Microbiological Testing in Customer–Supplier Relations

6.1 Introduction
The complete food chain from farm to fork is characterized by a sequence of supplier–customer
interfaces. These interfaces imply the establishment of contracts defining the requirements of the
customers with respect to their suppliers. These contracts also reflect the commitment of the supplier
to guarantee the delivery of goods in compliance with the agreed-upon requirements.
This sequence of interfaces plays an important role in fulfilling a Food Safety Objective (FSO) at
the level of the final consumer as defined by public health authorities. As shown in Fig. 6.1, individual

performance objectives (PO) can be established along the whole food chain at these interfaces.
These POs should be identical to FSOs if no changes in the level of the pathogen of concern occur
in the food chain up to the consumer. Different POs need to be defined to meet the final FSO if either
a decrease or an increase in the level of a hazard is anticipated in the food chain (ICMSF 2002).
If not done by authorities, customers or manufacturers have to define a PO that is suitable, considering
the impact of processing steps and conditions on the relevant pathogen, as well as the impact of
distribution and preparation by the consumer. While FSOs and POs are related to a single pathogen,
all significant hazards as well as other parameters such as indicators and spoilage microorganisms
need to be considered in customer–supplier relationships.
Formal articulation of FSOs by public health authorities is anticipated. Absence in 1, 10, 100 kg
have been proposed in the European Union for Cronobacter spp. and Salmonella in powdered infant
formula (EFSA 2004). Thus contracts between suppliers and customers are based on established
microbiological criteria, typically applying the worst case scenario established by commercial or
administrative people. This chapter discusses the relations between suppliers and customers and the
role of microbiological testing in these commercial interactions.
Requirements in contracts established between a supplier and a customer may apply to raw materials
or ingredients, semifinished products or finished products. These requirements may include
microbiological specifications with relevant parameters such as significant pathogens and indicator
microorganism or even spoilage microorganisms. Examples of such requirements can be found in the
different chapters in the book. The requirements may also include other elements related to the microbiological
conditions or status of the goods in question such as:
• Physico-chemical parameters that may have an impact on growth:
–– Gassing conditions and limits of residual oxygen
–– pH or acidity
–– Temperature maximum during transport and at reception
Chapter 6
Microbiological Testing in Customer–Supplier Relations
56 6 Microbiological Testing in Customer–Supplier Relations
–– Time lapse for transportation between supplier and customer
–– Requirement for intermediate pasteurization (e.g., liquid whey)
• Parameters related to hygiene:
–– Separation of goods during transport; e.g., according to the risk of contamination, formation
and transfer of off-odors etc.
–– Location of containers in a ship to avoid the formation of condensation due to temperature
differences
–– Type of packaging material used; e.g., the requirement of strippable bags to avoid contamination
during handling and tipping of critical ingredients (e.g., dry mixing)
–– Specific protection of packaging material; e.g., plasticized intermediate cardboard layers
between glass jars to avoid the presence of dust in normal cardboard
–– Cleaning procedures for containers and tanks used to transport raw materials or semifinished
product
6.1.1 Raw Materials and Ingredients Used by Manufacturers
The choice of parameters included in specifications for raw materials and ingredients depends on
several elements such as the point in the food chain, the impact of subsequent processing steps and
the regulatory environment.
6.1.1.1 Raw Agricultural Commodities
For unprocessed agricultural raw materials, visual qualitative or quantitative parameters play an
important role. Examples are:
• Absence or maximum percentage of moldy pieces in a bulk delivery (e.g., cocoa beans, peanuts,
grain or maize)
• Absence or maximum percentage level of rotten or unripe fruits or vegetables in a bulk delivery
from the field
• Defined characteristics of color or odor (absence of off-odors) for fresh meat or fish
Quantitative microbiological specifications for unprocessed agricultural raw materials that will be
further processed may also be included. They may, however, be expressed as percentage of positive
findings or as maximum levels of counts; e.g., for Salmonella in meat used to manufacture products

6.1 Introduction 57
such as salami or a maximal level of viable counts in fresh milk beyond which the raw material will
be downgraded, respectively. These limits are not necessarily used as acceptance criteria for delivered
materials. Rather they may be used to drive improvements by the supplying party through rewarding
good quality with a bonus and penalizing poor quality by deduction at payment.
