Power Toppings are simply ingredients used to power up Foodons by throwing the items at them. The Purple Pepper, for example, powered up Fruit Turtle. It was easily able to defeat Dim-Sum Deluxe, however the effects of the Power Topping also destroyed Fruit Turtle.
In the games, Toppings work slightly differently in that they can also harm a Foodon when thrown. Check out the list of the games ingredients.
In battle, throwing an ingredient at a Foodon that the Foodon is made with will heal that Foodon. Most of the time the status effect inflicted by ingredients is the same; sugar causes sleep, soup causes burn, etc., but there are exceptions, such as how sugar inflicts mold instead of sleep on Ramen. Regardless of which Foodon the topping is thrown at, and whether it would buff or debuff, Power Toppings can miss when thrown.
Throwing particular Power Toppings at particular Foodons can also give a power-up status called 三位一体Sanmi Ittai. Achieving this status requires balancing the recipe for your Foodon between meat, vegetables, and seasoning. For example: Omerice is made with eggs (meat) and ketchup (seasoning). Throwing green peas (vegetable) at it completes the "trinity", achieving Sanmi Ittai status. In this way, the Topping required will vary between Foodons. The Toppings required to achieve Sanmi Ittai can be found listed on the bottom line of a Foodon's in-game profile, or on its profile on this wiki.