Food safety scandals are not rare in China, because of a lack of governmental quality control and a highly profit driven attitude of the producers and vendors.
You can buy pretty much every kind of food in Beijing. There are big chain supermarkets like Carrefour, Auchan and Wal-mart that carry lots of foreign brands products. When shopping there, always check the expiry date carefully as some products may have been on the shelves for some time.
Monosodium Glutamate or MSG flavor enhancer is still widely used in Chinese cooking. It is freely sold in local supermarkets. While there is less chances that MSG is used by the western restaurants in Beijing, for a lot of Chinese restaurants is still a very common ingredient. Although MSG has been reported harmless for the human health, some people may have strong reaction to it. So, if you are worry about MSG in your food when you are eating out in the restaurant, ask the waiter, or even better, get to the kitchen to see the chef. MSG in Chinese is 味精 [wèijīng]/ weitsing.