Watercored Apples Research Articles

Identification of apple watercore based on ConvNeXt and Vis/NIR spectra

This paper proposes a method for discriminating between normal apples and watercore apples using visible/near-infrared spectroscopy technology, which combines Gramian Angular Fields (GAF) encoding technology and the ConvNeXt deep learning network. The existing feature extraction methods for visible/near-infrared spectroscopy data do not perform deeper information mining on the extracted features, which results in the quality of the established model being entirely determined by the extracted features. Additionally, the process of building a visible/near-infrared spectroscopy data classification model is complex and time-consuming, and the accuracy of the established model is not high. To address these issues, the experimental visible/near-infrared spectroscopy data of apples was first transformed into two-dimensional images using Gramian Angular Summation Fields (GASF) and Gramian Angular Difference Fields (GADF) with sizes of 64, 128, 256, and 512. These images were then input into the ConvNeXt network, and the performance of different encoding methods and sizes was compared. The results showed that, under the conditions provided in this paper, the GADF encoding method with a size of 256 achieved the highest classification accuracy of 98.48%. Next, ResNet, EfficientNet, and RegNet deep learning networks were selected to classify the encoded images under the same conditions. The results above indicate that the apple variety discrimination method based on GAF encoding technology and ConvNeXt network combined with visible/near-infrared spectroscopy technology can achieve deep information mining of visible/near-infrared spectroscopy data and provide a relatively simple method for establishing qualitative classification models of visible/near-infrared spectroscopy. This method has a relatively excellent discrimination effect between normal apples and watercore apples.

Heat shock pretreatment and low temperature fluctuation cold storage maintains flesh quality and retards watercore dissipation of watercored 'Fuji' apples

Watercored apples have a unique flavor and particular flesh morphology. However, watercored apples are subject to loss of water core, browning, and softening during postharvest storage. In this study, heat shock pretreatment, hot air (HA) or hot water (HW), was combined with low temperature fluctuation (LTF) cold storage to delay the disappearance of the water cores and the flesh browning and softening during a 120 d storage. The apples were evaluated for appearance characteristics, texture parameters, enzyme activities, reactive oxygen content, membrane lipid oxidation degree, tissue microstructure, and cell morphology during the storage period. The results showed that HW combined with LTF was most effective in maintaining the visual quality and texture quality of watercored apples compared with other treatments and the control. Moreover, HW-LTF could effectively inhibit the accumulation of malondialdehyde (MDA), retard the increase of electrolyte leakage (EL), reduce the membrane lipid peroxidation, and maintain the tissue microstructure and cell morphology. Meanwhile, HW-LTF inhibited the activities of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) and reduced the degree of flesh browning. Therefore, the HW-LTF is of guiding significance for the cold storage of watercored apples.

Establishment of a multi-position general model for evaluation of watercore and soluble solid content in ‘Fuji’ apples using on-line full-transmittance visible and near infrared spectroscopy

Watercore and soluble solid content (SSC) are important indicators for assessment of the internal quality of apples. Visible and near infrared spectroscopy (Vis-NIRS) has been successfully applied for on-line analysis of internal quality of apples. In practical application, the position of the detected apples is usually uncertain, which limits the effective application of traditional model developed based on the fixed position or the optimal position. This study established a multi-position general model for evaluation of watercore and SSC in ‘Fuji’ apples using on-line Vis-NIRS. First, the full-transmittance spectra of three positions (P1–P3) of each apple were acquired, and subsequently, LS-SVM and PLS-DA models were constructed based on full wavelength data of single and multiple positions for watercore classification, and LS-SVM and PLS models were also constructed based on the same data for the quantitative prediction of SSC. Then, the detection ability of the constructed single position and the multi-position general models for three independent position samples was compared to determine the optimal full wavelength models; Finally, different wavelength selection algorithms including MC-UVE, BOSS, SPA and their combinations were employed to optimize the full wavelength models. Results showed that the multi-position general MC-UVE-SPA-PLS-DA model was the optimal for classification of watercore apples with average accuracy of 95.96 %, and the multi-position general MC-UV-BOSS-LS-SVM model was the optimal for quantitative detection of SSC with RP of 0.856 and RMSEP of 0.723 %. The overall study revealed that the multi-position general model, combined with full-transmittance Vis-NIRS, was a better choice for on-line detection of watercore and SSC in ‘Fuji’ apples.

