Abstract
Purpose
The purpose of this paper is to evaluate the prevalence of Bacillus sporothermodurans in UHT milk brands in South Africa and to analyse the level of proteolysis in UHT milk due to the growth of B. sporothermodurans during short-term and long-term storage.
Design/methodology/approach
Different brands and batches of commercially available retail UHT milk packages were bought from different supermarkets, during different seasons and tested for the presence of B. sporothermodurans. Sterile UHT milk was spiked with B. sporothermodurans vegetative cells and incubated at 37°C for up to 172 hours. Total plate counts, pH, spore counts, UHT milk proteolysis and the headspace volatiles dynamics were analysed at different intervals.
Findings
The contamination of retail UHT milk packages by B. sporothermodurans was found to be prevalent. The growth of B. sporothermodurans in spiked UHT milk reached a maximum of 1.9×105 cfu/ml; however, the significant proteolytic activity in UHT milk due to B. sporothermodurans only occurred long after the exponential growth phase had been attained. Furthermore, the growth of B. sporothermodurans in UHT milk did not lead to significant changes in the headspace volatile profiles of spiked UHT milk samples. Proteolytic activity in retail UHT milk packages, contaminated with B. sporothermodurans, was significantly higher when the use-by dates were reached.
Practical implications
Significant proteolysis in UHT milk means the assurance of high-quality UHT milk with extended storage stability for up to 10-12 months is compromised. Proteolysis of casein may lead to rapid sedimentation in UHT milk compared to UHT milk without sedimentation.
Originality/value
This paper is of interest to manufacturers because it raises the awareness that UHT milk containing B. sporothermodurans may not have the same storage stability when compared those without B. sporothermodurans. The presence of B. sporothermodurans in commercial UHT milk packages may lead to international and national trade restrictions for manufacturers.
Subject
Food Science,Business, Management and Accounting (miscellaneous)
Reference23 articles.
1. Identification of microorganisms based on headspace analysis of volatile organic compounds by gas chromatography–mass spectrometry;Journal of Breath Research,2014
2. Occurrence of Bacillus sporothermodurans in integral and skimmed UHT milk;Ciencia e tecnologia de alimentos,2005
3. Flavor of heated milks: a review;International Dairy Journal,1992
4. Characteristics of proteinases and lipases produced by seven Bacillus sp. isolated from milk powder production lines;International Dairy Journal,2004
5. Volatile fraction of milk: comparison between purge and trap and solid phase microextraction techniques;Journal of Agricultural and Food Chemistry,2002
Cited by
4 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献