What is a "food grade" lubricant ?

"The concept of food grade lubricants or greases is directly related to protecting people's health and the economic consequences of doing so.
White oils: traditional oils which have undergone an enhanced treatment to make them as compatible as possible with the requirements associated with public health.  They are extremely clear – hence the name ""white oils"" – and are approved by the Codex Alimentarius Commission.

Accidental contact: the technical constraints required by modern technologies, as well as the constraints associated with public health requirements have resulted in the development of NSF-H1-registered lubricants for accidental food contact (the successor to the USDA-H1 standard). These are oils and greases that are not harmful to people's health if they accidentally come into contact with foodstuffs. ""Accidental"" means, for example, a leak that was not detected early enough to be stopped, or accidental splashes. 
Food Processing Aids: For situations when there is direct contact with foodstuffs, vegetable oils derived mainly from rape or sunflower seeds are used. These are very useful when removing biscuits from their moulds, for example: there is no way of avoiding contact with food, and so the components have to be even more carefully selected. These oils are referred to as ""Food Processing Aids"".

The food industry is gradually switching over to NSF-H-registered lubricants and vegetable oils.
NSF International is a US organisation which is considered an authority in the profession and which serves as a world reference for registering (or not registering) products depending on their composition.