Ongoings in the apple watercore: First evidence from proteomic and metabolomic analysis

The presence of watercored fruit with translucent mesocarp has attracted immense attention due to its unique morphology and taste, however, the metabolic reconstruction between watercored and non-watercored tissues remain elusive. Herein, the combined proteomic and metabolomic approach was carried out to characterize the protein abundance and metabolic profile in watercored apple. Results demonstrated that carbohydrate metabolism was prioritized enriched in watercored apple, including highly accumulated sucrose and sugar alcohols, and the increased level of transcription factor WHIRLY2 (WHY2), which is required in sugar reallocation. More than 50% overlap of differently abundant proteins involved in calcium ion binding, starch and sucrose metabolism implied the involvement of calcium signaling in watercore development. Moreover, significantly lower calcium content was detected in watercored apples. Sucrose synthase (SUSY) protein, which is involved both in calcium ion binding and sugar metabolism, was the potential basis of apple watercore development, which provided a likely candidate in regulation of apparent quality.

Online analysis of watercore apples by considering different speeds and orientations based on Vis/NIR full-transmittance spectroscopy

Watercore is a common internal disorder of ‘Fuji’ apples, which affects the quality and price of fruit. Moreover, the flesh of watercore apples is prone to browning during storage, resulting in a loss of commercial value. However, the online detection of watercore apples is very difficult in actual production due to the interference of many factors. In this study, visible and near infrared (Vis/NIR) full-transmittance spectroscopy (680-1000 nm) was used to online analyze watercore apples. Three different detection orientations (O1, O2 and O3) and speeds (S1, S2 and S3) were compared in detail. In order to determine the optimal detection speed and orientation, the partial least square discriminant analysis (PLS-DA) and least squares-support vector machine (LS-SVM) models were established based on the preprocessing spectra of Savitzky-Golay smoothing and standard normal variate (SGS-SNV). The results showed that S2 speed (0.5 m/s) and O3 orientation (apple stem-calyx axis horizontal and parallel to the moving direction of conveyor belt) were the most suitable for detection of watercore apples. A combination algorithm (MC-UVE-SPA) of Monte Carlo-uninformative variable elimination (MC-UVE) and successive projections algorithm (SPA) was used to select effective wavelengths for classification of watercore apples and quantitative prediction of watercore degree. MC-UVE-SPA-PLS-DA and MC-UVE-SPA-LS-SVM models established based on effective wavelengths obtained the same classification performance with the success rates of 100 % and 96.87 % for healthy and watercore apples, respectively. In order to predict the watercore degree of apples, the partial least squares (PLS), multiple linear regression (MLR) and LS-SVM models were established based on spectra obtained S2 speed and O3 orientation. MC-UVE-SPA-LS-SVM model coupled with eight effective wavelengths obtained the optimal prediction accuracy of watercore degree with 0.93 of RP and 2.12 % of RMSEP. The overall results indicated that online detection of watercore apples based on Vis/NIR full-transmittance spectroscopy was feasible, and the classification accuracy was related to the detection speed and the sample orientation. In addition, the results also showed that the LS-SVM model has good performance for classification of watercore apples and quantitative evaluation of watercore degree.

Online Detection of Watercore Apples by Vis/NIR Full-Transmittance Spectroscopy Coupled with ANOVA Method.

Watercore is an internal physiological disorder affecting the quality and price of apples. Rapid and non-destructive detection of watercore is of great significance to improve the commercial value of apples. In this study, the visible and near infrared (Vis/NIR) full-transmittance spectroscopy combined with analysis of variance (ANOVA) method was used for online detection of watercore apples. At the speed of 0.5 m/s, the effects of three different orientations (O1, O2, and O3) on the discrimination results of watercore apples were evaluated, respectively. It was found that O3 orientation was the most suitable for detecting watercore apples. One-way ANOVA was used to select the characteristic wavelengths. The least squares-support vector machine (LS-SVM) model with two characteristic wavelengths obtained good performance with the success rates of 96.87% and 100% for watercore and healthy apples, respectively. In addition, full-spectrum data was also utilized to determine the optimal two-band ratio for the discrimination of watercore apples by ANOVA method. Study showed that the threshold discrimination model established based on O3 orientation had the same detection accuracy as the optimal LS-SVM model for samples in the prediction set. Overall, full-transmittance spectroscopy combined with the ANOVA method was feasible to online detect watercore apples, and the threshold discrimination model based on two-band ratio showed great potential for detection of watercore apples.

