Image analysis to evaluate the browning degree of banana (Musa spp.) peel

Detection of Alternaria alternata infection in winter jujubes based on optical properties and their correlation with internal quality parameters during storage

In this work, a single integrating sphere system was applied to characterize the optical absorption (μ_a) and reduced scattering (μ_s') properties (550 - 1050 nm) in winter jujube flesh infected by Alternaria alternata during storage at 4 and 20 °C, respectively. Meanwhile, physical (L*, a*, weight loss) and biochemical characteristics (soluble solids content, titratable acids, chlorophyll, total phenolic, and ascorbic acid) of winter jujubes were measured. Among them, chlorophyll, weight loss and ascorbic acid were highly correlated with μ_a at 680 nm, 690 nm, while chlorophyll and a* had the best correlations with μ_s' at 700 - 920 nm. These optimal optical properties were proved efficiently contributed to the disease detection of winter jujubes after 12 days at 4 °C and 3 days at 20 °C during storage, with satisfactory discrimination accuracies (acc > 93.75 %). Consequently, optical properties in Vis-NIR region were available to detect the postharvest disease in winter jujubes.

Quality Characteristics of Rice-Based Ice Creams with Different Amylose Contents

Ice cream consumption has increased over the years. In this study, we investigated the potential of using rice varieties with varying amylose contents for ice cream production. We analyzed the physical and chemical properties and sensory quality characteristics (appearance, taste, texture, chewiness, aroma, and rice flavor) of rice-based ice cream made from five varieties with low and high amylose levels. To make the ice cream, we ground rice into a fine powder and combined it with skim milk powder, butter, sugar, glycerin esters of fatty acids, locust bean gum, and water to form a gelatinized mixture. This mixture was then aged, frozen, and hardened. The ice cream’s key quality characteristics, such as viscosity (2170–25,030 cP), hardness (4.27–49.55 N cm−2), and overrun (17.95–46.99%), showed a wide range. Ice cream made from Saemimyeon (high amylose content rice variety) exhibited the highest hardness value (49.55 N cm−2) among the varieties tested, but had relatively low viscosity (4030 cP), overrun (17.95%), and drip-through (0.75 g/min) values. These findings suggest that rice varieties with different amylose contents are suitable for making ice cream and have the potential to expand the rice processing market and increase its value.

Development of active packaging with chitosan, guar gum and watermelon rind extract: Characterization, application and performance improvement mechanism

The objective of this study was to make a film matrix containing chitosan (CS) and guar gum (GG), and to improve the physicochemical properties of the film using watermelon rind extract (WRE) as a cross-linker and active substance for the preservation of fresh-cut bananas. The results of Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy showed that the WRE and CG matrix formed intermolecular hydrogen bond interactions, which made the structure of the resulting films more compact. With increasing amounts of WRE, the mechanical properties of the films were significantly increased, but the permeability of water vapor and oxygen was significantly decreased (p < 0.05). Notably, when the amount of extract reached 4 wt%, the DPPH radical scavenging activity of the composite film significantly increased to 83.24 %, and the antibacterial activity also reached its highest value. Fresh-cut bananas were stored at room temperature with polyethylene film, CG and CG-WRE. The CG with 4 wt% WRE effectively inhibited the changes in appearance, firmness, weight, color and total soluble solids content of fresh-cut bananas during storage. Therefore, CG-WRE as a novel active food packaging material, has good physicochemical properties and great potential to extend the shelf life of foods.

A novel Ag2O-TiO2-Bi2WO6/polyvinyl alcohol composite film with ethylene photocatalytic degradation performance towards banana preservation

In this research, the Ag₂O-TiO₂-Bi₂WO₆(ATB) ternary heterojunction photocatalyst was synthesized by hydrothermal and surface deposition method, and the ATB/PVA composite film with ethylene photocatalytic degradation performance was constructed by the casting method. The structure and properties of ATB and ATB/PVA films were characterized and applied to banana preservation. The results showed that the addition of ATB could improve the mechanical properties, thermal stability, oxygen and moisture resistance, and reduce the crystallinity and light transmittance of PVA films. Compared with TiO₂, Bi₂WO₆ and TB photocatalysts, ATB had the best photocatalytic degradation effect of ethylene under LED light. Compared with blank group, the ethylene concentration decreased by 17.17%. This was mainly attributed to the formation of heterostructure among Ag₂O, TiO₂ and Bi₂WO₆, which promoted the separation and transfer of photogenerated carriers. The ATB/PVA composite coating could effectively prevent the respiration of the bananas by inhibiting gas exchange and degrading ethylene, which reduced the weight loss, inhibited glycogen decomposition, improved the pulp hardness, increased titratable acid content, reduced the PPO activity, hindered the phenol oxidation and keep better apparent color of bananas. The safety study suggested that the ATB/PVA film is safe for bananas packaging application.

