Definition of Sanitary valves :
Sanitary valves are used in food processing, wastewater and pharmaceutical industries.

"These sanitary valves perform various features like easy cleaning, crevice free, and polish contact surfaces.
Types among these sanitary valves can be seen in the form of sanitary ball valves, sanitary sewer valves, sanitary butterfly valves, sanitary check valves, sanitary globe valves and many other such sanitary valves.
Variations among these sanitary valves can also be seen in their working pressure and operating temperature. These sanitary valves carry gas and liquid media or liquid with suspended solids.

Metals like brass, bronze, copper, cast iron, ductile iron, stainless steel, and steel are used in the manufacture of these sanitary valves to ensure that they have a longer life."
Extracted from http://www.abctlc.com/courses/valvecontrols6hours.pdf, p. 61

Here are links to various manufacturers of such valves: 
http://www.alfalaval.com/solution-finder/products/Unique_RV-ST/Documents/Brochure%20-%20Flow%20control%20for%20hygienic%20use%20-%20Valves%20and%20automation%20-%20the%20complete%20line%20-%20EN.pdf 

http://www2.emersonprocess.com/en-US/brands/fisher/ControlValves/sanitary/Pages/Sanitary.aspx 

http://www.steriflowvalve.com/  

Siemens is a very large company with many divisions. It sells valves in its Building Services division, under different brand names such as Staeffa, Powermite, etc…:
http://www.buildingtechnologies.siemens.com/bt/us/Products__and__Systems/hvac_products/HVAC_components/valves/Documents/153701_ValveGuide.pdf
But you will find no sanitary valves in this division. 

Now, in our own A&D division, Siemens produces mostly actuators for any type of valve, such as the Sipart actuator line. But the valves themselves must be purchased from a specialist firm.

Hope this helps,
Daniel Chartier