Guide to Developing Accurate Nutrient Values

2. Collecting and handling the sample units

Once your sampling plan has been determined, it is important to collect the sampled units in an organized manner. Legible, permanent labelling of each food unit is critical. Whether the units are collected by quality assurance staff at the plant, by laboratory personnel at retail level or in other situations according to your sample design, it should not be possible to remove marks by rubbing, washing or freezing.

In addition, documentation of the food sample should include:

• identity of the person responsible for each step (e.g. sample collector, shipper, receiver at the laboratory)
• identification number (assigned by sampler)
• name of the product, including product variety, lot number or code, and possibly ingredient information
• size or amount of product collected
• place, date and time of collection
• name and address of the grower, processor, distributor, shipper, supplier, retailer, and so on
• description of the dispatch information (packing, shipping and handling) sent to the analytical laboratory
• shipping medium (such as plastic tub, parchment, foil, or polyethylene bags) and transport conditions
• any auxiliary information that will be needed in the statistical evaluation (e.g., stratum size, cluster size)

This information should accompany the sample and the analytical results through all stages, from sample pick-up to reporting of results.

3. Analyzing the sample units
Analysis of nutrients in food is a complex process. It requires appropriate equipment and expertise. The selection of a laboratory and the methods of analysis it will use are critical to obtaining accurate values. You want to ensure that the results obtained from laboratory analysis accurately represent the product tested. It is therefore important to minimize the variability in the laboratory measurements by choosing an experienced laboratory.

Minimizing variability of laboratory measurements

How do you select a good laboratory?
You may use an in-house laboratory or contract out the analysis of your products.
Several issues are important to consider:

• The laboratory should be able to demonstrate that it is technically competent by indicating accreditation by the Standards Council of Canada (SCC). Accreditation will also ensure compliance with internationally accepted standards for facilities, equipment and personnel.
• The laboratory should demonstrate experience in food testing and use of methods that have been validated for the food and the nutrient you want to have analyzed.

What is an accredited laboratory?
If you choose to use an outside laboratory, CFIA recommends those accredited to ISO 17025 standards by the SCC. Laboratories in other countries are accredited to the same standard. In Canada, ISO 17025 CAN-P-4D standards are embodied in the Program for the Accreditation of Laboratories/Canada (PALCAN),¹⁵ as described in the Guidelines for the Accreditation of Agricultural and Food Products Testing Laboratories.¹⁶

Examples of criteria set out in the ISO 17025 CAN-P-4D standard include:

• Samples are properly logged, stored, analyzed and archived.
• Integrity of the data is supported with a complete history of how the samples have been handled (e.g. compositing of laboratory samples, preparation and storage).
• Analysts are trained appropriately and tested for proficiency.
• Appropriate methods are used and validated.
• Equipment is calibrated and maintained.
• Internal quality assurance programs are followed.
• Results are checked for accuracy and reasonableness.
• The laboratory passes standards for tests of proficiency.

The laboratory should also provide access to technical personnel who can answer your questions and provide all of the information required. You may want to contact your industry association, as many of them have arrangements with laboratories for nutrient analysis. In addition, a quick search of your telephone book will usually yield a number of local laboratories. Not all of the laboratories listed will be experienced in testing nutrients in food, so you will need to confirm that the laboratory can meet the criteria discussed above and outlined in more detail in Appendix D.

The SCC Web site¹⁷ lists all of the laboratories that are currently accredited for analytical testing in Canada. Their extensive list includes both government and commercial laboratories accredited for various chemical, physical and microbiological tests.

• Most government laboratories do not analyze samples for non-government applications, so you will need to search for commercial laboratories.
• Not all laboratories perform analyses for food chemical composition, so you need to determine the scope for which the laboratory is accredited. This can be searched on the SCC Web site. Under Programs and Services, choose the Laboratory section from the left-hand menu, then select Accredited Clients, and key in the words "agriculture and food and chemical". Information on a number of laboratories will be provided.
• You can also use your commodity as the search criteria (e.g. "cereals and chemical").
• Once you have obtained the list, you should look at the details of each laboratory to ensure that they are experienced in testing your type of product. Cross-referencing this to laboratories you know are in your area (from your telephone book) will speed your search.

Are the methods they use important?
CFIA recommends using the methods of analysis published in the most recent version of the Official Methods of Analysis of AOAC INTERNATIONAL.¹⁸

For information on the methods of analysis used by CFIA and additional sources for methods, see Appendix 4 of the CFIA Nutrition Labelling Compliance Test,¹⁹ which lists methods recommended for the core nutrients.

If you require analysis of other nutrients or if your laboratory proposes to use a different method, they must be able to demonstrate the validity of that method and provide written assurance that the results are comparable to those obtained by recognized methods. Regardless of the source of the method, it should be validated for the particular type of food being analyzed.

