Determining the microbiological criteria for lot rejection from the performance objective or food safety objective

Formulating the best Helbat: A Tigraian semi-liquid fasting condiment

Helbat (hl'bət), a fasting semi-liquid condiment, is a popular indigenous traditional fermented product in Tigrai (a.k.a. Tigray), Ethiopia. It is formulated using Vicia faba flour prepared from mildly roasted dry beans. Despite its dietary, nutritional, religious, and cultural significance, the condiment is yet not exposed to scientific study. Hence, this research was carried out to: (a) ascertain the best faba bean variety for preparing high quality Helbat, (b) develop the formulation and preparation protocol of high quality Helbat, (c) determine the effects of fermentation and storage temperature and time on the physicochemical characteristics, proximate and mineral compositions, microbiological properties, and sensory qualities of Helbat, and (d) determine the shelf life of Helbat as the function of storage time and temperature. To this end, three faba bean varieties used in preparing Helbat as well as fermenting and stored Helbat products were studied using standard physicochemical, microbiological, and sensory evaluation procedures. Quantitative data were processed using inferential statistical methods and mean (±SD) values were compared at a priori set p-value of ≤0.05. The study showed that: (a) the best faba bean variety for making high quality Helbat was Megulat; (b) the best Helbat formulation constituted 400 wt units of bean flour, 7 wt units of garlic, 6 wt units of ginger, 5 wt units fenugreek, 5 wt units of corrorima, 8 wt units of red pepper, and 3 wt units of black mustard; (c) the best Helbat formulation was nutritionally rich to supplement fasting consumers with proteins, fats, and minerals; (d) the Helbat formulation remained safe for up to eight weeks while maintaining its attractive sensory qualities when stored at 11-15 °C, and (e) increasing the fermentation and storage times led to changes in its physicochemical properties (i.e., temperature, pH, total titratable acidity, and total soluble solute) and depletion of many nutritionally vital components such as fats, proteins, and minerals. Thus, unless production and storage conditions are somehow modified, Helbat needs to be consumed fresh after three to seven days of fermentation. But further research may be required to make this recommendation conclusively. Exploring into its antioxidant properties and lactic acid bacteria (LAB) may highlight its qualities further.

Anti-Escherichia coli O157:H7 as Natural Preservative to Control and Prevent Food Contamination in Meat and Fish Products

BACKGROUND AND OBJECTIVE

Shiga toxin-producing Escherichia coli O157:H7 is a troubled foodborne pathogen associated with contamination of meat, fish and poultry. The present work aimed to evaluate plant extracts as natural preservatives anti- Escherichia coli O157:H7 in meat and fish products.

MATERIALS AND METHODS

Antibacterial activity and minimum inhibitory concentrations (MICs) of seven herbal plants, clove, marjoram, sage, pomegranate peel, turmeric, Cassia fistula and black pepper and their different 6 mixes were examined against Escherichia coli O157:H7. Phytochemical qualitative analysis, phenolic compounds (HPLC), total phenolic, total flavonoid contents and antioxidant activities of individual extracts and their 6 mixes were evaluated. Combination Mix 5 extract was applied on meat and fish-fillet, then its antimicrobial effect against E. coli O157:H7 and sensory evaluation were assessed.

RESULTS

Five extracts exhibited good antibacterial activity against Escherichia coli O157:H7. The greatest inhibition zone was recorded by clove aqueous extract (25 mm). Mix 5 (clove, sage, pomegranate and Cassia fistula) showed the highest inhibition with MIC of 3.0 mg mL-1. This mix exhibited strong anti-bactericidal effect against E. coli O157:H7 in meat and fish-fillet products throughout 8 days of cold storage (4°C). The sensory evaluation revealed that Mix 5 was acceptable by panelists with concentration of 0.50% in beef burgers and 0.25% in fish-fillet.

CONCLUSION

This study suggests that the use of herbal extracts provide antibacterial potentials against food pathogens in meat and fish products.

