A separation material and method for separating and recovering a target gas from a mixed gas including the target gas and a hydrocarbon gas that has the same number of carbon atoms as the target gas, the target gas being a hydrocarbon gas having 2 or 4 carbon atoms and a carbon-carbon double bond. This gas separation material includes: a metal complex containing a 2,3-pyrazinedicarboxylic acid; an ion of at least one type of metal (M); and an organic ligand (B) capable of bidentate coordination to the metal ion represented by general formula (1) or general formula (2), where (M), formula (1) and formula (2) are as defined herein. The metal complex has a composition represented by M.sup.2+.sub.2A.sup.2.sub.2B where M.sup.2+ is the ion of the metal (M), A.sup.2 is a 2,3-pyrazinedicarboxylate dianion and B is the organic ligand (B) capable of bidentate coordination to the metal ion.

Disclosed are methods, systems, and articles of manufacture for molded fiber beverage containers capable of containing a variety of fluids, including beverage cups for drinkable beverages, such as hot or cold beverages, carbonated beverages, and/or alcohol beverages. In some aspects, a method for producing a physical barrier to liquids for fibers usable in manufacturing of paper-based beverage containers includes dosing a fiber with a stearate or a saturated long chain fatty acid salt; dispersing undissolved stearate or undissolved saturated long chain fatty acid salt to allow for preparation of a homogenous mixture including the dosed fiber; and adding a divalent or trivalent metal salt to precipitate the stearate or the saturated long chain fatty acid salt from the homogenous mixture, wherein the precipitate is on the surface of the fiber and forms a physical barrier to liquids into the fiber.

Disclosed are methods, systems, and articles of manufacture for molded fiber beverage containers capable of containing a variety of fluids, including beverage cups for drinkable beverages, such as hot or cold beverages, carbonated beverages, and/or alcohol beverages. In some aspects, a method for producing a physical barrier to liquids for fibers usable in manufacturing of paper-based beverage containers includes dosing a fiber with a stearate or a saturated long chain fatty acid salt; dispersing undissolved stearate or undissolved saturated long chain fatty acid salt to allow for preparation of a homogenous mixture including the dosed fiber; and adding a divalent or trivalent metal salt to precipitate the stearate or the saturated long chain fatty acid salt from the homogenous mixture, wherein the precipitate is on the surface of the fiber and forms a physical barrier to liquids into the fiber.

Provided are a flavoring agent that is a compound in which a moiety derived from a flavoring compound is represented by Formula 1 and which is decomposed into a lactone compound and a flavoring compound upon thermal decomposition, a composition including the flavoring agent, and a product including the flavoring agent.