Biotechnological Communication Biosc.Biotech.Res.Comm. Vol 13 Number (1) Jan-March 2020 Pp-23-29 Feasibility of Edible Coating, Storage Temperature and Packaging for Rancidity and Proteolytic Activity of Dry-Salted Snakeskin Gourami, Trichopodus pectoralis Minh Phuoc Nguyen Faculty of Biotechnology, Ho Chi Minh City Open University, Ho Chi Minh City, Vietnam ABSTRACT Snakeskin gourami (Trichopodus pectoralis) has been considered as a valuable and suitable species for breeding in fresh and brackish water regions in Vietnam. It has a high meat yield and favouritely consumed as dry-salted fish. However the dry-salted snakeskin gourami quality has gone down very fast owing to rancidity and proteolytic activity because it has high fat content and protease in its abdomen. It’s necessary to have an appropriate processing and preserving approach to accelerate its commercial value in local and international markets. Edible coating supports a natural cover on the product surface to control weight loss, oil rancidity and solute movements. Biodegradability, edibility and barrier attributes are some benefits of edible coating superior to plastic bag. Storage temperature and packaging procedure affected the rancidity and proteolytic activity in the dry-salted snakeskin gourami (Trichopodus pectoralis). Purpose of this research demonstrated the efficacy of carrageenan coating on storage of dry-salted snakeskin gourami (Trichopodus pectoralis). The dried snakeskin gouramis were coated by various concentrations of carrageenan (0.5%, 0.75%, 1.0%, 1.25%, 1.5%). The efficacy of carrageenan coating was defined via quality indicators of dry-salted snakeskin gouramis such as fat rancidity: Peroxide value (mEqO2/ kg), Thiobarbituric acid (mg maloaldehyde/ kg); proteolytic changes: total volatile base (TVB-N, mg N/100 g) nitrogen content and trimethylamine (TMA, mg N/100 g). In 3 month-interval, all coated samples were periodically analyzed during 12 months of preservation at ambient condition. Results showed that the carrageenan coating of 1.25% w/w, packed in vacuum bag and stored at 4oC could avoid microbial decomposition and fat oxidation of the dry-salted snakeskin gouramis. From this investigation, the dry-salted snakeskin gouramis had shelf-life at ambient storage for 12 months without deterioration. The research implied that the edible coating would be ideal to extend the stability of this valuable oil fish by inhibition of proteolytic reaction, reduction of fat rancidity and enhancement of overall acceptance. KEY WORDS: TRICHOPODUS PECTORALIS, CARRAGEENAN, PROTEOLYTIC reaction, RANCIDITY, stabiLITY. ARTICLE INFORMATION *Corresponding Author: [email protected] Received 13th Jan 2020 Accepted after revision 29th Feb 2020 Print ISSN: 0974-6455 Online ISSN: 2321-4007 CODEN: BBRCBA Thomson Reuters ISI Web of Science Clarivate Analytics USA and Crossref Indexed Journal NAAS Journal Score 2020 (4.31) SJIF: 2019 (4.196) A Society of Science and Nature Publication, Bhopal India 2020. All rights reserved Online Contents Available at: http//www.bbrc.in/ 23 DOI: 10.21786/bbrc/13.1/5 Nguyen INTRODUCTION et al., 2010). The effects of chitosan and different organic acid on fresh Japanese sea bass fillets were studied Snakeskin gourami (Trichogaster pectoralis) is one of (Qiu et al., 2014). Quality characteristics of Japanese the most common fish in paddy fields and rivers of sea bass (Lateolabrax japonicus) during refrigerated Vietnam. It lives in waters at low dissolved oxygen and storage were affected by e-polylysine, sodium alginate high organic accumulation and feeds on zooplankton, and e-polylysine/sodium alginate (Cai et al., 2015). The crustaceans and insect larvae (Jafaryan et al., 2014). effectiveness of edible chitosan coating on the quality It achieves good maturity stages after 3 months of changes of Indian oil sardines (Sardinella longiceps) was rearing. It has a high meat yield and is consumed as studied by Mohan et al. (2102). a dried fish in Vietnam. Farming area of snakeskin gourami has been opened dramatically in recent years Several studies mentioned to the processing and offering attractive income for local farmers (Minh et al., preservation of snakeskin gourami. The effect of 2019). The aquaculture sector contributes an important various salt concentrations and other soluble elements source of nutritious food for human consumption. Fish on the moisture content and water activity (aw) of and fishery products are among the most important dried snakeskin fish was studied (Muoi et al., 2008). agricultural commodities (Bharda et al., 2017). This The influence of sorbitol and ethanol on the water species is considered as an alternative species to shrimp activity and quality changes of dried snakeskin fish farming in rainy