Frequency-Following Responses in Sensorineural Hearing Loss: A Systematic Review

PURPOSE

This systematic review aims to assess the impact of sensorineural hearing loss (SNHL) on various frequency-following response (FFR) parameters.

METHODS

Following PRISMA guidelines, a systematic review was conducted using PubMed, Web of Science, and Scopus databases up to January 2023. Studies evaluating FFRs in patients with SNHL and normal hearing controls were included.

RESULTS

Sixteen case-control studies were included, revealing variability in acquisition parameters. In the time domain, patients with SNHL exhibited prolonged latencies. The specific waves that were prolonged differed across studies. There was no consensus regarding wave amplitude in the time domain. In the frequency domain, focusing on studies that elicited FFRs with stimuli of 170 ms or longer, participants with SNHL displayed a significantly smaller fundamental frequency (F0). Results regarding changes in the temporal fine structure (TFS) were inconsistent.

CONCLUSION

Patients with SNHL may require more time for processing (speech) stimuli, reflected in prolonged latencies. However, the exact timing of this delay remains unclear. Additionally, when presenting longer stimuli (≥ 170 ms), patients with SNHL show difficulties tracking the F0 of (speech) stimuli. No definite conclusions could be drawn on changes in wave amplitude in the time domain and the TFS in the frequency domain. Patient characteristics, acquisition parameters, and FFR outcome parameters differed greatly across studies. Future studies should be performed in larger and carefully matched subject groups, using longer stimuli presented at the same intensity in dB HL for both groups, or at a carefully determined maximum comfortable loudness level.

Validation of the acoustic change complex (ACC) prediction model to predict speech perception in noise in adult patients with hearing loss: a study protocol

BACKGROUND

Speech perception tests are essential to measure the functional use of hearing and to determine the effectiveness of hearing aids and implantable auditory devices. However, these language-based tests require active participation and are influenced by linguistic and neurocognitive skills limiting their use in patients with insufficient language proficiency, cognitive impairment, or in children. We recently developed a non-attentive and objective speech perception prediction model: the Acoustic Change Complex (ACC) prediction model. The ACC prediction model uses electroencephalography to measure alterations in cortical auditory activity caused by frequency changes. The aim is to validate this model in a large-scale external validation study in adult patients with varying degrees of sensorineural hearing loss (SNHL) to confirm the high predictive value of the ACC model and to assess its test-retest reliability.

METHODS

A total of 80 participants, aged 18-65 years, will be enrolled in the study. The categories of severity of hearing loss will be used as a blocking factor to establish an equal distribution of patients with various degrees of sensorineural hearing loss. During the first visit, pure tone audiometry, speech in noise tests, a phoneme discrimination test, and the first ACC measurement will be performed. During the second visit (after 1-4 weeks), the same ACC measurement will be performed to assess the test-retest reliability. The acoustic change stimuli for ACC measurements consist of a reference tone with a base frequency of 1000, 2000, or 4000 Hz with a duration of 3000 ms, gliding to a 300-ms target tone with a frequency that is 12% higher than the base frequency. The primary outcome measures are (1) the level of agreement between the predicted speech reception threshold (SRT) and the behavioral SRT, and (2) the level of agreement between the SRT calculated by the first ACC measurement and the SRT of the second ACC measurement. Level of agreement will be assessed with Bland-Altman plots.

DISCUSSION

Previous studies by our group have shown the high predictive value of the ACC model. The successful validation of this model as an effective and reliable biomarker of speech perception will directly benefit the general population, as it will increase the accuracy of hearing evaluations and improve access to adequate hearing rehabilitation.

Outcome for dizzy patients in a physiotherapy practice: an observational study

BACKGROUND

Dizziness is a common reason for referral to physiotherapy. Additional information on clinical characteristics, treatment effect and prognostic indicators in physiotherapy practice are needed.

METHODS

A retrospective observational study. Based on a standardised clinical evaluation patients were labelled as having Benign Paroxysmal Positioning Vertigo (BPPV) or not (no-BPPV). BPPV was treated with repositioning manoeuvres and exercises. In no-BPPV, treatment was based on additional clinical tests. Treatment was provided once per week and considered successful when the patient was free of symptoms confirmed by negative positional tests.

