Utilization of Whey for Eco-Friendly Bio-Preservation of Mexican-Style Fresh Cheeses: Antimicrobial Activity of Lactobacillus casei 21/1 Cell-Free Supernatants (CFS).

Using whey, a by-product of the cheese-making process, is important for maximizing resource efficiency and promoting sustainable practices in the food industry. Reusing whey can help minimize environmental impact and produce bio-preservatives for foods with high bacterial loads, such as Mexican-style fresh cheeses. This research aims to evaluate the antimicrobial and physicochemical effect of CFS from Lactobacillus casei 21/1 produced in a conventional culture medium (MRS broth) and another medium using whey (WB medium) when applied in Mexican-style fresh cheese inoculated with several indicator bacteria (Escherichia coli, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Listeria monocytogenes). The CFSs (MRS or WB) were characterized for organic acids concentration, pH, and titratable acidity. By surface spreading, CFSs were tested on indicator bacteria inoculated in fresh cheese. Microbial counts were performed on inoculated cheeses during and after seven days of storage at 4 ± 1.0 °C. Moreover, pH and color were determined in cheeses with CFS treatment. Lactic and acetic acid were identified as the primary antimicrobial metabolites produced by the Lb. casei 21/1 fermentation in the food application. A longer storage time (7 days) led to significant reductions (p < 0.05) in the microbial population of the indicator bacteria inoculated in the cheese when it was treated with the CFSs (MRS or WB). S. enterica serovar Typhimurium was the most sensitive bacteria, decreasing 1.60 ± 0.04 log10 CFU/g with MRS-CFS, whereas WB-CFS reduced the microbial population of L. monocytogenes to 1.67 log10 CFU/g. E. coli and S. aureus were the most resistant at the end of storage. The cheese's pH with CFSs (MRS or WB) showed a significant reduction (p < 0.05) after CFS treatment, while the application of WB-CFS did not show greater differences in color (ΔE) compared with MRS-CFS. This study highlights the potential of CFS from Lb. casei 21/1 in the WB medium as an ecological bio-preservative for Mexican-style fresh cheese, aligning with the objectives of sustainable food production and guaranteeing food safety.

Health Benefits of Consuming Foods with Bacterial Probiotics, Postbiotics, and Their Metabolites: A Review.

Over the years, probiotics have been extensively studied within the medical, pharmaceutical, and food fields, as it has been revealed that these microorganisms can provide health benefits from their consumption. Bacterial probiotics comprise species derived from lactic acid bacteria (LAB) (genus Lactobacillus, Leuconostoc, and Streptococcus), the genus Bifidobacterium, and strains of Bacillus and Escherichia coli, among others. The consumption of probiotic products is increasing due to the current situation derived from the pandemic caused by COVID-19. Foods with bacterial probiotics and postbiotics are premised on being healthier than those not incorporated with them. This review aims to present a bibliographic compilation related to the incorporation of bacterial probiotics in food and to demonstrate through in vitro and in vivo studies or clinical trials the health benefits obtained with their metabolites and the consumption of foods with bacterial probiotics/postbiotics. The health benefits that have been reported include effects on the digestive tract, metabolism, antioxidant, anti-inflammatory, anticancer, and psychobiotic properties, among others. Therefore, developing food products with bacterial probiotics and postbiotics is a great opportunity for research in food science, medicine, and nutrition, as well as in the food industry.

Antifungal Capacity of Poolish-Type Sourdough Supplemented with Lactiplantibacillus plantarum and Its Aqueous Extracts In Vitro and Bread.

This study aimed to evaluate the antifungal capacity of the aqueous extracts (AE) of poolish-type sourdoughs fermented with Lactiplantibacillus plantarum NRRL B-4496 on broth, agar, and bread. The aqueous extracts were obtained by centrifugation and separating the supernatant from the poolish sourdoughs once the fermentation time had ended. The aqueous extracts inhibited 80% of the growth of Penicillium chrysogenum and Penicillium corylophilum and <20% of Aspergillus niger in broth. The AEs delayed the radial growth rate and increased the lag time for the three molds tested. The addition of poolish-type sourdoughs inhibited fungal growth in bread for ten days. The extracts' fungistatic capacity was primarily attributed to lactic and acetic acids and probably the antifungal peptides occurring in the AE. The L. plantarum sourdough is an alternative to calcium propionate as an organic antifungal agent.

