Libor Červenka

Survival and inactivation of Arcobacter spp., a Current Status and Future Prospect

Arcobacter spp. has been isolated from food of animal origin (particularly meats) and from various kind of water. Despite its phylogenetically related neighbor Campylobacter, Arcobacter is regarded as an emerging foodborne pathogen. Since Arcobacter differs in its phenotypic characteristics, the physical and chemical treatments designed for elimination of campylobacters from food and environment needs to be verified. This review focuses on the occurrence, and mainly on susceptibility to various physical and chemical treatments for inactivation of Arcobacter spp. The existing studies have been critically discussed and new challenges were proposed for further studies.

Inhibitory Effects of Some Spice and Herb Extracts Against Arcobacter butzleri , A. cryaerophilus , and A. skirrowii

Seventeen spice and medicinal plant extracts (methanol and chloroform) were assayed for their antimicrobial activity against Arcobacter butzleri, A. cryaerophilus, and A. skirrowii. In general, all of the tested extracts were able, to a different extent, to inhibit the growth of the selected Arcobacter species. Cinnamon, bearberry, chamomile, sage and rosemary extracts showed strong antimicrobial activity toward arcobacter strains tested. Overall, the methanol extracts showed better activity than the chloroform extracts (P < 0.05); however, enhanced antibacterial activity of chloroform extracts of cinnamon and rosemary has been observed in comparison with their methanol counterparts. The inhibitory dose of the most active extracts (the diameter of zone of inhibition ≥ 20 mm) was determined using the disc-diffusion method as well.

Detection of aflatoxigenic fungi in feeds using the PCR method.

The possibility of using the polymerase chain reaction (PCR) to speed up and specify the detection of aflatoxigenic fungi isolated from feed was investigated. The method, applied to 2 genes encoding the biosynthesis of aflatoxins (apa-2 andver-1), was optimized on two collection cultures (Aspergillus flavus CCM F-108 andA. parasiticus CCM F-550). The specificity of the optimized PCR method was proved on collection cultures of different kinds of fungi. Fifty feed samples out of which 18 showed positive findings of aflatoxigenic fungi on anAspergillus Flavus and Parasiticus Agar (AFPA) medium were tested. Isolated strains ofAspergillus strains were verified using the PCR method; its reaction products were detected in 1% agarose gel by electrophoresis. The results almost exclusively matched those gained from the AFPA medium.

Voltammetric Determination of Tannic Acid in Beverages using Pencil Graphite Electrode

Vu D.L., Ertek B., Dilgin Y., Cervenka L. (2015): Voltammetric determination of tannic acid in beverages using pencil graphite electrode. Czech J. Food Sci., 33: 72-76. The pretreated pencil graphite electrode (Pre-PGE) prepared by a chronoamperometry technique was applied for the determination of tannic acid using anodic stripping differential pulse voltammetry. The currents obtained from voltammetry measurements at optimum conditions were linearly correlated with the concentration of tannic acid. Calibration curve was obtained for tannic acid in the concentration range of 5.0-500 × 10 -9 mol/l. The limit of detec - tion was found to be 1.5 × 10 -9 mol/l. The content of tannic acid in beverage samples determined with Pre-PGE was in good agreement with that obtained by the standard spectrophotometric method.

Antimicrobial effect of oxidized cellulose salts

Antimicrobial properties of oxidized cellulose and its salts in linters (-L) and microsphere (-M) form (OKCEL® H-L, OKCEL® Zn-M, OKCEL® ZnNa-L, OKCEL® ZnNa-M and OKCEL® Ag-L) were tested by a dilution method against a spectrum of microbial strains: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Bacillus licheniformis, Aspergillus niger, Penicillium chrysogenum, Rhizopus oryzae, Scopulariopsis brevicaulis, Candida albicans and Candida tropicalis. OKCEL® Ag-L exhibited antimicrobial activity in the range 0.1–3.5% w/v against all the bacteria and fungi involved in this study. Strong inhibition by OKCEL® ZnNa-M was observed for Staphylococcus epidermidis, Bacillus licheniformis, Rhizopus oryzae, Candida albicans and Candida tropicalis in the range 0.5–2.0% w/v. Antimicrobial effects of oxidized cellulose and its salts in textile form were investigated by a diffusion and dilution method against the spectrum of above-cited microbial strains extended by Clostridium perfringens. Generally, OKCEL® Ag-T, OKCEL® Zn-T and OKCEL® H-T showed high antimicrobial activity against populations of Pseudomonas aeruginosa, Bacillus licheniformis and Staphylococcus epidermidis. OKCEL® Zn-T was the only sample suppressing the growth of species.

