Leavening Agents

The leaven-agents in your pantry are biological (e.g., yeast) or chemical (e.g., baking powder and baking soda). This does not spoil in the ordinary sense, but its effectiveness decreases if it is too old.

Yeast is a living organism. It feeds on sugar and produces gas, and the gas is causes what to rise your bread.

Yeast goes bad, by dying, what makes it ineffective. And the yeast in a package not all die at once, so that its efficacy will cease after some time.

You can store unopened dry yeast at room temperature, but the refrigerator will extend their life. Once opened, store yeast in the refrigerator, where it will last for around four months, or in the freezer, where he will last for six months.

Chemical propellant agents, baking powder, and baking soda (they are not the same!) Work by production of gas by a chemical reaction when combined with other ingredients. The connection that generated the response, which loses its effectiveness over time, especially by the action of air, moisture, and temperature.

The full potency, replace these ingredients every six months. Like yeast, their diminshed effectiveness step by step: the year-old baking soda may also increase slightly, but not as much as it should.
Oils and fats

As mentioned above, oils and fats spoil by always rancid, and this is true for edible oils and solid shortening as well. Provided you store them in a cool, dry, dark place, vegetable shortening (such as Crisco) to keep for up to two years, if unopened. Opened, of a shortening can be for a year (or six months for the shortening sticks).

Liquid oil shelf life will vary depending on the type and how they are refined, and they degrade faster when opened. Refined oils are longer in total. Some oils, like grape seed or walnut, maybe only a couple of months, once opened. But as a General rule, a bottle of cooking oil will take a year, on average (or twice that if refrigerated).