Gelatin-starch composite coating containing cucumber peel extract and cumin essential oil: Shelf life improvement of a cheese model.

In this study, the effects of gelatin-starch (GS) composite coating containing cucumber peel extract (CPE) and cumin essential oil (CEO) were evaluated on the shelf life enhancement of ultrafiltered (UF) cheese during 56 days of storage under refrigerated conditions. The obtained hydroethanolic CPE by the microwave method showed the best results in terms of the total phenolic content, reducing power, 2,2'-diphenyl-1-picrylhydrazyl (DPPH) activity, and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging activity compared to the immersion and ultrasound methods. The studied treatments were as follows: Control (C), GS, CPE, CEO, GS-CPE, GS-CEO, and GS-CPE-CEO. Scanning electron microscopic surface morphology of treated cheese samples showed the formation of a firm, integrated, flawless, and homogenous layer on the cheese slices of the GS-CPE-CEO treatment. All treatments significantly (p ≤ .05) decreased the total viable count, psychotropic bacteria, and yeast-mold population compared to the control group. Adding CEO and/or CPE to GS significantly (p ≤ .05) controlled undesirable changes in physical characteristics, such as weight, color, and hardness of the cheese slices. Throughout storage time, the coated cheese slices showed more stable chemical features in comparison to the uncoated cheese samples in terms of moisture, lipid oxidation, pH, and titratable acidity (TA). Sensory evaluation of the preparations showed that the GS coating containing CPE and CEO significantly (p ≤ .05) had pleasant effects on the sensory features (taste, odor, texture, and overall acceptability) of the cheese samples during storage time. It was concluded that composite coating of GS containing CPE and CEO could improve the microbial, physical, chemical, and sensory features of ultrafiltration (UF) cheese during refrigerated storage.

Essential Oils from Indigenous Iranian Plants: A Natural Weapon vs. Multidrug-Resistant Escherichia coli.

Aim of this study was to investigate the antimicrobial properties of herbal plant essential oils (EOs) from selected Iranian plant species such as Ferulago angulata, Zataria multiflora, Cuminum cyminum, and Mentha longifolia against antibiotic-resistant Escherichia coli (E. coli) strains. For this purpose, the Escherichia coli strains, isolated from raw cow's milk and local dairy products (yogurt, cream, whey, cheese, and confectionery products) collected from different areas of Hamedan province, Iran, were investigated for their resistance to antibiotics (i.e., streptomycin, tetracycline, gentamicin, chloramphenicol, ciprofloxacin, and cefixime). Thus, the E. coli strains were tested for their susceptibility to the above-mentioned essential oils. Regarding antibiotics, the E. coli strains were highly sensitive to ciprofloxacin. In relation to essential oils, the most effective antibacterial activity was observed with Zataria multiflora; also, the bacteria were semi-sensitive to Cuminum cyminum and Mentha longifolia essential oils. All strains were resistant to Ferulago angulata essential oil. According to the results, the essential oil of Zataria multiflora can be considered as a practical and alternative antibacterial strategy to inhibit the growth of multidrug-resistant E. coli of dairy origin.

Stability and antibacterial activity of Thymus daenensis L. essential oil nanoemulsion in mayonnaise.

BACKGROUND: There is a growing demand in the food industry for the replacement of synthetic preservatives with their natural alternatives. This has led to the development of novel methods such as encapsulation of plants essential oil with appropriate physicochemical stability, and antibacterial and organoleptic properties. This study aimed to prepare an optimal nanoemulsion of Thymus daenensis L. essential oil for use as a natural preservative in mayonnaise. RESULTS: The analysis of droplet diameter, polydispersity index, zeta potential, encapsulation rate, and intrinsic stability showed that out of nine T. daenensis essential oil-containing nanoemulsions, two preparations of A and B had high stability scores. In vitro antibacterial tests showed the adverse effect of Tween 80 volume on the antibacterial properties of nanoemulsions. One nanoemulsion (essential oil:Tween 80, ratio 1:1, 15 min sonication) was considered to be optimal based on its long-term stability and antibacterial effects on Salmonella Typhimurium, Escherichia coli, and Listeria monocytogenes. However, compared to the optimal nanoemulsion, the pure essential oil showed more antibacterial effects. The bacterial control in mayonnaise was close to equal for sodium benzoate (in maximum limit 1 g kg-1 ) and the optimal nanoemulsion (½ MIC) for 24 h. The optimal nanoemulsion achieved significantly higher sensory scores (taste, appearance, and mouthfeel) than the pure essential oil in mayonnaise (P < 0.05). CONCLUSION: The results demonstrated similar antibacterial effects for the optimal nanoemulsion and sodium benzoate. The optimal nanoemulsion, due to its desirable sensorial attributes, long-term stability, and slow release of volatile compounds, can be considered an appropriate alternative to synthetic preservatives.

The effects of incorporated resveratrol in edible coating based on sodium alginate on the refrigerated trout (Oncorhynchus mykiss) fillets' sensorial and physicochemical features.

The goal of this study was examining the effects of sodium alginate coating (SA) containing resveratrol (R) on enhancement rainbow trout fillets' shelf-life. Treatments of the study were as follows: control, SA, SA-R 0.001% and SA-R 0.003%. Storage of the samples was done for 15 days at 4 °C. To analyze samples, 3-day intervals were used. Compared to the uncoated trout, the values of pH, peroxide and K were significantly lower in the coated samples (p < 0.05). R enhanced the impacts of alginate on extending the samples' shelf life. Sensory analyses showed that R improved the sensory scores significantly (p < 0.05); besides, it did not show more changes on the sensory features and was invisible in the surface of samples. In the conclusion, R was suggested to be a strong alternative to synthetic antioxidants in refrigerated trout fillet in very low concentrations with many health benefits.