Thermal dependencies of fruit puree density

Abstract

Density is among the key properties of liquid food media, affecting homogenisation and dispersion. The work aimed to study the temperature effect on fruit puree density, determine temperature constants and grade purees by density. The study included apple, pear and cherry plum purees. Pycnometric densities were measured at 20, 30, 40 and 50ºC temperatures. Different media were shown to vary in the density reduction rate at increasing measurement temperatures. The correlation coefficient was strongly dependent on the reference (baseline) density and extremely — on temperature coefficient. Correlation dynamics modelling of elevating temperature revealed the slope vs. temperature coefficient pairwise correlation to monotonously increase starting from very high baseline values of >0.999. The relative slope vs. baseline density pairwise correlation coefficient decreased monotonously from 0.9032. It was additionally found that the media density grading is temperature-dependent. Thus, the descending series was pear–apple–cherry plum at 0–+24.68ºC, pear–cherry plum–apple at +24.68–+84.34ºC, cherry plum–pear–apple at +84.34–+174.31ºC and cherry plum–apple–pear at ≥+174.31ºC. For three study media, the number of temperature ranges inducing puree density gradients was 4. This approach to study thermal impact on the density of food fluids is generally acknowledged and can be successfully applied in the areas, where physical density and its comparative assessment are substantive.