Rheological properties of low calorie jams with increased dietary fibre content made from tomato pomace
2018
Belović, Miona (https://orcid.org/0000-0002-1547-9072) | Torbica, Aleksandra (https://orcid.org/0000-0002-9627-1598) | Pajić-Lijaković, Ivana | Mastilović, Jasna (https://orcid.org/0000-0002-0921-8642)
Four low calorie jams with increased dietary fibre content based on tomato pomace powder were developed. The basic formulation (Jam 1) contained sucrose, which was partially (50%) replaced by stevioside in formulations of Jam 2 and 3, while in Jam 4 sucrose was completely replaced by fructose and stevioside. Jam formulations 1 and 2 were prepared without addition of gelling agents and represent concentrated suspensions of tomato pomace powder particles. Jam formulations 3 and 4 were prepared with the addition of lowmethoxyl (LM) pectin, which formed network structure around the dispersed tomato particles. Mechanical and thermal stability of jams were determined by application of steady shear and low oscillatory strain rheological measurements using a Haake MARS rheometer. Apparent viscosity and thixotropic loop areas were higher for the network systems (Jams 3 and 4) than for the suspension systems (Jams 1 and 2). This behaviour could be explained by the restriction of tomato particles mobility within pectin network, whose breakdown caused a drop in apparent viscosity. Opposite trend was observed for yield stress, storage (G‟) and loss (G‟‟) moduli values, which were higher for jams prepared without pectin (Jams 1 and 2) in comparison to jams prepared with pectin (Jams 3 and 4). Pronounced friction among the tomato pomace powder particles in suspension systems are the possible cause of these observations. Jams 1 and 2 were also shown to be more resistant to temperature change, having constant values of the storage and loss moduli with temperature increase from 25 to 90 °C. It can be concluded that jams prepared without pectin addition had higher mechanical and thermal stability which indicate their potential use as fruit fillings, while jams prepared with pectin had flow properties more desirable for processing and consumption.
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