Ultrasonic estimation of solid/liquid ratios in fats, oils and adipose tissue

Data are presented for the speed of transmission of pulses of 2.5 MHz ultrasound through fats and oils at temperatures in the range −50 to +110°C. It is suggested that a measurement of the speed of ultrasound (V), which is greater in solid fats (Vs) than in oils (VL), might be used to provide an estimate of the proportion of solid in a partially solidified fat. An acoustic parameter ϕ is defined such that: and it is suggested that ϕ might be used as a practical index for determination of the volume fraction of solid fat. This procedure might be useful under conditions unsuited to the established methods of dilatometry, calorimetry or nuclear magnetic resonance. As an example of a possible application, measurements are presented for the speed of ultrasound in pig adipose tissues selected to show a range of consistencies which, by subjective assessment and by penetrometer measurements, ranged from ‘soft’, and therefore unsuited for the manufacture of bacon, to ‘hard’. After allowing for the contribution of the fat-free tissue, it was estimated that the lipid in the tissues ranged from about 20 to 88% (by volume) solid. The variation in ϕ explained 88% of the variance in the penetrometer measurements.

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