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A baking-stable fruit filling preparation

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leostrog's picture
leostrog

A baking-stable fruit filling preparation

I have been experimenting with fruit filling for a long time, seeking for the perfect consistency, which will not drip out of the cake while baking. Unfortunately nowadays in shops you can find only jams and jellies which are rich with pectin. Those do not behave well during baking, being not thermo stable. One can also buy ready-to-use fruit cake fillings, but the percent of fruit there is very low.

Also we don’t have fresh berries sold here, only frozen (cherries, raspberry, and blackcurrants).

Keeping in mind all these obstacles, I decided to try some ideas from the works of Prof. Amos Nussinovitch, about hydrocolloids in food technology.

 Unfortunately I worked without exact measurements and quantities, next time I will follow the precise amounts:

For the filling I used the mix of Agar Agar, Alginate, Konjac and cornstarch ( all this components possible to purchase in shops for "molelecular cuisine".

500 gr. of berry mix, thawed.

 Preparation:

The berry mix was crused with blender into a smooth puree. Then I eliminated the seeds and the peel using a strainer. In the end there was 300gr of liquid fruit pulp to which I added 4tbsp of sugar, and heated till the sugar was dissolved.

In a little pan I made a liquid solution of 5gr of Agar flakes with 100gr of water. In another bowl I mixed with a blender 2.5gr of Sodium Alginate + 50ml of water + 1.5gr sodium citrate as a buffer (to prevent the inactivation of alginate in a low pH). The purpose was to create a combined Agar-Alginate gel, which will have the thermo stability of the Alginate and the easy shape forming of Agar.

Unfortunately I forgot the Calcium bath, so it was not a combined gel after all.

Then I mixed 5gr of maltodextrin with 2.5gr of konjac. 

With a blender I mixed the liquid Agar-alginate solution and the berry-sugar mix. Then I added two tsp. of cornstarch and the maltodextrin-konjac mix.  The blender was working constantly while I was mixing all together.

The puree got thick, and I put it in the fridge in a slightly oiled container.

In the next morning I took it out and cut it to nice pieces, then put it as a filling in a yeast dough (Briosche)

and a crusty pastry.

There are not "wet" dough under th filling, but a thin layer of marzipan.

The baking temperature was 200-210 0C * 15-20 min.

You can see that I didn’t become too fluid and runny, and stayed well on its place. It also didn’t make the baking around it wet, meaning that the water stayed in the filling and didn’t go out too much. The consistency is nice, smooth but not sticky or gooey. The taste and aroma of the berries was also well preserved. I can estimate a percentage of fruit flesh in filling as  about 65-70%.

My thought is that the Agar and Alginate contributed to its firm consistency during the low temperatures of baking, and then, during the high temperatures, the cornstarch began to firm.

As I said earlier, I forgot to cross link the Alginate with calcium, so I don’t know how much it really contributed to the firmness.

Next time I will try it with a lemon/orange juice.

ars pistorica's picture
ars pistorica

The most common fruit thickening agents used in the industrial-baking sector include pre-gelatinised starch (for home applications, tapioca works best), modified food starchs (waxy rice and maize offer the best results for this application), powdered agar-agar (remember there are three common types available; due to the wide discrepancy between activation temperature and syneresis temperature), and a low-amidated pectin system that incorporates an additional calcium source.

Due to the nature of agar gels (short, strong, brittle, low-shear), a secondary, weaker hydrocolloid that forms elastic, soft gels (in these cases, the agar forms the main water-binding network, and the secondary gel helps to increase water viscosity of the agar-bound water) is often called for, especially those that have synergistic effect with agar.  Xanthan comes to mind.  So do many starches, like tapioca.  I would caution against using other alginates for this purpose, which are costly and perform better in other applications.

Thankfully, agar has more synergies than almost every other hydrocolloid out there (other than the exopolysaccharides produced via microbial fermentation, like xanthan, dextran, and so on).

I would focus on the agar or a flavourless starch (preferably tapioca) as the main "strong" gel, and then add only one other weaker gelling agent.  Emergent synergies matter more for hydrocolloid use than using as many as possible.  Konjac, although sometimes used in these applications, won't be particularly helpful.

Try xanthan and tapioca starch.  Or agar, xanthan and locust bean gum.  Or a low-amidated pectin with an additional calcium source (sugar levels can be below 30% in this case) with agar.

(Btw, it's agar that exhibits the widest thermally-stable range of all the non-exopolysaccharide-derived alginates, which is why the carrageenans and sodium alginate are used in ice-cream production and most available types of agar, minus one, are not:  they melt more easily at low-temperatures.)

leostrog's picture
leostrog

thank you for such interesting and useful comments. About starch - I prefer to add them as little as possible because they give a "starchy" taste to filling. LM pectin - we do not have them at retail stores. I order Pomona pectin from on-line store, but it's too expensive for using it in a fruit filling (I use it for no-sugar jams ). Locust gum I use too ( in combination with other hydrocolloids, carrageenan, for example) in creams and ice-creams for give good "mouthfeel" to  low-fat desserts.

Next time I'll try , according to your advice, agar, xanthan and locust bean gum combination too. But to get good results it will be necessary also to find the right pecentage of components in the hydrocolloid mix. Meanwhile, alll my other mixes resulted as a failure.

ars pistorica's picture
ars pistorica

try
100 base
.1 xanthan
.4 to .8 lbg depending on texture you desire
.4 agar
cold shear xanthan
lbg at 50 c
agar separately in water, 2 m boil to activate

tapioca starch that has been pregelatinised in water has no starchy mouthfeel when used with xanthan.

1 - 4% tapioca starch
.2 xanthan