6.1.1.2 Processed Ingredients
For processed ingredients, microbiological specifications are established according to their further
use. Skimmed milk powder, for example, is an ingredient that is widely used in the manufacture of
many different products such as:
• Dry-mixing operations without any further heat-treatment:
–– Chocolate and confectionery
–– Infant formulae and infant cereals
–– Instant beverages
–– Dehydrated culinary products
• Wet mixing operations with subsequent heat-treatment:
–– Recombined liquid milks (pasteurized or UHT)
–– Fermented dairy products
–– Ice cream
–– Heat-processed refrigerated culinary products
–– Bakery products
The specifications for the skimmed milk powder thus depend very much on use, and they vary from
very stringent specifications (e.g., for critical products such as infant formulae) to less stringent ones
(e.g., for manufacture of UHT-milk). For example, when used in infant formula, specifications are
typically based on standards for finished products established by authorities. Conversely, for use in
UHT milk, more lenient specifications may be used for Salmonella and Enterobacteriaceae, but limits
for process-relevant spore formers are typically included by the customer to minimize the risks of
failure of the thermal process (see Chap. 24).
While the adherence to established microbiological requirements can be verified through sampling
and testing, limitations of sampling plans need to be considered (see Appendix A). Therefore, it is
important for a customer to assess the microbiological hazards and associated risks when using and
purchasing a given ingredient. This will allow categorization of the different ingredients according to
risk and defining the approach taken in handling ingredients after delivery.
For high risk ingredients used for sensitive products (e.g., skimmed milk for infant formulae) an
assessment of the confidence level in the suppliers is also needed. This assessment should be based
on audits against key parameters to ensure the manufacture of safe ingredients and may include, but
is not limited to, the following:
• Implementation of appropriate preventive prerequisite measures such as GHP
• Implementation of HACCP
• Validation of control measures including critical limits
• Implementation of verification measures such as environmental pathogen monitoring
• Historical data
• Trend analyses techniques
• Release procedures
• Appropriate sampling methods
• Analytical procedures such as the use of validated methods and participation in proficiency tests
58 6 Microbiological Testing in Customer–Supplier Relations
6.1.2 Interactions with Retailers
Microbiological specifications between manufacturers and retailers and food service are frequently
based on national or international criteria established by public health authorities. However, additional
or more specific requirements may be established by the retailer. Retailer requirements for raw
agricultural commodities, such as fresh fruits or vegetables, or for manufactured products may be
similar or identical to those outlined under Sect. 6.1.1. Additional elements may include:
• Elements related to the shelf life of refrigerated products, such as dairy or culinary products, to
meet their distribution channel needs
• Elements related to the composition of the products, such as salt or sugar content, or the heattreatments
used to manufacture the product
• Elements related to certification and auditing of the manufacturer
Such requirements may require the manufacturer to conduct challenge and storage tests to demonstrate
the stability and safety of the products with the specified recipe modification or the required shelf
life. A further requirement may also include monitoring retention samples.
6.1.3 Contract Manufacturers
Food manufacturers may subcontract the production of some products for several reasons:
• Small volumes which may benefit from existing production lines dedicated to the same or similar
products (cost reasons)
• Proprietary technologies used by contracted manufacturers that are not available at the factory of
the contracting party
• Temporary production of new products until it becomes clear that the product will be successful
and thus justify the investment for a new processing line
• Insufficient capacity in the manufacturer’s own factory thus requiring a contract manufacturer to
increase capacity
The main issue related to contracting production is the control over the quality and safety of the
product. The required quality can be achieved through the definition of the product characteristics
based on the recipe and processing conditions or though use of a contract manufacturer chosen
because of the quality attributes of the products they produce. However, ensuring the microbiological
safety of the products may not be easy to control. This is particularly true if the standards applied by
the manufacturer are different from those of the contracted organization. These differences must be
addressed to assure that the level of understanding and implementation of GHP and HACCP are
consistent to avoid the potential for increased microbiological risk.
