ISO 22000:2005 Decision Tree Logic and a Possible Decision Tree Model

The problems with ISO 22000 Decision Tree

Considering the ISO 22000:2005 decision tree logic, it does not fairly explained in any official or private discussions published over online or printed which is one of the very important areas of designing a system where ISO 22000 is clearly deviated from Codex HACCP. But unfortunately working groups of standard developers or system writers never concentrate on this specific area and various people has designed different initiatives but none has been shown promising or addressing the exact key points defined by the standard itself. On the other hand, when it comes to certification audits, auditors question the decision making logic but they never provide an accurate answer to the question of what is the recognized or recommended model. Thus lots of food safety teams adapted to digitally available models, but they seems to be lacking the adherence to the standard or more complex and too technical. Thus it is mandatory to address this area properly under the coming review with complete solutions to the lagging part of decision making process.    

According to the ISO 22000:2005, following description is given under 7.4.3 Hazard Assessment; A hazard assessment shall be conducted to determine, for each food safety hazard identified (see 7.4.2) whether its elimination or reduction to acceptable levels is essential to the production of a safe food, and whether its control needed to enable the defined acceptable levels to be met.

Each food safety hazard shall be evaluated according to the possible severity of adverse health effects and the likelihood of their occurrence. The methodology used shall be described, and the results of the food safety hazard assessment shall be recorded. As to the above requirements, the hazard identification, analysis, and classification of defined acceptable levels can be easily carried out with the explained model under the book published by the ISO and WTO, “ISO 22000 Food Safety Management Systems: An easy-to-use checklist for small business, Are you ready?” or using the HACCP seven principles or both.  This is further explained in the standard under the 7.4.4 Selection and assessment of control measures as follows: based on the hazard assessment     of 7.4.3, an appropriate combination of control measures shall be selected which is capable of preventing, eliminating or reducing these food safety hazards to defined acceptable levels. In this selection, each of the control measures as described in 7.3.5.2 shall be reviewed with respect to its effectiveness against the identified food safety hazards.

The control measures selected shall be categorized as to whether they need to be managed through operational PRP(s) or by the HACCP plan.

The selection and categorization shall be carried out using a logical approach that includes assessments with regards to the following:

a)   Its effect on identified food safety hazards relative to the strictness applied

b)  Its feasibility for monitoring (e.g. ability to be monitored in a timely manner to enable immediate corrections)

c)   Its place within the system relative to other control measures

d)  The likelihood of failure in the functioning of a control measure or significant processing variability

e)   The severity of the consequence(s) in the case of failure in its functioning

f)   Whether the control measure is specifically established and applied to eliminate or significantly reduce the level of hazard(s)

g)  Synergetic effects (i.e. interaction that occurs between two or more measures resulting in their combined effect being higher than the sum of their individual effects.)

Control measures are categorized as belonging to the HACCP plan shall be implemented in accordance with 7.6. Other control measures shall be implemented as operational PRPs according to 7.5.

The methodology and parameters used for this categorization shall be described in documents, and the results of the assessment shall be recorded. The entire description was given in the ISO 22000:2005 standard, but it does not explains any specific methods to decide on CCPs or OPRPs and PRPs where standard has given the opportunity of selecting a suitable methodology by the food safety team to segregate control measures.

In addition to that, following description was given in the book “ISO 22000 Food Safety Management Systems: An easy-to-use checklist for small business, Are you ready?” A logical process must be used to assess and sort the control measures into the three groups (PRPs, Operational PRPs and CCPs). This process should take into account a number of factors such as:

Its effect on the hazard relative to the strictness of its application;

The feasibility of monitoring it in a timely manner;

The impact of its failure;

Its role and capacity to eliminate, or significantly reduce, the level of hazard;

Its interaction or synergy with other control measures.

Decision trees may assist you in making these selections. The Codex Decision Tree was designed to identify CCPs which is one choice. On the other hand, the ISO 22000 approach, which will aid your food safety team in sorting control measures into the three groups.  

