Use of milk protein lactoferrin as a natural antimicrobial in meat products

Initial evaluation of factors influencing the antimicrobial activity of lactoferrin (LF) against the psychrotrophic meat spoilage organism Carnobacterium viridans and the pathogen E.coli O157:H7 were conducted in All Purpose Tween (APT) or Lauria Broth (LB). NaCl at levels found in cured meats as well as several compounds likely to interact positively with LF against bacteria were examined. Lactoferrin alone (8 mg/ml) killed 4 log10 CFU Carnobacterium viridans/ml at 4°C, 10°C and 30°C in both APT and LB broth, but when 2.5% NaCl was added, the antimicrobial effect became bacteriostatic. At 2.5% NaCl (while ≤ 160 mM sodium bicarbonate, SB, had no effect on LF activity), the addition of 5 mg/ml sodium hexametaphosphate (SHMP) restored LF lethal action, but only in APT broth and only at 30°C. Since both 2.5% NaCl or ≤5 5% w/v sodium lactate (SL) in LB broth with 0.5% NaCl reduced the antimicrobial activity of LF, it was concluded that increases in medium osmolarity due to salt addition reduced LF access to membrane binding sites following contraction of the cell membrane.; In contrast to C.viridans, 2.5% NaCl enhanced the antibacterial activity of LF against E.coli O157:H7. Furthermore, the antibacterial activity of LF with 2.5% NaCl at 10°C was found to be strain dependent. LF alone was bacteriostatic against strains 3081 and LCDC 7283 but 3 other strains grew. Antimicrobial effectiveness of LF was reduced in APT broth, but was enhanced by SB with 2.5% NaCl at 10°C where 4.0 log10 CFU/ml inoculated cells were killed. The addition of EDTA enhanced the antimicrobial action of the LF-SB combination. SL alone was effective against E.coli O157:H7 but a reduction in activity with 2.5% NaCl at 10°C was reversed by LF. The combinations LF-SHMP and LF-quercetin were more effective at 37°C and NaCl effects varied.; To overcome the negative effects of divalent cations and other compounds on the antimicrobial activity of LF against the tested organisms, LF was incorporated in two types of microcapsules. First, paste-like microcapsules were prepared as a water-in-oil (W1/O) emulsion from a mixture of 20% w/v LF in distilled water, 3% w/v SL or 20 mM SB, which was emulsified with an oil mixture of 22% butter fat plus 78% corn oil and 0.1% polyglycerol polyricinoleate. Second, freeze-dried double emulsion (W1/O/W2), powdered microcapsules were produced following emulsification of paste-like microcapsules in an external aqueous phase (W2) consisting of a denatured whey protein isolate solution, WPI. The release of LF from the W1/O microcapsules was dependent on temperature and NaCl concentration. LF was not released from the W1/O emulsion at < 5.5°C. At ≥ 10°C, its release was greater from W1/O microcapsules when suspended in 5% aqueous NaCl than in water, whereas LF release from freeze-dried microcapsules was not controlled by temperature change. Paste-like microcapsules were incorporated in edible WPI packaging film to test the antimicrobial activity of LF against C. viridans. The film was applied to the surface of bologna after its inoculation with the organism and stored under vacuum at 4 or 10°C for 28 d. The growth of C.viridans was delayed at both temperatures and microencapsulated LF had greater antimicrobial activity than when unencapsulated. The temperature sensitive property of the W 1/O microcapsules was reduced when they were incorporated in the WPI film.; The antimicrobial activity of LF against five non-pathogenic strains of E. coli O157:H7 and 7 meat starter cultures was assessed in a broth system under conditions similar to those used in the production of dry fermented sausages. LF alone was bacteriostatic against E. coli O157:H7 strains 0627 and 0628 but 3 other strains grew in the presence of 2.9% NaCl in LB broth at 13 or 26°C after 5d or 24h, respectively. However, the addition of EDTA to the reaction mixture enhanced its effects. LF alone did not affect the grow...