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Numerous natural ingredients and compounds have been investigated for potential as natural antimicrobials. Some of the most common have included a wide variety of plant extracts, essential oils and similar compounds. While many of these have been shown to harbor significant antimicrobial activity, effectiveness in food systems has often been found to be limited. <P>
Organic acids have also been extensively studied and provide effective antimicrobial activity in water-soluble form, but cannot be added directly to natural or organic products because of the "no chemical preservatives" requirement for labeling these products. Therefore, the most feasible options for supplementing the reduced antimicrobial activity of natural and organic processed meats appear to be increasing the effectiveness of the nitrite formed in these products and/or adding a natural antimicrobial ingredient that is effective synergistically or additively with nitrite in a meat system.<P> Therefore, this proposal has the following objectives; <OL> <LI> Determine the ingoing and residual concentrations of nitrite that are most critical for affecting growth of L. monocytogenes in a simulated natural/organic processed meat model system; <LI> Assess the role of cherry powder (ascorbic acid) and lemon powder (citric acid) in affecting the antimicrobial impact of nitrite in natural/organic cured meats; <LI> Determine the level of supplemental antimicrobial protection that cranberry concentrate and grapeseed offer in natural/organic cured meats; <LI> Manufacture naturally-cured meat products to compare the treatments that show greatest antimicrobial effects with conventionally cured products for antimicrobial impact and quality properties.</ol> It is expected that a better understanding of the factors important for the safety of these types of products will be realized and identified.
NON-TECHNICAL SUMMARY: The continued rapid growth of the organic/natural foods market is evident in the average increase in sales of 18.8% per year from 2005-2008 to over $32 billion. Meat and poultry products have been noted as the fastest growing category of natural and organic foods. Organic and natural cured meats such as frankfurters, hams and bacon cannot be produced by traditional methods where sodium nitrite is added as a curing agent because nitrite is a preservative and, as such, is not allowed in natural and organic foods. However, because nitrite is absolutely essential to the expected sensory and safety properties of cured meat products, an alternative system has been devised by processors whereby natural sources of nitrate (vegetables, sea salt) are combined with a nitrate-reducing bacterial culture (Staphylococcus carnosus) to produce natural nitrite in the product. <P>This process achieves most of the typical cured meat properties expected. Unfortunately, this process also most often results in less nitrite than that added in conventionally cured products. Because nitrite is a highly effective antimicrobial when used at maximum legally allowed levels, it has been suggested that the natural and organic processed meat products, containing much lower levels, represent greater food safety risk for growth of bacterial pathogens. This proposed research will explore the what significance the amount of nitrite produced in an alternative curing system is for controlling L. monocytogenes, the effects various ingredients have on the amount of nitrite produced and what synergist or additive effects ingredients with antimicrobial properties might have in controlling L. monocytogenes. Results from this research will be used to educate meat processors for improved safety in manufacturing natural or organic processed meat products.
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APPROACH: A model system using beaker sausage will be utilized for the Objectives 1, 2 and 3 to test nitrite concentration and the antimicrobial impact and effectiveness of experimental variables. For Objective 4, naturally-cured bologna will be manufactured to test and verify the safety improvement of the treatments that show the greatest potential in the model system. For the model system, lean ground pork will be blended with distilled water, 2% salt (NaCl), 0.3% celery powder and a commercial nitrate-reducing culture as is typically done in the natural curing process. Other ingredients that are experimental variables will be included as appropriate to the experimental design as described below. The meat mixture will be placed in 100 ml beakers, heated to 40C in a water bath for one hour to achieve nitrate-to-nitrite conversion and then heated to 71C internal. The beaker sausage will be chilled prior to inoculation with L. monocytogenes. <P>Objective 1: To establish a baseline for comparison, the model system will first be used to assess the antimicrobial effectiveness of nitrite concentrations in conventional curing by evaluating a gradient of sodium nitrite from 0 to 156 ppm, added directly to the mixture. This will provide a basis for determining the amount of additional inhibitory activity needed or antimicrobial added to make natural/organic processed meats comparable in safety to the conventionally cured products. <P>Objective 2: The natural-cure model system will then be used to evaluate addition of lemon powder at 0.001%, 0.003% and 0.006%. Since 0.001% and 0.003% are suggested usage levels, the 0.006% should represent the ultimate maximum use level. Cherry powder will be assessed in similar manner with concentrations of 0.1%, 0.3% and 0.6%. <P>Objective 3: All treatment samples will be inoculated with L. monocytogenes to yield 3-log CFU/ml and held at 4C for up to 4 weeks. Samples be assayed weekly for changes in listerial populations by plating on Modified Oxford agar. Both residual nitrite and growth of inoculated pathogens will be measured at the same time points. Following completion of Objectives 1, 2 and 3, the most successful ingredients and/or ingredient combinations will be included in a formulation to produce naturally-cured bologna in <P>Objective 4 to validate previous results in a commercial product. Manufacturing procedures for the bologna will follow standard formulations and processing procedures for those products established at the University of Wisconsin Meat Laboratory. Products will be heat processed, chilled, packaged and inoculated with pathogens in the same manner as for the model system. Storage, sampling and analyses will also follow the same protocols as established with the model system. In addition to these protocols, non-inoculated samples will also be manufactured and analyzed for Commission International d'Eclairage (CIE) L* (lightness), a* (redness), and b* (yellowness), cured meat color determined by reflectance ratio of wavelengths 650/570 nm, cured pigment concentrations (mononitrosylhemochrome), total pigment concentrations, and pH.