Fish is one of the most perishable food products, and therefore viable alternatives need to be found to contribute to the preservation of quality and increase the shelf life of fish and aquaculture products.
Some researchers argue that the freshness and quality of fish products decrease immediately after capture and death, due to the development of a series of post-mortem biochemical changes.
To reduce deterioration and preserve the shelf life of fish products, various technologies have been used. Traditional technologies include refrigeration, freezing, the use of modified and controlled atmospheres, canning, drying, dehydration, salting, and smoking. New technologies include high pressure processing, irradiation, bioconservation, active and intelligent packaging, and antimicrobial compounds, among others.
The use of natural compounds from plants, animals, and microorganisms is one of the most innovative practices, which includes natural extracts, essential oils, or derived compounds.
Researchers from the Universidad Autónoma de Nayarit, Universidad de Sonora, Universidad Estatal de Sonora, Universidad Nacional de Colombia, and Instituto Tecnológico de Estudios Superiores de Zamora evaluated the effect of a natural extract prepared from garlic on the quality and shelf life of tilapia fillets stored on ice for 18 days.
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Preparation of the garlic extract
Garlic (Allium sativum) is a vegetable with medicinal properties and biological activity due to its anticancer effect. Garlic stimulates the immune system, reduces cardiovascular diseases, and has antioxidant and antimicrobial properties.
The researchers prepared the extract by homogenizing 200 grams of peeled garlic cloves with 800 mL of distilled water, which was then centrifuged to obtain the extract. The supernatant was collected and refrigerated at a temperature of 2°C prior to use as a preserving agent.
The concentration of the extract was 87.5 g of dried garlic/L of water, and 20 mL were used per kilogram of fillet (1.75 g of dried garlic per kilogram of fillets).
Subsequently, the fish fillets were immersed in the extract, packed in high-density polyethylene bags, and stored on crushed ice for 18 days.
In the muscle of aquatic organisms, ATP degradation represents a significant post-mortem biochemical change in freshness and quality, where its degradation to IMP has been widely used to monitor freshness in fish products.
“Regarding storage time, only IMP and Hx concentrations showed significant changes, where IMP decreased for fillets with garlic extract and the control on day 18 of ice storage, while Hx increased for fillets with the extract and the control,” they report.
The K value or freshness index is important for determining the freshness and quality of fish products.
“With regard to the ice storage of tilapia fillets, a linear and significant increase in the determination of the K value was observed on day 18, reaching final values of 56.51% and 69.61% for tilapia fillets treated with garlic extract and the control, respectively,” the study reports.
Effect on microbiological quality
In general, the microbial load of fish products is closely related to the level of bacterial contamination and environmental conditions, as well as the applied preservation method that influences bacterial growth and survival.
According to the study results: “The behavior of mesophilic microbial load in tilapia fillets treated with garlic extract and the control during 18 days of ice storage showed values of 4.43 and 4.49 log CFU/g for fillets with the extract and the control, respectively.”
Furthermore, the study reports a significant increase in microbial count with respect to storage time, with values of 5.92 and 7.15 log CFU/g for fillets with the extract and the control, respectively.
“The determinations of the K value, total mesophilic count, total volatile bases, and pH showed their utility in evaluating the antibacterial effect of garlic extract, which, when applied by immersion to commercial tilapia fillets, extended the shelf life of the fillets by six days compared to the control batch,” they conclude.
Furthermore, the scientists highlight that the study results demonstrated the potential of garlic extract to extend the shelf life of tilapia fillets.
Reference (open access)
Jiménez-Ruíz, Edgar Iván, Víctor Manuel Ocaño-Higuera, Santiago Valdez-Hurtado, José Alberto Cruz-Guzmán, Cesar Benjamín Otero-León, Saúl Ruíz-Cruz, Alba Mery Garzón-García, Hebert Jair Barrales-Cureño, Dalila Fernanda Canizales-Rodríguez, Cinthia Jhovanna Pérez-Martínez, and et al. 2023. “Quality Improvement and Shelf-Life Extension of Iced Nile Tilapia Fillets Using Natural Garlic Extract” Fishes 8, no. 6: 325. https://doi.org/10.3390/fishes8060325