Survival of thermophilic spore-forming bacteria in a 90⁺ year old milk powder from Ernest Shackelton's Cape Royds Hut in Antarctica

Abstract

Milk powder taken to Antarctica on Shackelton's British Antarctic Expedition in 1907 was produced in New Zealand by a roller drying process in the first factory in the world dedicated to this process. Thermophilic bacilli are the dominant contaminants of modern spray-dried milk powders and the 1907 milk powder allows a comparison to be made of contaminating strains in roller-dried and spray-dried powders. Samples of milk powder obtained from Shackelton's Hut at Cape Royds had low levels of thermophilic contamination (< 500 cfu ml -1 ) but the two dominant strains (Bacillus licheniformis strain F and Bacillus subtilis) were typical of those found in spray-dried powders. Soil samples from the floor of the hut also contained these strains, whereas soils distant from the hut did not. Differences in the RAPD profiles of isolates from the milk powder and the soils suggest that contamination of the milk from the soil was unlikely. It is significant that the most commonly encountered contaminant strain in modern spray-dried milk (Anoxybacillus flavithermus strain C) was not detected in the 1907 sample.

A survey on occurrence of thermophilic bacilli in commercial milk powders in China

“…Bacillus subtilis was also reported as a common contaminant in milk powders (Ronimus et al, 2003;Ronimus, Rueckert, & Morgan, 2006;Ruckert et al, 2004). To our knowledge, Brevibacillus borstelensis and Bacillus thermoamylovorans were isolated for the first time from milk powders.…”

Genotyping of Present-Day and Historical Geobacillus Species Isolates from Milk Powders by High-Resolution Melt Analysis of Multiple Variable-Number Tandem-Repeat Loci

“…This may be the reason for the relatively low number of genotypes observed compared to the number of isolates obtained from samples and that the same genotypes are present today, as they were up to 17 years ago, in processing plants in the same region of Australia. This is not surprising, since the same genotypes of B. licheniformis found in present-day milk powder were also discovered in 90-year-old milk powder from Shackleton's hut in Antarctica (32).…”

Tracking spore-forming bacteria in food: From natural biodiversity to selection by processes

“…Combination of various environmental conditions encountered by sporeformers during the production of feed, concentrate or dried food ingredients might favour the dynamic succession of bacterial communities which surely impact on spore resistance and cultivability properties (Chopra and Mathur, 1984;Salem et al, 2009;Yan et al, 2008). Interestingly, A. flavithermus which is a common contaminant of spraydried milk powder could not be detected in roller-dried milk powders dating from 1907 (Ronimus et al, 2006).…”