How mushroom extracts can be an alternative yet effective antioxidant especially made for shrimps. 

By Melpha Abello

The use of mushroom extract as antioxidant can help reduce post-harvest losses among farmed
crustaceans by inhibiting the occurrence of melanosis or post-harvest blackening of the carapace for up to four days during ice storage, making it an effective natural alternative to synthetic melanosis-inhibiting agents.

According to Dr. Angel B. Encarnacion, officer-in-charge of the post-harvest and marketing division of the Bureau of Fisheries and Aquatic Resources Region 2 (BFAR RO2), the crude water soluble extract from edible mushroom Flammulina velutipes reportedly contains significant amount of 2-thiol-L-histidine-betaine also known as ergothioneine or ESH, a potent antioxidant that can prevent the development of melanosis in seafoods, meat, and other agricultural products.

After four days under ice storage, the mushroom extract-treated Pacific white shrimp on the right did not develop melanosis or blackening of the carapace, as opposed to the untreated shimp on the left.

In the case of economically important crustaceans such as black tiger shrimp (Penaeus monodon) and Pacific white shrimp (Litopanaeus vanamei), their market price can go down by almost half if the carapace is blackened, Encarnacion said during the presentation of his research
which qualified him as one of the finalists for the 2014 National Academy of Science and Technology (NAST) Talent Search for Young Scientists (TSYS). A project of the NAST,
the TSYS seeks to encourage young people (aged 35 years or younger) to pursue a career in science.

Encarnacion explained that the blackening is induced by the action of polyphenoloxidase (PPO), an enzyme generally referred to as tyrosinase. Although melanosis is a harmless natural mechanism, with the enzyme reactions starting as soon as crustaceans are taken from the water and come in contact with the oxygen in the atmosphere, Encarnacion points out that it is a costly phenomenon, as it results in a decline in the economic value of the seafood concerned.

Among the widely used synthetic anti-melanosic compounds and antioxidants for shrimp are sodium sulfite and 4-hexylresorcinol, whose residues are reported to pose possible health hazards and have negative effects on the taste of the seafood, prompting the need for safe at effective alternatives for food application.

When Encarnacion was granted scholarships by the government of Japan to pursue his masteral and doctoral studies at the Tokyo University of Marine Science and Technology in 2008 and 2011, respectively, he initiated research on the utilization of mushroom extracts from mushroom trimmings to control melanosis and lipid oxidation in farmed crustaceans and fish, considering key issues of food quality and safety, and waste utilization.

Together with his foreign co-researchers, they evaluated the in vivo (on site) melanosis-inhibiting properties of ESH-rich mushroom extract (ME) taken from the base and fruiting
body waste of F. velutipes on marketable-size black tiger shrimp and Pacific white shrimp, and compared the effects with the use of synthetic melanosis-inhibiting agents, sodium sulfite, and 4-hexylresorcinol using the immersion method.

The researchers also determined the inhibitory effects of the mushroom extract on mushroom PPO and its chelating activity to elucidate its prevention of melanosis in shrimp during ice storage.

After four days of ice storage, they found, with the use of enzyme assays, that immersion of live black tiger shrimp and Pacific white shrimp in a 0.5% solution of mushroom extract for one hour significantly decreased PPO activity by 73% and 61%, respectively, compared to the untreated
shrimp (control), which showed pronounced blackening in the carapace. This effect, Encarnacion said, is similar to thenatural mechanism, with the enzyme reactions starting as soon as crustaceans are taken from the water and come in contact with the oxygen in the atmosphere, Encarnacion points out that it is a costly phenomenon, as it results in a
decline in the economic value of the seafood concerned.

Among the widely used synthetic anti-melanosic compounds and antioxidants for shrimp are sodium sulfite and 4-hexylresorcinol, whose residues are reported to pose possible health hazards and have negative effects on the taste of the seafood, prompting the need for safe at effective alternatives for food application.