RESULTS

From 148 referred patients, 88 were labelled as having BPPV, 60 as no-BPPV. The symptom of a short-lasting spinning sensation provoked by head movements was highly suggestive of BPPV. On average, in BPPV treatment was completed after 2.27 ± 1.68 treatments, in no-BPPV this was after 4.91 ± 3.46 treatments. The delayed outcome was related to higher 'age' and 'concomitant neck pain' in BPPV and with higher 'age' only in no-BPPV. Favourable outcome was related to the feature 'dizziness provoked by movements in the horizontal plane' in BPPV.

CONCLUSIONS

Clinical evaluation and treatment in physiotherapy practice can be an effective and safe option for patients with dizziness. Several clinical variables with prognostic values were identified.Key messagesClinical evaluation and treatment in physiotherapy practice can be part of low threshold care for dizzy patients.Despite prior medical screening, one-third of patients without signs of BPPV were sent back for further evaluation, illustrating the need for interdisciplinary collaboration.Based on the description of the dizziness symptom (vertigo rather than light-headedness), provocation of the dizziness by movements, and a short duration of the dizziness attack, and positive clinical vestibular tests, BPPV treatment could be initiated.

ICF domains covered by the Tinnitus Questionnaire and Tinnitus Functional Index

PURPOSE

Tinnitus frequently causes disability as it affects daily living, which is objectified using several tinnitus questionnaires. To what extent they cover domains of the International Classification of Functioning, Disability and Health (ICF) is currently unknown. Therefore, this study aims to investigate which ICF domains are measured by two questionnaires and to describe the health status of somatic tinnitus patients in ICF terms.

MATERIALS AND METHODS

All questions of the Tinnitus Questionnaire (TQ) and Tinnitus Functional Index (TFI) were linked to the ICF using linking rules. A count-based method was used to link all individual answers of 80 tinnitus patients, to the ICF categories.

RESULTS

Most of the linked questions concerned "body functions". TFI covered more categories of "activity and participation" than TQ. Patients reported severe impairments in "mental functions", "sensory functions and pain", and "sleep functions". Additionally, severe limitations were scored in "focusing attention".

CONCLUSIONS

The TFI and TQ measure distinct domains but can be used complementary or solely, depending on the research question. The TFI identifies a broad spectrum of problems, where the TQ focuses on the psychological impact of tinnitus. Somatic patients in our study reported impairments and disabilities in all covered domains, especially in "onset of sleep" and "sound detection".Implications for RehabilitationThe Tinnitus Functional Index (TFI) and the Tinnitus Questionnaire (TQ) cover different domains of the International Classification of Functioning, Disability and Health.The TFI identifies problems in "body functions" and "activity and participation".The TQ focuses on the psychological impact of tinnitus.

Brainstem evoked auditory potentials in tinnitus: A best-evidence synthesis and meta-analysis

Introduction

Accumulating evidence suggests a role of the brainstem in tinnitus generation and modulation. Several studies in chronic tinnitus patients have reported latency and amplitude changes of the different peaks of the auditory brainstem response, possibly reflecting neural changes or altered activity. The aim of the systematic review was to assess if alterations within the brainstem of chronic tinnitus patients are reflected in short- and middle-latency auditory evoked potentials (AEPs).

Methods

A systematic review was performed and reported according to the PRISMA guidelines. Studies evaluating short- and middle-latency AEPs in tinnitus patients and controls were included. Two independent reviewers conducted the study selection, data extraction, and risk of bias assessment. Meta-analysis was performed using a multivariate meta-analytic model.

Results

Twenty-seven cross-sectional studies were included. Multivariate meta-analysis revealed that in tinnitus patients with normal hearing, significantly longer latencies of auditory brainstem response (ABR) waves I (SMD = 0.66 ms, p < 0.001), III (SMD = 0.43 ms, p < 0.001), and V (SMD = 0.47 ms, p < 0.01) are present. The results regarding possible changes in middle-latency responses (MLRs) and frequency-following responses (FFRs) were inconclusive.

Discussion

The discovered changes in short-latency AEPs reflect alterations at brainstem level in tinnitus patients. More specifically, the prolonged ABR latencies could possibly be explained by high frequency sensorineural hearing loss, or other modulating factors such as cochlear synaptopathy or somatosensory tinnitus generators. The question whether middle-latency AEP changes, representing subcortical level of the auditory pathway, are present in tinnitus still remains unanswered. Future studies should identify and correctly deal with confounding factors, such as age, gender and the presence of somatosensory tinnitus components.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021243687, PROSPERO [CRD42021243687].

