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Growth of thermophilic spore forming bacilli in milk during the manufacture of low heat powders
Author(s) -
MURPHY PATRICK M,
LYNCH DAVID,
KELLY PHILIP M
Publication year - 1999
Publication title -
international journal of dairy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.061
H-Index - 53
eISSN - 1471-0307
pISSN - 1364-727X
DOI - 10.1111/j.1471-0307.1999.tb02069.x
Subject(s) - evaporator , thermophile , skimmed milk , food science , bacilli , air preheater , bacillus licheniformis , chemistry , spore , bacterial growth , materials science , bacteria , bacillus subtilis , waste management , microbiology and biotechnology , biology , thermodynamics , engineering , genetics , heat exchanger , physics
The survival and growth of Bacillus stearothermophilus and Bacillus licheniformis, naturally present (30–300 colony forming units/ml) in late season skim milk, was monitored in a three effect evaporator during low heat skim milk powder manufacture. Substantial growth was shown to occur in the preheating stages prior to direct steam heating. A typical heat treatment (77°C, 15 s) used in the manufacture of low heat powder did not inactivate the bacteria, which continued to grow in the heater. The importance of preheaters in influencing thermophile growth in the evaporator is demonstrated by the finding that growth in the preheater stages was accompanied by growth in subsequent evaporator effects which significantly exceeded that observed when the final two preheaters were bypassed. A mid‐run mini‐clean procedure incorporating 0.2% hydrogen peroxide for decontaminating the evaporator was tested and may prove useful in extending evaporator run times