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.

Aroma Profile Characterization of Mahi-Mahi and Tuna for Determining Spoilage Using Purge and Trap Gas Chromatography-Mass Spectrometry.

Alcohols, aldehydes, ketones, amines, and sulfur compounds are essential aroma compounds related to fish flavor and spoilage. Gas chromatography-mass spectrometry (GC-MS) is an instrument that is widely used to identify and quantify volatile and semi-volatile compounds in fish products. In this research, a simple and accurate GC-MS method was developed to determine the aroma profile of mahi-mahi and tuna for chemical indicators of spoilage. In the developed GC-MS method, trichloroacetic acid (TCA) solution was used to extract analytes from homogenized fish samples. The purge and trap system was used for sample introduction, and the GC-MS with an RTX-Volatile Amine column was able to separate compounds without a derivatization procedure. The created purge and trap gas chromatography-mass spectrometry (PT-GC-MS) method could identify and quantify twenty aroma compounds in mahi-mahi (Coryphaena hippurus) and 16 volatile compounds in yellowfin tuna (Thunnus albacares) associated with fish spoilage. The amines (dimethylamine, trimethylamine, isobutylamine, 3-methylbutylamine, and 2-methylbutanamine), alcohols (2-ethylhexanol, 1-penten-3-ol and isoamyl alcohol, ethanol), aldehydes (2-methylbutanal, 3-methylbutanal, benzaldehyde), ketones (acetone, 2,3-butanedione, 2-butanone, acetoin), and dimethyl disulfide strongly statistically correlated with poorer quality tuna and mahi-mahi and were considered as the key spoilage indicators. PRACTICAL APPLICATION: A simplified and rapid purge and trap gas chromatography-mass spectrometry (PT-GC-MS) method developed in this research was able to identify and quantify important spoilage compounds in mahi-mahi and yellowfin tuna. This method is an efficient analytical method for determining volatile profiles of fish samples for industry analytical labs or the government. The identified analytical quality markers can be used to monitor the spoilage level of tuna and mahi-mahi.

Assessment of cellular and functional biomarkers in bivalves exposed to ecologically relevant abiotic stressors.

An understanding of the complex effects of the environment on biomarkers of bivalve health is essential for aquaculturists to successfully select field culture sites and monitor bivalve health in these sites and in hatcheries. We tested several whole-organism (functional) and cellular-level biomarkers as indicators of health of the cultured, stress-tolerant northern quahog (hard clam) Mercenaria mercenaria. We performed single- and dual-stressor experiments that were consistent with available water quality data from a clam culture area on the Gulf coast of Florida. Clams from the culture area were exposed over a 14-d period to low O2 (hypoxia), elevated temperature, hyposalinity, and a combination of elevated temperature and hyposalinity. There was no clear relationship between the functional and cellular-level biomarkers, with most of the treatment effects being detected at the whole-organism level but not the cellular level. Survival and burial ability were significantly affected by elevated temperature and by the combination of elevated temperature and hyposalinity. Glycogen content decreased over the experiment duration and did not differ significantly among treatments. There were no significant changes in expression patterns of eight stress proteins or in the levels of oxidatively damaged RNA. The results highlight the importance of investigating the effects of multiple stressors in short-term, controlled laboratory conditions and suggest that such cellular-level biomarker assays should be paired with functional biomarkers to better understand the responses of highly stress-tolerant species.

Continuous water quality monitoring for the hard clam industry in Florida, USA.

In 2000, Florida's fast-growing hard clam aquaculture industry became eligible for federal agricultural crop insurance through the US Department of Agriculture, but the responsibility for identifying the cause of mortality remained with the grower. Here we describe the continuous water quality monitoring system used to monitor hard clam aquaculture areas in Florida and show examples of the data collected with the system. Systems recording temperature, salinity, dissolved oxygen, water depth, turbidity and chlorophyll at 30 min intervals were installed at 10 aquaculture lease areas along Florida's Gulf and Atlantic coasts. Six of these systems sent data in real-time to a public website, and all 10 systems provided data for web-accessible archives. The systems documented environmental conditions that could negatively impact clam survival and productivity and identified biologically relevant water quality differences among clam aquaculture areas. Both the real-time and archived data were used widely by clam growers and nursery managers to make management decisions and in filing crop loss insurance claims. While the systems were labor and time intensive, we recommend adjustments that could reduce costs and staff time requirements.