The food industry's focus on sustainability has driven efforts to replace multilayer packaging with recyclable monolayers. Monolayers face challenges in providing adequate gas barriers in modified atmosphere packaging (MAP), making oxygen's impact on food safety a critical concern. This study investigated the effects of oxygen on the surface growth of Listeria monocytogenes under refrigerated conditions. Both the absence and presence of mild acid stress were considered, with particular attention to strain-specific differences. Growth experiments were conducted using three L. monocytogenes strains (LMG 23905, LMG 23194 and ADQP 105) at 7 °C on brain heart infusion (BHI) agar under controlled oxygen (0 % and 21 %) and pH conditions (6.2 and 7.6). Significant differences in growth rates were observed for strain LMG 23905 under mildly acidic conditions (pH 6.2) at 0 % oxygen versus 21 % oxygen (p = 1.99e-13). Under neutral conditions (pH 7.6) however, no significant differences were observed (p = 0.09). Strain ADQP 105 exhibited no oxygen sensitivity under both mildly acidified (p = 0.1), and neutral pH conditions (p = 0.52). The same holds for strain LMG 23194, having identical growth rates under air and 100 % nitrogen at neutral (p = 0.28) and mildly reduced pH (p = 0.38). These findings highlight the strain-dependent effects of oxygen on the surface growth of L. monocytogenes. This also demonstrates that there is interaction between mild acid stress and oxygen availability, offering important insights for improving shelf-life predictions and better reflecting real-world conditions for bacterial contamination in solid foods.

The microbial spoilage of raw meat is modulated by the packaging atmosphere, yet the volatile fingerprints underlying these processes remain only partially resolved. This study establishes a structured volatilome fingerprinting workflow based on comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOFMS) to analyze pork spoilage under air, high-N2, and high-O2/CO2 packaging conditions. The applied approach achieved a more comprehensive and confident chemical characterization of the volatilome when compared to currently available results with conventional gas chromatography mass spectrometry (GC-MS) or real-time mass spectrometry. A total of 199 volatile organic compounds (VOCs) were detected, including numerous low-abundance and metabolically related compounds that were annotated by complementary orthogonal criteria. Multivariate analysis based on selected VOCs revealed atmosphere-specific volatilome trajectories and identified key spoilage markers including pyruvate-derived metabolites (acetoin, 2,3-butanedione, 2,3-butanediol), 3-methyl-1-butanol and several aldehydes and ketones. Overall, GC × GC provides enhanced chemical resolution and thus delivers new insights into raw pork spoilage mechanisms via uncovering additional trace-level metabolites not previously observed by other approaches. Expanding and rigorously annotating the meat volatilome would reinforce spoilage assessment and targeted preservation strategies, through resolving microbial metabolism and accurately discriminating spoilage trajectories.

The development of active food packaging materials with controlled antimicrobial release is essential for improving food safety and extending shelf life. In this study, a plasma-polymerized bilayer coating was developed on polylactic acid (PLA), consisting of a citronellal-based antimicrobial layer (∼505 ± 13 nm) and a polycaprolactone (PCL) barrier layer with controlled thicknesses of 30 nm and 55 nm. Surface characterization confirmed successful deposition and partial preservation of citronellal functionality. Release studies demonstrated a strong burst release for the pristine citronellal coating, with most citronellal released within the first day, whereas the bilayer systems significantly reduced and controlled the release. For example, in 95% ethanol after 10 days, citronellal release decreased from 2724.4 μg/L (no barrier) to 210.9 μg/L (30 nm PCL) and 39.1 μg/L (55 nm PCL). Antimicrobial tests in vacuum-packed pork sausage showed that the pristine coating provided strong initial reductions (up to 2.93 log CFU/mL for Listeria monocytogenes (L. monocytogenes) and 2.48 log CFU/mL for lactic acid bacteria (LAB) by day 5), followed by regrowth due to depletion. In contrast, bilayer coatings enabled sustained antimicrobial activity over 11 days, achieving reductions of 3.97 and 3.37 log CFU/mL (30 nm PCL) and 3.14 and 2.09 log CFU/mL (55 nm PCL) for L. monocytogenes and LAB, respectively. The 30 nm PCL layer provided the optimal balance between release rate and antimicrobial efficacy. These results demonstrate that the PCL barrier effectively modulates citronellal release, enabling prolonged antimicrobial activity. The developed bilayer system represents a promising approach for controlled-release antimicrobial food packaging applications.

