Abstract: A closed cell, light weight packaging material having biodegradable properties and being formed initially from a nonmodified starch material which has been modified by reaction within an extrusion barrel with (i) a mild acid selected from the group consisting of malic acid, tartaric acid, citric acid, maleic acid and succinic acid in the presence of water and (ii) a carbonate composition to generate CO2 gas. This modified starch material has decreased molecular weight and a dominant pattern of nonuniformity of hydrogen bonding within and between starch chains, and a dominant pattern of structural randomness of the starch chains. The resultant packaging material has a closed cellular structure with a density less than 0.032 grams per cubic centimeter and with resilient properties which enable substantial return of the compressed structure to its original, expanded shape with structural integrity. Also set forth is a process for preparing this material, as well as modification for enhancing hydrophobicity.