Category Archives: Technology

Research – Evaluation of eight essential oils for postharvest control of Aspergillus carbonarius in grapes

Posted on May 11, 2020 by | Leave a comment

Journal of Food Protection

A wide range of fungal species is associated with post-harvest spoilage of grapes. However, Aspergillus carbonarius is the primary fungus responsible for the contamination of grapes with ochratoxin A, a mycotoxin causing several confirmed health effects to humans and animals. Aiming to find a method, safe for the consumers, to prevent post-harvest decay and ochratoxin A contamination of grapes, the potential use of essential oils as preservatives was investigated. Essential oils of Origanum dictamnus (dittany) , Origanum onites (oregano) , Origanum microphyllum (marjoram) , Thymbra capitata (thyme) , Satureja thymbra (savory) , Rosmarinus officinalis (rosemary) , Laurus nobilis (laurel) and Salvia officinalis (sage) were tested. The essential oil components were identified by GC/MS analysis. A first evaluation of the effectiveness of essential oils was performed in vitro , at a range of concentrations up to 300 μL L -1 . Based on the results of the in vitro tests, the four most effective essential oils ( O. dictamnus , O. onites , T. capitata and S. thymbra ) were tested on Sultana grapes, during post-harvest storage. The four essential oils tested, having the carvacrol and/or thymol as a common component, at a high concentration, significantly reduced, or even completely inhibited the growth of the fungus, in all treatments. As revealed from the results, the essential oils of O. dictamnus , O. onites and S. thymbra were the most effective, causing total inhibition on the growth of the fungus with a minimum concentration of 100 μL L -1 , followed by the essential oil of T. capitata , total effective with a minimum concentration of 200 μL L -1 . Essential oils of O. microphyllum , L. nobilis , S. officinalis and R. officinalis , although they had a significant effect on the growth of A. carbonarius , failed to inhibit its growth completely at any of the concentrations tested.

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Posted in Aspergillus, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, microbial contamination, Microbiology, Mould Toxin, Moulds, Mycotoxin, Research, Technology, Uncategorized

Research – Comparison of stomaching versus rinsing, for recovering bacterial communities from rainbow trout (Oncorhynchus mykiss) fillets.

Posted on May 11, 2020 by | Leave a comment

Journal of Food Protection

The use of high-throughput methods allows a better characterization of food-related bacterial communities. However, such methods require large amounts of high quality bacterial DNA, which may be a challenge when dealing with a complex matrix that has a low concentration of bacteria like fresh fish fillets. Therefore, the choice of method used to recover bacteria from a food matrix in a cost-effective way is critical, yet little information is available on the performance of commonly used methods. We assessed the recovery capacity of two such methods: stomaching and mechanical rinsing. The efficiency of the methods was evaluated through the quantitative recovery and compatibility with end-point qPCR. Fresh rainbow trout ( Oncorhynchus mykiss ) fillets were inoculated with a bacterial marker, Brochothrix thermosphacta , at different concentrations (7.52 to 1.52 log CFU/g). The fillets were processed by one of the two methods and the recovery of the marker in the suspensions was assessed by plate counting and qPCR targeting B. thermosphacta – rpoC . The same analyses were performed on 6 non-inoculated fresh fillets. Stomaching and mechanical rinsing allowed an efficient and repeatable recovery of the bacterial communities from the 42 inoculated fillets. No significant differences of Recovery Ratios were observed between the marker enumerated in the inoculation suspensions and in the corresponding recovery suspensions after rinsing and stomaching. However, the stomaching method allowed too many particles to pass through the filters bag, making necessary a limiting supplementary filtration step. As a consequence, only the rinsing recovery method allowed a proper PCR quantification of the inoculated B. thermosphacta. The mean recovered bacterial level of the fillets was around 3 log CFU/g. It seems more relevant and cost-effective to recover the endogenous bacterial microbiota of a fish fillet structure using the rinsing method rather than the stomaching method.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, microbial contamination, Microbiology, Research, Technology, Uncategorized

Research – Enhanced elimination of Salmonella Typhimurium and Campylobacter jejuni on chicken skin by sequential exposure to ultrasound and peroxyacetic acid

Posted on May 10, 2020 by | Leave a comment

Wiley Online

The present study investigated the effects of combined ultrasound (37 kHz, 380 W for 5 min) and peroxyacetic acid (PAA; 50–200 ppm) treatment on the reduction of Salmonella Typhimurium and Campylobacter jejuni on chicken skin. Ultrasound was not sufficient to inactivate S. Typhimurium (0.48 log CFU/g reduction) or C. jejuni (0.25 log CFU/g reduction), whereas PAA significantly (p < .05) reduced S. Typhimurium (0.93–1.59 log CFU/g reduction) and C. jejuni (0.77–1.52 log CFU/g reduction). However, maximum reductions of 2.21 and 2.08 log CFU/g were observed for S. Typhimurium and C. jejuni, respectively, for combined treatment with 5 min of ultrasound and 200 ppm PAA. Our results indicate that a combination of ultrasound treatment for 5 min and 200 ppm PAA was more effective in reducing S. Typhimurium and C. jejuni compared to the individual treatments, without significantly affecting the color or texture of the chicken skin, thus, demonstrating its potential to increase the microbial safety during poultry processing.

