Quality Index Method for Freshness Assessment of Chilled Japanese Flying Squid (Todarodes pacificus)

Aims: To develop and apply a quality index method (QIM) scheme for evaluating the freshness and estimating the shelf life of raw whole Japanese flying squid (Todarodes pacificus) stored at low temperatures.

Study design: A QIM scheme was developed through pre-observation and formation of a preliminary scheme, finalization of the protocol and training of judges. The scheme was then applied to evaluate the freshness of squid in comparison with control methods, which were quantitative descriptive analysis (QDA), Torry scoring, and total viable count (TVC) determination.

Place and duration of study: Nha Trang University, Vietnam, between February and June 2012; and from November 2019 to January 2020.

Methodology: A total of 399 Japanese flying squids (Todarodes pacificus) of 50-70 g stored at 0-2°C were used in the study. Seven judges engaged in the QIM establishment and application. Control methods were QDA, Torry and TVC check. Principle component analysis (PCA) was used for studying the dataset main variance. Partial least square regression (PLS-R) was carried out to evaluate the possibility to predict storage time of the developed QIM scheme.

Results: The formulated QIM scheme for Japanese flying squid stored at low temperatures composed of 8 parameters, which are odour, eyes, skin pigment, skin elasticity, body shape, body texture, ink sac integrity, and head-body connection, forming a quality index (QI) range of 0-15. The PLS-R showed that the developed QIM protocol could give a shelf life estimation accuracy of ± 1.0 day if 7 squids from each batch were evaluated. The PCA showed that QDA parameters clustered into good and bad attribute groups, which characterised flesh and old/spoilt squid, respectively. QDA, Torry and TVC results revealed a maximal squid shelf life of 12 days at 0-2 °C.

Conclusion: The QIM scheme for chilled Japanese flying squid (Todarodes pacificus) could be used to estimate the remaining shelf life of the product with the precision of ± 1.0 day, using at least 7 squids of the same storage time for assessment. Squid exhibited a shelf life of 12 days at 0-2 °C.