This study validated industrial baking processes for sugar waffles and cookies for the effective inactivation of vegetative pathogens. Although sweet bakery products are mostly perceived as microbial-safe, epidemiological data indicate foodborne outbreaks in flour and flour-related products caused mainly by Shiga toxin-producing Escherichia coli (STEC) and Salmonella spp. This study's first step compared observed inactivation of pathogen and potential surrogates during a lab-scale cookie baking process. Therefore, the flour was inoculated with one of the surrogates, i.e., Enterococcus faecium NRRLB-2354, Enterococcus faecium LMG11397, or Escherichia coli P1, or inoculated with one of the pathogenic strain(s), i.e., a Listeria monocytogenes cocktail, Salmonella Senftenberg, E. coli O157:H7 cocktail, or Salmonella spp. cocktail. Each dough was baked for 1, 2, 3, 4, 5, 7.5, and 10 min at 205 degrees C. The Salmonella spp. cocktail and E. faecium NRRLB-2354 showed the lowest observed inactivation and similar inactivation kinetics (remaining viable after a 10-min bake). Therefore, E. faecium NRRLB-2354 was chosen as the most suitable surrogate and used with the Salmonella spp. cocktail in a lab baking process for sugar waffles (195 s at 177 degrees C) to validate the surrogate in this food product. The reduction of E. faecium NRRLB-2354 was between 7.6 and 9.0 log CFU/g after the baking process of sugar waffles, which was similar to that of Salmonella spp. cocktail. Finally, the industrial baking processes of speculoos cookies and sugar waffles were validated with E. faecium NRRLB-2354, achieving a more than 7-log reduction in both processes, guaranteeing the absence of vegetative pathogens after baking.

Fresh-cut vegetables house a diverse microbial community, influenced by different pre- and post-harvest factors. The present study examined the temporal variability and the impact of a post-harvest washing process on the abundant and dominant microbial taxa of the indigenous microbiota of Equilibrium Modified-Atmosphere Packaged (EMAP) fresh-cut Romaine lettuce throughout the shelf-life. Whole heads of Romaine lettuce (Murcia, Spain) were sampled in triplicate in January, June and October 2022. Manually cut leaves were washed in potable water and a 200 mg/L chlorine solution, respectively, and stored in EMAP conditions (3 % O-2, 10 % CO2) at 7 degrees C for seven days. Quantitative data were obtained through plating on selective and non-selective culture media, followed by bacterial isolation and taxonomic identification using MALDI-TOF MS and 16S rRNA gene sequencing. The psychrotrophic aerobic plate count of unwashed lettuce ranged from 5.1 to 6.3 log CFU/g, reaching up to 7.5 log CFU/g by the end of the shelf-life. The 808 bacterial isolates were dominated by species from the phylum Pseudomonadota (90 %), with Pseudomonas and Pantoea as the core genera. Temporal variability on the microbiota was demonstrated, with a 1-log lower microbial load in June and the community composition varying across all sampling periods. The chlorine wash induced a reduction in total count up to 2.2 log CFU/g, but had no significant quantitative, nor qualitative impact on the microbial community throughout the shelf-life. These findings suggest that pre-harvest environmental conditions play a more crucial role than post-harvest washing in determining the variability of the Romaine lettuce microbiota.