Direct evidence for dynamics of cell heterogeneity in watercored apples: turgor-associated metabolic modifications and within-fruit water potential gradient unveiled by single-cell analyses

Watercore is a physiological disorder in apple (Malus × domestica Borkh.) fruits that appears as water-soaked tissues adjacent to the vascular core, although there is little information on what exactly occurs at cell level in the watercored apples, particularly from the viewpoint of cell water relations. By combining picolitre pressure-probe electrospray-ionization mass spectrometry (picoPPESI-MS) with freezing point osmometry and vapor pressure osmometry, changes in cell water status and metabolisms were spatially assayed in the same fruit. In the watercored fruit, total soluble solid was lower in the watercore region than the normal outer parenchyma region, but there was no spatial difference in the osmotic potentials determined with freezing point osmometry. Importantly, a disagreement between the osmotic potentials determined with two methods has been observed in the watercore region, indicating the presence of significant volatile compounds in the cellular fluids collected. In the watercored fruit, cell turgor varied across flesh, and a steeper water potential gradient has been established from the normal outer parenchyma region to the watercore region, retaining the potential to transport water to the watercore region. Site-specific analysis using picoPPESI-MS revealed that together with a reduction in turgor, remarkable metabolic modifications through fermentation have occurred at the border, inducing greater production of watercore-related volatile compounds, such as alcohols and esters, compared with other regions. Because alcohols including ethanol have low reflection coefficients, it is very likely that these molecules would have rapidly penetrated membranes to accumulate in apoplast to fill. In addition to the water potential gradient detected here, this would physically contribute to the appearance with high tissue transparency and changes in colour differences. Therefore, it is concluded that these spatial changes in cell water relations are closely associated with watercore symptoms as well as with metabolic alterations.

Chitosan films incorporating litchi peel extract and titanium dioxide nanoparticles and their application as coatings on watercored apples

Nano-titanium dioxide (nano-TiO2) and litchi peel extract (LPE) were added to chitosan (CS) matrix to develop a novel active packaging film and watercored apple coating. The addition of nano-TiO2 and/or LPE enhanced mechanical strength, water vapor barrier properties, and thermal stability of CS-based films. The total phenolic content and antioxidant capacity of the films were enhanced by LPE incorporation. Viscosity and wettability of the coating solutions and their impact on the storage quality of watercored Fuji apples at 0 ± 1℃ for 180 d were investigated. Coating treatment significantly inhibited respiration rate, weight loss, and softening. Polyphenol oxidase activity, electrolyte leakage and malondialdehyde accumulation were inhibited by coating treatment. A CS + TiO2+LPE coating was the most effective treatment for maintaining cold storage quality of watercored apples. This combination presents promising applications as an active food packaging film and fruit preservation coating.

Effect of pulsed controlled atmosphere with CO2 on the quality of watercored apple during storage

Watercored 'Fuji' apple with special water core and unique flavor is a characteristic fruit. However, the problems of water core disappearance and browning in the apples are outstanding during postharvest storage. In this study, pulsed controlled atmosphere (pCA) with CO2 was used to protect the water-core and resist browning of apples. Effects of different concentrations of CO2 on the quality of apple fruits was investigated, and CO2 injury characteristic to apple fruits were studied as well. Results showed that pCA with CO2 could effectively maintain the sensory and texture qualities of watercored apples. Treated with pulsed controlled CO2, the degree of membrane lipid peroxidation of the apples was effectively reduced and the membrane system was well maintained. Meanwhile, the activity of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) of the apples were inhibited and the browning was reduced. On the whole, pCA with 1% CO2 presented the most significant effects on the quality preservation of watercored apples while higher CO2 showed negative effects on the quality of the samples. Under the condition of pCA with 5% CO2, the endurance of watercored apples was less than 45 days and the internal browning was serious. In conclusion, 2%～3% O2 and pCA with 1% CO2 was the best and most effective in the long-term preservation of watercored apples, and it is beneficial to guide for the preservation of apple fruits.

