Secret ingredient conundrum

[Yuuki_]

I'm trying to make a Sweet Potato Salad for the cooking exhibition that is coming up.

When I add sugar it says "according to the recipe", giving 2 stars.
When I add spice it says "kinds funny but ohwell", also giving 2 stars.

When I add pepper or cinnamon it says "according to the recipe" again, but now giving 2,5 stars.
And when I add 1-star salt it "looks good", giving it 3 stars!?

So when is the ingredient 100% perfect for that dish? Which phrase are you looking for?

[Guest]

I'm trying to make a Sweet Potato Salad for the cooking exhibition that is coming up.

When I add sugar it says "according to the recipe", giving 2 stars.
When I add spice it says "kinds funny but ohwell", also giving 2 stars.

When I add pepper or cinnamon it says "according to the recipe" again, but now giving 2,5 stars.
And when I add 1-star salt it "looks good", giving it 3 stars!?

So when is the ingredient 100% perfect for that dish? Which phrase are you looking for?

Look here

[Yuuki_]

Still doesn't explain why an ingredient deemed "bad" will give the same star rank as an ingredient deemed "normal", and a different ingredient equally deemed "normal" will add half-a-star more. All on the same dish.

[Guest]

I'm trying to make a Sweet Potato Salad for the cooking exhibition that is coming up.

When I add sugar it says "according to the recipe", giving 2 stars.
When I add spice it says "kinds funny but ohwell", also giving 2 stars.

When I add pepper or cinnamon it says "according to the recipe" again, but now giving 2,5 stars.
And when I add 1-star salt it "looks good", giving it 3 stars!?

So when is the ingredient 100% perfect for that dish? Which phrase are you looking for?

Salt is the best secret ingredient for Sweet Potato Salad and the "looks good" is the phrase for the 100% perfect dish (obviously using high star level ingredients will give it the higher star level). Also, the differences in star level could be attributed to the sweet potato

[Arcy]

Difference in star level may also be because of the Cooking Achievements, if you have any. Each level adds a multiplier to the quality of the finished dish, so it may be boosting the quality of the "worst" secret ingredient to the same displayed level as the "neutral" option.

[Syncrietta]

Secret ingredient is used to give some bonus points to the final star rank of cooked dish. I think the star rank of the secret ingredient also in effect, since the resulting star rank can be different using 0.5-star sugar & 5-star sugar, from what I see.
Using good match will give you +30 points, using normal match will give you +5 points and bad match will give you -15 points. And the total points you can have for the dish (without using any golden crop) will cap at 300 points, so when you have higher trophy-associated bonus as mentioned by Arcy, you can ignore the bonus points offered by secret ingredient because the with medium to high crop quality the dish can achieve that 300 points.

For me, secret ingredient is useful to make the 1.5 star carrot soup for vendor request and to generally increase the overall star rank of cooked dish using low star food items such as the cheese, rice, butter, flour & herbs from the vendors.