Seaweeds, spices, condiments and other foods: composition, uses, quality, safety and storage.
Commercial vinegar is unusually shelf-stable because its acidity discourages most spoilage organisms. It can become cloudy, develop sediment, or form a vinegar mother without being spoiled. For preservation, however, an old bottle still needs the known acidity required by the tested recipe.
Iodized salt is the reliable iodine source because iodine is deliberately added. Sea salt may contain small, variable amounts naturally, but “sea salt” does not mean “iodized.” A sea salt can also be iodized if the manufacturer adds iodine and labels it accordingly.
Many lower-sodium salt substitutes use potassium chloride in place of some sodium chloride. They can reduce sodium intake, but they may taste more bitter or metallic and are not appropriate for everyone, especially people with impaired potassium excretion.
The main cooking difference is crystal size, not a dramatic sodium advantage. By weight, sea salt, table salt, and kosher-style salts are mostly sodium chloride; by teaspoon, coarse crystals pack less densely, so equal volumes can deliver very different amounts of salt and sodium.
Natural and artificial flavor are regulatory origin categories, not health grades. A natural flavor must derive its flavoring function from source materials listed in FDA rules; an artificial flavor is one whose flavor comes from other sources.
Old baking powder can look perfectly normal yet leave a cake flat. A hot-water test checks its remaining leavening power: strong immediate fizzing means it is still reactive; weak bubbling means it is time to replace it.
Old dry yeast is usually a performance problem rather than a spoilage problem: fewer cells remain active, so dough may rise slowly or not at all. A quick warm-water test can tell you whether it is still producing gas.
Cream of tartar is not creamy at all. It is potassium bitartrate, a dry acid that can stabilize whipped egg whites, supply the acid baking soda needs, and discourage large sugar crystals.
Cornstarch is roughly twice as powerful as all-purpose flour by volume for many sauces. It gives a glossy finish, while flour makes a more opaque, creamy sauce and works naturally in a roux.
Slightly wrinkled or dried-out ginger is often simply dehydrated. Cut into it: if the flesh is still firm, fibrous, and normally aromatic, it is usable; mold, wet softness, slime, or an unusual odor are reasons to discard it.
A blue-gray tint or distinct blue ring inside ginger can be completely natural in some types of ginger. If the flesh is firm, fibrous, and normally aromatic, with no mold or wet decay, the color alone is not a reason to throw it away.
Turmeric is the rhizome of Curcuma longa used as a spice and food ingredient. Curcumin is one of its major curcuminoids and contributes to turmeric's yellow color. Supplements can concentrate curcumin far beyond a culinary serving, so supplement trials should not be interpreted as evidence for a teaspoon of turmeric.