O-097 The presentation of medical risks and incentives in egg donation: an analysis of Belgian, Spanish and UK fertility clinic websites

Study question

How do fertility clinics’ websites of the UK, Belgium and Spain present the medical risks of egg donation and incentives?

Summary answer

Spanish and UK websites typically included more incentives to recruit egg donors compared to the Belgian websites. OHSS was overall the most discussed risk.

What is known already

People commonly turn to the internet for initial information. Primary presentations of information of a subject co-determine how an individual interprets the topic and thus influence later decisions. Considering the growing demand and clinics’ dependency on egg donors, some scholars have expressed concerns that clinics might (initially) misrepresent risks to recruit more egg donors. Offering appealing incentives may also encourage potential donors to dismiss possible risks and side-effects.

Therefore, it is important to see how incentives (both monetary and non-monetary rewards) and risks are presented on the websites of fertility clinics, the first source of information for egg donors.

Study design, size, duration

This study is part of the EDNA-project, a multi-phased comparative study (2017-2021), that aims to explore the social, political, economic and moral configuration of egg donation in the United Kingdom, Belgium and Spain. In this study, we only focused on the medical risks of egg donation and incentives presented on the fertility clinics’ websites of the three countries.

Participants/materials, setting, methods

We analysed the websites of all Belgian fertility clinics (n = 18), and a maximum variation sample in the UK (n = 21) and Spain (n = 23). The sampling was based on the geographical location of the clinic, size/number of cycles performed each year, the clinic’s status (independent or part of a larger clinical group) and whether the clinic was public or privately funded in the UK. Frame analysis and content analysis were used for analysis in Nvivo12.

Main results and the role of chance

No misrepresentation of risks was found. There was an extensive variety in the representation of risks. There were differences between the websites of the three countries (e.g. the risks of having acne was only discussed on Spanish websites), but also remarkable differences within the websites of a particular country (of the 40 risks, 13 were one-off mentions, each found on a single website). A description of a risk was generally accompanied by a minimization or normalization of the risk, or a statement about the fertility clinic’s excellent care for their egg donors. These three approaches were often combined.

Our analysis differentiated between incentives (i.e. external rewards) and emotional appeals. An appeal to emotions (e.g. empathy) can also motivate behavioural action (e.g. donation) but was not considered as an incentive since there is no external reward.

While Belgian websites used almost no incentives, Spanish and UK websites used gratitude and a rewarding experience as incentives. However, only Spanish websites used free medical tests as incentives, while UK websites were the only ones that used discounts received with egg sharing as an incentive. All countries’ websites used emotional appeals by enticing feelings of empathy for the recipients.

Limitations, reasons for caution

Not all UK and Spanish fertility clinics’ websites were analysed. However, our international team of researchers applied a maximum variation sampling strategy. This generated samples of clinics per country that were as diversified as possible.

Wider implications of the findings

The study shows that incentives are more often used on the UK and Spanish websites than on the Belgian websites. All three countries’ websites used emotional appeals. It should be studied how effective these incentives and emotional appeals are, and if there is a correlation with the potential donors’ risk-perceptions.

Trial registration number

not applicable

Post-harvest interventions decrease aflatoxin and fumonisin contamination in maize and subsequent dietary exposure in Tanzanian infants: a cluster randomised-controlled trial

A cluster randomised controlled trial was performed in three agro-ecological zones of Tanzania to evaluate the effectiveness of locally available post-harvest mitigation strategies in preventing and reducing aflatoxin and fumonisin contamination in maize. A total of 300 children, each from one household, were randomly selected from 30 villages (intervention: n=15). The mitigation strategies focused on hand sorting (prior to storage and use), drying maize on mat/raised platforms, proper sun drying, application of storage insecticides and de-hulling before milling. Maize sample was collected from each household at harvest (baseline) and six months after harvest. Maize intake by each child, estimated using the 24 h dietary recall technique and its body weight measured using standard procedures were taken at six months after harvest. Aflatoxins and fumonisins in the maize samples were determined using HPLC. Follow-up (six month after harvest) data were available for 261 of the 300 households (intervention: n=136). Mean concentration of aflatoxins, or fumonisins was significantly (P<0.05) lower in the intervention than in the control group: intervention effects: μg/kg (95% confidence interval (CI)) -4.9 (-7.3,-2.5), and -405, (-647,-162), respectively. The difference corresponds to 83 and 70% for aflatoxins, and fumonisins, respectively. At the end of the intervention, aflatoxin and fumonisin estimated mean intakes were lower in the intervention than in the control group by 78 and 65%, respectively. Six months after harvest, prevalence of underweight in the intervention group was 6.7% lower (P=0.014) than in the control group. Mean weight-for-age Z-score difference between the groups was 0.57 (95% CI; 0.16,-0.98; P=0.007). Post-harvest practices are effective in preventing and reducing aflatoxin and fumonisin contamination in maize and subsequent dietary exposure to infants. The interventions may be applied in these and other communities with similar environmental conditions or agricultural practices that favour production of aflatoxin and fumonisins in food crops. The trial was registered at ClinicalTrials.gov identifier: NCT02438774.

