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Reply	Ned Edwards says: I suggest it's is a reversible rising reaction. Rising agents are a mix of sodium bicarbonate and an acid. Some of the rising is due to reaction starting at room temepersture due to wetting the powder, so bringing the two components in contact. That reaction would not be reversible and would probably be already complete at the start of baking.BUT if there is excess sodium bicarbonate, some would survive into the higher temperature baking period. Above 60C it starts to to decompose:2NaHCO3 → Na2CO3 + H2O + CO2This probably helps form a fine bubble texture in the crumpets, because there isn't time for them to coalesce in the thickening dough.When the crumpets cool again to below 60C the reaction goes into reverse, very slowly reabsorbing the CO2 from the bubbles. This creates a slight vacuum in the porous gas-pockets of the crumpet, which suck in air from the surrounding gas in the encapsulation. If you put the pack in boiling water for some time, the bicarbonate should slowly decompose again, partly restoring the pack to the as-bought size.  (no votes) Tags: technology, unanswered, domestic science, human body.
	posted on 2008-12-03 16:35:00 | Report abuse

Reply	Dave says: I've noticed something very similar with supermarket bought beef mince. The mince was packaged in a plastic tray, sealed with a cellophane (or similar) lid. After a few days in the fridge (not freezer), I noticed that the whole package was slowly 'scrunching', while the mince itself turned grey in colour. After a week the appearance of the package was as if it had been vacuum packed, with the tray and lid now 'hugging' the mince. Unfortunately, the meat was now outside of its use-by date, and had to be discarded.The only clue I can offer is that the meat was 'Packaged in a protective atmosphere', which implies the airspace in the package may not have been air.  (no votes) Tags: technology, unanswered, domestic science, human body.
	posted on 2008-12-05 13:22:00 | Report abuse

Reply	Stewart says: There tends to be a general feeling that food packaging of this sort will not allow water to escape. This is not true. Over time, OH ions will certainly migrate across a thin plastic film and I think that this is what is happening. Crumpets have a high water content and so it is going to be fairly humid inside the package. The humidity in a freezer is low, all the water has formed frost and ice. This is an ideal environment for the water in the package to slowly migrate across the plasic film resulting in the contents shrinking as they dehydrate.This is one reason why freezer bags are thicker than standard sandwich bags.  (no votes) Tags: technology, unanswered, domestic science, human body.
	posted on 2008-12-09 23:46:00 | Report abuse

Reply	Michael Marshall says: Our thanks to Warburtons, the company that made these crumpets, for the following - EdWarburtons crumpets are a short shelf-life, high-moisture product and as such, are particularly susceptible to food spoilage organisms. The product is packaged in a carbon dioxide environment to extend the shelf life and to protect the crumpets against microbial spoilage, particularly aerobic organisms.Over time, the carbon dioxide gas is absorbed by the liquid in the product, and as it takes up less space in liquid form this reduces the internal pressure of the package. As long as the seals are intact, the differential in pressure means the packaging contracts. The lack of spoilage in the product is an indication that the seals are intact and the integrity of the product remains unaffected.Claire Minzey, Clarion Communications, London, UK  (1 vote) average rating:5 Tags: technology, unanswered, domestic science, human body.
	posted on 2009-07-01 17:28:36 | Report abuse

Reply	MarijaNova says: There is always a possibility that you have altered the structure and permeability of plastic with freezing and warming again if the product was not meant for freezer. And combined with different pressure, higher solubility at lower temperatures, humidity, chemical and biochemical reactions you end up with flattened crumpets.  (no votes) Tags: technology, unanswered, domestic science, human body.
	posted on 2009-07-02 10:47:38 | Report abuse

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