Do you need data on all nutrients?
Many laboratories offer package prices for particular combinations of analyses such as proximate components (fat, protein, carbohydrates, ash and moisture); fatty acids; basic minerals; and the 13 core nutrients for nutrition labelling. Thus it may be cost-effective to analyze your food sample for all of the nutrients included in the package price from the same sample. However, there are exceptions. If you substitute an ingredient, you may test only for the nutrients that are affected; or if a product is known not to contain a particular nutrient(s), you may choose not to test for that nutrient. For example:

• Products (e.g. cereals, vegetables) that do not contain animal fats will not contain cholesterol.
• Most milks, yogurts and meats do not contain dietary fibre.
• Most muscle meats do not contain Vitamin C.

What else do you need to discuss with the laboratory?

Prior to sending samples to the laboratory you have selected you should discuss your requirements with the laboratory personnel, obtain price quotes and provide detailed instructions to the laboratory. You first need to make the following decisions:

• How should the sample be sent to the laboratory?
  • The laboratory analysis depends on the integrity of the sample, so consideration should be given to the stability of the nutrients and the storage life of the product. The laboratory should be able to advise you on your options.
• How would you like the results reported?
  • The report should include the raw data. The same nutrient may be reported using different units of expression (e.g. grams, µg, RE) so care must be taken to ensure that the data you receive are expressed in the appropriate units and definitions for your application. (Refer to Appendix B.)
  • Some manipulation of the results may be required if the results are not reported for the portion size you need. You may wish to provide the serving size or ask for results per 100 grams.
  • If the report includes arithmetically treated data, ensure that the treatment will be appropriate for your application.
  • Will they conduct duplicate analyses and if so, how will these be included in the calculations?
  • Will they provide an estimate of variability or range?
  • What quality review is done on the data prior to calculations?

B. Assessing the Information

Assessing the information involves reviewing the laboratory results. It is important to obtain and review the unrounded values for each nutrient analyzed by the laboratory, even though some laboratories may be able to provide summary information, calculated values or camera-ready Nutrition Facts tables. A detailed checklist is provided in Appendix G. The following chart outlines a few simple checks you can do.

A Few Simple Ways to Review the Laboratory Results

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C. Calculating the Nutrient Values

One of the greatest strengths of the data obtained from sampling and laboratory analysis is the flexibility that they afford. The same data can be treated arithmetically in different ways for different uses.

For example, if you are a supplier of an ingredient, you may want to use the same laboratory data to provide results for a number of uses:

• Product specifications for customers may require averages per 100 gram, with estimates of overall variability and sample sizes for the laboratory testing.
• An industry or association database may require an average per gram, with your product included as part of a generic estimate combined with those of other producers.
• Nutrient labelling for your own retail use requires the typical nutrient amount in rounded label values given per serving size and in percent Daily Value (% DV) given per serving.

In each of these cases it is critical to have accurate, valid underlying data. A sound sample plan with a sufficient number of samples should provide data that can be used for all of the above purposes, by employing slightly different arithmetic treatments of the data.

The arithmetic treatment of the data for all of these uses must take into account the nature of the sample plan:

• If some parts of the product line had more emphasis or representation in the sampling (relative to their proportion of the product), then this will have to be taken into account in the development of the averages or variances.
• If the sample design was relatively simple then these calculations are quite straightforward and can usually be done with a hand calculator or a simple spreadsheet.
• If the sample design is more complex (perhaps with clustering, stratification, or sampling in a number of stages), then you may need the assistance of a statistician and more elaborate formulas in spreadsheets or specialized software.

The FDA Nutrition Labelling Manual (1998)²⁰ provides formulas for means and variances for simple sample designs from production lots (Section 5-1) as well as formulas for stratified designs, which is just one particular type of more complex sampling (Post Section 5-7). You will need to tailor your calculations to your sample design.

All of the calculations will need to take portion sizes into account. The laboratory results will need to be converted from the reported portion to the relevant serving size required for the intended use.

The treatment of data specifically for nutrition labelling is discussed in detail in Part 2, Chapter V (page 64).

D. Keeping Detailed Records

It is important to keep records of your ingredient information, product formulation and nutrient content calculations. It may be possible to incorporate this into your software program or it may be more efficient to use an electronic spreadsheet. You should also document how the sample units were collected and combined, methods of analysis, the date the analyses were done, and who conducted the analyses.

Some of the information that should be kept for a minimum of two (2) years is outlined in the chart on the following page.

Information to Be Kept for a Minimum of 2 Years

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IV. Generating Nutrient Values from Existing Sources

Another way to generate nutrient values is to determine them indirectly from existing sources. A number of different sources, each having different specificity, can be used to calculate nutrient data for end products or recipes from ingredient information. The first step is to collect data on your ingredients and the nutrients of interest. Once you have determined that the data you have are suitable for your application, you can combine the data on each ingredient to give you total values for each nutrient in your product. This can be fairly simple if your product has few ingredients and little processing, or can be quite complex.

