Oyster sauce salt, should be added to the sauce, since the oysters should provide all the savoury flavour. However, this method is prohibitively expensive. Many modern oyster sauces are thickened with cornstarch, flavoured with oyster essence or extract and darkened with caramel. Vegetarian oyster sauce prepared from mushrooms, often oyster mushrooms or shiitake mushrooms, is also popular and generally lower in price. It may contain more taste enhancers if less mushroom extract is used to reduce costs. Most of the oyster sauces available on the market contain added monosodium glutamate (MSG). In recent years MSG-free varieties can also be found. The taste
Oyster card points of their journey to calculate the fare due. Users must touch the Oyster card only once at the point of boarding: as London buses have a flat fare of £1.50 (which allows for unlimited bus journeys within an hour from the point of touching in), there is no need to calculate an end point of the journey. In July 2016, cash became the deprecated form of payment for travel on London Buses, with TfL heavily promoting the use of a contactless card or Oyster card. All major contactless cards are accepted which carry the 'contactless symbol', however tourists are