Insights on the effectiveness of pneumatic and ultrasonic atomization in combination with UVC light for processing of fruit juices.

This study evaluated the effectiveness of spraying juices, during shortwave ultraviolet irradiation (UVC) treatments as an alternative to promote more contact area, by means of ultrasonic atomization (UA) and pneumatic atomization (PA). Four juices with dissimilar physical characteristics were processed to assess the effect of suspended solids and turbidity. Antioxidant activity, anthocyanins, ascorbic acid, and inactivation of Saccharomyces cerevisiae inoculated in the juices were evaluated. Five decimal reduction cycles were reached after two passes of orange or grapefruit juice through the UVC + UA arrangement. On the other hand, five decimal reduction cycles were achieved after three passes in the UVC + PA arrangement. Losses of 11% and 14% of ascorbic acid were observed in orange and grapefruit juice, respectively, while anthocyanin content presented losses of 50% and antioxidant activity decreased by 40% for pomegranate and blueberry juice, correspondingly.

The impacts of antimicrobial and antifungal activity of cell-free supernatants from lactic acid bacteria in vitro and foods.

Lactic acid bacteria (LAB) are distinguished by their ability to produce lactic acid, among other interesting metabolites with antimicrobial activity. A cell-free supernatant (CFS) is a liquid containing the metabolites resulting from microbial growth and the residual nutrients of the medium used. CFS from LAB can have antimicrobial activity due to organic acids, fatty acids, and proteinaceous compounds, among other compounds. This review aims to summarize the information about CFS production, CFS composition, and the antimicrobial (antibacterial and antifungal) activity of CFS from LAB in vitro, on foods, and in active packaging. In addition, the mechanisms of action of CFS on cells, the stability of CFS during storage, CFS cytotoxicity, and the safety of CFS are reviewed. The main findings are that CFS's antibacterial and antifungal activity in vitro has been widely studied, particularly in members of the genus Lactobacillus. CFS has produced strong inhibition of bacteria and molds on foods when applied directly or in active packaging. In most studies, the compounds responsible for antimicrobial activity are identified. A few studies indicate that CFSs are stable for 1 to 5 months at temperatures ranging from 4 to 35°C. The cytotoxicity of CFS on human cells has not been well studied. However, the studies that have been performed reported no toxicity of CFS. Therefore, it is necessary to investigate novel growth mediums for CFS preparation that are compatible with food sensory properties. More studies into CFS stability and cytotoxic effects are also needed.

High-Intensity Light Pulses To Inactivate Salmonella Typhimurium on Mexican Chia (Salvia hispanica L.) Seeds.

Chia seeds provide a suitable environment for microorganisms. However, it is difficult to disinfect these seeds with water and/or chemical disinfectant solutions because the mucilage in the seeds can absorb water and consequently form gels. High-intensity light pulses (HILP) is one of the most promising emerging technologies for inactivating microorganisms on surfaces, in clear liquids and beverages, and on solid foods. The aim of this work was to evaluate the effect of HILP on Salmonella Typhimurium in culture medium (in vitro tests) and inoculated onto chia seeds (in vivo tests). HILP was effective against Salmonella Typhimurium under both conditions: 8 s of treatment (10.32 J/cm2) resulted in a 9-log reduction during in vitro tests, and 15 s of treatment (19.35 J/cm2) resulted in a 4-log reduction on the inoculated chia seeds. Salmonella Typhimurium inactivation kinetics were accurately described using the Weibull model (R2 > 0.939). These results indicate that the use of HILP for microbial inactivation on seeds could generate products suitable for human consumption.

Penicillium expansum Inhibition on Bread by Lemongrass Essential Oil in Vapor Phase.

