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on June 24, 2009

Research Digest: December 2008

Effective use of peracetic acid as a carcass disinfectant.

A number of antimicrobials are approved and available to the poultry processors to control food borne pathogens such as salmonella and campylobacter on finished products. Most of these antimicrobials are used as carcass rinses, dips or sprays, and few are utilized during immersion chilling.

Commercially available PAA

Chiller application of an antimicrobial uniquely provides for a longer contact time, albeit with potentially negative effects on carcass quality. Organic acids, especially in combinations, can be effective disinfectants at lower concentrations during immersion chilling process. Peracetic acid (PAA) with hydrogen peroxide is one such combination that is commercially available to be used in poultry chillers.

The maximum allowable concentrations of the chemicals in the mixture are 0.022% peroxyacetic acid and 0.012% hydrogen peroxide, providing both acidic and oxidizing properties in combination. The purpose of this study was not only to evaluate the effective concentration of PAA against salmonella and campylobacter, but also on carcass quality attributes in a chiller application.

PAA was mixed in poultry chiller overflow water to obtain five treatments: control, 30 ppm chlorine (sodium hypochloride), 25 ppm, 100 ppm and 200 ppm PAA. The average pH of the chlorine treatment was 6.0 and the PAA treatments were 4.5. For each replication, carcasses were inoculated with 106 cfu/mL Salmonella enteric typhimurium or Campylobacter jejuni. After 10 minutes of drying time, carcasses were placed in chill water treatments for one hour. All carcasses were then sampled by the carcass rinse method using buffered peptone water as rinsate.

Salmonella and campylobacter were direct-plated after serial dilution for quantification. For carcass shelf-life and quality assessments, broilers were processed and immersed in static chill water treatments of 100 ppm, 150 ppm and 300 ppm PAA, 30 ppm chlorine and plain water (control) at 4 C for two hours. Following chilling, carcasses were packaged in polyvinyl chloride, stored at 4 C, and sampled for total aerobic plate (APC),  psychrotroph (PSY), total coliforms and E.coli enumeration at one, seven, 10, and 15 days. On each sampling day, breast skin color was measured and breast fillets were subjected to sensory evaluation. Cooked breast fillets were evaluated by untrained panelists using a hedonic scale for appearance, texture, flavor, juiciness and overall acceptability.

Low concentrations prove effective

PAA concentrations as low as 25 ppm were effective in decreasing salmonella, whereas PAA levels of 200 ppm were required to decrease campylobacter significantly, as compared to the chlorine treatment. Effects of chill water treatments on other carcass microbial populations were limited to the first seven days with 150 ppm and 200 ppm of PAA showing significantly lower counts as compared to other treatments.

Although there were no differences in bacterial populations at 15 days of storage, no off-odors and colors were detected with 150 ppm and 200 ppm PAA treatments. In terms of quality, only few but negligible changes in skin color and sensory properties of breast fillets were detected through the 15-day storage period. Based on these results, authors have concluded that PAA may be an effective intervention strategy in poultry chiller applications without sacrificing organoleptic quality of the product.

Bauermeister, L. J., J. W. J. Bowers, J. C. Townsend, and S. R. McKee, 2008. The microbial and quality properties of poultry carcasses treated with peracetic acid as an antimicrobial treatment. Poultry Science 87:2390-2398.    

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