Managing biological invasions in urban environments with the acceptance sampling approach

Detections of invasive species outbreaks are often followed by the removal of susceptible host organisms in order to slow the spread of the invading pest population. We propose the acceptance sampling approach for detection and optional removal of susceptible host trees to manage an outbreak of the emerald ash borer (EAB), a highly destructive forest pest, in Winnipeg, Canada. We compare the strategy with two common delimiting survey techniques that do not consider follow-up management actions such as host removal. Our results show that the management objective influences the survey strategy. The survey-only strategies maximized the capacity to detect new infestations and prioritized sites with high likelihood of being invaded. Comparatively, the surveys with subsequent host removal actions allocated most of the budget to sites where complete host removal would minimize the pest's ability to spread to uninvaded locations. Uncertainty about the pest's spread causes the host removal measures to cover a larger area in a uniform spatial pattern and extend to farther distances from already infested sites. If a decision maker is ambiguity-averse and strives to avoid the worst-case damages from the invasion, the optimal strategy is to survey more sites with high host densities and remove trees from sites at farther distances, where EAB arrivals may be uncertain, but could cause significant damage if not detected quickly. Accounting for the uncertainty about spread helps develop a more robust pest management strategy. The approach is generalizable and can support management programs for new pest incursions.

Optimal Inspection of Imports to Prevent Invasive Pest Introduction

The United States imports more than 1 billion live plants annually-an important and growing pathway for introduction of damaging nonnative invertebrates and pathogens. Inspection of imports is one safeguard for reducing pest introductions, but capacity constraints limit inspection effort. We develop an optimal sampling strategy to minimize the costs of pest introductions from trade by posing inspection as an acceptance sampling problem that incorporates key features of the decision context, including (i) simultaneous inspection of many heterogeneous lots, (ii) a lot-specific sampling effort, (iii) a budget constraint that limits total inspection effort, (iv) inspection error, and (v) an objective of minimizing cost from accepted defective units. We derive a formula for expected number of accepted infested units (expected slippage) given lot size, sample size, infestation rate, and detection rate, and we formulate and analyze the inspector's optimization problem of allocating a sampling budget among incoming lots to minimize the cost of slippage. We conduct an empirical analysis of live plant inspection, including estimation of plant infestation rates from historical data, and find that inspections optimally target the largest lots with the highest plant infestation rates, leaving some lots unsampled. We also consider that USDA-APHIS, which administers inspections, may want to continue inspecting all lots at a baseline level; we find that allocating any additional capacity, beyond a comprehensive baseline inspection, to the largest lots with the highest infestation rates allows inspectors to meet the dual goals of minimizing the costs of slippage and maintaining baseline sampling without substantial compromise.

Microbiological and Modeling Approach to Derive Performance Objectives for Bacillus cereus Group in Ready-to-Eat Salads

In this article, the performance objectives (POs) for Bacillus cereus group (BC) in celery, cheese, and spelt added as ingredients in a ready-to-eat mixed spelt salad, packaged under modified atmosphere, were calculated using a Bayesian approach. In order to derive the POs, BC detection and enumeration were performed in nine lots of naturally contaminated ingredients and final product. Moreover, the impact of specific production steps on the BC contamination was quantified. Finally, a sampling plan to verify the ingredient lots' compliance with each PO value at a 95% confidence level (CL) was defined. To calculate the POs, detection results as well as results above the limit of detection but below the limit of quantification (i.e., censored data) were analyzed. The most probable distribution of the censored data was determined and two-dimensional (2D) Monte Carlo simulations were performed. The PO values were calculated to meet a food safety objective of 4 log₁₀ cfu of BC for g of spelt salad at the time of consumption. When BC grows during storage between 0.90 and 1.90 log₁₀ cfu/g, the POs for BC in celery, cheese, and spelt ranged between 1.21 log₁₀ cfu/g for celery and 2.45 log₁₀ cfu/g for spelt. This article represents the first attempt to manage the concept of PO and 2D Monte Carlo simulation in the flow chart of a complex food matrix, including raw and cooked ingredients.

Proposal of performance objectives and sampling schemes for Listeria monocytogenes in fresh meat intended to be eaten cooked under different storage practices

The goal of this study was to define a practical approach to derive risk management measures, such as performance objectives (POs), for Listeria monocytogenes in pork cuts intended to be eaten cooked. Moreover, sampling plans to verify the compliance of meat lots to such POs are presented. The POs were estimated as prevalence and/or concentration values that should not be exceeded at time of consumption. To derive possible POs for L. monocytogenes, ten lots of pork cuts, collected within the same slaughterhouse along a one-year period, were tested for the presence and concentration of the pathogen under four different scenarios through the product shelf life. Our results indicated that the median values of the prevalence distributions ranged between 0.41 and 0.68. The number of samples to be tested in order to verify lot compliance ranged between six, for samples tested immediately after packaging, and three, for samples tested at the end of the shelf life. The concentration values ranged between 2.02 log10 CFU/g, for samples tested immediately after packaging, up to 3.14 log10 CFU/g for samples tested after final storage at 14°C. The concentration of L. monocytogenes in the samples contaminated by less than 10 CFU/g was estimated between 7 CFU/10g to 7 CFU/g, after storage at retail and abuse temperature, respectively. Basing on the knowledge of log normal distributions, the maximum contamination level of the lots in order to achieve the suggested POs, was calculated. It was obtained that mean concentration estimated as PO should be between -0.43 and 0.48 log10 CFU/g. Other risk management options are further evaluated and discussed. These results would help food operators and authorities to establish safety targets and corrective actions regarding inhibition of L. monocytogenes in fresh pork meat.

