Raúl Avila-Sosa

Antifungal activity by vapor contact of essential oils added to amaranth, chitosan, or starch edible films

Antimicrobial agents can be incorporated into edible films to provide microbiological stability, since films can be used as carriers of a variety of additives to extend product shelf life and reduce the risk of microbial growth on food surfaces. Addition of antimicrobial agents to edible films offers advantages such as the use of small antimicrobial concentrations and low diffusion rates. The aim of this study was to evaluate inhibition by vapor contact of Aspergillus niger and Penicillium digitatum by selected concentrations of Mexican oregano (Lippia berlandieri Schauer), cinnamon (Cinnamomum verum) or lemongrass (Cymbopogon citratus) essential oils (EOs) added to amaranth, chitosan, or starch edible films. Essential oils were characterized by gas chromatography-mass spectrometry (GC/MS) analysis. Amaranth, chitosan and starch edible films were formulated with essential oil concentrations of 0.00, 0.25, 0.50, 0.75, 1.00, 2.00, or 4.00%. Antifungal activity was evaluated by determining the mold radial growth on agar media inoculated with A. niger and P. digitatum after exposure to vapors arising from essential oils added to amaranth, chitosan or starch films using the inverted lid technique. The modified Gompertz model adequately described mold growth curves (mean coefficient of determination 0.991 ± 0.05). Chitosan films exhibited better antifungal effectiveness (inhibition of A. niger with 0.25% of Mexican oregano and cinnamon EO; inhibition of P. digitatum with 0.50% EOs) than amaranth films (2.00 and 4.00% of cinnamon and Mexican oregano EO were needed to inhibit the studied molds, respectively). For chitosan and amaranth films a significant increase (p<0.05) of lag phase was observed among film concentrations while a significant decrease (p<0.05) of maximum specific growth was determined. Chitosan edible films incorporating Mexican oregano or cinnamon essential oil could improve the quality of foods by the action of the volatile compounds on surface growth of molds.

Fungal Inactivation by Mexican Oregano (Lippia berlandieri Schauer) Essential Oil Added to Amaranth, Chitosan, or Starch Edible Films

Edible films can incorporate antimicrobial agents to provide microbiological stability, since they can be used as carriers of a wide number of additives that can extend product shelf life and reduce the risk of pathogenic bacteria growth on food surfaces. Addition of antimicrobial agents to edible films offers advantages such as the use of low antimicrobial concentrations and low diffusion rates. The aim of this study was to evaluate inhibition of Aspergillus niger and Penicillium spp. by selected concentrations of Mexican oregano (Lippia berlandieri Schauer) essential oil added to amaranth, chitosan, or starch edible films. Oregano essential oil was characterized by gas chromatography-mass spectrometry (GC/MS) analysis. Amaranth, chitosan, and starch edible films were formulated with essential oil concentrations of 0%, 0.25%, 0.50%, 0.75%, 1%, 2%, and 4%. Mold radial growth was evaluated inoculating spores in 2 ways: edible films were placed over inoculated agar, Film/Inoculum mode (F/I), or the edible films were first placed in the agar and then films were inoculated, Inoculum/Film mode (I/F). The modified Gompertz model adequately described growth curves. There was no significant difference (P > 0.05) in growth parameters between the 2 modes of inoculation. Antifungal effectiveness of edible films was starch > chitosan > amaranth. In starch edible films, both studied molds were inhibited with 0.50% of essential oil. Edible films added with Mexican oregano essential oil could improve the quality of foods by controlling surface growth of molds.

Ultraviolet-C light effect on physicochemical, bioactive, microbiological, and sensorial characteristics of carrot (Daucus carota) beverages

The aim of this research was to evaluate the effect of ultraviolet-C light on physicochemical, bioactive, microbial, and sensory characteristics of carrot beverages. Beverages were formulated with different concentrations of carrot juice (60, 80, and 100% [v/v]) and treated with ultraviolet-C light at different flow rates (0, 0.5, 3.9, and 7.9 mL s−1) and times (5, 10, 15, 20, and 30 min), equivalent to ultraviolet-C dosages of 13.2, 26.4, 39.6, 52.8, and 79.2 J cm−2. Total soluble solids, pH, and titratable acidity were not affected by the ultraviolet-C light treatment. Ultraviolet-C light significantly affected (p < 0.05) color parameters of pure juice; however, at low concentration of juice, total color change was slightly affected (ΔE = 2.0 ± 0.7). Phenolic compounds (4.1 ± 0.1, 5.2 ± 0.2, and 8.6 ± 0.3 mg of GAE 100 mL−1 of beverage with 60, 80, and 100% of juice, respectively) and antioxidant capacity (6.1 ± 0.4, 8.5 ± 0.4, and 9.4 ± 0.3 mg of Trolox 100 mL−1 of beverage with 60, 80, and 100% of juice, respectively) of carrot beverages were not affected by ultraviolet-C light treatment. Microbial kinetics showed that mesophiles were mostly reduced at high flow rates in carrot beverages with 60% of juice. Maximum logarithmic reductions for mesophiles and total coliforms were 3.2 ± 0.1 and 2.6 ± 0.1, respectively, after 30 min of ultraviolet-C light processing. Beverages were well accepted (6–7) by judges who did not perceive the difference between untreated and Ultraviolet-C light treated beverages.

