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Testing glass as a food packaging material

: Gul, Khalid; Wani, Haroon Maqbool; Singh, Preeti; Wani, Idrees Ahmed; Wani, Ali Abas

Singh, Preeti (Ed.); Wani, Ali Abas (Ed.); Langowski, Horst-Christian (Ed.):
Food Packaging Materials. Testing & Quality Assurance
Boca Raton, Fla.: CRC Press, 2017
ISBN: 978-1-4665-5994-3 (prnt)
ISBN: 978-1-4665-5995-0 (electronic)
Book Article
Fraunhofer IVV ()

As a packaging material, glass has an extremely long history. The first glass objects used for holding food are believed to have been developed around 3000 BC (Moody 1963). Glass is defined as “an amorphous inorganic product of fusion that has been cooled to a rigid condition without crystallizing” (Scholze 1991). Although there are variations in the composition of glass, typically it is made by cooling a heated mixture of silicates, limestone, and soda ash to the point of fusion. In general, the glass for packaging is a variant of sodium or calcium salt. Silica (SiO2) from sand acts as a verifying agent, sodium oxide (Na2O) from sodium carbonate acts as a melting agent, and small quantities of sodium sulfate as a refining agent (Hugel and Pajean 1996). Calcium oxide (CaO), magnesium oxide (MgO), and aluminum oxide (Al2O3) act as stabilizing agents; cobalt (Co) and selenium (Se) are found in trace quantities as decolorants; iron oxides, chrome, manganese, cobalt, and so on act as coloring agents; and sulfates, carbon, and sulfides either act as colors and or as filtering properties. The production of glass containers involves preparation of vitrifiable raw material composition by heating a mixture of silica, sodium carbonate (the melting agent), and limestone/calcium carbonate and alumina (stabilizers) to high temperatures (1400°C–1450°C) until the materials melt into a thick liquid mass in the melting furnace. The mass is then poured into molds, followed by chemical conditioning of the glass and surface protection treatment. The glass containers then move for heat treatment and re-annealing in ovens to relive the stress generated by machine forming. Finally, each container is inspected for defects by appropriate equipment before being packed in a box or on a pallet.