Effect of clove (Syzygium aromaticum) and seaweed (Kappaphycus alvarezii) water extracts pretreatment on lipid oxidation in sun‐dried sardines (Rastrineobola argentea) from Lake Victoria, Tanzania

Abstract

Small indigenous fish species play a significant role in food and nutritional security of poor communities in developing countries. Sardines ( Rastrineobola argentea ) are fish species of Lake Victoria known to be a good source of health‐promoting omega‐3 fatty acids. Open sun drying is a common and traditional sardine processing and preservation method. Sun‐dried products suffer from characteristic off‐flavor due to lipid oxidation which discourage product consumption and limit diversification. This study investigated the use of clove ( Syzygium aromaticum ) and seaweed ( Kappaphycus alvarezii) water extracts as natural antioxidants to impede lipid oxidation in sun‐dried sardines. Lipid oxidation was assessed by peroxide value, volatile secondary oxidation products, and fatty acid profiles. The antioxidant capacity of extracts was evaluated by total phenolic content, 1, 1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, and iron (Fe 2+ ) chelating ability. Results showed that 5, 10, and 20 g/L clove extracts significantly reduced peroxidation in sun‐dried sardines by 38.7%, 54.6%, and 56%, respectively. Clove extracts resulted in higher retention of omega‐3 fatty acids and lower concentrations of secondary lipid oxidation products as opposed to seaweed counterpart. This research has demonstrated feasibility of pretreating whole, omega‐3‐rich small sardines with natural antioxidants to avert lipid oxidation during sun drying.

An optimised low‐salinity seawater decolourising method produces decolourised seaweed (Kappaphycuz alvarezii) as semi‐refined carrageenan raw material:

“…Liquid waste from LSS (3 g/L) treatment contained TFC (0.04 mg/g) and TPC (0.09 mg/g) and was attributed to high ABTS • (94.33%) and DPPH • inhibition (56.86%) (Table 2). Chaula et al (2019) reported that scavenging activities of K. alvarezii water extracts inhibited DPPH • by 29.67-50.56%. Plants, when stressed, tend to produce more reactive oxygen species (ROS) as by-products of aerobic metabolism, but they simultaneously employ antioxidant metabolites (Table 2) to prevent possible oxidative damage (Apel & Hirt, 2004).…”

Phyto-pharmacological investigation of algae Kappaphycus alvarezii (Doty) Doty ex Silva for oral diseases (Rhodophyta)

“…Вільні радикали значною мірою утворюються у морських водоростях, що зазнають дії світла та кисню як фотосинтезуючі організми. Це, в свою чергу, стимулює синтез багатьох протиоксидантних метаболітів для подолання пошкоджень внаслідок окислення (Chaula et al, 2019). Triphati et al (2019) повідомляють про використання лікопену з морських водоростей -каротиноїдного пігменту з протиоксидантною властивістю, в десять разів більшою, ніж мають альфа-токоферол, сечова кислота та екстракт зеленого чаю, які є активними сполуками у боротьбі із запаленням ясен.…”

Protection against Oxidation of Omega-3 Fatty Acids with Natural Antioxidants in Clove (Szygium aromaticum) Water Extracts during Storage of Sun dried Sardines (Ratrineobola argentea)

“…Lower concentrations of such compounds in pre-treated samples imply that the nutritionally valued PUFAs DHA and EPA were protected against oxidative damage during storage. Clove water extracts have been reported to retard lipid oxidation during sun-dry processing of sardines resulting into lower concentrations of volatile compounds in dry sardines [27]. Phenolic compounds are known to exert anti-oxidative effect by different mechanisms such as scavenging of free radicals, singlet oxygen quenching, oxygen scavenging, metal chelation and inhibition of oxidizing enzymes [21,22].…”

“…Elsewhere, the clove water extract has been found to contain substantial amounts of phenolic compounds and powerful antioxidant activity in linoleic acid emulsion [26]. Clove water extracts are reported to result in improved retention of nutritionally valued long chain PUFAs DHA, EPA and DPA during open sun and oven drying of sardines [27,28]. The aim of the current study was to evaluate the efficacy of clove (Szygium aromaticum) water extracts in protecting omega-3 fatty acids during extended storage of sun dried sardines.…”