A little water migration is just enough to keep dryness at bay.
An optimised cake recipe is not the only strategy for maximising fresh-keeping over time. If you use an indulgent fruity filling, there is another tactic you can draw on.
Here at DuPont, we call it controlled migration – the movement of a limited amount of water from the filling into the surrounding cake to maintain the feeling of moistness and softness.
The way to achieve that is by ensuring your filling has a water activity level slightly higher than that of the cake itself. Dry matter content plays a particularly important role in this regard. Knowing the water activity of your cake and filling is the first step towards migration control.
Migration on trial
For our own trials, we baked cakes with a water activity of just under 0.7. A filling with 40% fruit and less than 70% dry matter was tested – securing a water activity just high enough to ensure the right amount of migration. Too high, and the risk is unappealing sogginess and a tendency towards rapid mould development.
Developing a filling with the right water activity is one thing, securing the right texture and stability is another. This requires the use of a hydrocolloid. In most bakery fillings, the choice lies between pectin and modified starch. Although typically the more expensive of the two, we chose pectin for its flavour release and clean-label image.
Finding the right pectin
Pectins, too, vary in their sensory and gelling properties. Our priority was to achieve the right level of controlled migration and, at the same time, a filling with the optimum fruit flavour and spreadability.
We selected two pectins – one a standard, low amidated pectin, the other a speciality product - from the portfolio we normally draw on for jam applications and compared their performance in a filling applied after baking.
Fresher over time
Our findings indicate that controlled water migration from both pectin-based fillings leaves cake feeling moister and fresher during shelf life than a control without filling.
The difference lies in the sensory evaluation. Here, our trained sensory panel found that the filling with the speciality pectin stood out for its enhanced authentic fruit taste, flavour intensity and creaminess. From a processing perspective, it was also seen to deliver improved spreadability and pumpability, easing handling during processing.
This has helped us expand our knowledge of optimised fruit fillings for cakes. But, don’t forget – it all starts with the water activity. Write to me if you need any advice.