Under what condition are yogurt, sour cream, and ice cream considered non-kosher?

Yogurt, sour cream, and ice cream are considered non-kosher when non-kosher gelatin is used because gelatin is derived from animal collagen, which can come from animals that do not meet kosher dietary laws. For a product to be kosher, it must be made from ingredients that are certified kosher. When non-kosher gelatin is included in these dairy products, it compromises their kosher status, as the gelatin originates from an animal source that may not have been slaughtered according to kosher requirements. This is particularly significant because many dairy products like yogurt and ice cream may incorporate gelatin to create texture or stability. Thus, any product containing non-kosher gelatin cannot be deemed kosher regardless of its other ingredients.