Microbiological Risk Assessment in Foods

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This entry is adapted from the peer-reviewed paper 10.3390/foods12071483

Food safety is one the major goals to achieve worldwide; in fact, one of the most underestimated problems is the high incidence of foodborne diseases. The MRA (Microbiological Risk Assessment) is a specific set of guidelines to manage microbiological risk in the food industry. Two different approaches are possible: bottom-up or top-down.

hazard analysis ranking foodborne disease

1. Risk Analysis in the Food Industry

Risk analysis is a fundamental step to reduce to an acceptable level the problems occurring during the food production process and which can cause problems for the consumers’ health; according to FAO/WHO ^[1], it consists of three components: risk assessment, risk management, and risk communication. These phases were defined as follows:

Risk assessment is the scientific evaluation of potential, or known, adverse health effects resulting from human exposure to foodborne hazards.
Risk management is the operative consequence of risk assessment, and it consists in understanding policies and selecting the appropriate actions to achieve ALOP (appropriate level of protection).
Risk communication is an exchange of information, opinions, and data among all the stakeholders involved in risk analysis.

Risk assessment is a qualitative and quantitative process, and it can be performed according to different standards, such as the IEC 31010:2019 or FAO/WHO guidelines ^[2]. It is composed of three main steps: risk identification, risk analysis, and risk evaluation.

Identification starts from a study about the target food and is usually based on scientific data, expert opinions, and previous experience ^[3]. Thanks to an accurate knowledge of the matrix, it is possible to identify biological, chemical, and physical hazards; some examples are reported in Table 1.

Table 1. Examples of biological, chemical, and physical hazards in the food industry.

Biological Hazard	Chemical Hazard	Physical Hazard
Bacteria	Pesticides	Foreign bodies
Viruses	Heavy metals	Insects
Protozoa	Toxins	Employees’ personal items

Each risk is analysed to understand its nature, severity, and consequences, focusing on many factors and variables (uncertainties, likelihood, consuming scenario etc.). One of the most used techniques is the magnitude/likelihood matrix, which allows numerical values to be set for the magnitude and likelihood of the risk ^[4] and to display a rank for that risk in an intuitive graphical way; magnitude (M) is a measure of the harmful consequences of the risk, while likelihood (L) refers to the chance of something happening; thus, it is usually described using terms such as probability or frequency. According to this approach, risk level is the result of the following formula:

Risk Level = Magnitude × Likelihood

The magnitude/likelihood matrix is based on consequences scales which associate the magnitude and the likelihood of the risk to a numerical value (Table 2). After giving a value to these two factors, the results give a risk estimation (or risk level), as shown in Table 3; colour defines the risk weight as follows:

Table 2. Magnitude and likelihood scales ^[5].

Rating	Magnitude	Likelihood
5	Lethal	Expected likely
4
3
2
1	Irrelevant illness	Extremely unlikely

Table 3. Magnitude/likelihood matrix and risk level. Red, high risk; yellow, medium risk; green, low risk.

Magnitude rating	5	5	10	15	20	25
	4	4	8	12	16	20
	3	3	6	9	12	15
	2	2	4	6	8	10
	1	1	2	3	4	5
		1	2	3	4	5
		Likelihood rating

Green cells represent a low risk level.
Yellow cells represent a middle risk level.
Red cells represent a high risk level.

According to this matrix, authorities and participants of the food chain will focus on the higher risk level to find the right preventive strategies and to reduce the risk to an acceptable level.

In the food industry, the biological and chemical risks are the most feared because of the damage which they can cause to human health; the following sections of this paper address the topic of microbiological risk. For this purpose, the Codex Alimentarius Commission published a set of guidelines (CXG 30-1999) ^[6], while the FAO (Food and Agriculture Organization) and WHO (World Health Organization) released “Microbiological risk assessment: guidance for food” (MRA 36) ^[2], which updates and brings together in a single volume three previous guidance documents (MRA 3, MRA 7, and MRA 17) (MRA; Microbiological Risk Assessment) ^[7].

2. Risk Assessment for Microbiological Issues in the Food Industry

The MRA is a specific set of guidelines to manage microbiological risk in the food industry. Two different approaches are possible: bottom-up or top-down (Figure 1). In the top-down approach, the study is based on the knowledge about the main hazard which can occur in a food matrix, while the bottom-up approach uses epidemiological information to identify the most probable hazards and to assess the risk ^[8].

Figure 1. Graphical representation of the top-down (a), and bottom-up (b) approaches.

The MRA is divided into four phases, and each phase can be summarized by a set of a few questions. In the following paragraphs, all MRA steps ^[7] are briefly summarized, as shown in Figure 2.

Figure 2. Steps and questions in the Risk Assessment process.