Essential Oils Added to Edible Films

Edible films are defined as continuous matrices that can be formed by proteins, polysaccharides, and/or lipids. Furthermore, they have the potential to support the quality of a food after the package is opened, protecting it from changes in moisture, exchange of oxygen, and loss of color, flavor, and texture. Edible films have the possibility to incorporate essential oils and provide microbiological stability to the food as they can be used as carriers of a wide number of additives, which can extend the product shelf-life and reduce the growth risk of pathogenic bacteria and spoilage flora on food surfaces. The aim of this chapter is to describe and discuss the scientific basis of edible film formation and several applications that have been developed due to the addition of different essential oils to edible films.

Growth modeling to control ( in vitro ) Fusarium verticillioides and Rhizopus stolonifer with thymol and carvacrol

The aim of this study was to evaluate the antifungal activity (in vitro) of thymol and carvacrol alone or in mixtures against Fusarium verticillioides and Rhizopus stolonifer, and to obtain primary growth models. Minimal inhibitory concentration (MIC) was evaluated with fungal radial growth with thymol or carvacrol concentrations (0-1600mg/l). Mixtures were evaluated using concentrations below MIC values. Radial growth curves were described by the modified Gompertz equation. MIC values of carvacrol were 200mg/l for both fungi. Meanwhile, MIC values of thymol were between 500 and 400mg/l for F. verticillioides and R. stolonifer, respectively. A synergistic effect below MIC concentrations for carvacrol (100mg/l) and thymol (100-375mg/l) was observed. Significant differences (p<0.05) between the Gompertz parameters for the antimicrobial concentrations and their tested mixtures established an inverse relationship between antimicrobial concentration and mycelial development of both fungi. Modified Gompertz parameters can be useful to determine fungistatic concentrations.

Chapter 47 – Combinational Approaches for Antimicrobial Packaging: Chitosan and Oregano Oil

Abstract The aim of this chapter is to present recent advances regarding chitosan and oregano essential oil as well as approaches of their combination for antimicrobial packaging. Materials currently utilized for the manufacture of food packaging can be replaced by biopolymers (including chitosan) because some of their properties are similar to those of synthetic polymers. Furthermore, there could be mixtures of different biopolymers or mixtures thereof with synthetic polymers; selection of mixtures depends on needed application and type of food product to be packaged. Barrier properties (water vapor, oxygen, and carbon dioxide permeability) and mechanical properties (tensile strength and elongation) will determine the feasibility of formed films to meet desired functionality for the product to be packed. Chitosan is, after cellulose, one of the most abundant biopolymers in nature, with antimicrobial, antioxidant, and antiviral properties. When combined with oregano essential oil that has antimicrobial and antioxidant activities, it may produce effective edible films and packaging materials.

Modelización de la inactivación termosónica de Staphylococcus aureus, un enfoque multifactorial Modeling Staphylococcus aureus thermosonic inactivaction, a multi-target approach

In recent years different emerging technologies have been evaluated such as ultrasound, which is usually combined with other preservation factors in order to increase microbial inactivation. Staphylococcus aureus inactivation was performed by simultaneous application of heat (40, 50, or 60 °C) and low frequency ultrasound (20 kHz) at selected wave amplitudes (60, 75, or 90 µm) in culture broth (a w 0.96, and pH 3.5) with different concentrations of vanillin (200, 350, or 500 mg/kg). Death curves were fitted with the Fermi model. A synergic effect was observed when temperature is near to 40 °C at different ultrasonic amplitude waves and vanillin concentrations. Several studied combinations of ultrasound, temperature, and vanillin concentration could be applied in the food industry. En los últimos años se han evaluado diversas tecnologías emergentes como el ultrasonido, el cual es combinado con otros factores de conservación para aumentar su eficacia para la inactivación microbiana. La inactivación de Staphylococcus aureus, se llevó a cabo aplicando simultáneamente temperatura (40, 50 o 60 °C), ultrasonido de baja frecuencia (20 kHz) con diferentes amplitudes de onda (60, 75 o 90 µm), y diferentes concentraciones de vainillina (200, 350 o 500 mg/kg) como antimicrobiano, en medios de cultivo con a w 0,96 y pH 3,5. Se modelaron las curvas de muerte con el modelo de Fermi. Se encontró un efecto sinérgico de los factores estudiados, especialmente a temperaturas cercanas a 40 °C con diferentes amplitudes de onda ultrasónicas y concentraciones de vainillina. Los resultados obtenidos demuestran que varias de las combinaciones estudiadas podrían tener aplicación en la industria de alimentos.

