Guidelines for Product Sample Retention

Guidelines for Product Sample Retention


Bottled water quality assurance does not necessarily end with release of the final product into the marketplace. Occasionally, it may be necessary to review the original day-of-production analysis of the product and conduct additional testing in response to regulatory agency or consumer inquiries regarding product quality. In the event of product contamination, it is advisable to retain finished product samples for a period of time for confirmatory analysis.

The purpose of this document is simply to provide bottlers with guidance for retaining such samples, as desired. Implementation is optional. The document is not an IBWA Model Code or plant audit requirement. In addition, this is not intended to replace Appendix C of the IBWA Model Code (E. coli and Total Coliform Standard and Policy).


Types of Retained Samples

Retained samples are sealed finished product collected from the production line(s) at the time of bottling. It is important that samples collected for retention be representative of the production lot. Therefore, it is recommended that the following factors be included in determining the types of samples to be retained:

1. Product type.

2. Container size.

3. Container type.

4. Closure type.

Each of these factors can have an impact on the quality of the final product.

Recommendations for Size of Samples

When determining the amount of product to be retained, consider the type(s) of testing that would be performed upon receipt of an inquiry. At a minimum, it is recommended that enough volume be retained to conduct the following tests:

    • Total coliform / E. coli
    • Heterotrophic plate count
    • Total dissolved solids
    • pH
    • Specific conductance (conductivity)
    • Cap torque
    • Visual inspection prior to opening container
    • Yeast and mold (optional)


Generally, 250-300 ml of water is sufficient to perform these tests, but it is advisable to consider retaining more than the minimum volume to provide for outside laboratory analysis and potential legal evidence. Each set of analysis should be done from a sealed container; therefore it is recommended that enough volume be retained in sealed original containers for three sets of analyses.

Due to storage limitations, there may be instances when keeping larger sealed container sizes is not viable. An alternative is to keep product in the original sealed containers until routine microbiological testing has been completed. After which product can be opened and poured off into sterile sampling containers.

Taking into consideration various product types, container types, container sizes, and closure types, the following might be a listing of retained samples for one day’s production (one lot):

On May 27, plant ABC bottles the following products:

    • Purified water in 5 gallon polycarbonate bottles with spill-proof caps, 1.0 gallon HDPE bottles, and 0.5 liter PET bottles with sport caps.
    • Spring water in 0.5 liter PET bottles with beverage caps, 0.5 liter PET bottles with sport caps,1.0 liter PET bottles with sport caps, and 2.5 gallon HDPE containers.
    • The retained samples for the lot may be:
    • Purified water: 6-250 ml sterile cups split from 1-5 gallon polycarbonate bottle and 3-0.5 liter PET bottles with sport cap.
    • Spring water: 3-0.5 liter PET bottles with beverage cap, 3-0.5 liter PET bottles with sport cap, 3-1.0 liter PET with sport cap, 6-250 ml sterile cups split from 3-2.5 gallon HDPE containers.


Alternatively, for convenience of storage, bottlers may find advantages to retaining cases or multi-packs of product. For example, 1 case of purified water in 1 gallon HDPE bottles @ 4 bottles per case; or one six-pack of spring water in 0.5 liter PET bottles with sport caps.


Sample Retention Time

A common concern for sample retention is space limitations for storage of samples. The industry commonly employs a system of date coding adapted from New Jersey’s requirement for expiration dates on bottled water products. That 2 year period is often considered as a factor in sample retention. However, it may be more reasonable to consider the actual time product may be in the marketplace and the consumer’s home prior to consumption. The time will likely be significantly less than the 2 year expiration dating system.


Some examples are:

    • Plant ABC determines that its home and office delivery clients customarily consume their product in 5 gallon polycarbonate bottles within 30 days. Therefore, they establish 30 days as the sample retention period for 5 gallon polycarbonate bottle product. 
    • Plant XYZ determines that its spring water in one gallon HDPE and 0.5 liter PET containers is generally purchased and consumed within 90 days and one year, respectively. Those time frames become the sample retention period for the respective products.