Kiwi juice jelly?

[olmoelisa]

I like to prepare fruit jellies, such as strawberry or watermelon or ....

and last week for the first time I tried to prepare a kiwi jelly.

Ingredients: 1 liter of homemade kiwi juice, a little sugar, the right amount of jelly powder.

Result: nothing. After 3 hours (but also after a night) I found only kiwi juice in the mold!

A couple of days later, I tried again, this time using half kiwi juice and half orange juice.

Result: the same!

I'm sure the jelly powder is OK, because I used a bag from the same confection to prepare a wonderful strawberry jelly, so...what happened?

Is there anything in the kiwi that prevents the jelly powder to work the right way???

[Simon Lewinson]

Fresh pineapple contains bromelain, an enzyme that digests protein. Similarly, kiwi fruit contains actinidain and papaya has papain.

Bromelain is inactivated at about 70 degrees C, and the same goes for papain and actinidain, but I am unsure of the exact temperatures. I have some vague memory that chili will inactivate bromelain but cannot fine a reference yet. Update - our molecular friend Heston Blumenthal has used chili to inactivate bromelain - google is thy friend.

Agar and some other gelling agents are unaffected by these enzymes as they are not protein based.

Hope this helps

Simon

Edited May 3, 2013 by Simon Lewinson (log)

[Keith_W]

Yes, Simon has the right answer. Kiwifruit juice has the property of dissolving proteins. In fact you can use it to tenderize squid. Gelatin is protein based, so it will not work with Kiwi juice. I am not so sure if Agar would work that well either, because the gelling power of Agar is pH dependent. A bit of googling suggests that agar works best within a pH range of 4.5 - 9.0 (source) but Kiwifruit has a pH of 3.2 (source), so perhaps you need to both inactivate the enzyme and raise the pH.

Edited May 3, 2013 by Keith_W (log)

[Mjx]

Konjak (Amorphophallus konjac) powder may be the way to go, since it is apparently pH-stable at pHs between 2 and 7; it's a carbohydrate, so enzymatic activity shouldn't be an issue, and it is also readily available in shops that sell Asian food ingredients (and maybe health food shops).

This makes a very firm, even brittle gel, depending on how much of the powder you use, so you may need to tinker with it a bit to get the exact consistency you want.

You might not want to serve this to small children, since biggish chunks of the gel may pose a choking hazard.

[olmoelisa]

Thank you very much.

I tried the Konjac sometimes (trying to make spaghetti) but I did a mess.

I'll try with agar agar for the kiwi jelly. I cannot inactive the enzime but I'll try to raise the PH.

[Smithy]

I think my first choice would be to heat the juice to, say, 80C (to be safe) or even bring it to the boil (to eliminate the need for a thermometer) unless there's too much other material in the mix that can't be cooked. Was that what you meant by not being able to deactivate the enzyme?

[Mjx]

. . . .

I tried the Konjac sometimes (trying to make spaghetti) but I did a mess.

. . . .

I haven't experimented with making thin strands using konjak, but I haven't run into any problems working with it as a moulded gel, and the rapid setup is something I really appreciate.