Vacuum Impregnation of Foods: From Mass Transfer Intensification to Functional Design

Vacuum impregnation (VI) is a technique for porous foods that intensifies mass transfer by coupling gas expansion under vacuum with liquid imbibition during pressure restoration. During the vacuum step, trapped gases and some native liquids are partially removed from intercellular voids. Thus, when atmospheric or overpressure is restored, a surrounding external solution is driven into the newly available pore space by a pressure gradient, yielding rapid replacement of internal fluids relative to diffusion-limited mechanisms. Because the extent and kinetics of uptake depend on process settings (vacuum level, step times, pressure restoration rate, solution viscosity, and surface tension) and material structure (effective porosity, connectivity, deformation/relaxation behavior), VI offers a remarkable and well-controlled approach to food engineering in terms of both composition and functionality. Food processing applications include osmotic dehydration and acid/sugar infusion, anti-browning and preservative treatments, and salting or marinating, encompassing a broad range of food matrices including fruits, vegetables, cheese, fish, and meat, among others. Recently, the application of VI has expanded to include the delivery of minerals, vitamins, bioactive compounds, and viable probiotics, as well as hybrid processes that combine VI with emerging technologies to improve uniformity and shorten processing time. In this context, this work aimed to critically discuss technological progress in VI, including mechanisms and modeling, process and microstructure characterization, the range of applications, as well as challenges, drawbacks, and opportunities.