Ensuring food safety in the transition towards more sustainable packaging is critical, particularly given the persistent threat of Listeria monocytogenes in refrigerated modified atmosphere packaging (MAP). Although combining high CO2 and low O2 in refrigeration has been an effective strategy for controlling this pathogen, very little information is available on the effect of the presence of O2 on the growth of L.monocytogenes. This presence during storage is very difficult to avoid when switching to more gas permeable packaging materials. To better refine food safety strategies, extensive quantitative data under controlled conditions are needed to clarify the role of O2 and its interactions with key stressors (CO2, temperature, and pH). Thus, this study aims to analyze the individual effect of O2 and its combined effect with these key factors on L.monocytogenes behavior in a liquid medium under well-controlled atmospheres (60/0/40, 60/20/20, 60/2/38, 0/20/80, 0/0/100-CO2/O2/N2%) at different pH values (7.7, 6.2) and temperatures (4, 7 °C) through a gas-washing bottle incubation system (GBIS). Despite earlier reports suggesting no effect, O2 increased growth in CO2-free environment, which was more pronounced at 7 °C than at 4 °C. Moreover, lowering the pH from 7.7 to 6.2 enhanced the observed growth-increasing effect of O2. Most importantly, 60% CO2 (pH = 6.2) suppressed the effect of O2; even 20% O2 decreased maximum growth rate in the presence of CO2. Overall, this study shows a complex interaction between stress factors influencing the effect of O2 on L.monocytogenes growth.

Foodborne outbreaks have raised concern about the microbial safety of fresh produce. Comprehensive data on key bacterial pathogens in these products remain scarce. This study explores the prevalence of foodborne pathogens in unprocessed fruits and vegetables, focusing on the variability according to a temporal scale, the geographical origin, and the product type. A total of 12,808 fresh produce samples were collected over a period of ten years (2013-2022) and analyzed for Salmonella spp., Shiga-toxin-producing E. coli (STEC), L. monocytogenes, presumptive B. cereus, and coagulase-positive staphylococci. Overall, L. monocytogenes was the main pathogen detected (1.37%; 95% CI: 1.16-1.57%; n = 12,227), although only one sample exceeded the unsatisfactory threshold limit of 100 CFU/g. Enteric pathogens were less often detected, with a prevalence of 0.11% (95% CI: 0.05-0.17%; n = 11,538) and 0.02% (95% CI: 0.00-0.05%; n = 12,601) for STEC and Salmonella spp., respectively. Elevated levels (>100,000 CFU/g) of presumptive B. cereus were found in 0.34% (95% CI: 0.18-0.51%; n = 4,954) of cases, while coagulase-positive staphylococci were detected (>100 CFU/g) in 0.26% (95% CI: 0.11-0.42%; n = 4,169) of samples, with a maximum concentration of 190 CFU/g. The prevalence of L. monocytogenes fluctuated over time, varying from a minimum of 0.69% in 2022 to a maximum of 2.03% in 2017 and showing a seasonal effect, with an increased prevalence in June and from September to December. The major produce-pathogen combinations were L. monocytogenes and mushrooms (10.19%; 95% CI: 6.89-13.48%; n = 324) and head brassica (6.85%; 95% CI: 4.15-9.55%; n = 336); as well as STEC and legumes (0.47%; 95% CI: 0.00-1.39%; n = 213) and leafy brassica (0.40%; 95% CI: 0.00-1.17%; n = 252). This study provides valuable information for stakeholders, including farmers, distributors, retailers, and policymakers to be used in risk assessment.

Psychromonas arctica, Shewanella frigidimarina, and Pseudoalteromonas elyakovii have been identified and characterized as major spoilage bacteria in packed blue mussels (Mytilus edulis). This study aimed to analyze spoilage bacterial growth and to characterize the specific metabolic products of these spoilage bacteria. For this purpose, bacterial solutions were transferred onto irradiated mussel substrates and exposed to air or modified atmospheres (MAs) with the following compositions of (%CO2/O2/N2): (40/60/0) and (25/75/0). These packages were stored at 4 °C for 15 days, with quality monitoring of the headspace composition (% CO2/O2), pH, microbial analysis, and volatile organic compounds (VOCs) production. Selected-ion flow-tube mass spectrometry (SIFT-MS) was employed to monitor the evolution of VOCs over time. The findings reveal that when cultivated in irradiated mussel substrates and packaged under MAs, the populations of Psy. arctica, S. frigidimarina and Pseu. elyakovii exhibited limited growth with maximum levels of 6.1 ± 0.1 log CFU.g-1 along with limited production of VOCs. Conversely, under air packaging, bacterial proliferation exceeding 7 log CFU.g-1 was associated with the emission of unique VOCs. High production levels of dimethyl sulfide (1000-3280 ppbv) were attributed to S. frigidimarina, while Pseu. elyakovii multiplication led to high emissions of hydrogen sulfide (520-3840 ppbv) and methyl mercaptan (1680-6300 ppbv). The increase in ethanol levels (1150-7930 ppbv) was linked to Psy. arctica. Investigating VOCs in irradiated mussel substrates is significant for understanding bacterial metabolism suggesting their potential as spoilage-specific organisms.

