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- Author or Editor: Christopher Ference x
Visible/near-infrared (VIS/NIR) spectroscopy is a powerful tool for rapid, nondestructive fruit quality detection. This technology has been widely applied for quality detection of small thin-peel fruit, although less so for large thick-peel fruit because of the low signal-to-noise ratio of the spectral signal, resulting in a reduction of accuracy. More modeling work should be focused on solving this problem. This research explored a method of spectroscopy for the total soluble solid (TSS) content and acidity detection of ‘Shatian’ pomelo, which are two major parameters of fruit internal flavor. VIS/NIR spectral signal detection of 100 pomelo samples during storage was performed. Detection based on raw data, signal jitter, and scattered light noise removal, feature extraction, and deep learning were performed and combined with modeling detection to achieve an accurate step-by-step detection. Our results showed that 600 W is the optimal light intensity for detecting the internal flavor of pomelo. The TSS content of pomelo is optimally detected using Savitzky-Golay (SG) + multiplicative scatter correction (MSC) + genetic algorithm (GA) + principal component analysis (PCA) + convolutional neural network (CNN) + partial least squares regression (PLSR); however, acidity of pomelo is optimally detected using SG + MSC + GA + PLSR. With the optimal detection method, the coefficient of determination and root mean squared error (RMSE) of the validation set for TSS detection are 0.72 and 0.49, respectively; and for acidity detection are 0.55 and 0.10, respectively. Even though the accuracy is not high, the data are still acceptable and helpful in nondestructive quality grading of large quantities postharvest fruit. Therefore, our results demonstrated that VIS/NIR was feasible for detecting the TSS content and acidity of postharvest pomelo, and for providing a possible method for the nondestructive internal quality detection of other large thick-peel fruit.
‘Mopan’ persimmon (Diospyros kaki Thunb.) is a traditional astringent cultivar of persimmon and ‘Yoho’ persimmon (D. kaki) is a newly introduced Japanese nonastringent type of cultivar in northern China. Studies were conducted to investigate the physiological changes and expression of ripening-related genes in the postharvest process at different periods under the effects of endogenous ethylene in both cultivars. Persimmons were harvested and stored under room temperature for 20 days. An analysis of physiological changes showed significant differences between the two cultivars. Total soluble solids declined in ‘Mopan’ fruit, whereas those in ‘Yoho’ fruit increased during storage. Firmness, color, index of absorbance difference, total and soluble tannin contents, ethylene production, and respiration rates showed the same trend, but these values vary by cultivar. ‘Mopan’ fruit softened rapidly after harvest and attained edible quality in 20 days, with an increased rate of softening accompanied by increased expression of ripening-related genes. In contract, ‘Yoho’ fruit softening occurred slowly and did not soften even after 20 days, with minimal accumulation of the ripening-related genes. The information obtained from this study demonstrates that cell wall-hydrolyzing enzymes, the de-astringent process, and endogenous ethylene have critical roles in postharvest ripening, gene expression, and physiological property changes of ‘Mopan’ and ‘Yoho’ persimmon fruit during storage.
Coatings are generally applied to fruit as microemulsions, but nanoemulsions are still experimental. ‘Nova’ mandarins (Citrus reticulata) were coated with shellac or carnauba (Copernica cerifera) microemulsions or an experimental carnauba nanoemulsion; these were compared with an uncoated control during storage for 7 days at 20 °C. Coatings were also tested on ‘Unique’ tangors (C. reticulata × C. sinensis) stored for 14 days at 10 °C followed by a simulated marketing period of 7 days at 20 °C. Fruit quality evaluations included weight loss, gloss, soluble solids (SS), titratable acidity (TA), pH, SS/TA ratio, internal CO2, O2, fruit juice ethanol, and other aroma volatile content. Sensory visual shine and tangerine (C. reticulata) flavor rank tests after storage were conducted, followed by an off-flavor rating. The carnauba waxes resulted in less weight loss compared with the uncoated control and shellac coating during both experiments. There were no differences in gloss measurements of ‘Nova’ mandarins; however, shellac-coated fruit ranked highest for shine in a sensory test. For ‘Unique’ tangors, initially, shellac showed the highest gloss (shine) measurement; however, at the end of storage, the nanoemulsion exhibited the highest gloss, although it was not different from that of the microemulsion. Similarly, after storage, the nanoemulsion ranked highest for visual shine, although it was not different from that of the microemulsion. There were only minor differences in SS, TA, pH, and SS/TA among treatments. The internal CO2 gas concentration and juice ethanol content generally increased and internal O2 decreased during storage. The highest levels of CO2 and ethanol were found for the shellac treatment, as was the lowest O2, indicating anaerobic respiration. There were only minor differences among the other coating treatments; however, they were only sometimes different from those of the control, which generally had the highest O2, lowest CO2, and lowest ethanol. Shellac and the carnauba microemulsion also altered the volatile profile more than the control and the nanoemulsion did, especially for ‘Unique’ tangors. For ‘Unique’ tangors, the control and nanoemulsion ranked highest for tangerine flavor and had the least off-flavor at the end of storage. Among the coatings tested, the carnauba emulsions demonstrated less water loss, imparted more sustainable gloss, and caused less ethanol production than shellac, with the nanoemulsion exhibiting higher gloss measurements, less modifications of the atmosphere and volatile profile, and, consequently, better flavor compared with the microemulsion.
Fresh-cut mango (Mangifera indica) slices and chunks garner an exotic image and are highly appreciated for their unique flavor and nutritional value. However, processors tend to use firm unripe mangoes to achieve shelf life of 10 to 14 days, which compromises eating quality. The post-processing life of ripe fresh-cut mangoes is limited by tissue softening, translucency, and browning. The current study was undertaken to investigate whether edible coatings can extend the shelf life of fresh-cut mangoes processed at an eating-ripe stage. Three edible coatings, carboxymethylcellulose (1% w/v), aloe (Aloe vera) powder (2% w/v), and whey protein isolate (2% w/v), supplemented with calcium ascorbate 2% w/v (firming agent) and the antioxidants citric acid (0.8% w/v) and acetyl-N-cysteine (0.4% w/v), were used. The mixture of antibrowning agents, whether applied alone or with the edible coatings, was the most effective at reducing slice browning up to 10 and 11 days at 5 °C for ‘Tommy Atkins’ and ‘Kent’, respectively. In general, there were no differences in firmness and flavor among the three edible coatings. Calcium ascorbate alone did not suppress browning consistently, whereas citric acid appeared to be the ingredient having the greatest antibrowning effect on slice quality. Citric acid can easily be used by processors of fresh-cut mangoes to prevent browning.