Product Authentication Using Two Mitochondrial Markers Reveals Inconsistent Labeling and Substitution of Canned Tuna Products in the Taiwanese Market

Abstract

Fish of the tribe Thunnini represent a significant proportion of the stock caught by the fishing industry, with many of these fishes being collectively called tuna. However, only certain species can be used legally as an ingredient in canned tuna products, depending on regional food regulations. In Taiwan, only Thunnus species or Katsuwonus pelamis can be used as canned tuna. Here, we authenticated 90 canned tuna products, including 25 cat food samples, by sequencing two mitochondrial regions, 16S rRNA (16S) and the control region (CR). BLAST analysis revealed that Sarda orientalis, Euthynnus affinis, Auxis rochei, and Auxis thazard are all used as substitutes for legitimate tuna products. We found that 63.33% of investigated samples are true canned tuna, i.e., contain Thunnus species or skipjack tuna. We advocate that the Taiwanese government publishes an official standardized list of fishes, especially so that scientific, Chinese and vernacular names can be assigned unambiguously based on a “one species-one name policy”, thereby clarifying which species can be used in seafood products such as tuna. Furthermore, we feel that the large-scale and long-term monitoring of canned tuna products is warranted to fully assess the extent of tuna product adulteration in Taiwan.

Species authentication of canned mackerel: Challenges in molecular identification and potential drivers of mislabelling

“…Few data are available on the mislabelling of canned seafood products using molecular approaches and these are principally focused on tuna products (Boughattas et al, 2019;Chang et al, 2021;Nagalakshmi et al, 2016;Sotelo et al, 2018). Our results highlight cases of mislabelling in 45% of canned mackerel, higher than the mislabelling rate previously reported by other studies, with the exception of Boughattas Fig.…”

“…2021) reporting 100% mislabelling in five canned Zamburiñas (Mimachlamys varia) analyzed. All the other cases, including herrings, anchovies, tuna and octopus, showed a lower mislabelling rate, ranging from 0% to 16.9% (Chang et al, 2021;Chin Chin et al, 2016;Giusti et al, 2019;Nagalakshmi et al, 2016;Sotelo et al, 2018;Tinacci et al, 2019;Velasco et al, 2021). This contrasting scenario could be generated by the limited number of studies focused on canned seafood, but also to the weak and often ambiguous European legislation, which allows the use of generic information of species of fish used.…”

Molecular Barcoding: A Tool to Guarantee Correct Seafood Labelling and Quality and Preserve the Conservation of Endangered Species

“…In more recent years, several researchers have verified the presence of seafood fraud in Asia [ 137 , 138 , 139 ]. Hossain et al [ 137 ] experimented with a pair of universal primers with the aim to target a 198 bp fragment of the mitochondrial 16S rDNA to assess species identification in partially degraded samples.…”

“…A higher mislabelling rate was also found in canned tuna sold in Taiwan. Chang et al [ 139 ] sequenced two mitochondrial regions, 16S and the control region (D-Loop), to assess 90 canned tuna products, also including 25 animal food items. Results revealed that Sarda orientalis , Euthynnus affinis , Auxis rochei and Auxis thazard are commonly exploited as substitutes in place of declared tuna products.…”

“…Results revealed that Sarda orientalis , Euthynnus affinis , Auxis rochei and Auxis thazard are commonly exploited as substitutes in place of declared tuna products. Specifically, only 63.33% of investigated samples are true canned tuna, i.e., containing Thunnus species or skipjack tuna [ 139 ]. On the other hand, a low mislabelling rate was found in the study of Helgoe et al [ 140 ], in which Atlantic cod ( Gadus morhua ) samples ( n = 546) were collected from local markets, supermarkets and restaurants from eight cities across Spain.…”