Ensuring food safety in food donations: Case study of the Belgian donation/acceptation chain

The food donation process in Belgium is mapped and analyzed to identify bottlenecks in compliance with the legal framework and implementation of food safety management, based on literature search and interviews with stakeholders (donors, acceptors, regulators and facilitators) in Belgium and at EU level. The study revealed that the food donation/acceptation chain is far less structured and organized than the conventional food supply chain. The fragmented landscape of many small food banks and charity organizations (acceptors), often directed by and working with volunteers without training in food safety and lack of knowledge of legal food hygiene requirements is a bottleneck to generate trust among food donors and restricts the provision of perishable products in food donations. Lack of refrigerated transport and insufficient cold/freezing capacity in food banks and charity organizations was identified as a barrier to distribute perishable products. Furthermore, in two cities in Flanders (Belgium), at some food donation centers, donated perishable food samples (n=72) were taken and subjected to microbiological analysis to determine their overall food quality, hygiene and food safety status. Twenty-two of 72 analyzed samples showed marginal microbiological quality based on numbers of yeast, lactic acid bacteria or total viable count. In three samples Listeria monocytogenes was detected per 25g among which one ready-to-eat cooked meat product which showed increased numbers of L. monocytogenes (3.5logCFU/g) and Enterobacteriaceae (6.7logCFU/g). Overall, in Belgium, most of the donated foods considers nonperishable foods, with more or less half of the food collected by the food banks being purchased with funds from FEAD (Fund for European Aid to the Most Deprived) and thus not derived from food losses. Efforts are being made by facilitators to provide a platform for better coordination of donors and acceptors to make more efficient use of food losses. Regulators at the national level are taking action to clarify and provide some flexibility in food hygiene regulation and initiatives on EU level to facilitate food donation in the combat of food losses are pending. As from the side of the acceptors, it is recommended to professionalize the acceptation chain in Belgium and seek for a more harmonized approach and concerted action.

Quantitative farm-to-fork human norovirus exposure assessment of individually quick frozen raspberries and raspberry puree

A quantitative human norovirus (NoV) exposure model describing transmission of NoV during pre-harvest, harvest and further processing of soft red fruits exemplified by raspberries is presented. The outcomes of the model demonstrate the presence of NoV in raspberry puree or individual quick frozen (IQF) raspberry fruits and were generated by Monte Carlo simulations by combining GoldSim® and @Risk® software. Input data were collected from scientific literature, observational studies and assumptions. NoV contamination of soft red fruits is assumed to take place at farms by application of contaminated water for pesticides dilution or by berries' pickers shedding NoV. The model was built simulating that a collection center received berries from ten farms with a total of 245 food handlers picking soft red fruits during a 10-hour day shift. Given 0, 5 and 20 out of 245 berries' pickers were shedding NoV, these conditions were calculated to result in a mean NoV contamination of respectively 0.47, 14.1 and 36.2 NoV particles per kg raspberries in case all raspberries are mixed to one day-batch of 11tons. The NoV contamination of the fruits was mainly driven by the route of NoV shedding food pickers (95.8%) rather than by spraying contaminated pesticide water (4.2%) (baseline scenario with 5 shedding pickers and contaminated pesticide water). Inclusion of appropriate hand washing procedures or hand washing followed by hand disinfection resulted in estimated reductions of the mean NoV levels from 14.1 to 0.16 and 0.17 NoV particles per kg raspberries, respectively, for the baseline scenario with 5 out of 245 food pickers shedding NoV. The use of a mild heat treatment (30s at 75°C) during further processing of berries to purees was noted to reduce mean NoV levels substantially from 14.1 to 0.2 NoV particles per kg raspberry puree. For IQF raspberries, the NoV contamination is heterogeneously distributed and resulted in a mean contamination of 3.1 NoV particles per 250g package containing approximately 115 berries. This farm-to-fork model is a useful tool for evaluating NoV mitigation strategies in the soft red fruit supply chain.

