Lemon juice

I exclusively use fresh lemon juice in fruit preserves, where its presence is needed mostly for flavor—fresh simply tastes better to me than bottled. In fig preserves, canned tomato products, and in vegetable pickles like the Baby Artichokes with Lemon and Olive Oil and the Roasted Red Peppers with Lemon Juice, lemon juice is added not primarily for its flavor but for its acidity. Because the acidity of fresh lemon juice varies somewhat (in my testing from a pH of around 2.8 to 3.0), to be absolutely safe you should use bottled lemon juice (whose pH is usually lower and more consistent than fresh, coming in at around 2.75 in my tests). In jellies, syrups, and acidulated foods, measure strained lemon or lime juice; for jams and other preserves, unstrained is fine.