Selection of process conditions by risk assessment for apple juice pasteurization by UV-heat treatments at moderate temperatures

The effect of bactericidal UV-C treatments (254 nm) on Escherichia coli O157:H7 suspended in apple juice increased synergistically with temperature up to a threshold value. The optimum UV-C treatment temperature was 55 °C, yielding a 58.9% synergistic lethal effect. Under these treatment conditions, the UV-heat (UV-H55 °C) lethal variability achieving 5-log reductions had a logistic distribution (α = 37.92, β = 1.10). Using this distribution, UV-H55 °C doses to achieve the required juice safety goal with 95, 99, and 99.9% confidence were 41.17, 42.97, and 46.00 J/ml, respectively, i.e., doses higher than the 37.58 J/ml estimated by a deterministic procedure. The public health impact of these results is that the larger UV-H55 °C dose required for achieving 5-log reductions with 95, 99, and 99.9% confidence would reduce the probability of hemolytic uremic syndrome in children by 76.3, 88.6, and 96.9%, respectively. This study illustrates the importance of including the effect of data variability when selecting operational parameters for novel and conventional preservation processes to achieve high food safety standards with the desired confidence level.

The challenge of defining risk-based metrics to improve food safety: inputs from the BASELINE project

In 2002, the Regulation (EC) 178 of the European Parliament and of the Council states that, in order to achieve the general objective of a high level of protection of human health and life, food law shall be based on risk analysis. However, the Commission Regulation No 2073/2005 on microbiological criteria for foodstuffs requires that food business operators ensure that foodstuffs comply with the relevant microbiological criteria. Such criteria define the acceptability of a product, a batch of foodstuffs or a process, based on the absence, presence or number of micro-organisms, and/or on the quantity of their toxins/metabolites, per unit(s) of mass, volume, area or batch. The same Regulation describes a food safety criterion as a mean to define the acceptability of a product or a batch of foodstuff applicable to products placed on the market; moreover, it states a process hygiene criterion as a mean indicating the acceptable functioning of the production process. Both food safety criteria and process hygiene criteria are not based on risk analysis. On the contrary, the metrics formulated by the Codex Alimentarius Commission in 2004, named Food Safety Objective (FSO) and Performance Objective (PO), are risk-based and fit the indications of Regulation 178/2002. The main aims of this review are to illustrate the key differences between microbiological criteria and the risk-based metrics defined by the Codex Alimentarius Commission and to explore the opportunity and also the possibility to implement future European Regulations including PO and FSO as supporting parameters to microbiological criteria. This review clarifies also the implications of defining an appropriate level of human protection, how to establish FSO and PO and how to implement them in practice linked to each other through quantitative risk assessment models. The contents of this review should clarify the context for application of the results collected during the EU funded project named BASELINE (www.baselineeurope.eu) as described in the papers of this special issue. Such results show how to derive POs for specific food/biological hazard combinations selected among fish, egg, dairy, meat and plant products.

Optimal Food Safety Sampling Under a Budget Constraint

Much of the literature regarding food safety sampling plans implicitly assumes that all lots entering commerce are tested. In practice, however, only a fraction of lots may be tested due to a budget constraint. In such a case, there is a tradeoff between the number of lots tested and the number of samples per lot. To illustrate this tradeoff, a simple model is presented in which the optimal number of samples per lot depends on the prevalence of sample units that do not conform to microbiological specifications and the relative costs of sampling a lot and of drawing and testing a sample unit from a lot. The assumed objective is to maximize the number of nonconforming lots that are rejected subject to a food safety sampling budget constraint. If the ratio of the cost per lot to the cost per sample unit is substantial, the optimal number of samples per lot increases as prevalence decreases. However, if the ratio of the cost per lot to the cost per sample unit is sufficiently small, the optimal number of samples per lot reduces to one (i.e., simple random sampling), regardless of prevalence. In practice, the cost per sample unit may be large relative to the cost per lot due to the expense of laboratory testing and other factors. Designing effective compliance assurance measures depends on economic, legal, and other factors in addition to microbiology and statistics.

