Hard and bouncy yolks, widely associated with fake eggs made on the mainland, can also be found in real cooked eggs, Macau investigators say. They made their announcement yesterday as the Hong Kong Centre for Food Safety was investigating five complaints about suspected fake eggs received since last week. Macau investigators said their initial findings suggested that there was no evidence of fake eggs in Macau markets, and that they had managed to make a hard and bouncy yolk out of a real egg by controlling its transport and storage conditions. Ng Peng-in, an official with the Macau Civic and Municipal Affairs Bureau, who led the suspected fake-egg probe, said none of the samples that investigators analysed were fake. The investigators analysed one egg submitted by a resident and more than 20 eggs collected from marketplaces. 'The samples were found to contain no element believed to exist in artificial eggs as described on the internet,' Mr Ng said. 'The possibility of these eggs being artificial is very low.' He added that hard and bouncy yolks could develop in real eggs that had been shaken during transport and stored at very low temperatures. Investigators shook an egg for three hours and stored it at below freezing temperature. The egg ended up with a hard and bouncy yolk after being cooked. However, Macau authorities said they would conduct DNA tests on more egg samples. Chinese University chemistry professor Tso Wung-wai said inexperienced shoppers would find it quite difficult to distinguish between fake and real eggs, but they could try gently nipping the shell. 'The shells of real eggs should be harder, whereas the artificial shells of fake eggs can easily be broken when nipped,' Dr Tso said. Shells of real eggs would also include a layer of membrane, he added. He said that because the fake egg yolk and egg white were made of the same chemical, polysaccharide, they mixed together easily. But real egg yolk and egg white could only be mixed when beaten together. But in terms of density and weight, Dr Tso said fake eggs appeared not to be any different from real ones. 'When in doubt, it is best to take the eggs for a quick chemical analysis of protein,' he said. Wan Chai market vendors said they were confident that no fake eggs were sold at their stalls. 'We have a regular supplier with whom we have worked for decades,' said vendor Fok Wai-kuen. 'Other suppliers have approached us before, but their price was so cheap that we suspected there might be something fishy.' He said the cost of fake eggs could be as much as 50 per cent lower than normal ones, but he had not heard of any fake eggs for sale in Hong Kong. A Centre for Food Safety spokesman said it had received five complaints of suspected fake eggs since February 19. It had handed 11 samples to the government laboratory and was awaiting test results. He said the centre had received 22 complaints about suspected fake eggs last year, of which none of the samples tested were found to be fake.