More than one control measure is often required to control (a) specific food safety hazard(s)and more than one food safety hazard may be controlled by the same control measure (but not necessarily to the same extent). It is therefore advisable first to select suitable combinations of control measures for each of the hazards identified, followed by a consequential establishment of the whole range of control measures required to control all of them.

The information required to assess the effect of a control measure includes the following.

1. How the food safety hazards are affected by the control measure (i.e. reduction, controlling increases, and/or controlling the frequency of occurrence); these could be expressed as performance criteria.
2. To what extent the levels of food safety hazards are affected (qualitatively, semi-quantitatively or quantitatively). Very often the effect depends upon the rigorousness of the control measure (e.g. temperature, time, concentration, frequency). In carrying out the assessment, it may be useful to obtain data on the intensity-effect relationships.
3. The step or location, where the control measure is intended to be applied. Some control measures are more effective if applied after other control measures (e.g. after control measures that stress microorganisms)
4. Operational variables, including their operational uncertainty (e.g. fluctuation and/or probability of operational failure).
5. The practical operational range of intensity.

 The book has given an extension to what standard defined in 7.4.4, but it has not clearly provided a way-out to the question “how we segregate CCP, OPRP and PRP based on ISO 22000 7.4.4 requirements. Additionally, the book has provided following images on both Codex and ISO 22000 decision tree logics as examples for helping the food safety teams in selection of CCP, OPRP and PRP. 

ISO Official Decision Tree                                                Codex Decision Tree

However, ISO 22000 had not given any exact logical sequences like in the HACCP/Codex to decide which category is most suitable. There are no OPRP selections in the HACCP method where there is no much complexity over it, but when it comes to auditing, most of the auditors are questioning food safety team or food safety team leader; “what is your selection method and also how you arrive at the given decision?” Considering explanations, the official standard as well as their official book, there is no proper technical explanation to it. Thus this part of the standard is very weak when it compared with Codex explanation on decision tree logic, and ISO 22000 has tried to depend on it, but Codex decision tree cannot be used as it is due to the requirements defined in 7.4.4 of the standard. Furthermore, any of the existing publications or books does not clearly define the decision tree or logic to selection of CCP, OPRP and PRP according to the ISO 22000 explanation. If you consider ProCert decision tree for an example as given in the image, it is one of the possible answers easily find in internet, but it has no exact logical order even though it has certain capabilities of solving the problem.

                                                              ProCert Decision Tree

Nonetheless, it does not give you a proper way of understanding the requirements black and white when you record in a decision table. There are many other explanations available in the net, but none of them are user-friendly decision making tools. Thus following decision tree was designed after considering most of the possible answers as well as it defines based on the explanations given in the ISO 22000:2005 7.4.4, but not in the same logical sequence. 

                                        ISO 22000 Decision Tree – A possible Alternative

The requirements were used in a logical order to improve the understanding as well as to use it in a 9 columned table to get yes or no answers which is more familiar model used in HACCP decision tree. The given decision tree also may have many limitations which has to be identified with the use which may not be comprehensive and it has to be reviewed by industry experts before it fully pledged. However, it provides a possible answer to the problem like ProCert Decision Tree did and modifications may be possible according to the industry requirements before recognition as a possible solution.  

                         HACCP Plan – CCP/OPRP Decision Table – A possible alternative

Please download the reference table for more detailed understanding, which explains possible way of using 9 column table with 6 questions in the decision logic to be answered by the food safety team while preparing ISO 22000:2005 system for certification. The given example is for orthodox black tea manufacturing process which may not be a comprehensive expanation.

This article may be controversial and I request your comments since ISO 22000:2005 is under review and industry deserves better explanations and methods to implement systems rather than adhering to technical jargons which is not understandable for average person working in the food industry. If you need any further explanation or if you want to rectify any technical errors in this decision tree model, you are warmly welcome.