In-situ pH measurement of selected liquid foods under high pressure

The efficacy of high pressure treatments in food processing is often attributed to the pressure induced pH change. However, knowledge of in-situ pH values of foods subjected to high pressure is scarce, because of obvious limitations of existing pH measurement methods. In this work, pH (25 °C) of some select liquid foods was measured in-situ under high hydrostatic pressure up to 800 MPa using our previously validated high pressure pH sensor. Our measurements show an increase of acidity in all tested food and water samples with increasing pressure. In general, food samples exhibit a buffering action under pressure resisting changes in pH. Furthermore, the pressure-dependent pH change is apparently independent of the concentration of added antimicrobial acids. Thus, any potential strategy of increasing the level of antimicrobial acid addition for enhancement of process pH effects is of dubious efficacy.Industrial relevanceHigh pressure treatments in food processing require better understanding of in-situ pH values of foods subjected to high pressure. This paper describes in-situ pH measurement of some select liquid foods under high pressure using our high pressure pH sensor (Sastry & Samaranayake, 2009). The results of this study will assist product and process development in the food industry.

► pH values of some select liquid foods were measured in situ under high pressure up to 800 MPa.
► We found that all the food and water samples become acidic with increasing pressure.
► Generally, food samples have shown a buffering action under pressure resisting changes in pH.
► Sample chemistry and properties play a critical role in pressure-dependent pH change.
► Increasing concentration of added antimicrobial acids may not improve process efficacy.