Detection of Artificially Water-Injected Frozen Octopus minor (Sasaki) Using Dielectric Properties

Abstract

A few importers of marine products have practiced the fraud of artificially injecting water into Octopus minor for increasing their weights prior to the freezing process. These rampant practices have recently become a serious social issue and threaten public health. Therefore, it is necessary to develop the detection method for artificially water-injected frozen Octopus minor. This study was conducted to develop the nondestructive method for verifying adulterated Octopus minor by measuring dielectric properties using the coaxial probe method. Regardless of weight and measurement locations, a significant difference between ε values from normal octopuses was not observed. The ε values of Octopus minor were decreased in the microwave frequency range between 500 and 3000 MHz. The ε values of water-injected octopuses also showed similar trend with normal octopuses; however, the dielectric loss factor (ε″) values of adulterated octopuses were much lower than normal octopuses. After thawing normal, adulterated, and imported frozen Octopus minor, the ε values measured at the trunk part from these octopuses were compared and statistically analyzed. The ε″ values from normal frozen octopus were significantly different from adulterated and imported frozen octopuses. In addition, the ε″ values from the adulterated frozen octopus group that weight gain rate was less than 20% was significantly different from other adulterated octopus groups with higher weight gain rate than 20%. The ε″ values from adulterated frozen octopus groups with the range of weight gain rate between 20 and 30% were quite similar to imported frozen octopuses. Therefore, it was found that the measurement of ε″ values from Octopus minor has a great possibility to distinguish normal frozen octopuses and artificially water-injected frozen octopuses.