Achinewhu has analyzed more than fifty homegrown foodstuffs, which include seeds, nuts, tubers, spices, and herbs. These indigenous food items where examined and explored for their nutrient compositions and quality of protein content. Details of his findings are being used along with others in the compendium of Nigeria's food composition table.
He evolved the processing and production of coffee from coffee seed grown in Bayelsa State, Nigeria. 
He did research on cassava processing, which identified upgrade cassava cultivars with superior quality food values with regards to product output and other physico-chemical properties. He identified new cultivars with high starch yield and therefore high export potentials.
He developed a baby food (weaning) supplement employing the use of a combination of fermented plant food products. This was used to nourish children who were undernourished, in the days of Better Life Programme for Rural Women.