Formulating fruit fillings. Freezing and baking stability of a tapioca starch–pectin mixture model

Fruit fillings are a little-studied product. Their design and formulation must take a number of factors which are inherent to their applications into account, including stability during heat treatments such as baking and freezing, during which their quality must remain intact. The present study investigated systems containing native tapioca starch (TS), low methoxyl pectin (P, at two concentrations: 0.3% and 0.6%) and calcium, compared with TS alone and with a modified waxy corn starch (C), normally used in the industry, as control. All the systems were prepared with and without the addition of fruit. A method to measure the instrumental texture of filled pastries was developed and applied to study the effect of the baking process on two types of bakery products. The rheological results indicated that in the mixed TS-P systems pectin had the dominant role. The presence of fruit caused a significant rise in the G′ and G″ module values for all the thickener system formulations, but the effect was greater with the mixtures that contained pectin. This would indicate that the addition of solids and/or the extra pectin contributed by the fruit led to greater structuring. During freezing, the pectin gave rise to a different gel structure to that of TS alone and acted as a retrogradation and syneresis inhibitor. The extent of this effect depended on the added pectin concentration. Pectin also imparts the stability at high temperatures and conferred similar viscoelastic behaviour to that of the modified starch control (C). The TS-pectin system also proved bake stable.