Pineapple Ruins Jelly


Pineapple and its cross section

Pineapple, Source: Wikipedia

I have a tendency to experiment in the kitchen and most of the time it goes well. One particular experiment involved adding fresh pineapple to jelly. It didn’t set.

It was a disaster. I was making a tropical fruit inspired trifle. I was so incredibly confident of my predicted success that I had talked up this dessert and even incorporated components from some of the people attending. Instead of having set jelly to layer in amongst layers of cake and fruit, I had slush. I had three hours to make a replacement dessert. The pineapple slush was exiled to the back of the fridge while I frantically I made a pavlova covered in cream and tropical fruit.

After everyone had left and with the dishwasher whirring away, I brought out the bowl of pineapple slush. After 10 hours, it still had not properly set. I declared war on pineapple that night in the kitchen. I had to find out why the jelly hadn’t set. I was so annoyed because my stomach was looking forward to a tropical fruit trifle that never eventuated. Pavlova just wasn’t the same.

The reason why my pineapple jelly did not set and was not ever going to set despite the length of time spent in the fridge was because fresh pineapple contains an enzyme called bromelain. It is a plant extract that is usually used as a meat tenderiser. Jelly is made from gelatine which is made from the collagen found inside the skin and bones of animals. It is a common gelling agent in not just jelly but also in pharmaceuticals, marshmallows, photography and even found in some low-fat yoghurt.

Bromelain and other enzymes in the pineapple interfere with the preparation gelatine-based desserts because it breaks down the gelatine making it impossible for a wobbly jelly to form. This enzyme can be deactivated by heating the pineapple to a temperature above 65oC. A quick boil of fresh pineapple in either its own juices or water for a few minutes should suffice. Another alternative is to use canned pineapple where the heating processes before being canned has been high enough to deactivate the bromelain.

Other fruits to be wary of adding to jelly include fresh papaya and kiwi fruit. They also contain enzymes that interfere with the setting of jelly.

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3 Comments

Filed under chemistry365, Science

3 responses to “Pineapple Ruins Jelly

  1. Curt

    My kiwi jelly did not set. I tried redoing it and adding more pectin but it still did not set. it is like syrup. Is there a solution to save the 8 jars of syrup and make it jell?

    • I’m so sorry to hear about your kiwi jelly not setting. Now I’m curious enough to try a batch myself. Kiwi fruit has the enzyme actinidin in it that behaves in a similar way to bromelain.

      If pectin doesn’t work, you could maybe try adding unflavoured agar agar powder. This can be bought from health food stores and Asian groceries. I don’t know the exact conversion to gelatine for it to set but that will depend on how much jelly you’re making. I think a quick Google search will help out with that. It’s what I end up doing when using agar agar in place of gelatine.

      Good luck. Hope that is of some help.

  2. Pineapple has a chemical-called Bromelain which is a proteaser (it breaks down proteins) and because jelly has gelatine which is a protein, the bromelain in the pineapple breaks the collagen bonds, preventing it from setting. If you heat up pineapple to more than 70 degrees celcius (boiling), it can be put in to jelly as the bromelain has been extracted through heat.

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