Search Results (366)

The quality of Sichuan paocai in natural fermentation is often inconsistent due to the complexity of its microbial community and environmental influences. To address this, dominant microbial strains were selectively inoculated to improve the product’s quality and safety. However, vacuum freeze-drying, commonly used to prepare direct vat set (DVS) starters, can significantly damage strains due to freezing stress. This study aimed to optimize a freeze-drying protection system for Lactiplantibacillus plantarum and Bacillus subtilis to enhance their survival. Using response surface methodology, combinations of cryoprotectants were evaluated. A formulation comprising skim milk powder, glycerol, sucrose, and L-proline significantly improved strain viability after lyophilization, outperforming single cryoprotectants. Further investigation into storage conditions revealed that low temperatures (−20 °C) provided the best preservation for DVS starters. Furthermore, the optimized DVS starters demonstrated excellent fermentation performance in Sichuan paocai, enhancing its color, flavor, and sensory quality compared to natural fermentation. These findings offer a reliable freeze-drying protection strategy for survival and viability of L. plantarum and B. subtilis. Full article

Arid ecosystems constitute a promising source of actinobacteria producing new bioactive molecules. This study aimed to explore different biological activities of actinomycetes isolated from the rhizosphere of Phoenix dactylifera L. in the Ghardaia region, Algeria. A total of 18 actinobacteria were isolated and studied for their enzymatic and antimicrobial activities. All isolates shared cellulase and catalase activity; most of them produced amylase (94%), esterase (84%), lecithinase and lipoproteins (78%), caseinase (94%), and gelatinase (72%). The isolates could coagulate (56%) or peptonize (28%) skim milk. Overall, 72% of the isolates exhibited significant antibacterial activity against at least one test bacteria, while 56% demonstrated antifungal activity against at least one test fungi. Based on enzyme production and antimicrobial activity, isolate SGI16 was selected for secondary metabolite extraction by ethyl acetate. The crude extract of SGI16 was analyzed using DPPH and BSA denaturation inhibition tests, revealing significant antioxidant power (IC₅₀ = 7.24 ± 0.21 μg mL⁻¹) and protein denaturation inhibitory capacity (IC₅₀ = 492.41 ± 0.47 μg mL⁻¹). Molecular identification based on 16S rDNA analysis showed that SGI16 belonged to the genus Streptomyces. The findings highlight that date palms’ rhizosphere actinobacteria are a valuable source of biomolecules of biotechnological interest. Full article

Carbendazim (CBZ) is used to prevent fungal infections in agricultural crops. Given its high persistence and potential for long-term health effects, it is crucial to quickly identify pesticide residues in food and the environment in order to mitigate excessive exposure. Aptamer-based sensors offer a promising solution for pesticide detection due to their exceptional selectivity, design versatility, ease of use, and affordability. Herein, we report the development of an electrochemical aptasensor for CBZ detection. The sensor was fabricated through a one-step electrodeposition of platinum nanoparticles (Pt NPs) and reduced graphene oxide (rGO) on a glassy carbon electrode (GCE). Then, a CBZ-specific aptamer was attached via Pt-sulfur bonds. Upon combining CBZ with the aptamer on the electrode surface, the redox reaction of the electrochemical probe K₄[Fe(CN)₆] is hindered, resulting in a current drop. Under optimized conditions (pH of 7.5 and 25 min of incubation time), the proposed aptasensor showed a linear current reduction to CBZ concentrations between 0.5 and 15 nM. The limit of detection (LOD) for this proposed aptasensor is 0.41 nM. Along with its repeatable character, the aptasensor demonstrated better selectivity for CBZ compared to other potential compounds. The recovery rates for detecting CBZ in skim milk and tap water using the standard addition method were 98% and 96%, respectively. The proposed aptasensor demonstrated simplicity, sensitivity, and selectivity for detecting CBZ with satisfactory repeatability. It establishes a strong foundation for environmental monitoring of CBZ. Full article

