Characterization of the Flavor Profile of Bigeye Tuna Slices Treated by Cold Plasma Using E-Nose and GC-IMS

To avoid heat, treatment induces numerous physicochemical changes under severe conditions in the tuna, cold plasma (CP), as a non-thermal technology, possess objective potential on tuna processing. The effect of cold plasma on the volatile flavor compounds of bigeye tuna (Thunnus obesus) sashimi has been evaluated using electronic nose (E-nose) and gas chromatography-ion mobility spectrometry (GC-IMS). GC–IMS results revealed a total of 33 volatile compounds in tuna slices. The effect of CP treatment on tuna flavor was not significant, furthermore CP could protect volatile freshness compounds such as 1-hexanol. Principal component analysis (PCA) of the E-nose and GC–IMS results could effectively differentiate the effect of storage to tuna sashimi. There was a high correlation between the E-nose and GC–IMS results, providing a theoretical basis for establishing the flavor fingerprint of tuna sashimi.

Comparison of Physicochemical Changes and Water Migration of Acinetobacter johnsonii, Shewanella putrefaciens, and Cocultures From Spoiled Bigeye Tuna (Thunnus obesus) During Cold Storage

This study investigates the physicochemical changes and water migration of Acinetobacter johnsonii (A), Shewanella putrefaciens (S), and cocultured A. johnsonii and S. putrefaciens (AS) inoculated into bigeye tuna during cold storage. The physicochemical indexes [fluorescence ratio (FR), total volatile base nitrogen (TVB-N), thiobarbituric acid (TBA), trimethylamine (TMA), peroxide value (POV), and pH] of bigeye tuna increased cold storage. A significant decrease in trapped water was found in the AS samples, and direct monitoring of the water dynamics was provided by low-field nuclear magnetic resonance. Samples inoculated with A. johnsonii and S. putrefaciens also induced the degradation of myofibrillar proteins and weakness of some Z-lines and M-lines. Higher values of physicochemical indexes and water dynamics were shown in the coculture of S. putrefaciens and A. johnsonii than in the other groups. Therefore, this paper reveals that the coculture of A. johnsonii and S. putrefaciens resulted in a bigeye tuna that was more easily spoiled when compared to the single culture. This study provides insight into the spoilage potential of A. johnsonii and S. putrefaciens during cold storage, which further assists in the application of appropriate technologies to keep the freshness of aquatic foods.

Prediction in the Dynamics and Spoilage of Shewanella putrefaciens in Bigeye Tuna (Thunnus obesus) by Gas Sensors Stored at Different Refrigeration Temperatures

Shewanella putrefaciens have a faster growth rate and strong spoilage potential at low temperatures for aquatic products. This study developed a nondestructive method for predicting the kinetic growth and spoilage of S. putrefaciens in bigeye tuna during cold storage at 4, 7 and 10 °C by electronic nose. According to the responses of electronic nose sensor P30/2, the fitted primary kinetic models (Gompertz and logistic models) and secondary model (square root function model) were able to better simulate the dynamic growth of S. putrefaciens, with high R2 and low RMSE values in the range of 0.96–0.99 and 0.021–0.061, respectively. A partial least squares (PLS) regression model based on both electronic nose sensor response values and electrical conductivity (EC) values predicted spoilage of S. putrefaciens in bigeye tuna more accurately than the PLS model based on sensor signal values only. In addition, SPME/GC-MS analysis suggested that 1-octen-3-ol, 2-nonanone, 2-heptanone, dimethyl disulfide and methylamine, N, N-dimethyl- are the key VOCs of tuna inoculated with S. putrefaciens.

Analisis Filogenetik Ikan Tuna (Thunnus spp.) yang didaratkan di Pelabuhan Benoa, Bali

Tuna is one of the largest fisheries commodities in Indonesia after shrimp and demersal fish. The genus Thunnus is a type of tuna that dominates the international market. The genus Thunnus consisted of seven species of tuna. In some cases, the same morphological character has caused misidentification and data collection on tuna species. Therefore, this study aimed to identify tuna species that are landed at Benoa Harbor and analyzed their phylogenetic relationships. Species identification and phylogenetic analysed in this study used the mtDNA control region locus. The results of this study indicated that there are five tuna species landed at Benoa Harbor, namely yellowfin tuna (T. albacares), longtail tuna (T. tonggol), bigeye tuna (T. obesus), southern bluefin tuna (T. maccoyii), and albacore tuna (T. alalunga). Based on phylogenetic tree reconstruction, all samples were divided into five according to the number of tuna species resulted from molecular identification. Reconstruction of phylogenetic trees is supported by genetic distance between clades has a value of 0.075 - 0.212, with the closest kinship found in yellowfin tuna (T. albacares) with bigeye tuna (T. obesus) and the farthest found in yelowfin tuna (T. albacares) with albacore tuna (T. alalunga).