While implementation of the appropriate preventive measures, sampling and testing procedures is
usually negotiated as part of the contract, it may not always be possible to impose the requirements
of the contracting party. This may be the case if the volumes subcontracted are small in comparison
to the total volume produced by the chosen manufacturer. In such cases the contracting party may not
be in a position to implement or impose its own quality system and associated standards, and it may
be advisable to look for an appropriate alternative. However, different options may be possible and
depend on the type of product and its sensitivity in terms of risks for the consumer and risk for the
contracting manufacturer. Potential approaches include:
• The contract manufacturer agrees to manufacture and release product according to the specifications
and the implemented control measures are approved by the contracting party
6.3 Microbiological Data 59
• Production lines on which the subcontracted production takes place are under the direct supervision
of personnel from the contracting party
• Release is performed by the contracting party’s own quality assurance people, who are either
located at the contractors site or visit the contracted location during production
• Regular audits conducted by the contracting party (see Sect. 6.2)
6.2 Auditing
Auditing suppliers in a supplier–customer relationship plays an important role in assessing whether
the agreed-upon requirements will be met consistently and thus the confidence level in a particular
supplier. Audits of HACCP and of prerequisite measures such as GHP can be very different in their
nature and may range from a simple system audit to a full technical audit. In the first case, audits
focus on whether or not a HACCP plan has been established and whether the different steps of a
HACCP study have been addressed. In the second case, attention is given not only to the formal
aspects, but also to the technical and scientific content, such as the validity of the hazard identification,
and the appropriateness of control measures and derived critical limits. This will also include,
assessing validation information, the effectiveness of the proposed corrective actions, appropriate
verification procedures and improvement of the HACCP plan where necessary. These technical audits
require deep knowledge and understanding of the product, possible associated microorganisms, the
process and the processing conditions to determine whether the right decisions have been made.
These technical audits usually require multidisciplinary teams, including, at a minimum, process or
manufacturing specialists and hygienists or industrial microbiologists. This is important because
these audits go beyond the sole assessment of the HACCP plan, and also focus on the degree of
implementation and effectiveness of GHP, which provide the necessary foundation for a sound
HACCP plan. In addition, it is also necessary to audit the procedures designed to verify the effectiveness
of the measures. This may include environmental monitoring, verification of end product and
review of methods to ascertain if they are appropriate for the particular matrix and for environmental
samples. For details on process control, refer to Chap. 3.
Individuals conducting audits need to be qualified and trained to be effective in this role. Two
issues are relevant to consider; i.e., training to gain specific competencies and secondly registration
of auditors with an appropriate body according to the sector. This is important to avoid an auditor
with competence in, for example plastic packaging, from auditing a poultry factory. Ongoing verification
of auditor competence also needs to be considered. The auditor training course should be
registered with an appropriate training body and if an auditor needs to audit a facility for which they
are not competent, then a technical expert should accompany them on the audit. These are all especially
applicable where third party audits are used.
6.3 Microbiological Data
Usually the only microbiological data provided in supplier–customer relationships are limited to
results of the purchased goods and communicated, depending on the agreements or level of confidence
in the form of certificates of analysis (CoA) or certificates of conformance or compliance
(CoC). The first provide detailed analytical results of the parameters included in the specifications,
the latter represent a confirmation or guarantee that based on the implemented control measures and
verifications, the products are in compliance with the specification. This provides information on the
delivered lots and, since they have been released and shipped, indicates that they comply with the
60 6 Microbiological Testing in Customer–Supplier Relations
agreed-upon requirements. However, results of the CoA, will only provide information on the specific
lot and not on the overall performance or process capability of the supplier.
A much more useful approach would be for suppliers to share not only results for finished products,
but also data on line samples, historical data on lots manufactured on the same processing line
or during a time frame around the time delivered lots were manufactured, environmental data or other
relevant parameters. These data are more useful for the customer to confirm or modify their confidence
level in a particular supplier and could be considered a certificate of conformance and compliance
rather than a certificate of analysis.