Protein-enriched yogurts have become increasingly popular among consumers seeking to boost their daily protein intake. The incorporation of milk proteins and protein preparations in yogurt production not only enhances nutritional value but also improves texture, viscosity, and overall sensory properties—key factors that influence consumer acceptance. The main objective of this study was to evaluate the influence of casein and whey protein preparations on the physicochemical properties, viability of lactic acid bacteria, and sensory attributes of yogurts. Yogurts were enriched with 2% (w/w) protein preparations, including micellar casein preparation (CN85), whey protein isolate (WPI), whey protein concentrate (WPC60), and protein preparations obtained from skim milk by membrane filtration: micellar casein concentrate (CN75) and serum protein concentrate (SPC). The yogurts were produced using the thermostatic method, and their chemical composition, rheological properties, syneresis, firmness, lactic acid bacteria population, and sensory attributes were evaluated. The effects of high-protein preparations derived from skim milk through laboratory-scale membrane filtration processes (SPC, CN75) were compared with those of commercially available protein preparations (SMP, CN85, WPI, and WPC). Obtained results demonstrated that the membrane filtration-derived preparations (SPC and CN75) exhibited advantageous physicochemical properties and supported robust viability of yogurt and probiotic bacteria. However, their sensory quality was marginally inferior compared to the commercial preparations (SMP, CN85, WPI, and WPC). These findings indicate the potential applicability of membrane filtration-derived protein preparations in yogurt production while underscoring the necessity for further investigation to enhance and optimize their sensory characteristics. Full article

The current trend in food innovations includes developing products containing plant ingredients or extracts rich in bioactive compounds. This study aimed to prepare and characterize skimmed thermally treated goat’s milk powders enriched with lyophilized fruit extracts of Lycium ruthenicum Murray (GMLR) and Lycium barbarum L. (GMLB). Proximate analysis, ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), Fourier transform infrared spectroscopy using attenuated total reflection (FTIR-ATR), and electrophoretic analysis were assessed. Total phenolic content (TPC), total protein content, and antioxidant properties of enriched goat milk powders were determined spectrophotometrically, and prebiotic potential was evaluated by the broth microdilution method. A total of 25 phenolic compounds and 18 phenylamides were detected in the enriched goat milk powders. Electrophoretic analysis showed the absence of proteolysis in the prepared powders. The GMLR showed the highest TPC and displayed a ferric ion-reducing power, probably contributed by anthocyanins and some phenylamides. GMLR and GMLB had higher ABTS radical scavenging activity but lower ferrous ion-chelating capacity than control goat′s milk powder. GMLB and GMLR in a dose-dependent manner (0.3–5 mg/mL) showed a growth-promoting effect on probiotic strains. In summary, prepared goji/goat milk powders, primarily GMLR, might be used as prebiotic supplements or functional food additives. Full article

The refractive index (RI) of human milk serum (also known as whey, milk soluble fraction or milk plasma) depends on the individual molecular species dissolved in the serum and their concentrations. Although the human milk serum RI is known to influence milk analysis methods based on light scattering, the RI dependency on human milk serum composition is currently unknown. Therefore, we systematically evaluate how the RI depends on natural variations in macronutrient concentrations in the soluble fraction. We measure RI variations in serum simulating samples with controlled macronutrient concentrations, as well as skimmed and whole fore-, bulk, and hindmilk from 19 donors. For both types of samples, we relate the measured RI to the macronutrient composition. From the serum simulating samples, we observe that the RI depends more on variations in whey protein, than carbohydrate concentrations, while minerals have negligible influence. For all donated samples, the average RI was 1.3470 (range 1.3466–1.3474). Per donor, no significant differences were observed in RI between fore-, bulk, and hindmilk. We conclude that protein and solids-not-fat (i.e., the total contribution of carbohydrates, proteins and minerals present in milk) concentrations are most predictive for human milk serum RI. Full article

