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This work aimed to develop an edible coating based on Mexican lime (Citrus aurantifolia Swingle) pectic extract and essential oil on Haden mango (Mangifera indica L.) to extend its shelf life. Mango cubes were coated by immersion in a lime pectic extract (1% pectin w/v), lime essential oil (0.05% v/v), and glycerol (0.7% v/v) solution for 2, 5, and 10 min. Subsequently, coated and uncoated (control) test samples were stored for 21 days, and physical–chemical and microbiological analyses were performed every 3 days. The results showed no significant differences for total soluble solids, pH, and firmness. On the sixth day, bacterial growth was significantly lower in coated mangos than in the control (log 6.08 ± 0.49 and 7.63 ± 0.20 UFC g−1, respectively). The application of the edible coating extended the shelf life of minimally processed mangos by 3 days, delaying physical and chemical changes as well as bacterial growth.

Strains of Lactococcus lactis used for a long time as starter cultures in the production of cheese have not only acquired special features like fast utilization of lactose, but it is also believed that they have lost certain metabolic capabilities. Certain wild strains of L. lactis isolated from vegetables or raw milk products are able to generate flavors different from those produced by industrial strains. The aim of this work was to assess the production of volatile compounds in miniature Chihuahua-type cheeses manufactured with different strains of L. lactis isolated from vegetables, raw milk products, and industrial cultures. There was variation among volatile profiles in the miniature cheeses manufactured with different strains of L. lactis. However, some compounds were seen in most of the cheeses such as acetic, lactic, butyric, and caproic acids, acetoin, 3-methyl-1-butanol, and 2,3-butanediol. The source of isolation of the strains (plants, raw milk products, and industrial cultures) did not have a clear influence on the production of volatile compounds in miniature cheeses. According to principal component analysis, 19 out of 21 strains of L. lactis produced volatile profiles similar to the three pasteurized Chihuahua cheeses analyzed, but only 2 strains generated profiles similar to the commercial raw milk cheese. However, further research is required to understand the metabolic and genetic differences of these strains.

The antimicrobial properties of Mexican oregano (Lippia berlandieri Schauer) essential oil have been well documented; but its extraction process generates large amounts of agro-industrial wastes. This material can be used as support-substrate in solid-state fermentation, to release and/or accumulate molecules with industrial application. Therefore, the aim of this work was to evaluate the microbial effect of products derived from solid state fermentation of Mexican oregano waste by Aspergillus niger PSH. Microbial activity was tested by well diffusion test of aqueous and non-polar extracts from solid state fermentation, against fungi, foodborne pathogens and spoilage bacteria, as well as Lactic Acid Bacteria. Further, growth curves were done with Listeria monocytogenes and Lactobacillus lactis to describe the possible effect of extracts on bacterial growth. Polar and non-polar extracts from solid state fermentation had no deleterious effect against tested fungi and food-borne pathogenic bacteria (Escherichia coli O157:H7, Staphylococcus aureus, Salmonella enterica subgroup enterica subsp. Tiphymurium). Aqueous extract, at concentrations higher than 2.5 % had a bacteriostatic effect on L. monocytogenes. Lactic acid bacteria showed a growth increment in culture medium complemented with aqueous extracts, and this effect was confirmed by microbial growth curves. Non polar extracts had no antimicrobial effect. Aqueous extracts had a bacteriostatic effect in L. monocytogenes and promote the lactic acid bacteria growth; this extracts can be used as prebiotic or growth-enhancing supplement for lactic acid bacteria, but further research is needed.

Novel chalcone derivatives with different substituents attached to A and B-rings: hydroxyl, methoxyl, geranyl, and prenyl groups were synthesized. The obtained compounds were characterized by NMR, HRMS, UV-Vis, IR, and MS. The theoretical analysis was carried out in all the compounds using density functional theory (DFT) with the B3LYP, PBE0, and M06-2X functionals in combination with the 6-311G(d,p) Pople-type basis set. The excited state properties were calculated by time dependent density functional theory (TD-DFT) using the same methodology applied for the ground state properties. The calculated vertical absorption wavelengths (λmax) in gas phase and in ethanol as a solvent are consistent with the experimental ones, being the TD-DFT:B3LYP/6-311G(d,p) and PCM-TD-DFT:PBE0/6-311G(d,p) the best methodologies for these calculations with good approximation to the experimental values. The calculated reorganization energies indicated that, the four chalcone derivatives present an electron transfer character due to the smaller registered values. From these parameters it is proposed that these show an n-type semiconductor character. The localization of the frontier orbitals (HOMO and LUMO) shows that only the compound containing a hydroxyl group on the A-ring displays a marked delocalization favoring the charge-transfer process in this system. The HOMO-LUMO gap energies indicate that the inclusion of different donor groups in the rings does not improve the obtained values for this property.

