Yes, starch is a Scrabble word!

Verb

1. Stiffen with starch

Noun

1. A complex carbohydrate found chiefly in seeds, fruits, tubers, roots and stem pith of plants, notably in corn, potatoes, wheat, and rice; an important foodstuff and used otherwise especially in adhesives and as fillers and stiffeners for paper and textiles

2. A commercial preparation of starch that is used to stiffen textile fabrics in laundering