Pork is highly susceptible to microbial spoilage. The growth and metabolism of spoilage bacteria cause the formation of malodorous volatile organic compounds (VOCs), leading to sensory decline. Even though the atmosphere is a well-known extrinsic factor affecting microbial growth, the fundamental impact of bulk gas ratios on VOC production still needs to be further elaborated. The present research focuses on Pseudomonas fragi, one of the most dominant spoilage microbes in packaged meat, by studying its behavior as influenced by atmospheres. Solid pork simulation media inoculated with a pure meat-derived P. fragi strain were stored under four conditions with different bulk gas ratios (v/v% O2/CO2/N2: air, 0/0/100, 20/20/60, 20/40/40). For each atmosphere, characteristic microbial VOCs were identified by combining online and offline chemical analytical tools, namely selected-ion flow-tube mass spectrometry (SIFT-MS) and thermal-desorption gas chromatography mass spectrometry (TD-GC-MS). In total, fourteen compounds were linked to the investigated P. fragi strain, including methyl acetate, ethyl acetate, methyl mercaptan, and dimethyl sulfide. Despite slower microbial growth under 0/0/100 and 20/20/60 when compared to air, anaerobic metabolites including sulfur-containing compounds and ethyl acetate were produced in high quantities at a lower microbial level. On the contrary, 40% CO2 largely limited bacterial counts and VOCs. Overall, comprehensive volatolome analysis provides informative insights into the P. fragi metabolism and its relation with the atmosphere, thus improving the understanding of meat spoilage mechanisms.

Research on bread spoilage organisms is often focused on a selected list of reference moulds. However, as factors such as the characteristics of the product and geographic location affect the potential spoilage behavior, it is important to identify and target the product's associated spoilage species, resulting in an optimized preservation strategy. In this research, the spoilage organisms of spoiled, par-baked bread, produced in Western Europe and packaged under modified atmosphere, were identified using DNA barcoding. The 97 isolated and identified strains could be subdivided into thirteen different species, predominated by the Penicillium genus (97 %). The majority of spoilage was caused by growth of Penicillium palitans (29 %), P. chrysogenum (18 %), P. bialowiezense (11 %), and P. crustosum (11 %). Identification was possible by combining sequencing data of the internal transcribed spacer (ITS) region, the beta-tubulin gene, the calmodulin gene, and RNA polymerase second largest subunit II (RBP2) encoding gene. Based on our data, we propose a barcoding scheme for the thirteen different species isolated in this research to implement in future target-specific treatment options.

Vertical farming allows for precise control of environmental conditions, including light quality, enabling the optimization of plant growth and the synthesis of specific phytochemicals. However, the effects of such conditions on postharvest quality remain underexplored. In this study, butterhead lettuce (Lactuca sativa cv. ‘Alyssa’) was grown for three weeks under light-emitting diode (LED) lighting (190 µmol m−2 s−1; 89% red, 11% blue), with or without supplemental far-red light (ca. 50 µmol m−2 s−1). Growth and quality parameters were assessed at harvest, followed by postharvest evaluation of fresh-cut lettuce stored under equilibrium modified atmosphere packaging (EMAP: 3% O2, balance N2) at 7 °C in darkness for 13 days. The respiration rate of the produce was also determined. Far-red light supplementation increased dry weight (+17%) and elevated glucose (+57%) and fructose (+64%) levels at harvest, without affecting fresh weight, pigment content, vitamin C, or sucrose levels. Although respiration rates during storage were about 54% higher for lettuce grown under far-red light, visual quality seemed slightly better preserved. Total aerobic psychrotrophic counts showed no significant differences between treatments at harvest or during storage. These findings suggest that far-red light can enhance certain quality traits of lettuce, particularly carbohydrate accumulation and dry weight, but the associated rise in respiration may limit these benefits postharvest. Further research is needed to clarify its long-term impact in vertical farming systems.