Improvement of sampling plans for Salmonella detection in pooled table eggs by use of real-time PCR

Eggs and egg products have been described as the most critical food vehicles of salmonellosis. The prevalence and level of contamination of Salmonella on table eggs are low, which severely affects the sensitivity of sampling plans applied voluntarily in some European countries, where one to five pools of 10 eggs are tested by the culture based reference method ISO 6579:2004. In the current study we have compared the testing-sensitivity of the reference culture method ISO 6579:2004 and an alternative real-time PCR method on Salmonella contaminated egg-pool of different sizes (4-9 uninfected eggs mixed with one contaminated egg) and contamination levels (10°-10(1), 10(1)-10(2), 10(2)-10(3)CFU/eggshell). Two hundred and seventy samples corresponding to 15 replicates per pool size and inoculum level were tested. At the lowest contamination level real-time PCR detected Salmonella in 40% of contaminated pools vs 12% using ISO 6579. The results were used to estimate the lowest number of sample units needed to be tested in order to have a 95% certainty not falsely to accept a contaminated lot by Monte Carlo simulation. According to this simulation, at least 16 pools of 10 eggs each are needed to be tested by ISO 6579 in order to obtain this confidence level, while the minimum number of pools to be tested was reduced to 8 pools of 9 eggs each, when real-time PCR was applied as analytical method. This result underlines the importance of including analytical methods with higher sensitivity in order to improve the efficiency of sampling and reduce the number of samples to be tested.

Comparing the effect of various contamination levels for salmonella in chicken meat preparations on the probability of illness in belgium

At the urging of competent national authorities, a limited risk assessment on Salmonella in chicken meat preparations in Belgium was undertaken following a retail-to-table approach. The input distribution of Salmonella was based on surveillance data in Belgium. To analyze the relative impact of reducing the risk of salmonellosis associated with a decrease in the Salmonella contamination level, different distributions based on the actual situation but limiting the number of portions containing Salmonella at 1 CFU per 1, 10, and 25 g of meat were used in the quantitative microbial risk assessment model. The quantitative microbial risk assessment model also was run several times with a theoretical fixed input of Salmonella assuming all portions possessed the same fixed contamination level set at 1,000, 100, 10, and 1 CFU/g of meat and 1 CFU per 10, 25, 100, and 1,000 g of meat. With regard to the initial contamination level, the results indicate, both by the narrowing of the current distribution and by the fixed input, that especially the higher levels of contamination (>1 CFU/g) contribute to the increased risk for salmonellosis.

Application of quantitative microbial risk assessments for estimation of risk management metrics: Clostridium perfringens in ready-to-eat and partially cooked meat and poultry products as an example

The U.S. Department of Agriculture, Food Safety and Inspection Service is exploring quantitative risk assessment methodologies to incorporate the use of the Codex Alimentarius' newly adopted risk management metrics (e.g., food safety objectives and performance objectives). It is suggested that use of these metrics would more closely tie the results of quantitative microbial risk assessments (QMRAs) to public health outcomes. By estimating the food safety objective (the maximum frequency and/or concentration of a hazard in a food at the time of consumption) and the performance objective (the maximum frequency and/or concentration of a hazard in a food at a specified step in the food chain before the time of consumption), risk managers will have a better understanding of the appropriate level of protection (ALOP) from microbial hazards for public health protection. We here demonstrate a general methodology that allows identification of an ALOP and evaluation of corresponding metrics at appropriate points in the food chain. It requires a two-dimensional probabilistic risk assessment, the example used being the Monte Carlo QMRA for Clostridium perfringens in ready-to eat and partially cooked meat and poultry products, with minor modifications to evaluate and abstract required measures. For demonstration purposes, the QMRA model was applied specifically to hot dogs produced and consumed in the United States. Evaluation of the cumulative uncertainty distribution for illness rate allows a specification of an ALOP that, with defined confidence, corresponds to current industry practices.

