Simultaneous Determination of Amino Acids and Biogenic Amines in Tuna and Mahi-Mahi by Reversed-Phase Ultra-High Performance Liquid Chromatography

Determining spoilage of whiteleg shrimp (Litopanaeus vannemei) during refrigerated storage using colorimetric strips

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Colorimetric strips were found to be applicable to determine the spoilage level of the commonly consumed crustacean (shrimp).

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The strips are relatively easy to use and offer a cost-efficient alternative to sensory and laborious laboratory methodology for seafood quality assessment.

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Strip results aligned well with the current sensory seafood grading system used by FDA/NOAA for inspection and possibly could serve as a replacement for sensory analysis.

A reliable spoilage assessment method is needed to ensure sufficient quality control of shrimp. Colorimetric dye-based indicators that change color in response to pH changes can monitor food quality changes in a simple, quick, and accurate way and generate easy-to-interpret results. Significant positive correlations with storage time were observed for the results of the bromophenol blue (BPB) strips (r = 0.8513, p < 0.0001) and the rose bengal strips (r = 0.8981, p < 0.0001). The results of both colorimetric methods significantly correlated with sensory and chemical quality indicators, including sensory attributes “salty water-like”, “natto water-like” and “sour milk-like”, and volatile compounds such as 3-methyl-3-butenol, 2-methyl-1-butanol, 3-methyl-1-butanol, hexanol, 2-methyl-1-butanal, and 3-methyl-1-butanal. The BPB strips and rose bengal strips have the potential to be used as objective, accurate, and cost-efficient methods to evaluate shrimp quality and lead to consistent and easy-to-interpret results.

Development of a rapid colorimetric strip method for determination of volatile bases in mahi-mahi and tuna

Tuna (Thunnus albacares) and mahi-mahi (Coryphaena hippurus) are two major fish species responsible for scombroid poisoning in the United States. The purpose of this research was to develop a low-cost and easily operated colorimetric strip method for the rapid determination of spoilage degree via amine response in mahi-mahi and tuna. The color strip method was developed by investigating different types of dyes, filter papers, sample volume, water bath temperature, and other parameters. Ultimately rose bengal and bromophenol blue (BPB) dyes were chosen. These two dyes produced standard curves with good linearity (0-50 mg/L for the total biogenic amines) and uniformity of color change. The r² values for the standard curves of the rose Bengal and BPB were 0.9535 and 0.8883, respectively. Significant positive Pearson correlations coefficients (r) between the volatile biogenic amine levels detected by these two colorimetric strip methods with increasing spoilage grade of mahi-mahi (rose bengal: r = 0.8907, p < 0.0001; BPB: r = 0.8711, p < 0.0001) and tuna (rose bengal: r = 0.8351, p < 0.0001; BPB: r = 0.7362, p = 0.0001) were observed. For mahi-mahi, the volatile amines detected by the colorimetric strips correlated positively with increasing levels of eight biogenic amines, free alanine, four aldehydes, isoamyl alcohol, two ketones, and dimethyl disulfide. For tuna, the results determined by colorimetric strips positively correlated with three biogenic amines, three free amino acids, four aldehydes, and ethanol. The two validated colorimetric strips could rapidly monitor the spoilage degree of mahi-mahi and tuna at low-cost. PRACTICAL APPLICATION: Rose bengal strips and BPB strips were developed as a rapid, objective, analytical method that can serve as an alternative to sensory grading methods. These two nonspecific colorimetric strip methods provided good linear response and uniformity of color change. Volatile amine levels in fish determined by these colorimetric strip methods were statistically significant and positively correlated with the spoilage grade of fish.