Segregative Interactions in Single-Phase Mixtures of Gelling (Potato) Maltodextrin with Other Hydrocolloids

Potato maltodextrin (Paselli Excel; DE < 3) was used at a fixed concentration of 15 wt %. On holding at 5°C after rapid quenching from 45°C the onset of conversion from disordered coils to aggregated double helices was seen as a steep increase in turbidity (monitored by absorbance at 600 nm) after ∼50 min, and gelation was observed (visually) after ∼120 min. Incorporation of increasing concentrations of gum arabic (1, 2, 4 and 8 wt %) caused a large, progressive decrease in the time required for structure formation and gelation to occur. A similar massive increase in rate of self-association of maltodextrin was observed for mixtures with the same concentrations (1, 2, 4 and 8 wt %) of hydroxypropylmethylcellulose (HPMC). Unlike gum arabic, however, HPMC caused very large increases in the values of turbidity recorded immediately after quenching. This cannot be attributed to phase separation, since the mixtures did not resolve into two liquid layers on high-speed centrifugation, or to ordering of maltodextrin, which was seen as a sharp increase in turbidity at longer times. Our interpretation is that segregative interactions with disordered maltodextrin promote hydrophobic association of HPMC at temperatures where it would normally remain un-associated, in the same way as HPMC and gum Arabic promote self-association of maltodextrin. These conclusions accord well with a previous investigation which showed massive precipitation of low-DE potato maltodextrin from single-phase mixtures with disordered gelatin.