2.1. Hazard Identification

The aim of this first phase is to identify all the pathogens which can survive in the target food and which can be dangerous for consumers’ health; it is worth mentioning that the more correct the microorganism identification is, the more effective is the risk assessment. In this step, assessors should consider the properties of the food matrix (composition, intrinsic, and extrinsic factors), its technological story (possible thermal treatments or any other process which could affect pathogen survival), and pathogen physiology, as well as the main properties of the raw material and its origin.

Hazard identification, like any other stage, can be characterized by data and methodologies validated at the international level (for example, the surveys periodically performed by regulatory agencies; the tools of Predictive Microbiology, such as ComBase; or CB Premium) and supported by the experience of risk assessors or by the latest advances in the literature.

2.2. Hazard Characterization

The second phase consists of a qualitative and quantitative evaluation of the severity degree of the pathogen, considering the nature of issues such as fever, diarrhoea, and neural problems, among others. In this context, details of the severity of pathogens can be found in some reports of public agencies on foodborne diseases periodically published at the international level; an example is the report on zoonosis by the European Union ^[9]. The details required for this step are, among others, the kind of disease (infection or toxin production), the infectious dose, the pathways of disease (how the pathogen enters the host and the mechanisms involved in disease progression), host susceptibility, treatments required for disease remission, and epidemiological data (hospitalization, medical treatments, deaths).

2.3. Exposure Assessment

The third phase supplies information about the level of danger posed by the pathogen or toxin present in food during consumption, considering the different potential paths or moments of contamination, the impact of the various processing steps, the kind of food (raw material or processed food), and any relevant data related to the frequency and the quantity of consumption. In this step, assessors should focus on the flowchart of food production and point out all the hurdles that a pathogen could encounter (e.g., thermal treatments, acidification, storage, preparation before consumption); it is important to precisely define all conditions and their quantitative effect on the pathogen. It is also important to have access to survey data on the contamination of the raw material.

2.4. Risk Characterization

In this phase, the previous phases are integrated to gain a qualitative and/or quantitative evaluation of the risk as a background for correct risk management decisions. Generally, all details and information found throughout the hazard identification, hazard characterization, and exposure assessment steps are used as input values for algorithms or other modelling tools.

Risk assessment can be qualitative, semi-quantitative, and quantitative; qualitative assessment compensates for the lack of data by using expert opinions and intuitions, while quantitative risk assessment can be stochastic or deterministic; it is only based on strong and large data and/or statistics such as epidemiological reports, consumption rate, burden of disease, etc. and needs the support of specific software to collect, analyse and interpret the large amount of data.

The semi-quantitative risk assessment is a combination of qualitative and quantitative assessments, as each qualitative risk estimate is assigned a number which has a statistical weight, such as for probability ranges. One of the most common ways to represent semi-quantitative assessment is the risk matrix.

References

Pal, M.; Aregawi, W.; Singh, R. The Role of Hazard Analysis Critical Control Point in Food Safety. Beverage Food World 2016, 43, 33–36.
Microbiological Risk Assessment: Guidance for Food. Available online: https://www.who.int/publications/i/item/9789240024892 (accessed on 11 January 2023).
De Keuckelaere, A.; Jacxsens, L.; Amoah, P.; Medema, G.; Mcclure, P.; Jaykus, L.A.; Uyttendaele, M. Zero Risk Does Not Exist: Lessons Learned from Microbial Risk Assessment Related to Use of Water and Safety of Fresh Produce. Compr. Rev. Food Sci. Food Saf. 2015, 14, 387–410.
Australian Drinking Water Guidelines|NHMRC. Available online: https://www.nhmrc.gov.au/about-us/publications/australian-drinking-water-guidelines (accessed on 2 March 2023).
ISO-IEC 31010:2019-Risk Management—Risk Assessment Techniques. Available online: https://www.iso.org/standard/72140.html (accessed on 20 January 2023).
Guidelines|CODEXALIMENTARIUS FAO-WHO. Available online: https://www.fao.org/fao-who-codexalimentarius/codex-texts/guidelines/en/ (accessed on 20 December 2022).
Nakashima, A.A.; Gonzalez-Barron, U.; Bouchriti, N.; Hartnett, E.; Karunasagar, I.; Kiermeier, A.; Koutsoumanis, K.; Li, F.-Q.; Ross, T.; Schaffner, D.; et al. Microbiological Risk Assessment-Guidance for Food; Food & Agriculture Org.: Rome, Italy, 2021.
Gkogka, E.; Reij, M.W.; Gorris, L.G.M.; Zwietering, M.H. Risk Assessment Strategies as a Tool in the Application of the Appropriate Level of Protection (ALOP) and Food Safety Objective (FSO) by Risk Managers. Int. J. Food Microbiol. 2013, 167, 8–28.
European Food Safety Authority; European Centre for Disease Prevention and Control. The European Union One Health 2021 Zoonoses Report. EFSA J. 2022, 20, e07666.

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Gaetano Sollazzo

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Update Date: 18 Apr 2023

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