Metabolomics-based study for the quality prediction of Litopenaeus vannamei (white leg shrimp)

(Litopenaeus vannamei(バナメイエビ)の品質予測に資するメタボロミクス基盤研究)

Currently, the shrimp industry uses shrimp size as the basis for shrimp grading. Well known as count size, this unit counts the number of shrimp contains in one kilogram. Large-sized shrimps are considered luxurious and, therefore they are priced higher compared to the smaller shrimp. However, size is not known to impart a particular quality trait, leading to a potentially flawed tool for shrimp pricing. Metabolomics, the closest omics study to the phenotype can provide meaningful insights into the quality of shrimp at the molecular level. By employing metabolomics approach, this study aimed to establish the method for the quality prediction of Litopenaeus vannamei (white leg shrimp) as one of the important species in the aquaculture industry.

As the first strategy, GC/MS-based metabolomics analysis was performed on different-sized shrimps collected from multiple commercial farms in Indonesia. Principal component analysis (PCA) assisted the data analysis of a complex metabolome data matrix by suggesting the most important factor contributing to the separation of the sample. The result showed size contributed to the sample clustering in the PCA score plot. Furthermore, projection to latent structure analysis (PLS) confirmed the ability of metabolome data in predicting the size. This result suggested a significant metabolite alteration throughout different shrimp sizes might be related to the metabolism due to growth. The interpretation of metabolite that contributed to the model was assessed using the Variable Importance of Projection (VIP) score. A stronger correlation between variables is depicted from the highest VIP score. Among VIP metabolites with a score higher than 1, phosphate was the only metabolite that showed a positive correlation with size. The predictability of the size-based prediction model was further examined by increasing the number of explanatory variables and sample variabilities. expanding the coverage of metabolites, in hopes to investigate what phosphate represented. The expansion of metabolites coverage was done by reversed-phase ion-pair liquid chromatography-tandem with triple quadrupole mass spectrometry (RP-IP LC/QqQ/MS),in hopes to investigate what phosphate represented. A total of 11 samples from Indonesia was utilized to train the model, meanwhile, 3 commercial shrimp samples obtained from the market were subjected as a validation set. The result showed phosphate detected from GC/MS was correspond to nucleotides detected from RP-IP LC/QqQ/MS. The expansion of metabolites improved the model predictability with the findings of IMP, AMP, and NAD as the highest positive predictors-VIP metabolites. Furthermore, commercial samples were successfully validated the prediction model, suggesting a strong correlation between metabolite relative intensity and shrimp size. This result suggested VIP metabolites with a score higher than 1.5 can characterize the size of shrimp according to the size difference. Therefore, these metabolites can be regarded as size-dependent, where a specific trend was constantly observed regardless of the various sampling locations, days of culture, and origin. Lastly, sensory analysis was performed using the most traded commercial size (count size 41/50-21/25) to confirm whether the size affects shrimp sensory quality as seen through the metabolite profile. Metabolites that involve in metabolism are also known to impart five basic taste activities. This also applies to size-dependent metabolites that are mainly consisted of organic acids, amino acids, sugars, and nucleotides. Most importantly, IMP and AMP are known as important umami-tasting metabolites that might contribute to the higher palatability of large shrimp. Quantitative Descriptive Analysis (QDA) was performed by ten expert panelists using 14 attributes. The scoring of each attribute was done by a 15-cm un-interval scale. The result showed, juiciness, crispness, red color, and sweetness were significantly higher in larger shrimp. IMP and AMP as umami-tasting compounds contributed to the enhancement of sweetness through a synergetic mechanism. This result successfully demonstrated that count size can be used as a parameter to assess shrimp quality. Small shrimps might offer higher palatability as they contain a higher accumulation of taste-active compounds, suggesting a versatility in culinary usage. Meanwhile, large commercial shrimps are valued due to their appealing appearance, distinct texture attributes, and sweet taste. As the consumers use raw characteristics such as shrimp appearance, the criteria for shrimp purchasing can be justified according to the count size.