30F-3 |
Acidification kinetics of potato particles in acidified liquid foods |
S. GRABOWSKI1, M. Marcotte1, and P. Nijland2. (1) Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant O., St. Hyacinthe, QC J2S 8E3, Canada, (2) Food Science, Wageningen University and Research Centre, Costerweg 50, Wageningen, 6701 BH, Netherlands Thermal processing of low-acid acidified foods (pH<4.6) can be reduced to low-temperature and low-lethality Pasteurization process by acidification prior to the thermal processing. Acidification is the common practice for homogeneous, single-phase liquid foods such as juices, sauces, etc. For liquid, non-fermented foods, containing relatively large solid food particles (soups, gravies, etc.) it is very difficult to predict a sufficient processing (immersion) time to reduce the pH in every part of solid particles below the critical value of 4.6. The objective of this study was to examine the acidification process of solid food particles immersed in an artificially acidified liquid food. Potatoes of Russet variety were cut into cubes of two sizes: 0.5 and 0.25 inch. For each test seven 100-g samples of potato cubes were immersed in separate containers filled with citric and acetic acid solutions of the same pH (pH=1.85, 2, 2.5 and 3). The acidification effect was established using a pH-meter after the removal and the grinding of samples for given time (every 15 min for 6 samples) and the last after 72 h (equilibrium). The Fickian diffusion model was applied for the calculation of experimental coefficient of diffusion. An average value of this coefficient was relatively high, as compared to solid gain in osmotic dehydration, and reached approximate value of 10-6 m2/s. Higher concentration of acids in the solution (lower pH) and smaller size of cubes improved acidification effect. A small increase in the diffusion coefficients was observed when changed from citric to acetic acid. Obtained results could be applied to thermal processing of particulate liquid foods to reduce unwanted high-temperature thermal effects by switching from sterilization to acidification plus Pasteurization process.
Session 30F, Food Engineering: Transport processes and kinetics
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