When Encarnacion was granted scholarships by the government of Japan to pursue his masteral and doctoral studies at the Tokyo University of Marine Science and Technology in 2008 and 2011, respectively, he initiated research on the utilization of mushroom extracts from mushroom trimmings to control melanosis and lipid oxidation in farmed crustaceans and fish, considering key issues of food quality and safety, and waste utilization.

Together with his foreign co-researchers, they evaluated the in vivo (on site) melanosis-inhibiting properties of ESH-rich mushroom extract (ME) taken from the base and fruiting
body waste of F. velutipes on marketable-size black tiger shrimp and Pacific white shrimp, and compared the effects with the use of synthetic melanosis-inhibiting agents, sodium sulfite, and 4-hexylresorcinol using the immersion method.

The researchers also determined the inhibitory effects of the mushroom extract on mushroom PPO and its chelating activity to elucidate its prevention of melanosis in shrimp during ice storage.

The Flammulina velutipes mushroom is rich in an antioxidant called ergothioneine, which can be used to suppress melanosis in shrimp. (Photo from en.wikipedia.org)

After four days of ice storage, they found, with the use of enzyme assays, that immersion of live black tiger shrimp and Pacific white shrimp in a 0.5% solution of mushroom extract for one hour significantly decreased PPO activity by 73% and 61%, respectively, compared to the untreated
shrimp (control), which showed pronounced blackening in the carapace. This effect, Encarnacion said, is similar to the effects of the use of 0.05% sodium sulfite and 0.05% 4-hexylresorcinol
solutions.

Based on copper-chelating analyses, the prevention of melanosis was due to the possible direct interaction of ESH with copper at the putative binding sites of PPO. This means that ESH alters the enzyme by forming a chelate with the copper ion in the active site of the enzyme, so that no reaction such as melanosis can occur.

In a pilot-scale application on a shrimp farm in Vietnam to evaluate the efficacy of the mushroom extract and determine the immersion technique in controlling postharvest melanosis
in live L. vannamei shrimp during transport, the results revealed that untreated shrimp developed melanosis after three hours of transport on ice compared to the group that was pretreated with mushroom extract in a rearing tank.

Back in the Philippines, Encarnacion tested the technology using the locally abundant oyster mushroom and found it as effective as F. velutipes not only on crustaceans and fish, but on fresh meat as well. In fact, his formulation, whose patent application is now pending, is currently being used by a group of farmers in Cagayan who have found it to be very beneficial.

Simply put, the technology is applied by immersing live full-grown black tiger shrimp and Pacific white shrimp in a recommended solution of mushroom extract and water for one hour prior to ice storage. This, Encarnacion said, will prevent the shrimp carapace from blackening for up to four days in ice storage.

Aside from being effective and naturally safe, the mushroom extract anti-melanosic compound developed by

Encarnacion and his research team can also help minimize the problem of the disposal of agricultural waste, as it is converted to a useful product with industrial value.
Encarnacion reported that in Japan, for instance, a typical commercial mushroom processor with a daily capacity of one to two metric tons of F. velutipes generates about 100 to 300
kilograms of trimmings that are usually disposed of as waste.

In the Philippines, where ninety percent (equivalent to around 150 tons) of the mushrooms consumed yearly are imported, the technology of producing mushroom extract from trimming
wastes may be adapted to come up with an effective yet cheap antioxidant for application in aquaculture and food preservation, Encarnacion said. He added that the mushroom
extract is obtained from mushroom wastes using water and a centrifuge—hence the low cost.

In line with this, Encarnacion is currently working on the identification of seaweeds and plants that are potential sources of antioxidants for aquaculture use. This research, he said, also aims to reduce fisheries’ postharvest losses and to help our local fishery products, particularly shrimp, comply with the requirements of the foreign market for drug residues.

This is more significant in light of a recent report released by the University of the Philippines Natural Sciences Research Institute states that one of the reasons for the country’s low
aquaculture exports to European Union and the United States is its lack of a national control plan for drug residues in the aquatic products as a guarantee for safety compliance.

This story appeared in Agriculture Monthly’s June 2014 issue.