Fresh-cut iceberg lettuce is gaining popularity for its convenience, but it is highly susceptible to microbial spoilage. This study aimed to investigate the microbial community dynamics in commercially available fresh-cut iceberg lettuce packaged under controlled atmosphere in Belgium during storage at 7 °C for up to 12 days. To achieve a comprehensive understanding of the spoilage microorganisms and their interactions, a culture-complemented metataxonomic approach was conducted, including plating on non-selective and selective culture media for enumeration of total psychrotrophic counts (TPC), enterobacteria, Pseudomonas spp., psychrotrophic lactic acid bacteria (LAB) and yeasts. Throughout storage, TPC remained the predominant group, followed by Pseudomonas spp. until day 2, and by enterobacteria thereafter. The initial oxygen present in the commercial lettuce bags (1.5-2.0 %) was rapidly consumed within the first 24 h of storage (<0.1 %), resulting in a decrease in the dominance of Pseudomonas spp. (38.9 %) since then. By the end of storage, Pseudomonas spp. represented a minor group (<2 %), yet retained the capacity to grow. In contrast, Lactococcus spp. increased in abundance as CO2 rose (1.1-25.8 %), eventually dominating the bacterial community (>44 %) together with Serratia (21 %) and Rahnella (9.5-11 %) species. In fact, LAB showed the highest increase in population throughout storage, with levels rising from ∼1.8 log on day 0 to ∼7.5 log colony forming units per gram on day 12. These findings offer new insights into the deterioration mechanisms of fresh-cut lettuce stored under controlled atmosphere packaging, providing a basis for developing new strategies to prevent lettuce spoilage and thereby help the industry and retailers reduce food waste and associated economic losses.

The study of microbial hydrocarbons removal is of great importance for the development of future bioremediation strategies. In this study, we evaluated the removal of a gaseous mixture containing toluene, m-xylene, ethylbenzene, cyclohexane, butane, pentane, hexane and heptane in aerated stirred bioreactors inoculated with Rhodococcus erythropolis and operated under non-sterile conditions. For the real-time measurement of hydrocarbons, a novel systematic approach was implemented using Selected-Ion Flow Tube Mass Spectrometry (SIFT-MS). The effect of the carbon source (∼9.5 ppmv) on (i) the bioreactors' performance (BR1: dosed with only cyclohexane as a single hydrocarbon versus BR2: dosed with a mixture of the 8 hydrocarbons) and (ii) the evolution of microbial communities over time were investigated. The results showed that cyclohexane reached a maximum removal efficiency (RE) of 53 ± 4% in BR1. In BR2, almost complete removal of toluene, m-xylene and ethylbenzene, being the most water-soluble and easy-to-degrade carbon sources, was observed. REs below 32% were obtained for the remaining compounds. By exposing the microbial consortium to only the five most recalcitrant hydrocarbons, REs between 45 ± 5% and 98 ± 1% were reached. In addition, we observed that airborne microorganisms populated the bioreactors and that the type of carbon source influenced the microbial communities developed. The abundance of species belonging to the genus Rhodococcus was below 10% in all bioreactors at the end of the experiments. This work provides fundamental insights to understand the complex behavior of gaseous hydrocarbon mixtures in bioreactors, along with a systematic approach for the development of SIFT-MS methods.