Study of color kinetics of banana (Musa cavendish) under microwave drying by application of image analysis

Microwave drying works on the volumetric heating concept promoted by electromagnetic radiation at 0.915 or 2.450 GHz. In this study, banana (Musa Cavendish) was taken as the sample and treated under microwave drying. The effect of two process variables, namely slice thickness (2, 3.5, and 5 mm) and microwave power (180 W, 360 W, and 540 W), were studied on drying kinetics and color kinetics. It was observed that the inverse variation relationship exists between drying time and microwave power level while drying time and slice thickness exhibited a direct variation relationship. A Computer Vision System (CVS) was developed to measure the color values of banana in CIELab space using an algorithm written in MATLAB software. Once the color parameters were obtained, they were fitted in First and Zero-order kinetic models. Both models were found to describe the color values adequately. This study concludes that microwave drying is a promising dehydration technique for banana drying that reduces the significant time of drying. Application of CVS is an excellent approach to measure the surface color of banana.

Assessment of the optical properties of peaches with fungal infection using spatially-resolved diffuse reflectance technique and their relationships with tissue structural and biochemical properties

This research measured the optical absorption (µ_a) and reduced scattering (μ_s') properties in peaches during quality deterioration, and determine the relationships of the optical parameters with select structural and biochemical parameters. Spatially resolved reflectance was measured for healthy and fungal infected peaches, followed by physical (the size and tissue color), structural [membrane permeability and SEM], and biochemical (Vc, soluble sugar, titratable acid, chlorophyll, total phenolic content) measurements. Both µ_a and µ_s' were correlated well with the cellulosic structural and biochemical parameters of peaches, and they had the best correlations with those quality parameters at 675 nm. The correlation of μ_s' with membrane permeability was the highest from -0.962-0.743, while μ_a had the best correlation with the chlorophyll content at 675 nm which is an indicator of plant maturation and senescence. These findings would be useful for further development of an effective optical technique for early disease detection of peach fruit.

Evaluation of gas holes in "Queijo de Nisa" PDO cheese using computer vision

"Queijo de Nisa" is a traditional Portuguese cheese, granted with PDO label, produced with raw ewe's milk in which the aqueous extract of cardoon flower Cynara cardunculus L. is the only coagulant allowed. As in similar cheeses with no use of starter cultures or pasteurisation, the quality and food safety are depending on prevention, high hygienic standards and a proper manufacturing process. This study investigated the use of computer vision as novel method for the evaluation of gas holes in Queijo de Nisa in three different ripening dates (0, 15 and 35 days). A total of 48 samples were produced using cardoon flower from three different origins (C1, C2 and C3) and a commercial vegetable coagulant (C4). The results presented a high correlation between image-dependent attributes and physical-chemical properties during ripening time, especially within the first 15 days of ripening time, where major structural changes were observed inside the Queijo de Nisa cheese. Principal component analysis presented a strong correlation (p < 0.05) between image parameters and the physical-chemical evolution until 15 days. From 15 to 35 days, the evolution of cheeses was mainly depending on structural parameters, like G'_1 Hz and hardness. No influence was observed due to the geographical origin of cardoon flower.

Evaluation of the Structure and Biological Activities of Condensed Tannins from Acanthus ilicifolius Linn and Their Effect on Fresh-Cut Fuji Apples

Condensed tannins (CT_S) have been isolated and purified from leaves of Acanthus ilicifolius Linn. And their structures were investigated by three methods: ¹³C nuclear magnetic resonance (¹³C NMR), reversed-phase high-performance liquid chromatography (RP-HPLC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The results showed that the CT_S were a mixture of catechin/epicatechin, galatechin/epicatechin, and amphicin/epigalin, and that the polymer chain lengths were 3-mers to 14-mers. Antityrosinase activities and antioxidant activities of the CT_S from A. ilicifolius leaves were further studied. The IC₅₀ of the CT_S on mushroom tyrosinase activity was determined to be 19.7 ± 0.13 μg/mL, and inhibition type analyses indicated that the CT_S were mixed type inhibitors and their inhibition CT_S was reversible. The CT_S from A. ilicifolius leaves also exhibited potential antioxidant activity. The IC₅₀ of DPPH and ABTS scavenging activities were 104 ± 0.894 μg/mL and 86 ± 0.616 μg/mL, respectively. And the FRAP value was 758.28 ± 2.42 mg AAE/g. In addition, we found that the CT_S from A. ilicifolius leaves had an excellent effect on preserving the quality of fresh-cut apples by preventing apples from browning through reducing polyphenol oxidase activities in apples.

