Sentence:  In the absence of <WSD>additions</WSD> to the homogenate , the product formed is an iodinated particulate protein ( Fawcett and Kirkwood , 1953 ; Taurog , Potter and Chaikoff , 1955 ; Taurog , Potter , Tong , and Chaikoff , 1956 ; Serif and Kirkwood , 1958 ; De Groot and Carvalho , 1960 ) . 
Meaning of the word marked with <WSD> tags:  a component that is added to something to improve it