Effect of Atmospheric Pressure Plasma on Listeria monocytogenes Attached to Abiotic Surfaces.

Listeria monocytogenes can be introduced into food processing plants via raw material of animal or plant origin and can establish endemic populations through formation of biofilms. Biofilms are a continuous source of contamination for food products, and L. monocytogenes cells in biofilms are more resistant to stress and sanitizing agents than are planktonic cells. The use of gas-discharge plasmas may offer a feasible alternative to conventional sanitization methods. Plasmas are a mixture of charged particles, chemically reactive species, and UV radiation and can be used to destroy microorganisms. The purpose of this study was to measure the effectiveness of cold atmospheric pressure plasma (APP) treatments against bacteria attached to a solid surface and to evaluate the individual susceptibility of various L. monocytogenes strains. Attention was focused on the state of the cells after treatment, combining detection by viable counts and quantitative PCR (qPCR). Most of the culturable cells were inactivated after APP treatment, but the qPCR assay targeting the 16S rRNA revealed the presence of injured cells or their entrance into the viable but nonculturable state. These results were at least partly confirmed by a resuscitation experiment. After APP treatment, L. monocytogenes cell suspensions were incubated in brain heart infusion broth; some cells grew in the medium and therefore had survived the treatment. An understanding of the effects of APP on L. monocytogenes can inform the development of sanitation programs incorporating APP for pathogen removal. Methods other than those based of the culturability of the cells should be used to monitor pathogens in food processing plants because cultivation alone may underestimate the actual microbial load.

Chemical modifications of Tonda Gentile Trilobata hazelnut and derived processing products under different infrared and hot-air roasting conditions: a combined analytical study.

BACKGROUND: For the processing industry, it is crucial to know what effect the roasting process and conditions have on hazelnut quality. The present study investigates, for the first time, the effects of hot-air and infrared (IR) roasting at different time-temperature combinations on Tonda Gentile Trilobata hazelnut: whole kernels and derived processing products (paste and oil). RESULTS: The nutritional and physical characteristics of hazelnuts and processing products were investigated to determine the influence of the different roasting conditions as a function of intended use. The antioxidant profile (2.2-diphenyl-1-picrylhydrazyl radical, oxygen radical absorbance capacity and total phenolic content) were analyzed on roasted hazelnut and paste extracts. For a comprehensive understanding of the complex biochemical phenomena occurring during roasting, E-nose and near-IR spectroscopy were also applied. All analytical data were processed using univariate and multivariate data analyses. Hazelnuts derived from IR roasting at higher temperatures (195 °C) showed a richer antioxidant profile and a more intense flavour. On the other hand, the yield associated with the oil extraction under the same conditions was unsatisfactory, making this process completely inadequate for oil production. Oil obtained by hot-air roasting and IR roasting at lower temperature (135 °C) was found to be of good quality, showing rather similar acidity grade, peroxide number and acidic composition. In particular, a slightly but significantly lower acidity was related to lower roasting temperatures (0.21-0.22% versus 0.27% for higher temperatures). All roasting conditions tested allowed the quantitative homogeneous hazelnut paste to be obtained and, from a rheological point of view, a higher roasting temperatures resulted in pastes characterized by higher density and viscosity values. CONCLUSION: The use of IR was found to be a promising alternative method for hazelnut roasting, as a result of its capability with respect to preserving nutritional values and enhancing organoleptic quality. © 2018 Society of Chemical Industry.

Potentially active spoilage bacteria community during the storage of vacuum packaged beefsteaks treated with aqueous ozone and electrolyzed water.

The microbial contamination that occurs during the slaughtering process and during handling of the meat results in a shortening of the shelf-life of meat. In this study, which has had the aim of extending the shelf life of beefsteaks, pilot-scale treatments were carried out with aqueous ozone (AO) and electrolyzed water (EW) before vacuum packaging (VP). The development of the potentially active microbiota and the associated volatilome were followed over 15days of storage under refrigerated conditions (4°C), in order to define the potential long-term effects of the treatments and storage condition on microbiota. The targeted RNA-based amplicon sequencing identified Pseudomonas fragi as the most frequent species before and after the treatments with AO and EW, as well as in the untreated control. The tested treatments did not reduce the overall presence of this species, but they affected the intra-species distribution of its oligotypes, albeit slightly. With the progression of the refrigerated storage and the reduction of the oxygen availability, Lactobacillus sakei, Leuconostoc gasicomitatum and Lactococcus piscium became the dominant, potentially active, beef microbiota, as confirmed by microbiological data. When the OTU abundances and volatilome were coupled, a significant association was observed between the organic acids, esters and aldehydes and these lactic acid bacteria species. In spite of the limited effectiveness of the treatments over the short and long term, this study has provided a detailed view of beef spoilage using RNA as the sequencing target, strengthening and confirming the current knowledge based on DNA-amplicon sequencing.

Use of Cold Atmospheric Plasma to Detoxify Hazelnuts from Aflatoxins.

Aflatoxins, produced by Aspergillus flavus and A. parasiticus, can contaminate different foodstuffs, such as nuts. Cold atmospheric pressure plasma has the potential to be used for mycotoxin detoxification. In this study, the operating parameters of cold atmospheric pressure plasma were optimized to reduce the presence of aflatoxins on dehulled hazelnuts. First, the effect of different gases was tested (N2, 0.1% O2 and 1% O2, 21% O2), then power (400, 700, 1000, 1150 W) and exposure time (1, 2, 4, and 12 min) were optimized. In preliminary tests on aflatoxin standard solutions, this method allowed to obtain a complete detoxification using a high power for a few minutes. On hazelnuts, in similar conditions (1000 W, 12 min), a reduction in the concentration of total aflatoxins and AFB1 of over 70% was obtained. Aflatoxins B1 and G1 were more sensitive to plasma treatments compared to aflatoxins B2 and G2, respectively. Under plasma treatment, aflatoxin B1 was more sensitive compared to aflatoxin G1. At the highest power, and for the longest time, the maximum temperature increment was 28.9 °C. Cold atmospheric plasma has the potential to be a promising method for aflatoxin detoxification on food, because it is effective and it could help to maintain the organoleptic characteristics.

The effect of hazelnut roasted skin from different cultivars on the quality attributes, polyphenol content and texture of fresh egg pasta.

BACKGROUND: Hazelnut skin is the perisperm of the hazelnut kernel. It is separated from the kernel during the roasting process and is normally discarded. Recent studies have reported that hazelnut skin is a rich source of dietary fibre as well as of natural antioxidants owing to the presence of phenolic compounds. The aim of this study was to assess the use of hazelnut skins obtained from different cultivars for enhancing the nutritional value of fresh egg pasta. RESULTS: Skins obtained from roasted hazelnuts of four different varieties were used at three concentrations as a flour replacement in fresh egg pasta. Hazelnut skin concentration significantly influenced all evaluated physicochemical parameters as well as consumers' appreciation for the pasta, but significant differences were also observed between the four varieties. Although pasta produced with 10 and 15% hazelnut skin displayed the highest content of polyphenolic compounds and antioxidant activity in vitro, pasta containing 5% Tombul hazelnut skin showed maximum consumer preference. CONCLUSION: The results obtained in the present study highlighted that it is possible to use hazelnut skin in fresh pasta production to obtain a fortified food with high fibre content and antioxidant activity. The characteristics of the resulting pasta were strictly correlated with the hazelnut variety used for skin production and, of course, with the percentage of skin that was added.