Fractal analysis of the retrogradation of rice starch by digital image processing

Optical Anisotropy and Dimple Formation on Films Formed after Drying of Gelatinized Starch Solution Droplets

We study the microstructures in the drying droplets of gelatinized starch solutions on a flat substrate. Cryogenic scanning electron microscopy studies on the vertical cross-section of these drying droplets for the first time reveal a relatively thinner solid elastic crust of uniform thickness at the free surface, an intermediate mesh region below the crust, and an inner core of a cellular network structure made of starch nanoparticles. We find that the deposited circular films formed after drying are birefringent and azimuthally symmetric with a dimple at their center. We propose that the dimple formation in our sample occurs due to the evaporation-induced stress on the gel network structure in the drying droplet. The polarizing optical microscopic studies show that these films are optically uniaxial at their center and increasingly biaxial away from the center.

An Automated Image Processing Module for Quality Evaluation of Milled Rice

The paper demonstrates a low-cost rice quality assessment system based on image processing and machine learning (ML) algorithms. A Raspberry-Pi based image acquisition module was developed to extract the structural and geometric features from 3081 images of eight different varieties of rice grains. Based on features such as perimeter, area, solidity, roundness, compactness, and shape factor, an automatic identification system is developed to segment the grains based on their types and classify them by using seven machine learning algorithms. These ML models are trained using the images and are compared using different ML models. ROC curves are plotted for each model for quantitative analysis to assess the model’s performance. It is concluded that the random forest classifier presents an accuracy of 77 percent and is the best-performing model for the classification of rice varieties. Furthermore, the same algorithm is efficiently employed to determine the price of adulterated rice samples based upon the market price of individual rice.

New insights into the alleviating role of starch derivatives on dough quality deterioration caused by freeze

The alleviating role of starch derivatives on the quality deterioration of frozen steamed bread dough was investigated in terms of derivative structure, the bread characteristics and dough properties including freezable water contents, yeast activity as well as dough viscoelasticity. The addition of starch derivatives including short-clustered maltodextrin (SCMD), DE2 maltodextrin (MD) and pregelatinized starch (PGS) significantly increased the specific volume and decreased the hardness of steamed bread compared with Control bread after 8-week frozen storage. Lower freezable water content was found in PGS dough than SCMD dough, which was consistent with the results of water absorption index of starch derivatives. The analysis of dough gassing rate and yeast survival ratio demonstrated SCMD could provide more cryoprotection for yeast cells. Meanwhile, a higher elastic module and a more continuous gluten-network structure of SCMD dough were found after 8-week frozen storage. These results indicated starch derivatives especially SCMD were promising to be used as the alternative improvers in frozen dough production.

Effects of Microwave Vacuum Drying on Macroscopic Properties and Microstructure of Lotus (Nelumbo nucifera Gaertn.) Seeds

The structural characteristics of lotus (Nelumbo nuciferaGaertn.) seeds preserved by microwave vacuum drying (MVD) were investigated under various drying parameters, including microwave power density and vacuum degree. Dried lotus seeds were examined for microstructure by field emission scanning electron microscopy. Fractal dimension of the microscopic images was calculated by the box counting method. The apparent physical changes of the seeds, namely shrinkage ratio, rehydration rate, and hardness index, were determined to correlate well with their microstructural changes computed by the normalized changes of the fractal dimension (ΔFD/FD0). The samples at −90 kPa, 15 W/g exhibited a lower shrinkage ratio (46.2 %), higher rehydration rate (187.5 %) and lower hardness (3692.4 N). Although the physical and microstructural changes of the samples prepared by different drying methods (MVD, microwave drying, and hot air drying) varied, the changes of the ΔFD/FD0of the dried samples exhibited the same trends.