Application of Predictive Inactivation Models to Evaluate Survival ofStaphylococcus aureusin Fresh-Cut Apples Treated with Different Plant Hydrosols

A Novel Edible Coating Produced from a Wheat Gluten, Pistacia vera L. Resin, and Essential Oil Blend: Antimicrobial Effects and Sensory Properties on Chicken Breast Fillets

Antimicrobial edible coatings can eliminate the risk of pathogen contamination on the surface of poultry products during storage. In this study, an edible coating (EC) based on wheat gluten, Pistacia vera L. tree resin (PVR), and the essential oil (EO) of PVR was applied on chicken breast fillets (CBF) by a dipping method to prevent the growth of Salmonella Typhimurium and Listeria monocytogenes. The samples were packed in foam trays wrapped with low-density polyethylene stretch film and stored at 8 °C for 12 days to observe the antimicrobial effects and sensory properties. The total bacteria count (TBC), L. monocytogenes, and S. Typhimurium were recorded during storage. The samples coated with EC, containing 0.5, 1, 1.5, and 2% v/v EO (ECEO), showed significant decreases in microbial growth compared to the control samples. The growth of TBC, L. monocytogenes, and S. Typhimurium was suppressed by 4.6, 3.2, and 1.6 logs, respectively, at the end of 12 days on the samples coated with ECEO (2%) compared to the uncoated controls (p < 0.05). Coating with ECEO (2%) also preserved the appearance, smell, and general acceptance parameters better than uncoated raw chicken (p < 0.05) on the fifth day of storage. In grilled chicken samples, ECEO (2%) did not significantly change the appearance, smell, and texture (p > 0.05) but increased the taste and general acceptance scores. Therefore, ECEO (2%) can be a feasible and reliable alternative to preserve CBFs without adversely affecting their sensory properties.

Antibacterial Potential of Microwave-Assisted Extraction Prepared Hydrolates from Different Salvia Species

Salvia is a widely used herb that also contains essential oils and other valuable compounds. In this work, the hydrolates of five Salvia sp. were evaluated for their potential antimicrobial and antioxidant activity against four bacterial strains. The hydrolates were obtained from fresh leaves by microwave-assisted extraction. Chemical composition analysis by gas chromatography and mass spectrometry revealed that their major constituents were isopulegol (38.2-57.1%), 1,8-cineole (4.7-19.6%), and thujone (5.6-14.1%). The minimum inhibitory concentration (MIC) of the plant hydrolates was tested by the microdilution method at concentrations ranging from 1.0 to 512 μg/mL. The hydrolates prepared from Salvia officinalis and S. sclarea showed inhibitory activity on the tested Gram-positive and Gram-negative bacteria, taxon Salvia nemorosa showed inhibitory activity only partially. The hydrolate of S. divinorum had practically no antibacterial effect. Enterobacter asburiae was the only bacterium for which we found sensitivity to the hydrolate of S. aethiopis, with a MIC50 value of 216.59 µL/mL. The antioxidant activity of the hydrolates was low, ranging from 6.4 to 23.3%. Therefore, salvia hydrolates could be used as antimicrobial agents in medicine, cosmetics, and food preservation.

Application of mathematical models for bacterial inactivation curves using Hypericin-based photosensitization

AIMS

The aim of this study was to evaluate which of the three mathematical models (Weibull, Geeraerd and Logistic) makes the best approximation for Hypericin-based photosensitization bacterial inactivation.

METHODS AND RESULTS

The inactivation of common food-borne pathogens Listeria monocytogenes and Bacillus cereus has been analysed. Three models, Weibull, Logistic and Geeraerd, have been used for different treatment conditions (10(-7 ) mol l(-1) and 10(-8)  mol l(-1) Hypericin concentrations and 2 and 60 min incubation time). The Logistic method showed better correspondence (estimated R(2)  ≥ 0·98, RMSE ≤ 0·41), than the Weibull (estimated R(2)  ≥ 0·91, RMSE ≤ 0·90) and the Geeraerd model (R(2)  ≥ 0·83, RMSE ≤ 1·27). After evaluation of best fitting model for the dependence of bacterial population reduction on irradiation time, the parameters describing treatment efficiency have been calculated.

CONCLUSIONS

Our results indicate that the Logistic model described in the best way the inactivation of B. cereus and L. monocytogenes by Hypericin-based photosensitization.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study identified a best model for describing bacterial inactivation by hypericin-based photosensitization, which provides a way to evaluate the efficacy of different treatment conditions for this novel decontamination technique.

Enantioselective GC-MS analysis of volatile components from rosemary (Rosmarinus officinalis L.) essential oils and hydrosols

Essential oils and hydrosols were extracted from rosemary harvested in different seasons, and the chemical compositions of volatile components in the two fractions were analyzed by gas chromatography-mass spectrometry (GC-MS). Enantiomers of some volatile components were also analyzed by enantioselective GC-MS. Classification of aroma components based on chemical groups revealed that essential oils contained high levels of monoterpene hydrocarbons but hydrosols did not. Furthermore, the enantiomeric ratios within some volatile components were different from each other; for example, only the (S)-form was observed for limonene and the (R)-form was dominant for verbenone. These indicate the importance of determining the enantiomer composition of volatile components for investigating the physiological and psychological effects on humans. Overall, enantiomeric ratios were determined by volatile components, with no difference between essential oils and hydrosols or between seasons.