Electrostatic spray drying (ESD) of a milk protein matrix comprising whey protein isolate (WPI), skim milk powder (SMP), and lactose was compared to conventional spray drying (CSD) and freeze-drying (FD). ESD and CSD were used to produce powders at low (0.12–0.14), medium (0.16–0.17), and high (0.31–0.36) levels of water activity (a_w), while FD powders targeted low a_w (0.12). Maillard reaction indicators were studied after drying and during storage for up to 28 days at 20, 40, or 60 °C by measuring free -NH₂ groups, as an indicator of available lysine, and 5-hydroxymethylfurfural (HMF). After drying, levels of residual free -NH₂ groups were ~15% higher in ESD and FD powders than in their CSD counterparts. CSD powders also had ~14% higher HMF concentrations compared to their ESD and FD counterparts. Storage led to reductions in free -NH₂ groups and increases in HMF content in all powders, the extent of which increased with increasing storage temperature. Reductions in free -NH₂ groups followed first-order reaction kinetics at 20 and 40 °C but second-order reaction kinetics at 60 °C. Lactose crystallization was detected in high-a_w CSD powders after 14 d at 40 °C and in both CSD and ESD powders after 7 d at 60 °C. Overall, we found that ESD is a gentle drying technology which enables production of powders with lower Maillard reaction markers. Full article

The amino acid (AA) content of multiple samples of various dairy powders was determined, providing a comprehensive evaluation of the differences in AA profiles attributable to distinct manufacturing processes. Products examined included whole milk powder (WMP), skim milk powder (SMP), cheese whey protein concentrate (WPC-C), lactic acid casein whey protein concentrate (WPC-L), high-fat whey protein concentrate (WPC-HF), hydrolyzed whey protein concentrate (WPH), whey protein isolate (WPI), and demineralized whey protein (D90). WMP and SMP exhibited broadly similar AA profiles, with minor differences likely due to the minimal milk fat protein content, which is nearly absent from SMP. Comparative analysis of WPC-C and WPC-L indicated higher levels of threonine, serine, glutamic acid, and proline in WPC-C but lower levels of tyrosine, phenylalanine, and tryptophan, attributed to the different methods of separation from casein proteins. WPI and WPC-HF originate from similar sweet whey streams but follow divergent processing methods; consequent on this were variations in the levels of all AAs except histidine. The nanofiltration step in D90 production retains its non-protein nitrogen content and affects its AA profile; consequently, D90 consistently exhibited lower AA levels than WPC-C. These findings underscore the significant impact of manufacturing processes on dairy powder AA composition. Full article

The influence of heating as a pretreatment on the structural and functional attributes of milk protein concentrate (MPC) powders derived from ultrafiltered/diafiltered (UF/DF) skim milk is under-reported. This research delves into the impact of pH and heat treatment on skim milk’s properties before UF/DF and how these changes affect the resulting MPC powders. By adjusting the pH of skim milk to 6.5, 6.8, or 7.1 and applying thermal treatment at 90 °C for 15 min to one of two divided lots (with the other serving as a control), we studied the protein interactions in MPC. Post-heat treatment, the skim milk’s pH was adjusted back to 6.8, followed by ultrafiltration and spray drying to produce MPC powders with protein content of 82.38 ± 2.72% on a dry matter basis. MPC dispersions from these powders at 5% protein (w/w) were also evaluated for particle size, viscosity, and heat coagulation time (HCT) to further understand how the protein interactions in skim milk influence the properties of MPC dispersions. Capillary electrophoresis was used to assess the casein and whey protein distribution in both the soluble and colloidal phases. Findings revealed that preheating skim milk at pH 7.1 increased serum phase interactions, while heating skim milk preadjusted to a pH of 6.5 promoted whey protein–casein interactions at the micellar interface. Notably, the D (4,3) of casein micelles was larger for dispersions from milk with a preheated pH of 6.5 compared to other pH levels, correlating positively with enhanced dispersion viscosity due to increased volume fraction. These results support the potential for tailoring MPC powder functionality in various food applications through the precise control of the milk’s pre-treatment conditions. Full article

