engleski

Effect of plant extracts on secondary oxidation products during shrimp marination process

Consumers demand for minimally processed foods is increasing, thus alternatives to artificial additives and processing methods have been a focus of research with an aim to obtain safe and healthier food products. In marinated products, acidic conditions promote lipid oxidation generating oxidative degradation products such as, malondialdehyde (MDA). This study aimed to investigate the influence of different plant extracts (individual and their mixtures) on MDA content during shrimp marination process. Rosmary (R, {;Rosmarinus officinalis};), lemon balm (LB, {;Melissa officinalis};), lavender (L, {;Lavandula spica};), oregano (O, {;Origanum vulgare};) and satureja (S, {;Satureja montana};) water extracts have been prepared using ultrasound bath for 2 hours at 60°C (15 g plant/100 mL water). Water:discolored red vinegar solution in ratio 3:1, and 6 % salt was used as marinating bath (MB). Shrimp meat (50 g) was packed into glass jars with 100 mL of MB, plus 2, 3 and 5 mL of plant extracts. Additionally, different plant extracts were mixed and added to the jars containing shrimp and MBs. Total phenolics (TP) of the MBs were analysed according to Folin-Ciocalteu method and expressed as mg galic acid equivalent per liter (GAE/L). Marination was carried out for 7 days, afterwards the MBs were discarded and drained shrimps packed into sunflower oil and stored for two months before thiobarbituric reactive substances (TBARS) assay, as an index of lipid oxidation, was done. The lipid oxidation of marinated shrimps changed under influence of TP from extracts. For all five plant extracts MDA levels in shrimp meat were lowered as the extract concentration increased. The lowest MDA levels, ranging from 1.66 to 2.37 μmol MDA/100 g were observed for samples marinated in S and O extracts. TP content of these MBs ranged from 289.93 to 398.27 mg GAE/L. MBs prepared with R and LB extracts had the highest TP content (in range of 459.60-562.60 mg GAE/L) but shrimp meat from these MBs had lower TBARS values than those prepared with S and O extracts. Addition of 2 mL of R and LB extracts resulted in 3.99 and 5.14 μmol MDA/100 g of shrimp meat. TBARS values obtained in shrimp marinated with addition of 5 mL R and LB extracts lowered the TBARS values to 2.79 and 2.69 μmol MDA/100 g, respectively. Increasing the volume of L extracts resulted in higher TP content ranging from 308-366 mg GAE/L and lowered the TBARS values in marinated shrimp (3.29-2.37μmol MDA/100 g). Addition of mixed extracts to MBs showed better results than individual plant extracts and TP content ranged from 436 to 541 mg GAE/L. Although some MBs containing R and LB extracts had just as high TP content, the effect on secondary oxidation products during shrimp marination process was more prominent when mixed extracts were used. Mixed extracts showed better antioxidant properties than individual extracts, the highest TP content was observed when 1 mL of each extract was added to MBs (541 mg GAE/L) corresponding the lowest TBARS of all tested samples (1.23 μmol MDA/100 g). The lipid oxidation process leads to the formation of several components causing off-flavours and reduced nutritional quality. Secondary oxidation products, such as MDA, have negative implications on the human body due to their cytotoxic, mutagenic and neurotoxic action. Addition of plant antioxidants can delay lipid oxidation process of shrimp meat during marination. However, the secondary oxidation products, such as MDA, during shrimp marination process might depend on more factors than just TP content. Mixing the extracts of different plants might enhance antioxidative properties obtained by individual plants.

antioxidation ; TBARS ; malondialdehyde ; plant extracts ; marinated shrimp

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