Spoilage microorganisms including Brochothrix thermosphacta are associated with various volatile organic compounds (VOCs) and off-odors in meat. Modified atmosphere packaging (MAP) limits microbial growth and affects metabolic activities. However, the exact impact of gas compositions on B. thermosphacta still remains unclear, especially regarding the direct relationship between its growth and VOC accumulation. This study thus aimed to investigate and model these behaviors by growing B. thermosphacta on solid pork simulation media under different packaging atmospheres. Five O2/CO2/N2 ratios (v/v%: air, 0/0/100, 60/40/0, 5/40/55, 0/40/60) were examined to study the synergy of MAP gases on the aerobic/anaerobic metabolism of B. thermosphacta. The quantities of VOCs (ppbv) were fitted against respective bacterial numbers (log CFU/g) of different individual samples assessed at regular storage intervals. Results suggest that VOCs including acetoin, ethanol, benzaldehyde, and 3-methyl-1-butanol are the major metabolites of B. thermosphacta. Under air, the observable increase of multiple VOCs started at 5.9-6.6 log CFU/g and was closely correlated with microbial growth. In contrast, 100 % N2 caused low acetoin levels and high ethanol emission because of shifting to an anaerobic metabolism. Under high-CO2 atmospheres, concentrations of most VOCs were reduced, likely linked to limited microbial counts. Through this study, predictive modeling offers novel insights into the impact of the atmosphere on bacterial growth and VOC production. This helps to fully understand microbial spoilage and contributes to the development of suitable meat storage strategies.

While effectively extending the shelf life of perishable foods at low temperatures by delaying the growth of spoilage microorganisms, modified atmosphere packaging (MAP) may favor the growth of certain pathogens under refrigerated and anaerobic environments. In particular, Listeria monocytogenes poses a major safety concern and has caused a significant increase in foodborne outbreaks over the last five years in EU. Although this pathogen has received great attention in the field of predictive microbiology, the exact relations between its growth and interconnected stress factors (CO2, pH, and temperature) still need to be better understood, calling for extensive data collection. Thus, this study aims to understand the impact(s) of these factors by analyzing the behavior of L. monocytogenes in a liquid medium under well-controlled anaerobic conditions with varying CO2 levels (0-20-40-60 %), pH values (7.7, 6.2), and temperatures (4, 7 °C). Three primary growth models - Logistic, modified Gompertz, and Baranyi - were evaluated to fit the growth data from controlled experiments, performed under anaerobic atmospheres employing an innovative gas-washing bottle incubation system (GBIS). The Baranyi model presented the best growth model to fit the growth data. This study showed that higher CO2 (60 %) individually reduced the maximum growth rate (μmax, 1/day) from 0.32 to 0.21 at 4 °C and from 0.46 to 0.39 at 7 °C. Similarly, lower pH decreased the μmax from 0.40 to 0.32 at 4 °C and from 0.68 to 0.46 at 7 °C. Moreover, decreasing temperature from 7 °C to 4 °C led to a reduction in μmax from 0.68 to 0.40 at pH 7.7 and from 0.46 to 0.32 at pH 6.2, while μmax decreased from 0.39 to 0.21 in the presence of 60 % CO2. In terms of interactions, lower temperature enhanced the growth-reducing effect of higher CO2. The same stressing factor, conversely, reduced the low pH-induced effect on the growth in CO2-free conditions. Similarly, lower pH decreased the growth-reducing effect of lower temperature. These insights highlighted the importance of studying well-controlled experimental conditions when aiming at designing MAP packaging to achieve safe, sustainable packaging solutions.

The microbial spoilage of meat is associated with the generation of volatile organic compounds (VOCs) and off-odors. While predictive modeling benefits shelf-life determination, predicting the volatolome is very complex as the related microbial metabolism is easily affected by the packaging O2/CO2 composition. Whereas traditional supervised learning mostly focuses on predicting one single target, this study introduces the concept of multi-target prediction (MTP) by presenting a study on predicting multiple VOCs produced by Brochothrix thermosphacta under different packaging atmospheres. The used dataset comprises the total plate counts (TPC), volumetric O2/CO2 ratios, and VOC concentrations of 840 individual pork simulation medium samples inoculated with B. thermosphacta which are stored under 20 different atmospheres (O2: 0%-70%, CO2: 0%-60%, N2 as a filler gas: 0%-100%) for different time periods (0-10 days). Since certain VOCs can be linked via pathways, a two-branch neural network is introduced as the first attempt in the food domain to predict the interactions between paired inputs, namely (1) microbial counts and gas ratios in each medium sample and (2) metabolism information of each VOC. MTP-based regression and classification models are able to predict VOC levels under a given atmosphere after training and validating on data from the 19 other atmospheres. Overall, these outcomes indicate the promising potential of MTP in volatolomics. When handling a more complex dataset based on real meat matrices, it is essential to gain more data to represent instances (e.g., microbiota or foodomics for meat/microbial samples) and targets (e.g., chemical information for VOCs).

