A water in oil emulsion is used in which of the following food products?

A water in oil emulsion is characterized by tiny droplets of water dispersed throughout a continuous oily phase. Mayonnaise is a prime example of this type of emulsion, as it is created by mixing oil with an egg yolk (which contains emulsifiers) and vinegar or lemon juice. In this case, the water from the vinegar or lemon juice is emulsified in the oil, which creates the creamy texture and stability that is characteristic of mayonnaise.

Other options like vinegar and fruit juice do not form emulsions since they are primarily aqueous solutions. Stock is a mixture of water and other ingredients, including vegetables and meat, but it does not involve emulsification and is not considered an emulsion. Hence, mayonnaise is the only product from the given choices that successfully demonstrates a water in oil emulsion.