Rheological properties of thermally or non‐thermally treated juice/nectar/puree: A review

Determining and controlling the changes in rheological properties are essential for estimating the quality characteristics of the final product and production cost. The effects of different treatments (conventional-thermal, microwave, ohmic heating, pressure-based-treatments, pulsed electric field, ultrasound, gamma irradiation, UV-light, addition of components, and ozone application) applied to fruit juice/nectar/puree on some rheological properties of products were systematically summarized with this review. Also, the general effect of each individual thermal or non-thermal thermal technology on rheological properties and the causes of these changes were discussed. The effect of ultrasound on the rheological properties changes during treatment time in many juices, while viscosities of juices increase after most pressure based treatments. Although the matrix or even fruit cultivar significantly effects the change of rheological parameters after the treatments, some treatments have affected the particular rheological properties of fruit juice/nectar/puree similarly to pressure-based treatments. Novelty Impact Statement The review reveals the relationship between thermal/non-thermal processing and rheological properties of different fruit/vegetable products (juice, nectar, puree), and gives ideas, especially to process designers, and also points out the chance to reduce cost of processing. While the viscosity changes during the ultrasound process, the effect of ultrasound on juice/puree viscosity after treatment cannot be generalized to all fruits and vegetables. On the oher hand, pressure-based technologies generally increase the viscosity of juice.