Antimutagenic activity of natural phenolic compounds present in the common bean ( Phaseolus vulgaris ) against aflatoxin B 1

Polyphenols with antimutagenic and anticarcinogenic properties are present in fruits, vegetables and legumes. In this study, the Salmonella typhimurium tester strains TA98 and TA100 were used in the microsuspension assay to examine the antimutagenic effect of phenolic compounds extracted from the common bean (Phaseolus vulgaris) against mutagenicity induced by aflatoxin B 1 (AFB 1 ). A dose-response curve was constructed for AFB 1 ; from which a level of 40ng AFB 1 /tube was selected for all antimutagenicity assays. The AFB 1 and phenolic extract (PE) were not toxic to the bacteria at concentrations tested. In the case of PE, results were similar to the number of spontaneous revertants for TA98 and TA100. The inhibitory effect of PE against AFB 1 mutagenicity was dose-dependent at the lower concentrations tested (2.5, 5, 10, 12.5, 15 and 25 μg-equivalent ( + )-catechin/tube for TA98; 0.5, 1, 1.5, 2.5, 5, 10 and 25 μg-equivalent ( + )-catechin/ tube for TA100). Further, a two-stage incubation procedure was used to investigate the potential interaction between PE and AFB 1 . The greatest inhibitory effect of the PE on AFB 1 mutagenicity occurred when PE and AFB 1 were incubated together. When the bacteria were first incubated with PE followed by a second incubation with AFB 1 , lower inhibition was observed. Lower inhibition was also observed when the bacteria were first incubated with AFB 1 followed by a second incubation with PE. The results suggest that the mechanism of inhibition could involve the formation of a chemical complex between of PE and AFB 1 .     

Optimization of nanocapsules preparation by the emulsion-diffusion method for food applications

The aim of this work was to establish the conditions to obtain polymeric nanocapsules containing food ingredients by the emulsification-diffusion method. The Response Surface Methodology was used to optimize the process. The variables studied were shear rate (3070-18,920 s⁻¹), polymer-wall concentration: poly-?-caprolactone (PCL, 100-300 mg), and stabilizer concentration: polyvinyl alcohol (PVAL, 25-100 g/L). The analyzed responses were particle size (PS), polydispersion index (PDI), density (ρ_nc), and zeta potential (ζ). The results of ρ_nc and micrographs confirmed the presence of capsular structures. The most efficient conditions to obtain nanocapsules were 10,917 s⁻¹, 50 g/L of PVAL and 256 mg of PCL, predicting a response of PS = 250 nm, ρ_nc = 1.021 g/cm³, PDI = 0.045, and ζ = −20.02. It was concluded that keeping the same preparation conditions, the formation of nanocapsules is also possible from other food oily materials with similar characteristics (predicting values PS ≈ 300 nm and ζ ≈ −25). The proposed nanocapsules may have application in food preservation and storage.     

Modeling of Enzymatic Hydrolysis of Whey Proteins

The aim of this work was to emphasize the limitations of modeling complex phenomena under unrealistic model assumptions. As a case study, the whey protein hydrolysis mechanism was modeled. A stirred batch reactor was used to study the degree of hydrolysis of sweet whey protein concentrate by using the protease alcalase. A completely random two-factorial experimental design was used, three levels of initial enzyme concentrations (E ₀) (1.58, 3.18, 6.36 AU (Anson units)/L) times three levels of initial substrate concentrations (S ₀) (18.73, 38.45, 81.16 g/L). All treatments were carried out at optimal alcalase—activity conditions: pH 8 and 50 °C. Reactions were monitored for 180 min. The degree of hydrolysis (h) curves was finally adjusted for each treatment to the exponential model using nonlinear regression techniques but not assuming a Michaelis–Menten relationship. From the estimation process, the coefficient b was constant (27.26 ± 1.37) and independent of E ₀ and S ₀, while coefficient a depended directly on the ratio E ₀/S ₀, ranging from 0.0017 to 0.0497. A noncritical strategy of forward modeling based on unrealistic assumptions was misleading in the face of complex phenomena; instead, a modeling strategy moving from data to the identification and estimation of parameters of practical interest must be considered.     

Quality parameters and antioxidant and antibacterial properties of some Mexican honeys

A total of 14 Mexican honeys were screened for quality parameters including color, moisture, proline, and acidity. Antioxidant properties of complete honey and its methanolic extracts were evaluated by the DPPH, ABTS, and FRAP assays. In addition, the antimicrobial activity of complete honeys against Bacillus cereus ATCC 10876, Listeria monocytogenes Scott A, Salmonella Typhimurium ATCC 14028, and Sthapylococcus aureus ATCC 6538 was determined. Most of honeys analyzed showed values within quality parameters established by the Codex Alimentarius Commission in 2001. Eucalyptus flower honey and orange blossom honey showed the highest phenolic contents and antioxidant capacity. Bell flower, orange blossom, and eucalyptus flower honeys inhibited the growth of the 4 evaluated microorganisms. The remaining honeys affected at least 1 of the estimated growth parameters (increased lag phase, decreased growth rate, and/or maximum population density). Microorganism sensitivity to the antimicrobial activity of honeys followed the order B. cereus > L. monocytogenes > Salmonella Typhimurium > S. aureus. The monofloral honey samples from orange blossoms, and eucalyptus flowers demonstrated to be good sources of antioxidant and antimicrobial compounds. All the Mexican honey samples examined proved to be good sources of antioxidants and antimicrobial agents that might serve to maintain health and protect against several diseases. PRACTICAL APPLICATION: The results of the study showed that Mexican honeys display good quality parameters and antioxidant and antimicrobial activities. Mexican honey can be used as an additive in the food industry to increase the nutraceutical value of products.     

