Catalyzes the NADP dependent reduction of L-sorbose to D-glucitol. Can also convert fructose to mannitol, but less efficiently. D-sorbitol + NADP(+) = H(+) + keto-L-sorbose + NADPH Optimum pH is 6.2. Carbohydrate degradation; L-sorbose degradation. Homotetramer. Belongs to the short-chain dehydrogenases/reductases (SDR) family.