Heat-induced tolerance to browning of fresh-cut lily bulbs (Lilium lancifolium Thunb.) under cold storage

Fresh-cut lily bulbs were submerged in hot water at 50°C for 3 min as a condition of heat treatment (HT), and then stored at 4°C for 15 days to investigate the effects of HT on browning. Results showed that heat-treated samples exhibited lower browning degree and had reduced cell death rate and cell membrane permeability when compared to control samples during storage. HT resulted in a significant inhibition in total phenol content and the activities of phenylalanine ammonialyase, polyphenol oxidase, and peroxidase. HT also stimulated the activities of superoxide dismutase and catalase, however, inhibited lipoxygenase activity and malondialdehyde accumulation. Correlation analysis showed that lipid peroxidation of cell membrane was significantly correlated with browning of fresh-cut lily bulbs. The results indicated that HT could serve as an effective approach to retard browning of fresh-cut lily bulbs. PRACTICAL APPLICATIONS: The effect of heat treatment (HT) on fresh-cut lily bulbs by treating in hot water (50°C) for 3 min was investigated. It provided experimental basis for further studies of HT in extending the shelf life of fresh-cut lily bulbs. Furthermore, it is a foundation for the application of HT in the processing of fresh-cut lily bulbs. The results suggested that HT could be a promising method to inhibit browning and sustain the quality of fresh-cut lily bulbs.

Evaluation of browning ratio in an image analysis of apple slices at different stages of instant controlled pressure drop-assisted hot-air drying (AD-DIC)

BACKGROUND

Computer vision-based image analysis systems are widely used in food processing to evaluate quality changes. They are able to objectively measure the surface colour of various products since, providing some obvious advantages with their objectivity and quantitative capabilities. In this study, a computer vision-based image analysis system was used to investigate the colour changes of apple slices dried by instant controlled pressure drop-assisted hot air drying (AD-DIC).

RESULTS

The CIE L* value and polyphenol oxidase activity in apple slices decreased during the entire drying process, whereas other colour indexes, including CIE a*, b*, ΔE and C* values, increased. The browning ratio calculated by image analysis increased during the drying process, and a sharp increment was observed for the DIC process. The change in 5-hydroxymethylfurfural (5-HMF) and fluorescent compounds (FIC) showed the same trend with browning ratio due to Maillard reaction. Moreover, the concentrations of 5-HMF and FIC both had a good quadratic correlation (R²  > 0.998) with the browning ratio.

CONCLUSION

Browning ratio was a reliable indicator of 5-HMF and FIC changes in apple slices during drying. The image analysis system could be used to monitor colour changes, 5-HMF and FIC in dehydrated apple slices during the AD-DIC process. © 2016 Society of Chemical Industry.

Keyframes Global Map Establishing Method for Robot Localization through Content-Based Image Matching

Self-localization and mapping are important for indoor mobile robot. We report a robust algorithm for map building and subsequent localization especially suited for indoor floor-cleaning robots. Common methods, for example, SLAM, can easily be kidnapped by colliding or disturbed by similar objects. Therefore, keyframes global map establishing method for robot localization in multiple rooms and corridors is needed. Content-based image matching is the core of this method. It is designed for the situation, by establishing keyframes containing both floor and distorted wall images. Image distortion, caused by robot view angle and movement, is analyzed and deduced. And an image matching solution is presented, consisting of extraction of overlap regions of keyframes extraction and overlap region rebuild through subblocks matching. For improving accuracy, ceiling points detecting and mismatching subblocks checking methods are incorporated. This matching method can process environment video effectively. In experiments, less than 5% frames are extracted as keyframes to build global map, which have large space distance and overlap each other. Through this method, robot can localize itself by matching its real-time vision frames with our keyframes map. Even with many similar objects/background in the environment or kidnapping robot, robot localization is achieved with position RMSE <0.5 m.