Non-destructive Evaluation of Bread Staling Using Gray Level Co-occurrence Matrices

Different methods for textural evaluation of freeze-dried candies during storage

The textural changes during storage of two freeze-dried candies developed from blackcurrant fruits, unflavored yogurt, and different alternative sweeteners, one sweetened with honey/isomalt (HI) and another sweetened with isomalt/stevia (IS), were analyzed using three different methods (instrumental, sensory, and image analysis). Fresh candies were in the supercooled state and presented different structural and textural characteristics (HI: compact and homogeneous, and IS: porous and crunchy), with Fmax values of 139 ± 14 and 174 ± 16 N for HI and IS, respectively. After storage, the instrumental analysis showed approximately 60% average drop in Fmax and W values, in agreement with the decrease observed by sensory analysis in hardness, fracturability, and crispness. Image analysis showed an increase in parameters related to the homogeneity and the uniformity/smoothness for HI. Pearson's correlation coefficients analysis showed that there was a good correlation between the three techniques used, suggesting that the joint use of these methods could be performed for a better understanding of complex food texture.

Image analysis-based quantification of the visual attributes of fish, with emphasis on color and visual texture

Images of Red Sea goatfish Parupeneus forsskali were taken in a light box to perform color and visual texture analyses. The average L* and b* values did not change significantly during storage of 7 days, but the a* values decreased (P < 0.05). The change of visual texture parameters energy and entropy (calculated based on histograms, and based on co-occurrence matrices [COM]), box counting-based fractal results, and texture change index (TCI) values are presented. The appearance of fish became “smoother” over time. The entropy values calculated by histograms decreased with storage (P < 0.05), and the maximum range was 0.395. That for COM-based entropies was 71.96. TCI also decreased with storage (P < 0.05) with a maximum range of 10.67. However, energy values increased during storage. The maximum range of the energy values calculated by histograms over time for any color channel was 0.0036. That for COM-based energies was 5.7. There was no observable change in fractal dimension. These image analysis-based parameters were compared with sensory analysis. A trained sensory panel evaluated the visual texture of a sub-set of images. The R2 values for equation fit between sensory score and texture features were, in increasing order: COM based energy (0.185), COM-based entropy (0.313), histogram-based energy (0.375), histogram-based entropy (0.386), TCI values (0.575). Since TCI correlated better with sensory values, it is recommended to be used in this type of visual texture evaluation.

Nondestructive evaluation of baking parameters on pogácsa texture

This study aimed to investigate the potential application of image texture processing method on visible crumb structure of salty cake pogácsa, which was prepared with different baking times (5 and 7 min) and temperatures (200, 215, and 230°C). For this purpose, changes in gray level co-occurrence matrix (GLCM) features including energy, contrast, correlation, homogeneity, and entropy were monitored and their relationship with the instrumental texture parameters (hardness, adhesiveness, cohesiveness, springiness, gumminess, and chewiness) were assessed. The pore ratios were also extracted and visualized using image processing technique. Texture profile parameters indicated strong correlation (p < .01) with the image pattern parameters in different pogácsa groups. Gumminess showed strong correlation with contrast (0.503), correlation (-0.498), and homogeneity (0.401). Hardness also exhibited correlation with contrast (0.517), entropy (0.341), and correlation (-0.476). The pore ratio showed marked variation in crumb structure when different times and temperatures were used. Baking at 230°C for 7 min maximized the pore ratio (0.56). Penalty analysis revealed that oiliness, pore structure, and color of products were linked with baking time and temperature. Overall, the results suggested that the GLCM-based technique had the potential to be used as a nondestructive method for rapid quality assessment of pogácsa.

Effect of potato flour on quality and staling properties of wheat-potato flour bread

To elucidate the impact of potato flour (PF) on quality changes and staling characteristics of the composite bread from wheat-potato flour (WPF), the physicochemical (specific volume, colority, sensory value, texture, and viscosity) properties, and staling (X-ray diffraction and water migration) properties of bread were investigated. The quality of composite bread was comparable to wheat bread when addition level of PF at 20%, but decreased when the addition level increased to 30% or more, and became unacceptable at 50%. A chewy mouthfeel and an elastic and none-crumbly texture were observed on composite bread, which had higher hardness than wheat bread, and could keep on both longer linear distance and higher linear force during compression test. It indicated that such new parameters other than hardness should be introduced to coordinate with the texture quality of composite bread. During storage, the higher addition level of PF significantly decreased crystallinity of composite bread and slowed water migration rate from the crumb to crust, suggesting that PF had antistaling effect on composite bread, which was further emphasized by the fact that the setback value of the WPF decreased with the increase of PF addition.