A modified DNA-barcoding method to identify jumbo squid (Dosidicus gigas) substitution in canned octopus products

In recent years, the United States Food and Drug Administration (US FDA) has documented several instances where more abundant, and lower priced, jumbo squid (Dosidicus gigas) has been substituted for octopus (family Octopodidae) in a variety of products (e.g. frozen, canned) resulting in the products being misbranded and/or adulterated. FDA typically utilises a short (approx. 655 base pair) fragment of the cytochrome c oxidase subunit 1 (COI) mitochondrial gene (a.k.a. DNA barcoding) for the identification of seafood products. However, this method is not applicable for the identification of canned products due to DNA fragmentation that occurs during the retort process. Described herein is a modified DNA barcoding method using standard DNA marine invertebrate barcoding primers in combination with degenerate forward and reverse internal primers to create two smaller (313-316 base pair) fragments. The fragments are sequenced separately then assembled to form a nearly full-length DNA barcode fragment. Using this method, 11 of the 12 canned jumbo squid and octopus products tested, in a variety of forms (i.e. in hot sauce, in garlic sauce, smoked, etc.), were successfully identified. This method is fit for the purpose of ad hoc regulatory identification of canned squid and octopus products to confirm product labelling or to be used as a screening tool to prevent species substitution, economic adulteration, and fraud.