Characterization of a Panela cheese with added probiotics and fava bean starch

Of 20 Lactobacillus and 8 Bifidobacterium species examined, only Bifidobacterium breve ATCC 15700 was able to ferment starch from fava beans. Bifidobacterium breve ATCC 15700 and Lactobacillus rhamnosus GG ATCC 53103 were selected as probiotics for use in fresh-style Panela cheese. Two types of fresh cheese (with and without 3% fava bean starch) were manufactured with 3 combinations of probiotics: L. rhamnosus GG only, B. breve only, or both L. rhamnosus GG and B. breve. During 4 wk of storage at 4°C, the addition of fava bean starch to the cheese was not found to cause significant differences in the viability of either probiotic strain. However, the microstructure and texture of Panela cheese were altered, resulting in a much softer product. A sensory panel showed that the presence of added fava bean starch in Panela cheese was less desirable to consumers, whereas probiotic supplementation had no effect on perceived taste or appearance. Panela cheese could be a suitable food for inclusion of probiotic bacteria.     

Physicochemical Characterization of Extruded Blends of Corn Starch�CWhey Protein Concentrate�CAgave tequilana Fiber

The objective of this work was to prepare extruded blends of corn starch supplemented with whey protein concentrate and Agave tequilana fiber (AF). The extruded blends were prepared by blending whey protein concentrate (WPC 80, 25%) with a mixture of corn starch (60%, 67%, and 74%) and A. tequilana fiber (1%, 8%, and 15%) and then adjusting its pH (5 and 8). The extrusion process was performed using a laboratory single-screw extruder. The screw compression ratio was 2:1 with a 5.0-mm die nozzle. Barrel temperature in the final zone was 140 °C. Small differences in expansion index and bulk density values were found between extruded samples with or without fiber addition, while the samples extruded at pH 5 showed the lowest penetration force. Alkaline pH and high fiber content resulted in the highest total and insoluble dietary fiber. The addition of fiber to the extruded formulations decreased lightness, greenness (−a), and total color (ΔE). AF incorporation increased water absorption index in all the assays, but these values were not significantly different. In vitro digestibility values varied between 83% and 90%, and the addition of AF in different levels did not change these values. The inclusion of AF into extruded blends of whey protein and corn starch reduced peak, minimum, and final viscosity but increased the extent of gelatinization when highest levels of AF were added in the blends. Extruded samples showed good functional characteristics with improved health benefits (more fiber and protein content) due to whey protein and fiber addition to starch.     

Hibiscus sabdariffa L. extracts inhibit the mutagenicity in microsuspension assay and the proliferation of HeLa cells

ABSTRACT:  Hibiscus sabdariffa L. is used as a refreshing beverage and as a traditional medicine. The objective of this study was to determine the in vitro effect of phenolic compounds present in aqueous, ethyl acetate, and chloroform extracts of H. sabdariffa against mutagenicity of 1-nitropyrene (1-NP), and also the antiproliferative effect of these extracts. Inhibition of cell proliferation and DNA fragmentation were tested on transformed human HeLa cells. The hot aqueous extract (HAE) contained 22.27 ± 2.52 mg of protocatechuic acid (PCA) per gram of lyophilized dried extract, and was not statistically different from the cold aqueous or chloroform extracts; the ethyl acetate extract produced the least amount of PCA. The H. sabdariffa extracts inhibited mutagenicity of 1-NP in a dose-response manner. The inhibition rate on HeLa cells of HAE was also dose-dependent. The HAE did not induce DNA fragmentation. The results suggest that H. sabdariffa L. extracts have antimutagenic activity against 1-NP and decrease the proliferation of HeLa cells, probably due to phenolic acid composition.     

Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes by underwater shock waves

Underwater shock waves are pressure discontinuities generated by means of high voltage electric discharges in water. Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes were exposed to shock waves. The influence of the pulse of light produced by the electric discharge, acoustic cavitation produced by the shock waves, the phase of growth and shock wave dosage on bacteria inactivation was evaluated. Inactivation of bacteria by shock waves ranged from 0 to 3.18 log₁₀ CFU/ml. L. monocytogenes was the most susceptible microorganism, 3.17 log₁₀ CFU/ml inactivation was achieved with 350 shock waves. At the same shock wave dosage, 1.68 log₁₀ CFU/ml and 0.56 log₁₀ CFU/ml inactivation was achieved for S. Typhimurium and E. coli O157:H7, respectively. Even if the achieved inactivation still is of little practical value, higher shock wave energy may enhance bactericidal activity. The analysis of variance revealed that synergy between light and the other factors contributed to bacterial inactivation. Differences in the response of bacteria, along with data analysis, suggest different mechanisms of inactivation by shock waves.Industrial relevance: Underwater shock waves generated via high voltage electric discharge or the use of explosives have been reported for microbial inactivation and for softening of animal tissue. The current paper deals with the interaction of underwater shock waves, the associated cavitation and pulse of light generated in the UV and visible spectra. Although the data generated don't show spectacular microbial inactivation, systematic studies like this can lead to the development of new combination processes with specific applications (e.g., microbial inactivation within containers).