A high degree of hydrolysis can reduce the allergenicity of milk, while lactic acid bacteria (LAB) fermentation can further enhance the antioxidant ability of enzymatic milk. LAB with a strong antioxidant ability was screened, and the effects of LAB on the bitterness, taste and flavor of enzymatic skim milk (ESM) with a high degree of hydrolysis were investigated in this paper, in addition to the response surface methodology optimized the conditions of the LAB fermentation of ESM. The results indicate that the skim milk hydrolyzed by Protamex has a higher degree of hydrolysis and lower bitterness. The scavenging rate of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical, the inhibition rate of hydroxyl radical (·OH) and the superoxide dismutase (SOD) activity of Lactiplantibacillus plantarum 16 and Lactococcus lactis subsp. lactis m16 are significantly higher than those of other strains (p < 0.05), while the improvement effect of L. plantarum 16 on the bitterness and flavor of ESM is better than that of L. lactis subsp. lactis m16. The fermented ESM has a strong antioxidant ability and low bitterness when the inoculum quantity of L. plantarum 16 is 5%, fermentation at 37 °C for 18 h and the pH of the ESM is 6.5, for which the DPPH free radical scavenging rate is 61.32%, the ·OH inhibition rate is 83.35%, the SOD activity rate is 14.58 and the sensory evaluation is 4.25. The contents of amino acids related to bitterness and antioxidants were reduced and increased, respectively. The ESM fermented by L. plantarum 16 has a good flavor, antioxidant ability and low bitterness. Full article

Aflatoxin M₁ (AFM₁) in milk poses a significant threat to human health. This study examined the capacity of Bacillus licheniformis CotA laccase to oxidize AFM₁. The optimal conditions for the CotA laccase-catalyzed AFM₁ oxidation were observed at pH 8.0 and 70 °C, achieving an AFM₁ oxidation rate of 86% in 30 min. The Km and Vmax values for CotA laccase with respect to AFM₁ were 18.91 μg mL⁻¹ and 9.968 μg min⁻¹ mg⁻¹, respectively. Computational analysis suggested that AFM₁ interacted with CotA laccase via hydrogen bonding and van der Waals interactions. Moreover, the oxidation products of AFM₁ mediated by CotA laccase were identified as the C3-hydroxy derivatives of AFM₁ by HPLC-FLD and UPLC-TOF/MS. Toxicological assessment revealed that the hepatotoxicity of AFM₁ was substantially reduced following oxidation by CotA laccase. The efficacy of CotA laccase in removing AFM₁ in milk was further tested, and the result showed that the enzyme agent achieved an AFM₁ removal rate of 83.5% in skim milk and 65.1% in whole milk. These findings suggested that CotA laccase was a novel AFM₁ oxidase capable of eliminating AFM₁ in milk. More effort is still needed to improve the AFM₁ oxidase activity of CotA laccase in order to shorten the processing time when applying the enzyme in the milk industry. Full article

Hazelnut oil cake, a by-product in the cold-pressing of hazelnut oil, is a rich in valuable nutrients, which makes it a promising option for supplementation or as a raw material in the development of functional products. The aim of this work was to study the influence of partial or complete replacing of skim milk powder (SMP) with hazelnut press cake flour (HPCF) in varying ratios (0%, 25%, 50%, 75%, and 100%) on the physicochemical properties and sensory attributes of milk ice cream. The replacement modified the chemical composition of the ice cream mixture, resulting in a reduction (p < 0.05) of milk solids non-fat (MSNF), protein, and carbohydrates content, while simultaneously elevating the hazelnut content, and total fat content. This modification influenced the rheological characteristics of the ice cream mixtures, leading to an increase in the consistency coefficient from 1.32 to 7.66 Pa sⁿ. Furthermore, a decline in overrun values (from 26.99% to 15.85%), an increase in hardness (from 6881.71 to 23,829.30 g), retarded melting properties, and variations in colour attributes were observed with higher concentrations of HPCF. In the sensory evaluation test, it was found that consumer acceptance was enhanced for the samples with partial substitution of SMP when compared to standard milk ice cream. The findings suggest that a replacement of milk powder with hazelnut cake by up to 75% is achievable, in order to obtain functional ice cream with adequate physicochemical and sensorial qualities. Full article