Flavor and Texture Characteristics of 'Fuji' and Related Apple (Malus domestica L.) Cultivars, Focusing on the Rich Watercore.

Watercore is a so-called physiological disorder of apple (Malus domestica L.) that commonly occurs in several well-known cultivars. It is associated with a rapid softening of the flesh that causes a marked changed in flavor and texture. In Asia, apples with watercore are preferred and considered a delicacy because of their enhanced sweet flavor. The ‘Fuji’ cultivar, the first cultivar with rich watercore that is free from texture deterioration, has played a key role in the development of the market for desirable watercored apples. This review aimed to summarize and highlight recent studies related to the physiology of watercore in apples with special focus on ‘Fuji’ and related cultivars.

みつ入り果の香気を再現したエチルエステル類添加リンゴ加工品の官能特性

みつ入り果の香気を再現したエチルエステル類添加リンゴ加工品の官能特性

Comparison of the sub-cellular compartmentation of sugars in mature apples of two cultivars susceptible to different types of watercore and grown in different climates

SummaryThe cellular compartmentation of sugars was compared between mature ‘Orin’ and ‘Fuji’ apple fruit (Malus × domestica Borkh.) which are susceptible to early and late watercore, respectively. Fruit were grown in a warmer climate (Ehime) and in a cooler climate (Aomori). Slight watercore, with a score of 1.4 (i.e., a remaining trace of early watercore), was detected in ‘Orin’ at Ehime, whereas severe late watercore, with a score of 3.0, was observed in ‘Fuji’ at Aomori. Sorbitol contents were significantly higher in watercored fruit than in non-watercored apples, not only in the intercellular spaces, but also in the cytoplasm and vacuoles, irrespective of the type of watercore. The permeability of the tonoplast to sorbitol was higher in watercored fruit than in non-watercored fruit in both cultivars, while a lower permeability of the plasma membrane to sorbitol was observed in watercored apples. Late watercore, which affected ‘Fuji’ at Aomori, showed similar levels of sorbitol to early watercore in ‘Orin’ at Ehime, despite the significantly higher watercore score in ‘Fuji’, suggesting that sorbitol may play only a minor role as a causative agent in the development of late (or low temperature-promoted) watercore compared with early (or high temperature-induced) watercore.

Cellular compartmentation and membrane permeability to sugars in relation to early or high temperature-induced watercore in apples

Early watercore was observed in apples ( Malus domestica Borkh.) from the outer canopy of ‘Orin’, an early watercore susceptible cultivar, while there was no watercore in ‘Orin’ fruit from the inner canopy and resistant ‘Fuji’. Sorbitol content was higher not only in the free space but also in the vacuole and cytoplasm in watercored ‘Orin’ than in other non-watercored fruit. Comparing watercored apples to non-watercored fruit of ‘Orin’, higher fructose and glucose in the vacuole and no significant difference in the distribution rate of sorbitol to each compartment were observed. Watercored ‘Orin’ apples showed significantly higher permeability of tonoplast to fructose, glucose, and sorbitol than those in other non-watercored apples. The permeability of plasma membrane to each sugar was much higher than that of tonoplast but no marked difference was observed among the treatments. The results suggest that metabolism of sorbitol could be active even in watercored ‘Orin’ apples and the accumulated sorbitol in the intercellular spaces might be primarily due to an active unloading from the phloem and not be brought by increased leakage from the cells.

Seasonal changes in cellular compartmentation and membrane permeability to sugars in relation to early or high temperature-induced watercore in ‘Orin’ apples

SummaryThe intensity of watercore in ‘Orin’ apples (Malus domestica Borkh.) from the outer canopy increased from early-July to mid-August, followed by a decrease through late-October, while no watercore was detected in inner canopy fruit during the same period. Seasonal changes in sorbitol content in each cellular compartment paralleled the development of watercore. Significantly higher sorbitol, fructose and glucose contents in the vacuoles of cells in outer canopy fruit than in inner canopy fruit suggest that active metabolism and uptake of sorbitol might occur in watercored apples in mid-August. The permeability of sorbitol across the tonoplast was significantly higher in outer than in inner canopy fruit after mid-August, whereas no difference was observed between bearing position for the other sugars or for the plasma membrane. These data suggest that elevated sorbitol levels in the intercellular spaces might result from active apoplastic unloading and not from an inhibition of metabolism and/or an increase in leakage from cells.

