Adiabatic Compression Heating Characteristics of Selected Food Materials during High Pressure Processing

Abstract:

During high pressure processing (HPP), the work of compression always causes the food materials to undergo a reversible adiabatic temperature increase. This phenomenon results in nonuniform temperature distribution during processing. The compression heating can also influence the inactivation of bacteria, spore and enzyme. But knowledge in this filed is still very limited. In this study, adiabatic compression heating characteristics of food materials during HPP was investigated using a specially designed experimental setup. Selected liquid and solid food materials were studied at different pressure levels (100~400MPa) and different initial temperatures (15~45℃). At 25℃ initial temperature, ethanol had the highest δ (adiabatic temperature increase up to 12.8℃/(100MPa)) of the samples examined, and δ value was decreased with increasing pressure. Compared to high water content foods(26~4.0℃/(100MPa)), fats and oils showed higher δ values (7.3~10.7℃/(100MPa)), which were also decreased with increasing pressure. For high water content foods, δ values was increased with increasing initial temperature, but fats and oils had little or no effect of initial temperature. An empirical equation was established to predict the adiabatic temperature increase value during HPP at different pressure levels and different initial temperatures for food materials. The thirdorder polynomial was used to fit the δ values of orange juice, honey, whole milk, semiskimmed milk, soybean oil, beef and ethanol. The regression coefficients of these equations were all above 0.97. This study provides useful information for the optimization of high pressure processing.