The Use of Alkaline Water During Processing

Dr Scott M. Russell, extension poultry scientist at the University of Georgia describes a study into the use of alkaline water to remove faecal material from chicken carcasses during processing in the May 2004 issue of the University's Poultry Tips.
calendar icon 1 January 2008
clock icon 5 minute read

Faecal contamination of broiler carcasses is strictly regulated by the USDA-Food Safety Inspection Service (FSIS). Under current inspection rules, FSIS requires the removal of all visible faecal contamination by trimming or washing the carcass, either on or off the processing line. These carcasses are then subject to reinspection and must meet finished product standards applied by plant employees and verified by FSIS inspectors before the carcasses enter the chiller.

In some facilities, when inspectors have observed very small amounts of ingesta or fecal material on the surface of carcasses, the plants were shut down, the chillers were drained, and each of the 15,000 carcasses in the chiller had to be manually rewashed and disinfected. Because the USDA has a 'zero tolerance' rule in effect, the category for 'faeces' has been removed from the list of defects in the poultry finished product standards. This means that no faecal contamination is allowed.

Contamination of carcasses with faeces may occur in two ways. Faecal material may be caked on the breast skin of the chicken coming into the plant and remain on the skin throughout the scalding and picking processes. This problem is especially prevalent during the summer, when humidity is high and growers must spray or mist live chickens with water in the grow-out houses.

Removal of this type of contamination is difficult and must be accomplished using pre-scald brushes and agitation and hot water within the scalder. Companies have experimented with various chemicals applied during scalding to enhance removal.

Sodium hydroxide is the most commonly used chemical and has met with mixed results, depending on how it is used. Theoretically, it should be excellent if used correctly because it will saponify, i.e. make soap of. the fats in the skin of the chicken, essentially forming a soapy film. This helps to wash the faecal material from the skin.

Another way that carcasses can become contaminated is when faecal material is released from the intestinal tract onto the surface of the carcass during evisceration and remains on the skin after inside/outside bird washing and final bird washing.

Electrolyzed, alkaline (EB) water (dilute solution of sodium hydroxide) has been shown to be effective for allowing incidental contamination with caecal material – which is much more difficult to remove than faecal material – to be removed later in the process.

Drs Yen-Con Hung and Chyer Kim conducted a study (unpublished) to determine if EB water was able to effectively saponify the skin of a chicken carcass post-pick, making it easier to remove caecal material later on in the process. These researchers applied tap water, trisodium phosphate (TSP) or EB water after picking, then applied caecal material to the dorsal skin of the carcass, sprayed the carcasses with tap water, TSP or EB water to determine which combination was most effective for enhancing removal of the caecal material. The results are presented in Table 1.

Table 1. The effect of various washing treatments on the removal of caecal material on the dorsal area of chicken carcasses
Treatment before applying caecal material Treatment after applying caecal material Caecal material score before washing Caecal material score after washing Reduction
Tap water 4.43 2.03 2.40
Tap water Tap water 4.00 1.60 2.47
Alkaline water
4.03 2.28 1.75
Alkaline water
Alkaline water
3.77 1.36 2.42
Trisodium phosphate 3.97 2.03 1.93
Trisodium Phosphate Trisodium Phosphate 4.08 1.48 2.60
Electrolyzed Alkaline water 4.13 1.60 2.53
Tap water Trisodium Phosphate 3.98 1.62 2.37

The most effective treatments are designated by bold typeface. Drs Hung and Kim found that pre-treatment with EB water or TSP and post-treatment spraying with EB or TSP were very effective for removing caecal material from carcass skin. Although in this study, pre- and post-treatment with tap water performed very well, it is believed that scalding in EB water would greatly enhance the release of caecal material during the final rinse process. Moreover, although TSP performed well, it is becoming more difficult to use this chemical because of concerns over discharge of large amounts of phosphate to the wastestream.

Use of EB water for scalding, post-pick spraying and final rinse spraying may be an effective means of removing caked on or incidental faecal contamination during processing.

December 2008

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