Increasing regulatory emphasis on food safety has spurred an incresing number of scientific studies on how to defeat the pathogens that can lead to human sickness.
One study by Kathrin Scherer and others found high levels of Campylobacter in chicken legs at retail stores, especially in early spring and the hottest months of the summer.
During the one-year study the scientists found two peaks of Campylobacter contamination occurred, one between February and March, and the second during July and August.
In February in March the rates of contamination ranged from 90 per cent to 100 per cent of the samples. About 90 per cent of the legs tested positive in July and August.
Over the one year period 66 per cent of the 140 skin samples tested positive for the presence of Campylobacter. About 27 per cent of 115 sampled chicken legs tested positive for internal contamination.
The external contamination was significantly higher than the internal. In both skin and muscle samples, Campylobacter jejuni had a much higher incidence than Campylobacter coli. C. coli was isolated at higher colony counts than C. jejuni on the surface of chicken legs.
The reduction of Campylobacter jejuni on chicken wings by chemical treatments is the subject of another study by Tong Zhao and Michael Doyle.
They found that a combination of acidic calcium sulfate, lactic acid, ethanol, sodium dodecyl sulfate, and polypropylene glycol (ACS-LA) was highly effective in chilled water at killing C. jejuni on chicken.
If the mixture is recycled, the mixture may be a useful treatment in chill water tanks for poultry processors to reduce campylobacters on poultry skin after slaughter, they stated.
The scientists studied eight chemicals. Glycerol monolaurate, hydrogen peroxide, acetic acid, lactic acid, sodium benzoate, sodium chlorate, sodium carbonate, and sodium hydroxide were tested individually or in combination for their ability to inactivate Campylobacter jejuni at 4°C in suspension.
The results showed that treatment for up to 20 min with 0.01 per cent glycerol monolaurate, 0.1 per cent sodium benzoate, 50 or 100 mM sodium chlorate, or one per cent lactic acid did not substantially reduce C. jejuni populations.
However treatment with between 0.1 per cent and 0.2 per cent hydrogen peroxide for 20 min reduced C. jejuni populations.
Treatments with 0.5, 1.0, 1.5, and 2 per cent acetic acid, 25, 50, and 100 mM sodium carbonate, and 0.05 and 0.1 N sodium hydroxide also reduced C. jejuni populations.
A combination of 0.5 per cent acetic acid plus 0.05 per cent potassium sorbate or 0.5 per cent acetic acid plus 0.05 per cent sodium benzoate also reduced C. jejuni populations within one minute. However, substituting 0.5 per cent lactic acid for 0.5 per cent acetic acid was not effective.
A combination of acidic calcium sulfate, lactic acid, ethanol, sodium dodecyl sulfate, and polypropylene glycol (ACS-LA) also reduced C. jejuni in suspension within 1 minute.
All chemicals or chemical combinations for which there was a 5-log/ml reduction of C. jejuni in suspension were further evaluated for C. jejuni inactivation on chicken wings.
Treatments at 4°C of two per cent acetic acid, 100 mM sodium carbonate, or 0.1 N sodium hydroxide for up to 45 seconds reduced C. jejuni populations. Treatment with ACS-LA at 4°C for 15 seconds also reduced C. jejuni to an undetectable level.
Salad dressing manufacturers can rest easy after one study found that shelf-stable, dairy-based, pourable ranch and blue cheese salad dressings should not be considered as potentially hazardous. The tests showed, by scientists Larry Beuchat and others, that the dressings manufactured by three companies and stored at 25°C do not support the growth of Salmonella, E. coli O157:H7, and L. monocytogenes.
The study determined the death rates of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in three commercially manufactured full-fat ranch salad dressings, three reduced-fat ranch salad dressings, two full-fat blue cheese salad dressings, and two reduced-fat blue cheese salad dressings.
The dressings were inoculated with low and high amounts of separate five-strain mixtures of each pathogen and stored at 25°C for up to 15 days. Regardless of the initial inoculum population, all test pathogens rapidly died in all salad dressings. Overall, the type of dressing and level of fat in the dressings did not have a marked effect on the rate of inactivation of pathogens.