Reduction of Aqueous Chlorine by Organic Material

Aqueous chlorine, used to reduce surface bacteria populations on carcasses of slaughter animals after evisceration, during chilling, and after transport, dissipates in the presence of organic matter. This study characterized the amount of residual chlorine present when aqueous HOCI was exposed to bovine serum albumin, bovine lean muscle, porcine adipose tissue, or Trypticase soy agar (TSA) surfaces. Test chlorine solutions, made using Ca (OCl)₂, contained 0, 50, 100, 200, 400, 800, 1,600, or 3,200 ppm chlorine, the latter two concentrations being used only in the case of albumin. Chlorine depletion by albumin was almost instantaneous, but was influenced by the amount of albumin present and the initial chlorine concentration. Chlorine exposed to organic surfaces was reduced most readily by lean muscle, then by TSA, and least by adipose tissue. Available chlorine was reduced by about 62% when the volume of aqueous chlorine was 22 ml/cm² of lean muscle and by about 89% when the volume of aqueous chlorine was 0.69 ml/cm². With increasing exposure time, the exposure to lean and fat decreased available chlorine by an average of about 10% in 4 min, 27% in 32 min, and 45% in 96 min. Thirteen pure bacterial cultures and two mixed cultures associated with meat were exposed to aqueous chlorine to characterize the effectiveness of the chlorine. All cultures except Bacillus cereus and Enterococcus faecalis were destroyed within 15 s by 3 ppm chlorine. Based on the data, the authors conclude that (a) available chlorine reduction is dependent on exposure time, chlorine concentration, and amount/source of organic material and (b) bacterial inactivation by aqueous chlorine is species specific. These data are of value for estimating chlorine dose for carcass decontamination during washing/chilling and for confirming that bacterial resistance to HOCI is species specific.