Can Certo be substited for Sure-Jell?

No, you shouldn't substitute Sure-Jell with Certo. Both Certo and Sure-Jell are fruit pectin, but they are made differently and have different purposes. Certo is made with a low-methoxyl pectin, while Sure-Jell is made with a high-methoxy pectin. Low-methoxy pectin requires a higher sugar content to set than high-methoxy pectin, so if you try to substitute Certo for Sure-Jell, your jam or jelly may not set properly.

Additionally, Certo is typically used for making jams and jellies with clear juices, while Sure-Jell can be used for a wider variety of fruits, including those with cloudy juices. So if you're making a jam or jelly with a cloudy juice, you're better off using Sure-Jell.