a b s t r a c t
Immersion vacuum cooling is a novel method for cooling meat products. This method has
notable advantages including lower water loss rate of products during the cooling process.
However, excessive solution boiling and spillage during immersion vacuum cooling process
are considered as the serious problems limiting its wide-spread application. In this
study, the mechanism of water boiling and spillage during vacuum cooling was studied by
capturing the images of boiling phenomena with a high speed camera. Results show that
the growth of bullet bubble is a major reason for more than 42% of water loss during
boiling, because the diameter of a bullet bubble can increase to the diameter value of the
test tube in 0.36 s. Our results also show that using moderate volumetric displacement of
vacuum pump (for instance 0.0012 m3 s1 in this paper) and controlling the chamber
pressure in the range of 10e2 kPa can weaken the intensity of boiling and spillage of water.
These results are discussed in the context of 'classical pool boiling' theory.
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