Each of these steps as well as the type of documentation that you should maintain is discussed in this chapter.

A. Gathering Information on Your Ingredients

In this approach your first step is to collect data on your ingredients and the specific nutrients of interest. It is also important to determine the effects of processing on each of these nutrients.

1. Information on ingredients

Nutrient information can be divided into two broad categories:

• Ingredient-specific information can be obtained from the supplier of the specific ingredient or from certain databases that specify the nutrient information according to the specific manufacturer.
• Generic information, which is not brand-specific or specific to any one manufacturer or supplier, can be found in various food composition databases.

A database is a collection of data brought together and stored in some manner for future retrieval. It could be as simple as a file folder containing information on each ingredient, or as complex as a set of relational electronic files. A database can contain ingredient-specific data, generic data, or a combination of both. There are several types of databases, including databases that are company-specific, government reference databases, and commercial databases (each described below). It is important to note that any of these types of databases may not contain all of the nutrients in which you are interested.

Company-specific databases
Company-specific databases may be specific to an ingredient supplier or a manufacturer. The databases used by an ingredient supplier may contain information about its products only. A manufacturer's database may be a compilation of nutrition information on all specific ingredients that are used in its products as well as nutrient information on its finished products.

The purpose of a company-specific database is to collate nutrient data about a specific ingredient or food and allow for the calculation of values that will take into account the nutrient changes due to processing. For example, a manufacturer may collect data from each of its suppliers on each ingredient used, and use the data to calculate the nutrient values in its end product.

Government reference databases
The primary purpose of government databases such as the CNF ²¹ and the USDA-SR²² is to provide standard reference data to all researchers and health professionals who are assessing the dietary intake of the population, thus increasing the degree to which their results are comparable. The databases can also be used by dietitians and the public to assess individuals' eating habits.

Reference databases can also be created for other purposes, such as the database created by the US FDA to provide nutrient values for the voluntary labelling of the 20 most frequently consumed raw fruit, vegetables and fish in that country.²³ The data in this type of database could be the same as in other generic databases of foods consumed in the same area. However, the final values could be different as they may be rounded values, as well as take into consideration nutrition labelling compliance test standards.

Commercial databases
A number of custom commercial databases also exist. They contain generic information from the CNF or USDA-SR as well as data from other sources such as industry brand-name data. As these databases contain both generic and brand-specific data, it is important to ensure that the data you choose to use will reflect your actual ingredients or products. The characteristics of the values in these databases may vary depending on the original source of the data.

It is important to understand the distinction between a food composition database and a nutrient analysis software program. Regardless of its size or complexity, a database is simply a collection of nutrient data recorded in some manner. Retrieval of these data, if stored electronically, can be difficult without the assistance of database management software. As a result of this many commercial custom databases come packaged within a software program. As the only way to access these data is through the software, the distinction between the data and the software tends to become blurred. Nevertheless you should assess the data contained within the package separately from the software features manipulating this data. Both the data and the software must match your intended application.

The ease of access and the availability of brand name data make these programs very popular for individual diet assessments by both dietitians and the general public alike. Some care should be exercised when considering the brand name foods as factors such as industry processes, changes in products on the market and their nutrient profile, and availability of new ingredients can cause this data to become quickly out of date. For example, the fatty acid profile for many margarines on the market has changed many times over the past 10 years while the margarine still carries the same brand name.

The utility of these various databases will depend on your application:

• Product-specific information is appropriate for generating nutrient values for labelling and advertising purposes where the values must comply with precise expectations and standards on how they should accurately reflect the content of the final product.
• In addition to dietary assessment, generic information compiled in reference databases may be appropriate for the calculation of recipes where the ingredients used may vary.
• Generic information compiled in a special reference database may also be appropriate for the labelling and advertising of products that are sold as a generic category of food (e.g. apples or round steaks).

15 PALCAN can be found on the SCC Web site: www.scc.ca
16 Standards Council of Canada: Guidelines for the Accreditation of Agricultural and Food Products Testing Laboratories. CAN-P-1587, 2003
www.scc.ca/en/publications/criteria/labs/agriculture.shtml
17 SCC Web site: www.scc.ca
18 For information on the Official Methods of Analysis of AOAC INTERNATIONAL:
www.aoac.org/pubs/oma_revised.htm
19 CFIA Nutrition Labelling Compliance Test, Appendix 4 www.inspection.gc.ca/english/fssa/labeti/nutricon/nutricone.shtml
20 FDA Nutrition Labeling Manual, Section 5-1 and Post Section 5-7
www.cfsan.fda.gov/~dms/nutrguid.html
21 CNF: www.healthcanada.ca/cnf
22 USDA-SR: www.nal.usda.gov/fnic/foodcomp/Data/SR17/sr17.html
23 See US Code of Federal Regulations Title 21, Part 101.108, Appendices C and D www.access.gpo.gov/nara/cfr/waisidx_04/21cfr101_04.html