The hydro distillation method was used in this study to get essential oils (EOs) from cumin (Cuminum cyminum L.), clove (Eugenia caryohyllata) and Elecampane (Inula helenium L.) and the co-hydro distillation method (addition of fatty acid ethyl esters as extraction cosolvents) to get functional extracts (EFs). The MIC (Minimum Inhibitory Concentration) and the MBC (Minimum Bactericidal Concentration) were determined on five pathogenic strains (Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, Yersinia enterocolitica, Campylobacter jejuni, Clostridium perfringens, Staphylococcus aureus and Toxoplasma Gondi). The results showed that essential oils of cumin and clove and their functional extracts are effective on concentrations from 500 mg/L to 750 mg/L. The essential oils with functional extracts were used on meat samples at three different concentrations: 750, 1,500 and 2,250 μL. The cumin essential oil produced a reduction of 3.78 log UFC/g with the application of 750 μL, the clove essential oil produced a reduction of 3.78 log UFC/g with the application of 2,250 μL and the cumin and clove functional extracts got a reduction of 3.6 log UFC/g. By chromatography, eugenol was identified in the clove oil, cuminaldehyde in the cumin oil and the isoalactolactones and alactolactones in the elecampane oil as main compounds on the chemical composition of the essential oils and functional extracts obtained.

Sol gel technique, using tetrametoxysilane (TMOS) as precursor, was evaluated as a method for immobilization of a xylanase-producing Aspergillus niger sp strain. Although alcohol released by the hydrolysis–condensation reaction of silicon alkoxides during sol gel formation usually has a potential denaturing activity for the entrapped biological material, Aspergillus niger cells were resistant to this condition, maintaining part of its microbial activity and xylanase production ability after the immobilization process. Optical microscopy showed a significant mycelia growth in the inner part of the support after incubation in liquid cultures; meanwhile, in shake flasks cultures, immobilized cells maintained 56% of glucose uptake and retained 24% of xylanase activity, compared to free cells after 168 h of incubation at 37 °C. Results suggested that even though this fungus was able to overcome solvent toxicity caused by the sol gel immobilization technique, diffusional limitations were the reason for low glucose consumption and the drop in the production of the enzymatic activity observed. In our knowledge, this study is the first in which the immobilization of an A. niger strain in sol gel material is reported, and from this work further study is underway to improve the characteristics of the gel material used for immobilization, as well as to increase the xylanase and other polysaccharase production by sol gel entrapped fungus.

Antimicrobial activity of fractions obtained from Mexican oregano (Lippia berlandieri Schauer) chloroform extract was tested by growth inhibition against Escherichia coli, Staphylococcus aureus and Bacillus cereus, and antioxidant capacity was tested by inhibition of linoleic acid oxidation. Fractions were obtained by differences in polarity or structure (phenolic and non-phenolic fraction). Gram-positive organisms were more susceptible to Mexican oregano extracts. Fraction 3 (by polarity) and phenolic fractions I, II, III, IV and V were the extracts with higher antimicrobial activity. The non-phenolic fraction had effect against B. cereus. Polarity fraction 5 and phenolic Fraction II had a high antioxidant capacity; a 0.08% concentration of fraction 5 had a similar effect as butylated hydroxytoluene at 0.01% concentration. Fractions of Mexican oregano with different polarity and functional groups had antioxidant and antimicrobial activity and can be used in a variety of applications.

Methyl tert-Butyl Ether (MTBE) has been used in gasoline as a substitute for lead-based additives, which have been demonstrated to be toxic. MTBE however, is persistent in soil and water, showing high affinity for water and low affinity for soil, and has become an important contaminant. Therefore, the aim of this work was to isolate and identify soil microorganisms capable of degrading MTBE. Two samples were taken from a gasoline-contaminated soil at a service station and 59 different bacterial strains were isolated by enrichment culture with three consecutive selective transfers. Biochemical and morphological characterization of the bacterial isolates classified them into the following groups: Bacillus, Rhodococcus, Micrococcus, Aureobacterium and Proteus. Twelve strains were selected for evaluation of MTBE biodegradation depending on visual growth and biomass production of the isolates in minimal salt broth. Six strains significantly reduced MTBE concentration (22–37%) compared to an abiotic control after 5 days of incubation. Although it has been considered that MTBE is degraded mainly by cometabolism, our results demonstrate that these microorganisms are able to reduce MTBE concentration when MTBE is the sole source of carbon.