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Posted in Campylobacter, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, microbial contamination, Microbiology, Research, Salmonella, Technology, Uncategorized

Research -The impacts of tomato residuum extract with Arabic gum and dill essential oil on the shelf life improvement of trout fillets stored at chilly condition

Posted on May 10, 2020 by | Leave a comment

Wiley Online

The objective of this study was to evaluate the effects of tomato residuum extract (TRE) dipping and Arabic gum (AG) coating enriched with dill essential oil (DEO) on the shelf life extension of refrigerated trout fillets. Gas chromatography/mass spectrometry analysis revealed that the main constituents of DEO were alpha‐phellandrene (30.17%), limonene (28.31%), and carvone (21.31%). Antioxidant activities of acetone, ethanol, methanol, cold, and hot water extracts of tomato residuum were examined using reducing power and 2,2‐azinobis‐3‐ethylbenzothiazoline‐6‐sulphonic acid assays in maceration, ultrasound, and combined ultrasound and maceration extraction methods. The strongest antioxidant activities were found in the ultrasound‐assisted extraction with ethanol 50%. Thiobarbituric acid, total volatile basic nitrogen, and peroxide values indicated that TRE 3%–AG–DEO 2% and TRE 6%–AG–DEO 2% treatments could significantly (p ≤ .05) extend the shelf life of the fillets. Also, sensory evaluation showed that TRE along with DEO had significant (p ≤ .05) pleasant effects on the sensory characteristics of the fillets. It was concluded that TRE dipping along with AG coating containing DEO could be a suitable alternative for the synthetic preservative in the refrigerated trout fillets.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Technology, Uncategorized

Research – How silver ions kill bacteria

Posted on April 10, 2020 by | Leave a comment

Science Daily

The antimicrobial properties of silver have been known for centuries. While it is still a mystery as to exactly how silver kills bacteria, University of Arkansas researchers have taken a step toward better understanding the process by looking at dynamics of proteins in live bacteria at the molecular level.

Traditionally, the antimicrobial effects of silver have been measured through bioassays, which compare the effect of a substance on a test organism against a standard, untreated preparation. While these methods are effective, they typically produce only snapshots in time, said Yong Wang, assistant professor of physics and an author of the study, published in the journal Applied and Environmental Microbiology.

 

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Posted in Bacteria, bacterial contamination, Bacterial Infections, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, microbial contamination, Microbiology, Research, Technology, Uncategorized

Research- Effect of cultivars and irrigation waters on persistence of indicator bacteria on lettuce grown in high tunnel

Posted on March 31, 2020 by | Leave a comment

Wiley Online

Abstract

Effect of irrigation with groundwater (GW), primary‐treated wastewater (PTWW), secondary‐treated wastewater (STWW), and roof‐collected rainwater (RCR) on the microbial quality of lettuce cultivars “Annapolis,” “Celinet,” and “Coastline” grown in high tunnel was investigated. Lettuce plants were spray irrigated with irrigation waters once a week for 2 weeks and analyzed for indicator and pathogenic bacteria. PTWW irrigation resulted in the highest Escherichia coli recovery on the lettuce plants (4.7 log MPN/g) as compared to irrigation with other three waters on 0 day post irrigation (dpi). Lettuce cultivars affected the bacterial die‐off rate, where E. coli populations reduced the most by 1.5 log MPN/g on “Annapolis” lettuce on 2 dpi. The STWW and RCR irrigation did not significantly influence indicator bacterial populations on lettuce as compared to GW irrigation. The STWW and RCR containing low populations of indicator bacteria may be suitable for lettuce irrigation in Mid‐Atlantic area without affecting its microbial quality.

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Posted in E.coli, Food Micro Blog, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, microbial contamination, Microbiology, Research, Technology, Uncategorized

Research – Salmonella enterica Elicits and Is Restricted by Nitric Oxide and Reactive Oxygen Species on Tomato