Assessing the status of food safety management systems for fresh produce production in East Africa: evidence from certified green bean farms in Kenya and noncertified hot pepper farms in Uganda

The farms of fresh produce farmers are major sources of food contamination by microbiological organisms and chemical pesticides. In view of their choice for farming practices, producers are influenced by food safety requirements. This study analyzes the role of food safety standard certification toward the maturity of food safety management systems (FSMS) in the primary production of fresh produce. Kenya and Uganda are two East African countries that export green beans and hot peppers, respectively, to the European Union but have contrasting features in terms of agricultural practices and certification status. In the fresh produce chain, a diagnostic instrument for primary production was used to assess context factors, core control and assurance activities, and system output to measure the performance of FSMS for certified green bean farms in Kenya and noncertified hot pepper farms in Uganda. Overall, our findings show that in Uganda, noncertified hot pepper farms revealed only a "basic level of control and assurance" activities in their FSMS, which was not satisfactory, because no insight into potential pesticide microbial contamination was presented by these farmers. On the other hand, certified green bean farms in Kenya had an "average level of control and assurance," providing insight into the delivered food safety and quality by the farmers. Farm size did not impact the maturity level of FSMS. This study confirms the role played by food safety standard certification toward the maturity of FSMS implemented in developing countries and demonstrates the possibility of Ugandan farms to upgrade agricultural practices in the fresh produce sector.

Belgian and Spanish consumption data and consumer handling practices for fresh fruits and vegetables useful for further microbiological and chemical exposure assessment

A consumer survey was organized in Spain and Belgium to obtain consumption data and to gain insight into consumer handling practices for fresh vegetables consumed raw or minimally processed (i.e., heads of leafy greens, bell peppers, tomatoes, fresh herbs, and precut and packed leafy greens) and fruits to be consumed without peeling (i.e., apples, grapes, strawberries, raspberries, other berries, fresh juices, and precut mixed fruit). This information can be used for microbiological and/or chemical food safety research. After extensive cleanup of rough databases for missing and extreme values and age correction, information from 583 respondents from Spain and 1,605 respondents from Belgium (18 to 65 years of age) was retained. Daily intake (grams per day) was calculated taking into account frequency and seasonality of consumption, and distributions were obtained that can be used in quantitative risk assessment for chemical hazards with chronic effects on human health. Data also were recalculated to obtain discrete distributions of consumption per portion and the corresponding frequency of consumption, which can be used in acute microbiological risk assessment or outbreak investigations. The ranked median daily consumption of fruits and vegetables was similar in Spain and Belgium: apple > strawberry > grapes > strawberries and raspberries; and tomatoes > leafy greens > bell peppers > fresh herbs. However, vegetable consumption was higher (in terms of both portion and frequency of consumption) in Spain than in Belgium, whereas the opposite was found for fruit consumption. Regarding consumer handling practices related to storage time and method, Belgian consumers less frequently stored their fresh produce in a refrigerator and did so for shorter times compared with Spanish consumers. Washing practices for lettuce heads and packed leafy greens also were different. The survey revealed differences between these two countries in consumption and consumer handling practices, which can have an impact on outcomes of future microbiological or chemical risk assessment studies.

Microbiological performance of a food safety management system in a food service operation

The microbiological performance of a food safety management system in a food service operation was measured using a microbiological assessment scheme as a vertical sampling plan throughout the production process, from raw materials to final product. The assessment scheme can give insight into the microbiological contamination and the variability of a production process and pinpoint bottlenecks in the food safety management system. Three production processes were evaluated: a high-risk sandwich production process (involving raw meat preparation), a medium-risk hot meal production process (starting from undercooked raw materials), and a low-risk hot meal production process (reheating in a bag). Microbial quality parameters, hygiene indicators, and relevant pathogens (Listeria monocytogenes, Salmonella, Bacillus cereus, and Escherichia coli O157) were in accordance with legal criteria and/or microbiological guidelines, suggesting that the food safety management system was effective. High levels of total aerobic bacteria (>3.9 log CFU/50 cm(2)) were noted occasionally on gloves of food handlers and on food contact surfaces, especially in high contamination areas (e.g., during handling of raw material, preparation room). Core control activities such as hand hygiene of personnel and cleaning and disinfection (especially in highly contaminated areas) were considered points of attention. The present sampling plan was used to produce an overall microbiological profile (snapshot) to validate the food safety management system in place.