Background/Objectives: Heterodera avenae is a highly significant plant-parasitic nematode, causing severe economic losses to global crop production each year. Trichoderma species have been found to parasitize nematodes and control them by producing enzymes that degrade eggshells. The T. longibrachiatum T6 (T6) strain has been demonstrated the parasitic and lethal effects on H. avenae cysts and eggs, associated with the increased serine protease activity and trypsin-like serine protease gene (PRA1) expression. Methods: Our present study aimed to purify the recombinant PRA1 protease through a prokaryotic expression system and identify its nematicidal activity. Results: The recombinant PRA1 protease was identified as S1 family trypsin-like serine protease, with a molecular weight of 43.16 kDa. The purified soluble protease exhibited the optimal activity at 35 °C and pH 8.0, and also demonstrating higher hydrolytic ability toward casein and skimmed milk. Meanwhile, the Ca²⁺ and Mg²⁺ enhanced its activity, while the inhibitor PMSF significantly reduced it. The contents of H. avenae eggs leaked out after treatment with the recombinant PRA1 protease, with egg hatching inhibition and relative hatching inhibition rates at 70.60% and 66.58%, respectively. In contrast, there was no sign of content dissolution, and embryos developed normally in the control group. Conclusions: Our present study revealed that the PRA1 protease of T6 strain has a lethal effect on H. avenae eggs, which providing a theoretical basis for developing biocontrol agents to control nematodes. Full article

In this study, hydrogel films of biocomposite comprising bacterial cellulose (BC) and silk (S) were successfully fabricated through a simple, facile, and cost-effective method via biosynthesis by Acetobacter xylinum in a culture medium of coconut skim milk/mature coconut water supplemented with the powders of thin-shell silk cocoon (SC). Coconut skim milk/mature coconut water and SC are the main byproducts of coconut oil and silk textile industries, respectively. The S/BC films contain protein, carbohydrate, fat, and minerals and possess a number of properties beneficial to wound healing and tissue engineering, including nontoxicity, biocompatibility, appropriate mechanical properties, flexibility, and high water absorption capacity. It was demonstrated that silk could fill into a porous structure and cover fibers of the BC matrix with very good integration. In addition, components (fat, protein, etc.) in coconut skim milk could be well incorporated into the hydrogel, resulting in a more elastic structure and higher tensile strength of films. The tensile strength and the elongation at break of BC film from coconut skim milk (BCM) were 212.4 MPa and 2.54%, respectively, which were significantly higher than BC film from mature coconut water (BCW). A more elastic structure and relatively higher tensile strength of S/BCM compared with S/BCW were observed. The films of S/BCM and S/BCW showed very high water uptake ability in the range of 400–500%. The presence of silk in the films also significantly enhanced the adhesion, proliferation, and cell-to-cell interaction of Vero and HaCat cells. According to multiple improved properties, S/BC hydrogel films are high-potential candidates for application as biomaterials for wound dressing and tissue engineering. Full article

The shear flow and solid–liquid transition of mixed milk protein dispersions with varying concentrations of casein micelles (CMs) and serum proteins (SPs) are integral to key dairy processing operations, including microfiltration, ultrafiltration, diafiltration, and concentration–evaporation. However, the rheological behavior of these dispersions has not been sufficiently studied. In the present work, dispersions of CMs and SPs with total protein weight fractions (ω_PR) of 0.021–0.28 and SP to total protein weight ratios (R_SP) of 0.066–0.214 and 1 were prepared by dispersing the respective protein isolates in the permeate from skim milk ultrafiltration and then further concentrated via osmotic compression. The partition of SPs between the CMs and the dispersion medium was assessed by measuring the dry matter content and viscosity of the dispersion medium after separating it from the CMs via ultracentrifugation. The rheological properties were studied at 20 °C via shear rheometry, and the sol–gel transition was characterized via oscillatory measurements. No absorption of SPs by CMs was observed in dispersions with ω_PR = 0.083–0.126, regardless of the R_SP. For dispersions of SPs with ω_PR ≤ 0.21, as well as the dispersion medium of mixed dispersions with ω_PR = 0.083–0.126, the high shear- rate-limiting viscosity was described using Lee’s equation with an SP voluminosity (v_SP) of 2.09 mL·g⁻¹. For the mixed dispersions with a CM volume fraction of φ_CM ≤ 0.37, the relative high shear-rate-limiting viscosity was described using Lee’s equation with a CM voluminosity (v_CM) of 4.15 mL·g⁻¹ and a v_SP of 2.09 mL·g⁻¹, regardless of the R_SP. For the mixed dispersions with φ_CM > 0.55, the relative viscosity increased significantly with an increasing R_SP (this was explained by an increase in repulsion between CMs). However, the sol–gel transition was independent of the R_SP and was observed at φ_CM ≈ 0.65. Full article