Quantitative risk assessment of Listeria monocytogenes in French cold-smoked salmon: II. Risk characterization

A model for the assessment of exposure to Listeria monocytogenes from cold-smoked salmon consumption in France was presented in the first of this pair of articles (Pouillot et al., 2007, Risk Analysis, 27:683-700). In the present study, the exposure model output was combined with an internationally accepted hazard characterization model, adapted to the French situation, to assess the risk of invasive listeriosis from cold-smoked salmon consumption in France in a second-order Monte Carlo simulation framework. The annual number of cases of invasive listeriosis due to cold-smoked salmon consumption in France is estimated to be 307, with a very large credible interval ([10; 12,453]), reflecting data uncertainty. This uncertainty is mainly associated with the dose-response model. Despite the significant uncertainty associated with the predictions, this model provides a scientific base for risk managers and food business operators to manage the risk linked to cold-smoked salmon contaminated with L. monocytogenes. Under the modeling assumptions, risk would be efficiently reduced through a decrease in the prevalence of L. monocytogenes or better control of the last steps of the cold chain (shorter and/or colder storage during the consumer step), whereas reduction of the initial contamination levels of the contaminated products and improvement in the first steps of the cold chain do not seem to be promising strategies. An attempt to apply the recent risk-based concept of FSO (food safety objective) on this example underlines the ambiguity in practical implementation of the risk management metrics and the need for further elaboration on these concepts.

Applying the food safety objective and related standards to thermal inactivation of Salmonella in poultry meat

The objective of this study was to investigate the practicality of designing a heat treatment process in a food manufacturing operation for a product governed by a Food Safety Objective (FSO). Salmonella in cooked poultry meat was taken as the working example. Although there is no FSO for this product in current legislation, this may change in the (near) future. Four different process design calculations were explored by means of deterministic and probabilistic approaches to mathematical data handling and modeling. It was found that the probabilistic approach was a more objective, transparent, and quantifiable approach to establish the stringency of food safety management systems. It also allowed the introduction of specific prevalence rates. The key input analyzed in this study was the minimum time required for the heat treatment at a fixed temperature to produce a product that complied with the criterion for product safety, i.e., the FSO. By means of the four alternative process design calculations, the minimum time requirement at 70 degrees C was established and ranged from 0.26 to 0.43 min. This is comparable to the U.S. regulation recommendations and significantly less than that of 2 min at 70 degrees C used, for instance, in the United Kingdom regulation concerning vegetative microorganisms in ready-to-eat foods. However, the objective of this study was not to challenge existing regulations but to provide an illustration of how an FSO established by a competent authority can guide decisions on safe product and process designs in practical operation; it hopefully contributes to the collaborative work between regulators, academia, and industries that need to continue learning and gaining experience from each other in order to translate risk-based concepts such as the FSO into everyday operational practice.

Management of microbiological safety of ready-to-eat meat products by mathematical modelling: Listeria monocytogenes as an example

The recent Commission Regulation (EC) No 2073/2005 establishes microbiological criteria in foods. For the pathogen Listeria monocytogenes in the category ready-to-eat foods able to support its growth, other than those intended for infants and for special medical purposes, two different microbiological criteria are proposed: (i) L. monocytogenes levels should be <100 cfu/g throughout the shelf-life of the product, (ii) absence in 25 g of the product at the stage before the food has left the immediate control of the food business operator, who has produced it. The application of either the first or the second of these criteria depends on whether or not the manufacturer is able to demonstrate that the level of L. monocytogenes in the food product will not exceed 100 cfu/g throughout its shelf-life. This demonstration should be based on physico-chemical characteristics of the target product and consultation of scientific literature, and, when necessary, on quantitative models and/or challenge tests. Once the characteristics of the product as well as scientific literature show that the pathogen has potential to grow on a specific food commodity, it seems adequate to use quantitative models and/or perform challenge tests to study the extent to which L. monocytogenes could grow. In this study, we aim to illustrate with an example in cooked ham the application of quantitative models as a tool to manage the compliance with these criteria. Two approaches were considered: deterministic and probabilistic, in three different commercial brands (A, B, and C). The deterministic approach showed that the limit 100 cfu/g was exceeded largely at the end of the shelf-life of all three; however, when reducing the storage time, the level of L. monocytogenes remained below 100 cfu/g in B. The probabilistic approach demonstrated very low percentiles corresponding to 100 cfu/g; when reducing the storage time, percentiles for three products increased, especially in products B and C (from 4.92% to 75.90%, and from 0.90% to 73.90%, respectively). This study shows how different storage times influence the level of L. monocytogenes at the end of the shelf-life of cooked ham, and, depending on the level reached, the microbiological criterion applied should be different, as stated above. Beside this, the choice of either point-estimate or probabilistic approach should be determined by the competent sanitary authority, and, in case of selecting the second approach, a certain percentile for the level 100 cfu/g should be established.