The effect of acetic acid, citric acid, and trisodium citrate in combination with different levels of water activity on the growth ofArcobacter butzleri in culture

The influence of weak organic acids and trisodium citrate in combination with a high or a reduced water activity (aw) was investigated when a population ofArcobacter butzleri was exposed to a low concentration of acetic or citric acid, and trisodium citrate combined with high (0.993) and reduced (0.977)aw in culture broth at 30 °C. Regardless of water activity, acetic and citric acid (>0.2 %) inhibited the growth ofA. butzleri with no viable cells detected after 4–5 h of incubation. Enhanced survival was found at reducedaw with addition of acetic acid. In contrast, after exposure to citric acid in combination with reducedaw inactivation was more rapid than that after being exposed to high water activity. Incorporation of trisodium citrate in combination with reducedaw (0.977) would probably not confer any extra protection. Concentrations of organic acid widely used in meat decontamination processing represent feasible tools for reducingA. butzleri contamination and hence the risk ofArcobacter infection.

Persistence of Arcobacter butzleri CCUG 30484 on plastic, stainless steel and glass surfaces

The persistence of A. butzleri CCUG 30484 on various surfaces under 32% and 64% relative humidity suspended in physiological saline or nutrient broth to simulate relatively clean or soiled conditions was studied using various isolation techniques. Our study revealed that A. butzleri CCUG 30484 cells were able to survive for a considerable period of time, even after the droplet of suspending medium has been visibly dried. An extended survival on polypropylene coupons at both humidity levels was observed, particularly at soiled conditions.

Inhibition of Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii by plant oil aromatics.

The inhibitory effect of some plant oil aromatics against three strains of Arcobacter butzleri, two strains of Arcobacter cryaerophilus, and one strain of Arcobacter skirrowii was evaluated. When MICs were determined using the broth macrodilution method, cinnamaldehyde was most inhibitory followed by thymol, carvacrol, caffeic acid, tannic acid, and eugenol (P < 0.001). Sublethal concentrations of the three most potent plant oil aromatics also were examined. Overall, cinnamaldehyde was the most bacteriostatic against all arcobacters tested except A. butzleri when these strains were exposed to the MIC25 of this aromatic aldehyde. The bacteriostatic activities of thymol and carvacrol were concentration and species dependent.

Moisture sorption isotherms and glass transition temperature of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) roots at 25°C

Sorption isotherms of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) root samples were obtained at 25 °C. Elecampe exhibited hysteresis loop in the range of 0.35–0.90 aw, whereas burdock roots showed significant differences between adsorption and desorption isotherms from 0.65 to 0.80 aw. Blahovec–Yanniotis was considered to give the best fit over the whole range of aw tested. Various parameters describing the properties of sorbed water derived from GAB, Henderson and Blahovec–Yanniotis models have been discussed. Differential scanning calorimetric method was used to measure the glass transition temperature (Tg) of root samples in relation to water activity. The safe moisture content was determined in 12.01 and 14.96 g/100 g d. b. for burdock and elecampe root samples at 25 °C, respectively. Combining the Tg line with sorption isotherm in one plot, it was found that the glass transition temperature concept overestimated the temperature stability for both root samples.

Is air-drying of plant-based food at low temperature really favorable? A meta-analytical approach to ascorbic acid, total phenolic and total flavonoid contents

ABSTRACT The aim of this work was to review the studies that evaluated the effect of drying temperature on the content of ascorbic acid (AA), total phenolic (TPC), and total flavonoid contents (TFC) in fruits and vegetables, and quantify whether drying at 40 °C is more favorable than at higher temperatures. For the purpose of this study, AA, TPC, and TFC values for 40 °C were compared with those obtained at 50 °C, 60 °C, and 70–80 °C. A meta-analysis was performed using the weighted response ratio calculated for each experiment. Despite the fact that other variables significantly influenced the nutrient content in individual experiments, the meta-analysis provided a general view on the effect of air-drying temperature on the quality of plant-based food products from outcomes of various studies.