Antibacterial Effect of a Mixed Natural Preservative against Listeria monocytogenes on Lettuce and Raw Pork Loin

Abstract

A mixed natural preservative, including grapefruit seed extract (GSE), cinnamaldehyde (CA), and nisin, was investigated for the reduction of Listeria monocytogenes growth on lettuce and raw pork loin. The MIC of each natural preservative was investigated for L. monocytogenes strains tested. Following central composite design, lettuce and pork loin were inoculated with a cocktail of three strains of L. monocytogenes (ATCC 15313, H7962, and NADC 2045 [Scott A]) and treated with the mixed natural preservative that included GSE (0.64 to 7.36 ppm), CA (1.6 to 18.4 ppm), and nisin (0.48 to 5.5 ppm). The MIC of GSE was 31.25 ppm in tested L. monocytogenes strains, and of CA was 500 and 1,000 ppm in L. monocytogenes ATCC 15313 and the other L. monocytogenes strains, respectively. The MIC of nisin was 250 ppm. The R2 value of this model was more than 0.9, and the lack of fit was not significant. The mixed natural preservative showed a synergistic antimicrobial effect and reduced the growth of L. monocytogenes by 4 to 5 log CFU/g on lettuce. In addition, the reduction of L. monocytogenes on pork loin was 3 log CFU/g. The mixed natural preservative, which consisted of GSE (6 to 8 ppm), CA (15 to 20 ppm), and nisin (5 to 6 ppm), increased the antibacterial effect against L. monocytogenes. These results suggest that the use of the mixed natural preservative could reduce the economic cost of food preparation, and response surface methodology is considered effective when measuring synergy among antimicrobials.

Antilisterial Effect of a Natural Formulation Based on Citrus Extract in Ready-To-Eat Foods

“…The test carried out on lettuce showed one of the most satisfactory results—even applying just 10% of the treatment, a total reduction of the pathogen was achieved on the fifth day of sampling, with “absence” results after pre-enrichment in Fraser broth and subsequent plate culture. These results can be contrasted with those obtained by Yu et al [ 37 ], who demonstrated the efficacy of citrus extracts obtained from grapefruit against L. monocytogenes in lettuce. Vázquez-Armenta et al [ 38 ] also obtained similar results in the tests carried out on lettuce leaves using a flavonoid-rich grape extract as a natural preservative, with microbial reductions of 1.8 logarithmic units in the case of E. coli and 0.86 logarithmic units of L. monocytogenes .…”

Partial Characterization of an Anti-Listerial Bacteriocin from Enterococcus faecium CJNU 2524

“…Nisin also showed antibacterial activity against L. monocytogenes, which was artificially inoculated into raw pork loin. In the study, a mixed natural preservative including nisin, grapefruit seed extract, and cinnamaldehyde showed synergistic effects to control the pathogenic bacteria in the meat (Yu et al, 2019). Pediocin PA-1/AcH, a class IIa bacteriocin, has been also used for controlling L. monocytogenes in food systems (Cui et al, 2012).…”

Antimicrobial effects of three herbs ( Brassica juncea , Forsythia suspensa , and Inula britannica ) on membrane permeability and apoptosis in Salmonella

“…Furthermore, synergistic effects have also been reported for the inhibition of biofilm formation on the surface of foods using grapefruit and cinnamaldehyde from cinnamon bark (Yu et al . 2019) and dental enamel using essential oils (Miladi et al . 2017).…”