Fractal Dimension and Mechanism of Aggregation of Apple Juice Particles

Abstract

Turbidity of freshly squeezed apple juice is produced by a polydisperse suspension of particles coming from the cellular tissue. After precipitation of coarse particles by gravity, only fine-colloidal particles remain in suspension. Aggregation of colloidal particles leads to the formation of fractal structures. The fractal dimension is a measure of the internal density of these aggregates and depends on their mechanism of aggregation. Digitized images of primary particles and aggregates of depectinized, diafiltered cloudy apple juice were obtained by scanning electron microscopy (SEM). Average radius of the primary particles was found to be a = 40 ± 11 nm. Maximum radius of the aggregates, R(L), ranged between 250 and 7750 nm. Fractal dimension of the aggregates was determined by analyzing SEM images with the variogram method, obtaining an average value of D(f) = 2.3 ± 0.1. This value is typical of aggregates formed by rapid flocculation or diffusion limited aggregation. Diafiltration process was found to reduce the average size and polydispersity of the aggregates, determined by photon correlation spectroscopy. Average gyration radius of the aggregates before juice diafiltration was found to be R(g) = 629 ± 87 nm. Average number of primary particles per aggregate was calculated to be N = 1174.

Effects of silica gel on reduction in gluten during several beer brewing stages

“…Twenty different SEM images of SG aggregates were subjected to the FERImage program which calculates fractal dimension ( D f ) by means of a variogram and a Fourier power spectrum (Bianchi & Bonetto, ). The methodology described was previously used with aggregates of apple juice (Benítez et al ., ) and beer (Benítez et al ., ).…”

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

“…[4,6] Unlike citrus juice, in apple juice suspended cloud particles should be removed to make a clear juice by different methods like enzyme clarification. [29,41] It was reported that the aggregation of cloud particles took place immediately after pectin de-esterification by adding pectolytic enzymes to the turbid apple juice. [29] It was also mentioned that a de-esterified colloid particle diffuses until it meets another particle to create a 'fractile cluster' or an 'island structure' or joins an existing island to extend it.…”

“…[29,41] It was reported that the aggregation of cloud particles took place immediately after pectin de-esterification by adding pectolytic enzymes to the turbid apple juice. [29] It was also mentioned that a de-esterified colloid particle diffuses until it meets another particle to create a 'fractile cluster' or an 'island structure' or joins an existing island to extend it. This island structure is in agreement with self-similarity properties of a fractal structure.…”

“…This island structure is in agreement with self-similarity properties of a fractal structure. [29,41] It was found that the L*-value and the FD reduced as the temperature increased. Lightness had a direct relation with PME activity (Fig.…”

“…[20][21][22]27,28] The formed fractal structures by aggregation of colloidal particles were also applied to understanding the structure, aggregation, and stability of particles that are responsible for the cloudy appearance of apple juice. [29] FD and lacunarity were studied to evaluate the structural changes in quality of the fresh papaya sliced during environmental conditions. [30] Rising in FD and reduction in lacunarity were found due to exposure of the sliced papaya to environmental conditions and breakdown of tissue after cutting the fruit which resulted in physicochemical changes such as carotene stability reduction.…”