Assessment of the antimicrobial and antioxidant activity of oil seed meals against food-borne pathogens, and their application in poultry meat product

Abstract

This study was undertaken with the aim to identify the efficacy of ultrasound-assisted extraction of Moringa oleifera seed meal extract (ME), Camellia oleifera seed meal extract (CE) and Nigella sativa seed meal extract (NE) as a greener and more natural antioxidant and antibacterial alternative, applicable to the food industry. The first part of the test involved the screening of the seed meals to select the suitable ethanol concentration for phenolic extraction that exhibited optimum antioxidant and antibacterial activities. The sample to solvent ratio of 1:10 w/v was used in this study. From the results, 60% ethanol concentration was selected for the ultrasound-assisted extraction (UAE) of the seed meals, which was performed at different time and power conditions (10min, 20min and 30 min; and 100 W, 200 W and 300 W respectively). The ultrasonic extraction duration of 20 minutes and power of 200 W for ME (ME200/20) with 460.86±2.94 mg GAE/g extract, and likewise CE200/30 with and NE300/20 gave the highest total phenolic content (TPC), and subsequent higher antioxidant activity in the DPPH and FRAP assay, respectively. The The minimum inhibitory concentration (MIC) exhibited by ME200/200 and NE300/20 against E. coli among the gram-negative, was 3.1g/g and 12.5mg/g respectively and MIC against Bacillus cereus among the gram-positive bacteria was at 3.125mg/g, for both ME200/200 and NE300/20. HPLC results showed improved phenolic recovery with ultrasound assisted extraction with predominant gallic acid content(158.3±12.5mg/100g extract) in ME, quercetin (28.49±1.64) in CE, and chlorogenic acid (99.00±1.42) in NE.The cellular leakage test confirmed nucleic acid and protein leakage from ME200/200, NE300/20 and CE300/20-treated E. coli and B. cereus. Scanning electron microscopy revealed the damage done to the bacterial cell membrane by the antimicrobial extracts. ME showed the highest antibacterial activity amongst the three seed meals in disc diffusion and MIC, and hence was further selected for the inoculation test in chicken sausages with E. coli and B. cereus. ME200/20 at 0%, 1%, 3% and 5% concentrations, dissolved in 1% chitosan solution, were used as antibacterial coating in raw chicken sausages. 3% extract solution showed around 2 log reduction, with B. cereus, on the third day of inoculation. Until the 9th day, the bacteria showed suppressed growth of 3.4 and 3.3 log CFU/g for B. cereus, and 3.6 and 3.7 Log CFU/g for E. coli, at 3% and 5% of the extract concentrations. The results indicate the inactivation activity of ME against both E. coli and B. cereus in the chicken sausages used as a real food system.

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