Effect of pH and Mexican Oregano (Lippia berlandieri Schauer) Essential Oil Added to Carboxymethyl Cellulose and Starch Edible Films on Listeria monocytogenes and Staphylococcus aureus

The aim of this work was to evaluate the effect of pH and Mexican oregano essential oil (MOEO) added to carboxymethyl cellulose (CMC) and starch (S) edible films on Listeria monocytogenes and Staphylococcus aureus. CMC and S edible films were formulated with different concentrations (0%, 0.25%, 0.50%, 0.75%, and 1%) of MOEO at different pH (5, 6, or 7). Antimicrobial assay was performed. Inhibition curves were fitted to the Fermi model. Significant differences ( ) were found in tc (time to reduce 50% of microbial population) and (slope of the curve around ), being lower at acidic pH. For L. monocytogenes, CMC films exhibited a higher antimicrobial effectiveness (0.50% of MOEO) compared to S films which need a higher concentration of MOEO (0.75%). S. aureus was inhibited with CMC films at 0.50% MOEO and pH 5 and 6. Microbial modeling has allowed estimating key intrinsic factors as pH and MOEO concentration with the synergistic effect against two important food-borne pathogens.

Preparation and Characterization of Proteinaceous Films from Seven Mexican Common Beans (Phaseolus vulgaris L.)

Bean protein concentrate (BPC) as a protein source from seven varieties of Mexican common beans (alubia, flor de mayo, garbancillo, peruano, pinto, mantequilla, and negro) was utilized for formulating edible films (EF). EF were prepared with BPC (3% w/w) and glycerol as a plasticizer by the casting method; their thickness, water content, soluble matter, protein solubility, color, puncture strength, elongation, water vapor permeability (WVP), and chemical properties (Fourier transform infrared, FTIR, and spectroscopy) were evaluated. Tested EF had an average thickness of  mm. Good stability was observed since the studied polymers did not exceed 35% of the total soluble matter while protein solubilities were not greater than 3%. EF made from peruano bean protein presented a lower value of total matter solubility (%) than the other tested EF. A low value of WVP ( g m/Pa s m2) was observed in films from negro bean protein, while EF from flor de mayo bean protein exhibited the highest values of puncture strength ( MPa) and elongation (%). Most bean protein EF had reddish or brownish color; however, films from alubia and peruano bean proteins displayed light yellowish colors. FTIR spectra of EF revealed that glycerol did not react with the studied bean proteins through covalent bonds.

Modeling the Inhibition of Vibrio cholerae Non-01 in Trypticase Soy Broth by Chitosan of Low and High Molecular Weight

Chitosan has proved to have antimicrobial properties, which can be used to protect seafood from contamination and growth of pathogens such as Vibrio cholerae. The aim of this study was to model the inhibition of Vibrio cholerae Non-01 by low and high molecular weight chitosan. Chitosan of low (LMWC) and high (HMWC) molecular weight (15 and 32 KDa respectively) was used at final concentrations of 600 and 1,000 mg/L and antimicrobial assays were carried out at temperatures of 5 and 35°C. Data were fitted to the Weibull distribution and b and n values were used to plot resistance frequency curves. Inhibition curves showed that the four treatments were effective at 5oC, with 5.5 log reduction after 312 h with the highest chitosan concentration tested, while the effect of the 600 mg/L chitosan concentration was bacteriostatic rather than bactericidal (3.5 log reduction at 388 h). The 1,000 mg/L chitosan concentration was bactericidal at 35°C (6 log reduction) at a shorter time (12 h). No differences were observed by the different molecular weight of the chitosan used. Weibull model fit adequately (R2>0.8908) with experimental data, the highest cellular damage occurs significantly (p<0.05) with high chitosan concentrations regardless of molecular weight and treatment temperature. Resistance frequency plots showed a greater resistance of LMWC, with the maximum values of V. cholerae Non-01 resistance presented in the first minutes of the treatments regardless of the temperature.