Extraction of pectin from navel orange peel assisted by ultra-high pressure, microwave or traditional heating: A comparison

Ultra-high pressure (UHP) was applied for pectin extraction from navel orange peel. The effects of pressure, temperature and pressure-holding time on the extraction yield and viscosity of pectin were investigated. A 2-factor 3-level design, following a single-factor experiment, was carried out to optimize the extraction parameters and the optimal conditions of UHP extraction were determined as pressure 500 MPa, temperature 55 °C, pressure-holding time 10 min. Under the optimal conditions, the yield of pectin (20.44% ± 0.64) was significantly higher than those extracted by traditional heating (15.47% ± 0.26) and microwave (18.13% ± 0.23). The physicochemical properties and rheological characteristics of pectin extracted by ultra-high pressure, traditional heating and microwave as well as commercial pectin were also compared. The results showed that the intrinsic viscosity and viscosity-average molecular weight of pectin extracted by UHP (0.7604 L/g and 3.063 × 105 Da) were much higher than those extracted by traditional heating (0.4276 L/g and 1.521 × 105 Da), microwave (0.3591 L/g and 1.230 × 105 Da), and the commercial pectin (0.2160 L/g and 0.663 × 105 Da). The same results were also obtained in the rheological characteristics, activation energy and gelling properties determination. These results clearly demonstrated that UHP is a more efficient, time saving, and eco-friendly alternative for pectin extraction from navel orange peel, especially for pectin with higher viscosity and stability.