Background

The reduction of E. coli O157:H7 in both pre- and post-harvest areas continues to be a major goal of the beef industry. It has been demonstrated that cattle hides are the major source of E. coli O157:H7 contamination in processing plants. The reduction of E. coli O157:H7 on cattle hides will go a long way in ensuring the safety of the beef supply.

Researchers and beef packers/processors have addressed beef safety concerns by developing a variety of methods that are now implemented, or are being further developed, to reduce numbers of bacteria on beef and beef products and improve microbiological safety. These microbiological decontamination technologies include:

• Animal cleaning;
•  Chemical dehairing at slaughter;
• Spot-cleaning of carcasses by knife-trimming or steam/hot water vacuuming; and
• Spraying/washing/rinsing of carcasses before evisceration and/or before chilling, with water, chemical solutions and/or steam or hot water.

The most commonly used decontamination strategies involve the use of water and steam at various temperatures and spray pressures. Other decontamination strategies involve the use of FDA-approved chemicals applied through water-based sprays. The objectives of this study were:

1. to analyze the effectiveness of seven hide wash treatments for reducing E. coli O157:H7 and Salmonella spp. and
2. assess how each treatment affects the value of the hide as a raw material for leather manufacture.

Methodology

Cattle hides were artificially contaminated with E. coli O157:H7 and Salmonella spp. These hides were then subjected to one of eight treatments designed to reduce microbial contamination levels. The eight treatments are as follows (Treatments 1-5 and 8 were sprayed and treatments 6 and 7 were poured on the cattle hides):

1. Water (Control)
2. 4% sodium metasilicate
3. 3% sodium hydroxide
4. 10% acetic acid
5. 10% lactic acid
6. 2.4% potassium cyanate (chemical dehairing)
7. 6.2% sodium sulfide (chemical dehairing)
8. 1.5% sodium hydroxide followed by a high-pressure chlorine wash (200 ppm)
   

Each of the eight treatments reduced microbial contamination to some degree. Treatment 7, the 6.2% sodium sulfide, chemical dehairing treatment, reduced the E. coli O157:H7 load completely (-100%) and nearly eliminated Salmonella spp. (-95%). The hide washing treatment that reduced microbial contamination levels the most was the dual treatment of sodium hydroxide followed by a chlorine wash (treatment 8). This treatment reduced E. coli O157:H7 levels by 96% and decreased Salmonella spp. levels by 83%.

The data in Table 1 show that while each treatment did reduce microbial levels of both pathogens, there were wide variations by treatment. E. coli O157:H7 levels were reduced from a low of 37% for treatment 2 to high of 100% for treatment 7. Salmonella spp. levels were reduced from a low of 18% for treatment 6 to a high of 95% for treatment 7.

Hides then tanned and processed to evaluate the effect of the treatments on leather quality. With the exception of treatment 7, which had a deleterious effect on leather quality, the treatments actually had a positive effect on leather quality.

Implications

All of the hide washing/dehairing treatments decreased pathogen counts on cattle hides. With the exception of one dehairing treatment (Potassium Cyanate), leather quality was actually enhanced due to the treatment. These results suggest that, with one exception, these treatments have a positive effect on hide quality and a positive effect on beef safety.