The antimicrobial activity of lemongrass (Cymbopogon citratus) essential oil (EO) in the vapor phase on the growth of Penicillium expansum inoculated on bread was evaluated, followed by a sensory evaluation of the bread's attributes after EO exposure. The lemongrass EO was extracted from dry leaves of lemongrass by microwave-assisted steam distillation. The chemical composition of the lemongrass EO was determined using a gas chromatograph coupled to a mass spectrometer. The refractive index and specific gravity of the EO were also determined. Bread was prepared and baked to reach two water activity levels, 0.86 or 0.94, and then 10 µL of P. expansum spore (106 spores per mL) suspension was inoculated on the bread surface. Concentrations of lemongrass EO were tested from 125 to 4,000 µL/Lair, whereas mold radial growth was measured for 21 days. For sensory evaluation, breads were treated with lemongrass EO vapor at 0, 500, or 1,000 µL/Lair for 48 h and tested by 25 untrained panelists. The EO yield was 1.8%, with similar physical properties to those reported previously. Thirteen compounds were the main components in the EO, with citral being the major compound. P. expansum was inhibited for 21 days at 20°C with 750 µL of EO/Lair, and its inhibition increased with increasing concentrations of EO. Sensory acceptance of bread exposed to vapor concentrations of 500 or 1,000 µL of EO/Lair or without EO was favorable; similar and no significant differences (P > 0.05) were observed among them.

Antimicrobial activity of whey protein films supplemented with Lactobacillus sakei cell-free supernatant on fresh beef.

The aim of this work was to evaluate the antimicrobial activity of whey protein isolate (WPI) films supplemented with Lactobacillus sakei NRRL B-1917 cell-free supernatant on beef inoculated with Escherichia coli ATCC 25922 or Listeria monocytogenes Scott A; additionally, sensory evaluation was performed on wrapped beef cubes. Supernatant concentrates were obtained from Lb. sakei cultures in MRS broth after centrifugation, filtering, and freeze-drying. Films were prepared with WPI (3% w/w), alginate (0.625% w/w), rehydrated supernatant (18 mg/ml), and glycerol. Films were used to wrap beef cubes inoculated with ≈103 CFU/g E. coli or L. monocytogenes. Sensory evaluation was carried out on grilled beef wrapped or not with the studied antimicrobial films. During refrigerated storage, antimicrobial films reduced 1.4 log10 CFU/g of L. monocytogenes after 120 h, while E. coli decreased 2.3 log10 CFU/g after 36 h. Grilled beef wrapped with antimicrobial film was well accepted by panelists, besides scores evidenced no significant differences (p > 0.05) between wrapped and unwrapped beef.

Description of Aspergillus flavus growth under the influence of different factors (water activity, incubation temperature, protein and fat concentration, pH, and cinnamon essential oil concentration) by kinetic, probability of growth, and time-to-detection models.

A Box-Behnken design was used to determine the effect of protein concentration (0, 5, or 10g of casein/100g), fat (0, 3, or 6g of corn oil/100g), aw (0.900, 0.945, or 0.990), pH (3.5, 5.0, or 6.5), concentration of cinnamon essential oil (CEO, 0, 200, or 400µL/kg) and incubation temperature (15, 25, or 35°C) on the growth of Aspergillus flavus during 50days of incubation. Mold response under the evaluated conditions was modeled by the modified Gompertz equation, logistic regression, and time-to-detection model. The obtained polynomial regression models allow the significant coefficients (p<0.05) for linear, quadratic and interaction effects for the Gompertz equation's parameters to be identified, which adequately described (R2>0.967) the studied mold responses. After 50days of incubation, every tested model system was classified according to the observed response as 1 (growth) or 0 (no growth), then a binary logistic regression was utilized to model A. flavus growth interface, allowing to predict the probability of mold growth under selected combinations of tested factors. The time-to-detection model was utilized to estimate the time at which A. flavus visible growth begins. Water activity, temperature, and CEO concentration were the most important factors affecting fungal growth. It was observed that there is a range of possible combinations that may induce growth, such that incubation conditions and the amount of essential oil necessary for fungal growth inhibition strongly depend on protein and fat concentrations as well as on the pH of studied model systems. The probabilistic model and the time-to-detection models constitute another option to determine appropriate storage/processing conditions and accurately predict the probability and/or the time at which A. flavus growth occurs.