season. They are good sources of was examined (Truc et al., 2009). Ethanol treatment to proteins, macro-nutrients, minerals and some vitamins. eliminate fishy ordor; addition of salt, sorbitol, as well The mineral elemental levels and vitamins of this species as dry temperature that affected to to water activity is a function of the availability preferential accumulation. (aw), microbial load (coliform, cfu/g), sensory score of Aquaculture of P. elongatus in the Ca Mau province dried snakeskin gourami (Trichogaster pectoralis) were (Vietnam) has developed rapidly during the past decade thoroughly investigated. Shelf-life of the dried product due to relatively high demand and high marketable value was also evaluated during preservation (Minh et al., (Minh et al., 2019). 2019). At death, the pH value in fish muscle begins to decrease In Vietnam, the snakeskin gourami P. elongatus is a high due to formation of lactic acid from glycogen via a value species and has high potential for aquaculture series of enzymatic reactions in the muscles. Enzymes in the Mekong Delta. P. elongatus aquaculture has from spoilage microorganisms produce different volatile developed rapidly to supply the high demand of compounds causing bad smell. The combination of domestic consumers. However there was not any research ammonia (NH3) and TMA in fish is accounted for the mentioned to the investigation of carrageenan coating total volatile base (TVB-N) nitrogen content of the fish to the dry-salted snakeskin gouramis (Trichopodus and is normally considered as an indicator of quality pectoralis) as well as the effect of storage temperature decomposition. With the proliferation of spoilage and packing procedure to oil rancidity and proteolytic bacteria after death in fish, a subsequent increase in activity. Purpose of this research was to demonstrate the TMAO reduction to TMA happens. On the other hand, feasibility of carrageenan coating, storage temperature the increase in the TVB-N is mainly created by the and packaging procedure in prolonging product quality formation of TMA, which is prevalent in spoiled fish of dried snakeskin gouramis (T. pectoralis). Coatings can that have TMAO (mainly in marine pelagic fish) and is be considered as a barrier to protect against discoloration, the most common cause of fishy odor. Aeromonas spp., degradation and oxidative rancidity. psychrotolerant Enterobacteriaceae, Photobacterium phosphoreum, Shewanella putrefaciens-like organisms MATERIAL AND METHODS and Vibrio spp. are the bacteria that are able to reduce TMAO to TMA (Heising et al., 2014). Material: Snakeskin gourami (Trichopodus pectoralis) were harvested from Ca Mau province, Vietnam. After Rancidity is a matter in fatty fish related to the dried harvesting, they were cooled below 4oC and moved to preservation. Indeed, the shelf-life of dried fatty fish laboratory as soon as possible for further experiments. usually ends with the onset of rancid flavors. The speed They were washed and sanitized under washing tank of hydroperoxide formation strongly relates to fat having 20 ppm per acetic acid with air bubble blowing oxidation in its early stages. Aldehydes, ketones and to remove foreign matters. Besides snakeskin gourami similar compounds are the secondary products which we also used other material during the research such as form as the hydroperoxides react. The reactions lead per acetic, salt, carrageenan. Lab utensils and equipment to aldehydes and other products that can be evaluated included digital weight balance, Rotronic, stomacher, using the thiobarbituric acid (TBARS) test (Turienzo incubator, colony counter, and dry oven. Oil rancidity et al., 2011). There were several notable researches of dry-salted snakeskin gouramis was carried out by mentioned to application of edible coating in fishes carrageenan coating during storage: They were soaked to control oxidation and proteolytic change. Whey in 20 minutes with solution containing 4.0% salt, 1.0% proteinbased coatings delayed lipid oxidation of salmon sugar, 0.1% monosodium glutamate, 0.5% garlic extract, fillets (Turienzo et al., 2011). The chitosan coatings and 0.5% honey. After that they were dried at 50oC to 18% packaging might have been sufficient to retard lipid moisture content. Various carrageenan concentrations oxidation in lingcod (Ophiodon elongates) fillets (Duan were verified (0.5%, 0.75%, 1.0%, 1.25%, 1.5%) on BIOSCIENCE BIOTECHNOLOGY RESEARCH COMMUNICATIONS RANCIDITY AND PROTEOLYTIC ACTIVITY OF DRY-SALTED SNAKESKIN GOURAMI, 24 Nguyen the dry-salted snakeskin gouramis. Oil rancidity was by 1,1,3,3-tetraethoxypropane (Torres-Arreola et al., evaluated by Peroxide value (mEqO2/ kg), Thiobarbituric 2007). Standard methods recommended by Food and acid (mg maloaldehyde/ kg). All coated