Relation between microbiological quality, metabolite production and sensory quality of equilibrium modified atmosphere packaged fresh-cut produce

The quality of four types of fresh-cut produce, packaged in consumer-sized packages under an equilibrium modified atmosphere and stored at 7 degrees C, was assessed by establishing the relation between the microbial outgrowth and the corresponding production of nonvolatile compounds and related sensory disorders. In vitro experiments, performed on a lettuce-juice-agar, demonstrated the production of nonvolatile compounds by spoilage causing lactic acid bacteria and Enterobacteriaceae. Pseudomonas fluorescens and yeasts, however, were not able to produce detectable amounts of nonvolatile metabolites. The type of spoilage and quality deterioration in vivo depended on the type of vegetable. Mixed lettuce and chicory endives, leafy tissues, containing naturally low concentrations of sugars, showed a spoilage dominated by Gram-negative microorganisms, which are not producing nonvolatile compounds. Sensory problems were associated with visual properties and the metabolic activity of the plant tissue. Mixed bell peppers and grated celeriac, on the other hand, demonstrated a fast and intense growth of spoilage microorganisms, dominated by lactic acid bacteria and yeasts. This proliferation resulted in detectable levels of organic acids and the rejection by the trained sensory panel was based on the negative perception of the organoleptical properties (off-flavour, odour and taste). The applied microbiological criteria corresponded well with detectable changes in sensory properties and measurable concentrations of nonvolatile compounds, surely in the cases where lactic acid bacteria and yeasts were provoking spoilage. Consequently, the freshness of minimally processed vegetables, sensitive for outgrowth of lactic acid bacteria and yeasts (e.g., carrots, celeriac, bell peppers, mixtures with non-leafy vegetables) can be evaluated via analysis of the produced nonvolatile compounds.

Predictive modelling for packaging design: equilibrium modified atmosphere packages of fresh-cut vegetables subjected to a simulated distribution chain

The impact of temperature fluctuations in a simulated cold distribution chain, typical of commercial practice, was investigated on both the microbial and sensorial quality of equilibrium modified atmosphere (EMA) packaged minimally processed vegetables. The internal O2 concentration of the designed packages could be predicted for the different steps of the simulated distribution chain by applying an integrated mathematical system. The internal atmosphere in the packages remained in its aerobic range during storage in the chain due to the application of high permeable packaging films for O2 and CO2. Spoilage microorganisms were proliferating fast on minimally processed bell peppers and lettuce. Yeasts showed to be the shelf-life limiting group. Visual properties limited the sensorial shelf-life. Listeria monocytogenes was able to multiply on cucumber slices, survived on minimally processed lettuce and decreased in number on bell peppers due to the combination of low pH and refrigeration. Aeromonas caviae was multiplying on both cucumber slices and mixed lettuce, but was as well inhibited by the low pH of bell peppers. Storage temperature control was found to be of paramount importance for the microbial (spoilage and safety) and sensorial quality evaluation of EMA-packaged minimally processed vegetables.

Effect of high oxygen modified atmosphere packaging on microbial growth and sensorial qualities of fresh-cut produce

The application of High Oxygen Atmospheres (HOA) (i.e. > 70% O2) for packaging ready-to-eat vegetables was evaluated as an alternative technique for low O2 Equilibrium Modified Atmosphere (EMA) packaging (3% O2-5% CO2-balance N2) for respiring products. Comparative experiments between both techniques were performed in-vitro and in-vivo. Typical spoilage causing microorganisms (Pseudomonas fluorescens, Candida lambica), the moulds Botrytis cinerea, Aspergillus flavus and the opportunistic psychrotrophic human pathogenic microorganism associated with refrigerated minimally processed vegetables. Aeromonas caviae (HG4), showed a retarded growth during the conducted in-vitro studies at 4 degrees C in 70%, 80% and 95% O2 as examples of HOA compared to the in-vitro experiments in 5% O2 (as example of EMA packaging) and the effect was more pronounced in 95% O2. The effect of the high O2-concentrations on the human pathogen Listeria monocytogenes resulted in an extended lag phase (95% O2). The plant pathogen Erwinia carotovora was increasingly stimulated by increasing high O2-concentrations. During a storage experiment of three types of ready-to-eat vegetables (mushroom slices, grated celeriac and shredded chicory endive), which are sensitive to enzymatic browning and microbial spoilage, the effect of EMA and HOA (95% O2-5% N2) on their quality and shelf life was compared. High O2 atmospheres were found to be particularly effective in inhibiting enzymatic browning of the tested vegetables. Also, the microbial quality was better as a reduction in yeast growth was observed. The HOA can be applied as an alternative for low O2 modified atmospheres for some specific types of ready-to-eat vegetables, sensitive to enzymatic browning and spoilage by yeasts.

