Incidence and survival of Bacillus sporothermodurans during processing of UHT milk

Abstract

Purpose

The presence of Bacillus sporothermodurans in retail UHT milk along with milk from different points of a processing line was determined. This paper aims to investigate the effect of chilling, pre‐heating, UHT, reprocessing and H₂O₂ individually and in combination on the survival of B. sporothermodurans in broth.

Design/methodology/approach

Standard plate counts were conducted for all milk samples and isolates from UHT milk were characterised using PCR. BS vegetative cells and spores in broth were subjected to various stresses encountered, during UHT processing of milk. Survival counts were conducted after all treatments.

Findings

B. sporothermodurans was detected in retail UHT milk packs from only one processor. UHT treatment at 140°C for 4s eliminated B. sporothermodurans in broth. The combination of chilling and UHT was more effective in eliminating B. sporothermodurans spores than UHT treatment alone. H₂O₂ was also effective in eliminating B. sporothermodurans spores after 15 min of exposure. The adopted real time (RT) PCR with SYBR Green method was effective for the confirmation of B. sporothermodurans.

Originality/value

This research is the first to be conducted with regards to the detection of B. sporothermodurans in UHT milk in South Africa and determining the effect of UHT processing stresses on their survival. These results can be used to design processing parameters so as to effectively eliminate B. sporothermodurans spores during UHT processing. This research is the first in which RT PCR with SYBR Green has been used to characterise B. sporothermodurans.

Citation

Tabit, F.T. and Buys, E.M. (2011), "Incidence and survival of Bacillus sporothermodurans during processing of UHT milk", British Food Journal, Vol. 113 No. 4, pp. 505-518. https://doi.org/10.1108/00070701111123989