This study aimed to trace the sources of molds causing gingerbread spoilage. A total of 114 samples, including air, swabs, Rodac plates, ingredients, and products, were collected from a bakery during production. Molds were initially recovered from samples using OGYE and DG-18 agar media. For source tracking, gene sequence analysis was performed on 39 selected isolates. The spoilage potential of molds was assessed through their enzyme activity. All air samples, surface areas, and overhead ventilator units were mold-contaminated, with 18 to > 200 CFUs/m(3) in air, 0 to 11 CFUs/25 cm(2) on surfaces, and > 100 CFUs/25 cm(2) on DG-18 agar. The cooling room samples, including swabs, ingredients, products, and nebulizers, showed high contamination levels. Air in the processing environment was gingerbread's main source of mold contaminants. A total of 151 isolates were identified at the genus level. Aspergillus spp. was the most frequently encountered mold in the 151 isolates, followed by Penicillium spp. The strains recovered from gingerbread samples were Aspergillus niger (A. niger), Penicillium chrysogenum (P. chrysogenum), and P. decumbens. Of these, only A. niger and P. chrysogenum were able to grow on gingerbread in challenge tests. A. niger exhibited amylase, protease, and lipase activity, while P. chrysogenum expressed only amylase and protease.

Plant secondary metabolites are an interesting source of natural antifungals and offer an alternative to synthetic preservatives. In this study, the activity of 218 secondary metabolites was evaluated against nine Penicillium species and one Aspergillus species, isolated from spoiled par-baked bread. By comparing agar and liquid-based assays, it was found that the hydrophobic nature of these compounds led to an underestimation of the activity in agar-based assays. In liquid medium, it was possible to evaluate the effect quantitatively and differentiate between strong and weak inhibitors. Of the most interesting compounds, the minimal inhibitory concentration (MIC) was determined, and synergistic interactions were studied. This revealed an interesting interaction between benzyl isothiocyanate and carvacrol, which was further investigated through validation in par-baked bread. Antifungal efficacy was assessed in a shelf life and challenge test, revealing that spray application of 200 to 400 µg/mL benzyl isothiocyanate and 1000 to 2000 µg/mL carvacrol significantly increased shelf life. Furthermore, application of benzyl isothiocyanate and carvacrol was as effective as 0.15% propionic acid was incorporated in the dough. A sensory triangle test indicated that benzyl isothiocyanate and carvacrol influenced the flavour of fully baked bread; however, the effect was not perceived negatively.

Recently, interest in eco-friendly techniques for producing antibacterial food packaging films has surged. Within this context, plasma polymerization is emerging as a promising approach for applying degradable antibacterial coatings on various plastic films. This research therefore employs an atmospheric pressure aerosol-assisted plasma deposition technique to create polyethylene glycol (PEG)-like coatings embedding zinc oxide nanoparticles (ZnO NPs) of varying sizes on polyethylene (PE) substrates. The antimicrobial efficacy of these plasmapolymerized PEG-ZnO coatings against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) is assessed, demonstrating a robust antibacterial effect, particularly when using smaller ZnO NPs (35-45 nm). The deposition of uniform, conformal PEG-ZnO nanocomposites with a chemical composition akin to standard PEG polymers has been achieved. In addition, ZnO NPs are homogeneously dispersed within the PEG matrix, up to a concentration of 1 wt%. To assess the antibacterial performance in contact with real food, pasteurized pork sausages inoculated with a mixture of L. monocytogenes or LAB strains are wrapped in plasma-coated PE and vacuum-packed. Bacterial growth is monitored during storage at 7 degrees C over time, demonstrating that the developed plasmapolymerized PEG-ZnO nanocomposite effectively inhibits bacterial growth during refrigerated storage, with a more pronounced effect on LAB. The release of Zn from the developed PEG-ZnO nanocomposite into various food simulants also remains below the specific migration limit (5 mg kg-1 or L-1 food), confirming coating safety. Overall, plasma-polymerized PEG-ZnO nanocomposite coatings thus show great promise as effective degradable antimicrobial films for food packaging applications.