Identification of Ingredient in Mullet Roe Products by the Real-Time PCR Method

Abstract

Mullet roe is a product of high economic value in a number of Asian countries, particularly Taiwan. However, actual mullet roe is commonly adulterated by the addition of other species, such as escolar and oilfish. The purpose of this study was to develop a method to detect the ingredient of mullet roe products. Based on the TaqMan real-time PCR assay, we designed the specific primers-probe set (mullet) that targets the mitochondrial 16S ribosomal RNA gene. Meanwhile, the positive amplification control is designed based on the eukaryotic 18S rRNA gene. The PCR amplicon used to identify fish species in processed roe products is smaller than 200 bp. Method specificity was evaluated by analyzing tissue samples of 29 food fish and 9 puffer fish species. No indications of cross-reactivity toward non-target species were observed. Sensitivity and linearity tests were conducted using five-fold serial dilutions of target DNA from processed mullet roe, and we determined that our proposed method has a sensitivity of 1.2 ng. Further tests on a random survey of commercial fish roe products demonstrated the efficacy of the technique in the detection of mullet DNA. The real-time PCR methods developed in this study could be used to verify the labeling of actual mullet roe products.