On the stabilisation of calcium-fortified acidified soy milks by pomelo pectin

Abstract

Although a number of studies existed on the stabilisation of acidified milk with commercial pectin, no data is made available on the stabilising behaviour of pectin from other sources. In this work, we focused on the use of pomelo pectin to stabilise acidified soy milk (ASM) samples with and without calcium fortification. The stability of ASM with varying concentrations of pomelo pectin (0.5–1.5% w/w) was examined through their rheological properties, particle size, and microstructure analyses. It was found that the addition of 0.5% pomelo pectin in ASM sample was not adequate to prevent the aggregation of soy protein during 4 °C storage for up to 15 days. On the contrary, the presence of pectin at 1 and 1.5% stabilised the ASM effectively and no phase separation was observed. All stabilised samples were shown to behave as viscoelastic liquids with its stability enhanced by increasing pectin content. Their flow behaviour was Newtonian with low viscosity of about 0.02–0.06 Pas. Furthermore, the fortification of calcium at 300–1200 mg/l to ASM sample stabilised with 1% pectin did not significantly affect its rheological properties. Additionally, confocal laser scanning microscopy was used to assess protein mobility in the ASM samples. It was found that the microstructure of soy proteins was coarser and more heterogeneous in ASM sample without pomelo pectin addition than that with the pectin stabilisation. The microstructure was also affected by pectin and calcium concentrations. Overall, it can be concluded that pomelo pectin is a promising ingredient for stabilising calcium-fortified ASM without chelating agents.