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A study of some factors affecting the methylene blue test and the effect of freezing on the bacterial content of ice cream
Author(s) -
ALEXANDER JEAN,
ROTHWELL J.
Publication year - 1970
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.1970.tb01582.x
Subject(s) - cereus , methylene blue , ice crystals , ice cream , food science , chemistry , bacteria , freezing point , bacillus cereus , biology , biochemistry , thermodynamics , meteorology , physics , genetics , photocatalysis , catalysis
Summary The effect of E. coli and B. cereus on methylene blue reduction time in ice cream was studied. A general correlation was established between reduction time and numbers of organisms. Lower numbers of B. cereus than E. coli were required to bring about reduction in the same times. Considerable destruction of bacteria was observed during freezing in vertical and soft serve freezers accompanied by an increase in reduction time. This was shown to occur very rapidly after a critical point of ice crystal formation was reached, irrespective of temperature. Increased concentration of total solids did not increase this destruction and bacterial destruction was attributed to mechanical damage.