grapefruit showed the densest CBSS cover (1072 ${\mathrm{mm}}^{-2}$) together with the highest oil-gland density (2.77 ${\mathrm{mm}}^{-2}$); bitter orange showed the largest CBSS area (23.7 $\mathsf{\mu }{\mathrm{m}}^2$) and the thickest peel (13.1 mm); mandarin showed the most directionally oriented flavedo film ($A_F=0.0885$); and lemon showed the most open albedo (${\phi }_{2D}=36.2\%$). Oil-gland equivalent diameter was essentially invariant (∼45 $\mathsf{\mu }$m) across the five fruits, while gland density varied 4.4-fold. The structural metrics define a layered descriptor space—a dense isotropic surface relief versus a thick cellular bulk—that supplies two distinct bioinspired-design priors: dense surface films as a structural prior for selective-permeability membranes and layered cellular cores as a prior for impact-absorbing panels. A modified-atmosphere packaging (MAP)-compatible biomimetic film is identified as one downstream design hypothesis requiring direct gas-permeability verification on synthetic membranes.