The Theory of Decompression Failure in Polymers During the High-Pressure Processing of Food

The occurrence of blistering and the formation of bubbles in matrices after a sudden pressure drop is a well-known phenomenon in many fields, including in the petroleum industry (“explosive decompression failure”), in diving (decompression sickness), in the infrastructure of hydrogen fuel cells, in the foaming of polymers, and in the high-pressure processing of food. This usually undesirable effect is caused by the increased absorption of gas in the polymer under high-pressure conditions and the subsequent supersaturation and increase in free energy on rapid pressure release. The exact mechanisms of the resulting expansion of gas, and hence the formation of bubbles, are not fully understood. Regarding the high-pressure processing of food where pressures of up to 6000 bar are reached at moderate temperatures, little information is available about the key factors involved in decompression failure. This review summarizes results and findings from relevant research areas to understand polymer decompression failure. The first part of this review describes the transport properties of gases in polymers under high pressure (sorption and desorption, diffusion coefficient, and permeability coefficient). The second part focuses on damage mechanisms and discusses parameters such as material properties, the nature of the gas, and process conditions (e.g., temperature, decompression rate). Knowledge gaps and proposed research are highlighted.