Effect of oregano and thyme essential oils on the microbiological and chemical quality of refrigerated (4 °C) ready-to-eat squid rings

Enhancement of Lipid Stability and Acceptability of Canned Seafood by Addition of Natural Antioxidant Compounds to the Packing Medium-A Review

Seafoods are known to include high contents of valuable constituents. However, they are reported to be highly perishable products, whose quality rapidly declines post-mortem, thus demanding efficient processing and storage. Among the traditional technologies, canning represents one of the most important means of marine species preservation. However, owing to the thermal sensitivity of the chemical constituents of marine species, remarkable degradative mechanisms can be produced and lead to important quality losses. The demand for better quality food makes the need for advanced preservation techniques a topic to be addressed continually in the case of seafood. One such strategy is the employment of preservative compounds obtained from natural resources. The current review provides an overview of the research carried out concerning the effect of the addition of bioactive compounds to the packing medium on the thermal stability of canned seafood. This review addresses the preservative effect of polyphenol-rich oils (i.e., extra virgin olive oil) and different kinds of products or extracts obtained from plants, algae and seafood by-products. In agreement with the great incidence of lipid damage on the nutritional and acceptability values during high-temperature seafood processing, this work is especially focussed on the inhibitory effect of lipid oxidation development.

A new advanced packaging system for extending the shelf life of refrigerated farmed fish fillets

BACKGROUND

An innovative pilot-plant packaging was developed and evaluated for applying oregano essential oil (OEO) vapours in conditions of high vacuum for exploring the antimicrobial effect of essential oil vapours applied immediately before packaging of fish fillets. Farmed sea bream (Sparus aurata) fresh fillets have been used as a model for validating this new technology. These fillets, as a refrigerated product under modified atmosphere packaging (MAP), have a relatively short shelf life (12-14 days) mainly due to the fast microbial growth. The effects of conventional OEO dippings [pretreatment dipping (0.1% of OEO) of whole fish (T1) and filleted sea bream (T2)] were compared with the OEO application in vapour phase (67 μL L^-1 ) under vacuum (5-10 hPa) immediately before MAP fillet packaging (T3).

RESULTS

T3/T2 samples showed the lowest microbial growth after 28 days at 4 °C, with loads up to 1/2.6 log units for Enterobacteria/lactic acid bacteria compared to untreated samples. The initial trimethylamine nitrogen (TMA-N) content (2.6 mg kg^-1 ) increased in T1 and T2/T3 samples by 9.6 and 6/7 units, respectively, after 28 days. Quality Index Method (QIM) better reflected the fish fillets shelf life than texture and colour measurements. The shelf life of T3/T2 samples was established in at least 28 days (4 °C), while the QIM threshold (6) was exceeded after 7/21 days in untreated/T1 fillets.

CONCLUSION

The fish shelf life was extended with vapour OEO treatment using this new technology, similarly to OEO dipping treatment, according to QIM, corroborated by the microbial quality and TMA-N contents. © 2020 Society of Chemical Industry.

Antioxidative Activity of Thyme (Thymus vulgaris) and Oregano (Origanum vulgare) Essential Oils and Their Effect on Oxidative Stability of Minced Pork Packaged Under Vacuum and Modified Atmosphere

The antioxidant stability of minced pork treated with thyme and oregano essential oils (EOs) was determined. Minced pork containing different concentrations (0%, 0.3%, 0.6%, or 0.9%) of thyme (TEO) or oregano essential oil (OEO) and packaged under vacuum or modified atmosphere (MAP) (30%O₂ /50%CO₂ /20%N₂ ) was evaluated within 15 days of refrigeration (3 ± 1 °C) storage. EOs were examined for scavenging capacity toward 2,2-diphenyl-1-picrylhydrazyl, nitric oxide radicals, and hydroxyl, and inhibition of lipid peroxidation and ferric ion reducing antioxidant power (butylated hydroxytoluene was used as positive controls). The order of antioxidative effectiveness was as follows: butylated hydroxytoluene > OEO > TEO, with significant differences between agents (P < 0.05). Lipid oxidation in meat was determined by monitoring malondialdehyde (MDA) formation and lipolysis was assessed by measuring the acidity index immediately and after 3, 6, 9, 12, and 15 days of storage. EOs significantly (P < 0.05) increased the stability of minced pork with respect to lipid oxidation compared with the control, and the antioxidative effect was dose-dependent. Moreover, vacuum packaging resulted in mince with significantly lower oxidation and lipolysis levels than modified atmosphere packaged mince (P < 0.05). The results demonstrate that both EOs examined effectively reduced lipid oxidation in raw pork mince after 2 weeks' storage. PRACTICAL APPLICATION: The natural food preservatives market is growing rapidly, as is high demand for organic foods. These results are likely to be of interest to the scientists, researchers, and persons who work in the meat industry. Results and discussion can contribute to a better understanding of antioxidative properties of essential oils in food model. Furthermore, no study has reported the effect of these MAP on pork oxidative stability.

Effect of thyme and oregano essential oils on the shelf life of salmon and seaweed burgers

The effect of different essential oils on the quality and shelf life of fish and seaweed burgers during storage was evaluated. For this purpose, thyme and oregano essential oils were selected at a concentration of 0.05% (v/w). Three types of salmon and seaweed burgers were prepared: without essential oil, burgers with red thyme essential oil (0.05% (v/w)) and burgers with oregano essential oil (0.05% (v/w)), which were vacuum packaged and stored at 4 ℃ for 17 days. Physicochemical and microbiological analyses were carried out periodically throughout storage. The addition of both essential oils did not have any effect on the evolution of the pH, the moisture content or texture parameters. Only the thyme essential oil managed to slightly slow down the increase of total volatile basic nitrogen and trimethylamine nitrogen. The samples with oregano essential oil and especially those with thyme essential oil showed minor oxidation. The salmon and seaweed burgers without essential oils and those which contained oregano essential oil showed a faster increase of mesophilic counts than those which had thyme essential oil, but no noticeable improvement was observed in the shelf life of the burgers with thyme essential oil. To improve the shelf life of the fish and seaweed burgers, it would be necessary to increase the concentration of both essential oils.