AN OPTICAL METHOD FOR DETECTING WATERCORE AND MEALINESS IN APPLES

Spectral reflection in the wavebands between 600 and 1100 nm was tested for its ability to classify applesaccording to the presence of watercore and mealiness. A model developed by partial least squares (PLS) regression using four,10 nm wide wavebands at 690, 700, 820, and 830 nm separated watercore and normal apples with an error of 4%. It was foundthat watercore could only be detected shortly after the apples were harvested. Classification of the watercore apples intoslight, moderate, and severe categories may be possible if models are based on a higher number of samples. Mealy applescould be detected from normal and watercore apples in all cases using the reflectance in the 1020, 1040, 1050, and 1095 nmwavebands. Attempts to measure the degree of mealiness, based on spectral reflection, provided no useful results.

APPLE WATERCORE SORTING SYSTEM USING X-RAY IMAGERY: I. ALGORITHM DEVELOPMENT

Watercore is an internal disorder that leads to breakdown of tissue and possibly loss or downgrade of theproduct. It is very difficult to determine whether an apple contains watercore or not, especially in the early stages, basedsolely on external information, since watercore does not alter external texture until after severe internal breakdown. Inthis study, we explored the possibility of using two-dimensional (2-D) X-ray imaging to detect internal watercore damagein apples. The algorithm to detect Red Delicious watercore apples consists of two stages, the first stage extracts featuresfrom the apple x-ray image and the second stage categorizes apples into different watercore levels using the featuresidentified. A total of eight features were extracted from an x-ray scanned apple image and these features were fed intoneural network classifier to categorize them into three different classes, clean, mild, and severe. The results showed thatthe system was able to correctly recognize apples into clean and severe categories within 5-8% false positive and negativeratios. The result also showed that the algorithm was able to recognize apples independent of apple orientation, but onlyif the stem-calyx axis made a fixed angle with the x-ray beam. Sorting at random apple orientation was not tested. Theestimated speed of the system, if implemented on a DSP board, will be fast enough to keep up with the current appleprocessing line.

HYDRAULIC SORTING OF WATERCORE APPLES

The presence of watercore in apples occurs significantly about one out of every three years in Washington State. It is desirable to separate fruit that are affected from those that are not, since moderately to severely affected fruit cannot be successfully stored for an extended period. The lack of a practical method to separate fruit with watercore from those without leads to the untimely marketing of fruit that otherwise could have been placed into long term storage. This paper presents the results of our research on development of a high volume separation device, compatible with existing apple packing lines. The prototype device creates a region of controlled lower density fluid through which fruit passes and in which the fruit is separated. The prototype correctly separated 100% of fruit that were moderately or severely affected (specific gravities equal to or greater than 0.90) from those that were less affected, irrespective of fruit size. Fruit that were less than moderately affected (specific gravities between 0.90 and 0.88) were separated from those with slight or no watercore with 80-90% accuracy, depending on fruit size. The blind test used 245 'Red Delicious' apples that were sorted under 5 conditions with 3 replications each (n = 3,675).

INFLUENCE OF PRE-STORAGE TREATMENTS ON THE MORTALITY OF THE SAN JOSÉ SCALE (HOMOPTERA: DIASPIDIDAE) ON APPLES HELD IN STORAGE

AbstractThe pre-storage treatment of fruit with either an antiscald inhibitor or an alcohol solution for segregating water core apples, increased the rate of mortality of the San José scale, Aspidiotus perniciosus Comstock, on Winesap apples held in storage.The dewaxing and waxing process had little effect on the mortality of the San José scale. The process mechanically removed the scale from the cheeks and shoulders of stored apples but not from the calyx and stem ends.

NOTE ON A FLOTATION METHOD FOR SEGREGATION OF WATER CORE APPLES

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