Posted on March 29, 2020 by | Leave a comment

Frontiers in Microbiology

The enteric pathogen Salmonella enterica can interact with parts of the plant immune system despite not being a phytopathogen. Previous transcriptomic profiling of S. enterica associating with tomato suggested that Salmonella was responding to oxidative and nitrosative stress in the plant niche. We aimed to investigate whether Salmonella was eliciting generation of reactive oxygen species (ROS) and nitric oxide (NO), two components of the microbe-associated molecular pattern (MAMP)-triggered immunity (MTI) of plants. We also sought to determine whether this interaction had any measurable effects on Salmonella colonization of plants. Biochemical, gene expression and on-plant challenge assays of tomato vegetative and fruit organs were conducted to assess the elicitation of ROS and NO in response to Salmonella Newport association. The counter bacterial response and the effect of NO and ROS on Salmonella colonization was also investigated. We detected H2O2 in leaves and fruit following challenge with live S. Newport (p < 0.05). Conversely, NO was detected on leaves but not on fruit in response to S. Newport (p < 0.05). We found no evidence of plant defense attenuation by live S. Newport. Bacterial gene expression of S. Newport associating with leaves and fruit were indicative of adaptation to biotic stress in the plant niche. The nitrosative stress response genes hmpA and yoaG were significantly up-regulated in S. Newport on leaves and fruit tissue compared to tissue scavenged of NO or ROS (p < 0.05). Chemical modulation of these molecules in the plant had a restrictive effect on bacterial populations. Significantly higher S. Newport titers were retrieved from H2O2 scavenged leaves and fruit surfaces compared to controls (p < 0.05). Similarly, S. Newport counts recovered from NO-scavenged leaves, but not fruit, were higher compared to control (p < 0.05), and significantly lower on leaves pre-elicited to produce endogenous NO. We present evidence of Salmonella elicitation of ROS and NO in tomato, which appear to have a restricting effect on the pathogen. Moreover, bacterial recognition of ROS and NO stress was detected. This work shows that tomato has mechanisms to restrict Salmonella populations and ROS and NO detoxification may play an important role in Salmonella adaptation to the plant niche.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, microbial contamination, Microbiology, Research, Salmonella, Technology, Uncategorized

Research – Scale‐up model of forced air‐integrated gaseous chlorine dioxide for the decontamination of lowbush blueberries

Posted on March 27, 2020 by | Leave a comment

Wiley Online 

Gaseous chlorine dioxide (ClO2) is a promising sanitizer for frozen products because of its efficacy under nonthermal and waterless conditions. A major knowledge gap exists between laboratory trials and effectiveness at the industrial scale. To address this, a pilot study implementing a pallet‐sized fumigation container (60 harvest totes) was designed for gaseous ClO2. Fifty kilograms of blueberries were exposed to initial dose of 57.46 mg/L, representing a treatment of 2.35 mg/g of blueberries. Blueberries remained enclosed for 10 hr. Reduction of all viable cells, coliforms, yeasts, and molds were measured by plating treated samples on Tryptic Soy Agar, Violet Red Bile Agar, and Dichloran Rose Bengal Chloramphenicol Agar and compared to untreated controls. The results demonstrate that a significant reduction of 1.5 log CFU/g can be achieved against coliforms after ClO2 exposure. Our findings demonstrate a cost‐effective procedure that could be adapted to commercial processing.

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Posted in Coliforms, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, microbial contamination, Microbiology, mold, Moulds, Research, Technology, Uncategorized, Yeasts

Research – Modeling the inactivation of Bacillus cereus by infrared radiation in paprika powder (Capsicum annuum)

Posted on March 26, 2020 by | Leave a comment

Wiley Online 

Infrared (IR) irradiation, a novel technology for modeling of decontamination of Bacillus cereus in paprika powder was evaluated and the effect on temperature profiles and total phenolic content was determined. The highest reduction in B. cereus count (2.3 log CFU/g) was achieved after a holding time of 1 min at 200 W IR power and 5 cm distance. The rapid rise in temperature was observed in surface paprika powder and the highest temperature at 200 W IR power and 5 cm distance reaching to 127.8°C. An increase in IR power and a decrease in sample distance of the IR lamp caused a significant decrease in the total phenolic content. The Double Weibull model closely predicted the inactivation of B. cereus in paprika powder by IR irradiation.

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Posted in Bacillus, Bacillus cereus, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Technology, microbial contamination, Microbiology, Research, Technology, Uncategorized

Research – Eliminating viruses in our food with cranberries and citrus fruit

Posted on February 29, 2020 by | Leave a comment

Science Daily

Fresh produce is a major vehicle for noroviruses, a group of viruses that are the most common cause of gastroenteritis in developed countries. However, the viruses are quite resistant to cold pasteurization treatments such as irradiation, which are used to destroy bacteria, moulds, parasites, and insects. The irradiation process uses gamma rays or X-rays to destroy these viruses but at the dose needed to eliminate them, it can affect the physicochemical properties of fresh produce.

Professor Monique Lacroix, a researcher at Institut National de la Recherche Scientifique (INRS), has developed an edible coating based on cranberry juice and citrus extract that makes noroviruses more sensitive to gamma irradiation, making it possible to eliminate them while preserving the quality of food, all without risk to consumers.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Technology, Food Virus, microbial contamination, Microbiology, Norovirus, Research, Technology, Uncategorized, Virus