The combined effect of supercritical carbon dioxide and mild temperatures on pectin methylesterase inactivation in orange juice.

Pectin methylesterase (PME) is the target-enzyme in orange juice processing, and its inactivation preserves the original juice's cloud, a valuable quality attribute for consumers. This study was primarily undertaken to evaluate the combination of supercritical carbon dioxide (SC-CO₂) and mild temperatures on PME inactivation in the juice. Physicochemical and color parameters were also evaluated. Pressures (P) in the range of 74 to 351 bar, temperatures (T) between 33 °C and 67 °C, and holding times (t) varying from 20 to 70 min were tested using a central composite rotational design. Determination of PME activity, pH, titratable acidity, soluble solids, ratio, lightness, °hue and chroma in freshly extracted/raw and treated juice samples, and total color difference (TCD) between raw and treated juice were carried out. The percentage of PME reduction widely ranged from 13.7% to 91.8%. The variable P had a significant effect (p ≤ 0.05) on TCD and acidity variation. T exhibited a significant effect on the PME reduction, TCD, and soluble solids variation; however, t impacted on the soluble solids variation only. The interaction between P and t (P.t) affected the soluble solids and acidity variation, and T.t affected TCD. The combination of SC-CO₂ and mild temperatures is potentially capable of inactivating PME in orange juice.