Where there are shifts in food types involving reduction in food hardness or changes in how these foods are processed, most investigators have found a reduction in gross wear.
能详细剖析一下：Where there are shifts in food types involving reduction in food hardness or changes in how these foods are processed；不理解这是where引导的什么句子。
Where there are shifts in food types involving reduction in food hardness or changes in how these foods are processed.这个其实就是一个地址状语从句，只是where在这里要理解为在……的情形下。字面意思是:当食品种类发生转变，且这类转变与食物硬度的减少或者食物加工方法的改变有关的状况下………
