Cloud stability of sour orange juice as affected by pectin methylesterase during come up time: Approached through fractal dimension

Cloud stability of the juice is affected by pectin methylesterase (PME) activity. Come up time (CUT) of thermal treatment showed inactivation effect on PME. In this study, lacunarity and fractal dimension (FD) were used to evaluate the effect of CUT on PME activity and appearance of the sour orange juice. The CUT lasted 2.68, 2.58, 2.51, 2.46, 2.43, 2.33, and 2.28 min at 60, 65, 70, 75, 80, 85, and 90°C, respectively. The fractal dimension and lacunarity were estimated using the box counting method. PME activity, cloud value and lightness were measured according to Kimball, spectroscopy methods, and image processing, respectively. Higher PME inactivation and cloud value and lower lightness of the juice were obtained at a higher temperature. FD showed a high correlation with changes in PME activity, cloud, and lightness of the juice. Lacunarity was used to describe the shape and gap distribution within the image. As the combination of FD and lacunarity was useful in the study of the image, these factors could be applied to evaluate the effect of CUT on some of the physical and chemical properties of fruit juice.