Determination of Fish Flesh Content in Frozen Coated Fish Products (Modification of AOAC Official Method 971.13): Collaborative Study

Abstract

An intralaboratory1 collaborative study evaluated a modified version of AOAC Official Method 971.13 for determining the fish flesh content (FFC) in frozen coated fish products by comparing it with the on-line method. Eleven collaborators analyzed 36 products (a total of 6336 test samples). Each product targeted one of 4 percent fish flesh (PFF) levels (35, 50, 65, and 80). Products were manufactured from one of 3 raw materials (fillet blocks, minced blocks, and natural fillets) and processed in one of 4 forms (sticks, portions, formed portions, and fillets) and one of 4 styles (raw breaded, batter-dipped, precooked, and fully cooked). Each "official" test sample was tracked through the processing system and weighed (1) before battering and/or breading and, depending on product style, before frying; and (2) after battering and/or breading and, depending on product style, after frying; so that it served as its own control. These weights were used to calculate actual percent fish flesh (APFF) and considered to be generated by the on-line method. Collaborators weighed official test samples (1) before scraping; and (2) after scraping. These weights were used to calculate determined percent fish flesh (DPFF) and considered to be generated by the modified AOAC method. APFF and DPFF were the primary data for statistical analysis. Recoveries ranged from 71.75 to 106.40%. Repeatability (method precision indicator for a single collaborator) relative standard deviation (RSDr) values ranged from 1.04 to 8.37%. Corresponding reproducibility (method precision indicator among collaborators) relative standard deviation (RSDR) values ranged from 1.41 to 11.95%. The DPFF mean was lower than the APFF mean for 30 (83.33%) of 36 products. For 29 of these 30 products, the differences between method means (APFF minus DPFF) ranged from 0.38 to 6.51%. For the remaining product within this group (C/06, fillet blocks, fully cooked portions), the difference between method means was 21.73%. For the remaining 6 (16.67%) of 36 products, the DPFF mean was greater than the APFF mean. The differences between method means ranged from -0.03 to -2.76%. RSD values were considered acceptable (i.e., RSDr < 9% and RSDR < 12%) for all products studied. The modified method for determining FFC in frozen coated fish products has been adopted first action to replace AOAC Official Method 971.13.