Ask Peter: Panna cotta (+ recipe)
Just wondering if a panna cotta is freezable, and if so how long before serving should you take it out of the freezer? Thanks, Earle and Belinda.
Freezing foods can be a god-send — preserving leftovers and fresh food alike. But it can also be problematic. The problem with freezing is what it does to the water content of what you’re freezing.
Think of an ice cube tray, how you fill it to the rim before placing in the freezer. Then when you take it out, notice how the cubes aren’t level, but "swollen'’. The water has expanded — which is very odd as cooling things tends to make them shrink. I think I once read that this is one of the great oddities of science, or maybe it just doesn’t make sense. Whereas it’s heat that causes things to expand — think of that pot of soup that boiled over.
It’s the expansion (from freezing) and then the collapse and shrinkage (from defrosting) that causes problems with food, as delicate cell walls are ruptured and burst and this causes things to split, or rupture when they are defrosted. Think of the liquid that comes out of defrosted prawns or scallops (ones that haven’t been soaked in water in the first place to add weight and make more profit for the exporter).
On the other hand, it’s believed that freezing paua and calamari helps to tenderise them as the cell wall breakdown loosens the flesh. However, foods that are very fine and delicate themselves (a tarakihi fillet or a whole strawberry) will suffer when frozen. A tub of soup or some bacon rashers are fine as the former is a puree or mixture of textures which won’t show signs of breaking down when frozen, and the latter is so fatty that it simply doesn’t go completely rigid when frozen. The porky meaty bits will a little of course (and probably leak some water when defrosted), but the fat protects itself and no water is leaked from that.
Alcohol and sugars are components that are less affected by freezing — remember the bottle of vodka you used to keep in the back of the freezer that never actually froze? Through chemical reactions, sugar in its various guises such as granulated, glucose or honey, and alcohol prevent ice crystals forming which means when products are brought back to room temperature they don’t break apart. Using these in recipes therefore will mean less damage to the finished dish.
Depending on the panna cotta recipe you use, most will be fine to freeze and defrost — but you should check a small batch of them first, and you must always defrost on a tray in the fridge, slowly and gently. If you were to defrost them out on your bench in summer heat you’re likely to kick off a mild case of food poisoning, so make sure you have enough time to do it properly, ideally overnight.
Milk and cream with high fat content will help keep your panna cotta looking good when defrosted, and the type of sugar you use will also have an impact. I sometimes make a panna cotta that includes condensed milk which should work well for freezing, but adding some glucose to your mixture will help, as it doesn’t really sweeten it too much but keeps things smooth. You could also try adding honey or golden syrup to your heated milk and cream, both of which will help prevent too many ice crystals forming.
This panna cotta from my book Peter Gordon Everyday includes condensed milk,. When blackberries are out of season use strawberries, raspberries or blueberries.
Panna cotta with balsamic blackberries
½ vanilla bean, split lengthways and seeds scraped out (or 1 tsp vanilla extract)
400g can condensed milk
6 leaves gelatine (or 1 Tbsp powdered gelatine)
60g caster sugar
1 Tbsp water
1 Tbsp balsamic vinegar
- Slowly bring the milk, cream, vanilla bean and scrapings and the condensed milk almost to boiling point, whisking occasionally as it heats up, then turn the heat off and leave for a few minutes.
- Soak the leaf gelatine in very cold water for 5 minutes. Drain it, gently squeezing out excess water, and stir it into the hot cream (if using powdered gelatine, sprinkle it over 2 Tbsp cold water and stir until dissolved, then mix into the hot cream).
- Strain the mixture through a sieve (or simply remove the vanilla bean) and pour the mixture into six 200ml dariole moulds*.
- Leave to cool to room temperature, then cover tightly and place in the fridge to set for at least 8 hours.
- Put the sugar in a saucepan with the water, place over moderate heat and stir until the sugar dissolves then, without stirring, cook to a light caramel. Turn the heat down, add the blackberries and the balsamic (be careful as this will create hot steam) and cook until some of the berries collapse into the caramel, mashing a few with a spoon as they cook. Take off the heat and leave to cool.
- To serve, dip each mould into a bowl of hot water for a few seconds, then invert on to the centre of a plate and shake gently to release the panna cotta. Spoon the berries and their juices on top and around.
* As an alternative to dariole moulds use souffle moulds or heavy duty porcelain coffee/tea cups. See more in the glossary.
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