Assessing the effects of low pH on taste, amino acid composition of black tiger shrimp

Results indicate P. monodon could become less palatable due to ocean acidification and lower production of some amino acids

low ph
This study evaluated the potential effect of pH on survival, body properties, amino acid composition of black tiger shrimp (Penaeus monodon), and results suggested ocean acidification may affect its future quality and production. Photo by Pawar Pooja, via Wikimedia Commons.

Ocean acidification (OA) has become a key issue that has been investigated extensively during the past few decades. According to current projections, continued uptake of atmospheric carbon dioxide oceans may lead to a decrease in the average pH [a measure of how acidic/basic water is] of open ocean surface water of 0.4 to 0.5 by the end of the twenty-first century. Beyond those predictions, coastal waters seem to be acidifying at much faster rates than the open ocean. Moreover, the decreasing pH trend is superimposed on a very large natural pH variability in coastal waters. Critical insights into the impacts of ocean acidification (OA) may be gained by investigating its effects on the physiology of marine organisms and how seafood may be affected.

A large body of evidence is available on the negative impacts of projected OA on the survival, growth, calcification, immune responses, and reproduction of marine organisms. Only recently, however, have a very small number of experimental studies attempted to estimate the possible socio-economic consequences of OA acidification due to the altered quality of seafood, and one study revealed that culturing shrimp in acidified seawater negatively affected their flavor. There is a pressing need to expand our understanding of the effects of acidification on the quality of seafood products.

The flavor of seafood comes mainly from amino acids, nucleotides, sugars and mineral salts. Amino acids in particular are thought to modulate the sensory qualities of shrimp, including sweetness, bitterness and “umami” [or savoriness, one of the five basic tastes, which has been described as savory and is characteristic of cooked meats and broths] taste. In humans, amino acids activate specific taste receptors as well as nutrient demand. As such, the concentrations and relative proportions of amino acids in shrimp and other seafood can have important repercussions for consumers and seafood producers. Researchers testing how OA could impact the taste of seafood mussels and its appeal to consumers have reported that the attributes of mussels that are affected by OA also tend to determine consumers’ preferences and that people would only be prepared to buy mussels affected by OA if they were 52 percent cheaper than they are at present.

The black tiger shrimp (Penaeus monodon) is a key species in the shrimp industry worldwide, with desirable texture and very good flavor, and with global trade worth several billion U.S. dollars annually. The species naturally inhabits brackish, estuarine (juveniles), and marine (adults) environments that extend from Africa to southern Asia. Increasingly, black tiger shrimp are farmed in the coastal and wetland regions of south Asian countries. These coastal waters are currently affected by rapid ocean acidification which may threaten or affect the health, production rates, and meat quality of future black tiger shrimp.

This article – adapted and summarized from the original publication (Weerathunga, V. et al. 2021. The effects of low pH on the taste and amino acid composition of tiger shrimp. Sci Rep 11, 21180 (2021)) – reports on a study comparing survival rate, carapace properties and flesh sensory properties and amino acid composition of P. monodon shrimp exposed for 28 days to pH conditions covering the present (pH 8.0) and near-future (pH 7.5) average pH conditions in coastal ecosystems.

Global Seafood Alliance, 15 November 2021. Press release.

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