AOAC Methods for Review in Codex STAN 234_11-2018

AOAC Official Methods Listed in CXS 234 for Milk and Milk Products

81

FOOD COMPOSITION AND ADDITIVES

Extension of Dry Ash Atomic Absorption and Spectrophotometric Methods to Determination of Minerals and Phosphorus in Soy-Based, Whey-Based, and Enteral Formulae (Modification of AOAC Official Methods 985.35 and 986.24): Collaborative Study

C OOK : J OURNAL OF AOAC I NTERNATIONAL V OL . 80, N O . 4, 1997

K ATHLEEN K. C OOK U.S. Food and Drug Administration, Office of Food Labeling, Division of Science and Applied Technology, 200 C St, SW, Washington, DC 20204

Collaborators: R. Allen; A. Choudhry; R. Fleener; F.E. Greene; C. Johnson; N. Miller-Ihli; R. Powell; W.-L. Yip

A collaborative study was performed to confirm that the dry ash atomic absorption method for determination of Ca, Mg, Zn, Cu, Fe, Mn, K, and Na in ready-to-feed milk-based infant formula, AOAC Official Method 985.35 , and the spectrophotometric method for phosphorus in milk- based infant formula, AOAC Official Method 986.24, could be extended to determination of these minerals in all types of in- fant formula and enteral products. In the original collaborative studies of methods of analysis for infant formula, 3 liquid ready-to-feed (RTF) milk-based formulae were analyzed and the same analysis was repeated on a different day (1, 2). For the study reported here, 3 RTF for- mulae and 2 soy-based powders were selected to represent a plant source matrix, which was not included in the original study. A whey-based powder and a casein-based enteral for- mula were also included to represent other matrixes derived from a milk base. Eight collaborators, including the author, used Method 985.35 (3), and 7 collaborators, including the author, used Method 986.24 (4) to analyze soy, whey, and en- teral formulae. In addition, each collaborator was asked to add a spiking solution to one of the following: the enteral formula, an RTF soy-based formula, a soy powder formula, or the whey powder formula. The protocol of the International Union of Pure and Applied Chemistry (IUPAC; 5) was used to interpret study results. This protocol uses sequential application of the Cochran and Grubb’s tests to the data to identify outliers. The same protocol was used to determine recovery. Results (Tables 1–11) show that Methods 985.35 and 986.24 are reliable and applicable to other formulae. Powders The contents of 6 cans from the same lot of a particular brand of powder formula were composited by adding half of their 12 to 16 oz. contents to a large beaker. After thorough Collaborative Study

Eight laboratories participated in a collaborative study of AOAC Official Method 985.35, Minerals in Ready-to-Feed Milk-Based Infant Formula and Pet Foods, Atomic Absorption Spectrophotometric Method; and 7 laboratories participated in a study of AOAC Official Method 986.24, Phosphorus in Milk-Based Infant Formula, Spectrophotometric Method, to extend these methods to infant formu- lae (other than milk-based) and enteral products. Three ready-to-feed soy-based formulae and 2 soy- based powder formulae were chosen to represent the plant matrix. A whey-based formula and a ca- sein-based enteral formula were also included in the study. Soy formulae containing nearly identical concentrations of particular elements were matched, and an application of the Youden “closely matched pair” approach was used to estimate repeatability parameters. Average reproducibility values were as follows: calcium, 9.3 % ; copper, 9.7 % ; iron, 5.5 % ; po- tassium, 4.0 % ; magnesium, 5.2 % ; manganese, 10.6 % ; sodium, 4.7 % ; phosphorus, 10.5 % ; and zinc, 7.3 % . At similar analyte concentrations, the between- laboratory variabilities compared well with those re- ported for the official methods. Most repeatability and reproducibility parameters compared well with the original collaborative study. AOAC Official Meth- ods 985.35 and 986.24 have been modified to ex- tend their applicability to infant formulae (other than milk-based) and enteral products.

Submitted for publication October 28, 1996. The recommendation was approved by the Methods Committee on Food Nutrition, and was adopted by the Official Methods Board of the Association. See “Official Methods Board Actions” (1997) J. AOAC Int. 80 , 35A, and “Official Methods Board Actions” (1997) Inside Laboratory Management , March issue.

10/9/2018