A combination of high oxygen atmosphere and equilibrium modified atmosphere packaging to improve the keeping quality of red fruits

When high-barrier material is used to package fresh whole fruit in high oxygen atmospheres, shelf life is limited due to the accumulation of its produced CO2 and its creation of an anaerobic atmosphere. In this study, the effect of the combination of High Oxygen Atmosphere and Equilibrium Modified Atmosphere Packaging was tested on the shelf life of two non-climacteric red fruits, particularly strawberries and raspberries, at 7 degrees C. Herefor, the following packaging systems are compared: the conventional method of packaging in a macroperforated high-barrier film (air conditions) (1), Equilibrium Modified Atmosphere (EMA, i.e. 3-5% O2 and 5-10% CO2-balance N2) (2) and two novel modified atmospheres: High Oxygen Atmosphere (HOA, i.e. > 70% O2-balance N2) in a high-barrier film (3) and HOA in a EMA film with an adjusted film permeability (4). The shelf life of the fruits was determined by evaluating the evolution of the internal oxygen, carbon dioxide and ethylene concentrations in the packages, the microbial and sensorial quality during the storage, the loss of weight due to transpiration and respiration of the fruit and the loss of marketable fruit due to visual decay or to Botrytis growth. The High Oxygen Atmosphere in the EMA film re-established after five days to an equilibrium of 3% O2 and 5% CO2. The High Oxygen Atmosphere in the high-barrier film remained high during the first five days of storage, but decreased then rapidly to anaerobic conditions, resulting in off-flavours and odours. To avoid an accumulation of ethylene inside the high-barrier package, an ethylene adsorbing monolayer was added. Shelf life of strawberries and raspberries, packed in air conditions, was limited by growth of moulds and yeasts, rather than by sensorial unacceptance. On the other hand, sensorial properties limited the shelf life of the fruits packed under modified atmosphere. Especially High Oxygen Atmosphere improved the microbial quality, due to the inhibiting effect on yeasts and moulds. However, when oxygen was depleted and carbon dioxide had accumulated, sensorial quality (odour, taste andfirmness) was deteriorated. As this is not the case with high O2 in an EMA film, the latter can be assumed as a promising configuration for respiring fresh produce, combining the beneficial effect of high O2 and EMAP.

Behavior of Listeria monocytogenes and Aeromonas spp. on fresh-cut produce packaged under equilibrium-modified atmosphere

Storage experiments were conducted to follow the behavior of pathogens on fresh-cut vegetables (trimmed brussels sprouts, grated carrots, shredded iceberg lettuce, and shredded chicory endives) packaged under an equilibrium-modified atmosphere (EMA) (2 to 3% O2, 2 to 3% CO2, and 94 to 96% N2) and stored at 7 degrees C. As a comparison, fresh-cut vegetables were also packaged in a perforated high-barrier film (air conditions) and stored at 7 degrees C. In a first step, the shelf life of the vegetables in the two kinds of packages was determined by evaluating the microbiological quality as well as the sensorial quality (appearance, taste, and odor). In general, sensorial properties were faster in limiting the shelf life than microbiological criteria. The shelf life of the vegetables stored under an EMA was extended by 50% or more, compared with the air-stored vegetables. In a second storage experiment, the four fresh-cut vegetables were inoculated with a cocktail of psychrotrophic pathogens (Listeria monocytogenes, Aeromonas caviae [HG4]) and A. bestiarum (HG2) before packaging under an EMA and air at 7 degrees C. The inoculated pathogens were more influenced by the type of vegetable than by the type of atmosphere. No growth was detected on the brussels sprouts or on carrots (L. monocytogenes). Aeromonas spp. had a higher growth rate than L. monocytogenes on the shredded chicory endives and shredded iceberg lettuce at 7 degrees C.