Fresh Jujube Research Articles

Study on the Metabolic Basis of the Color Formation of Two Color-Presenting Types of Jujube Fruits.

Jujube is a plant of the genus Ziziphus in the family Rhamnaceae; its fruit has high nutritional value, and it is rich in polyphenols, flavonoids, and other secondary metabolites. The color of its peel is an important indicator for evaluating the appearance of the fruit. However, the mechanism of the difference in color presentation between the seedling offspring of the 'Red Fruit' (TLHH) and the 'Green Fruit' (TLHL) of the fresh jujube cultivar 'Tailihong' is not clear. Therefore, this study used targeted metabolomics techniques to accurately and quantitatively analyze the metabolic pathways of carotenoid and anthocyanin metabolites during the ripening process of two color-presenting types of jujube fruits. Through the analysis of the dynamic changes in the pigment content of the jujube peel, it was found that 30 DAP (days after pollination), 80 DAP, and 110 DAP were the key periods for the development of the color of the peel of 'TLHL' and 'TLHH' jujube and that the substances responsible for the main differences were chlorophyll, carotenoids, and anthocyanins. Furthermore, we used an LC-MS/MS metabolic analysis to compare the differences in the carotenoids and anthocyanin metabolites between the two color-presenting types of jujube peels at the key periods of 30 DAP, 80 DAP, and 110 DAP. We detected 32 carotene metabolites and 75 anthocyanin metabolites, respectively, among which lutein had the highest content of carotenoids; it reached the maximum value (93.05 µg/g) and was higher than that of 'TLHH' (74.14 µg/g) at 30 DAP of 'TLHL'. Both showed a decreasing trend with fruit ripening. The anthocyanin with the highest content was cyanidin-3-O-(tartaryl)rhamnoside-5-O-glucoside, which reached the maximum value (258.32 µg/g) at 30 DAP of 'TLHH' and was 51.6 times that of 'TLHL'; similarly, both showed a decreasing trend with fruit ripening. These results elucidate the main metabolites of carotenoids and anthocyanins in the two types of jujube peel and their accumulation characteristics, suggesting that the key metabolites of the difference in color between 'TLHL' and 'TLHH' jujube fruits were lutein and cyanidin-3-O-(tartaryl)rhamnoside-5-O-glucoside, increasing the understanding of the color mechanism of jujube peel and providing a reference for targeted genetic breeding of jujube peel color.

Functional Nutrients and Jujube-Based Processed Products in Ziziphus jujuba.

Jujube (Ziziphus jujuba Mill.) is the first tree species in China, with a long history and abundant yield. However, fresh jujubes have a short shelf-life and are not resistant to storage. Therefore, more and more processed jujube products are being studied. These processed products can extend the shelf-life of jujubes and attract widespread attention for their rich functional nutrients. This review summarized changes in nutrients of fresh jujube and processed products and the research progress of different preparation methods of jujubes. Meanwhile, the pharmacological effects of bioactive components in jujube-based products were concluded. Jujube and its processed products contain rich polysaccharides, vitamin C, and other functional nutrients, which are beneficial to humans. As the initial processing method for jujubes, vacuum freezing or microwave drying have become the most commonly used and efficient drying methods. Additionally, processed jujube products cannot be separated from the maximum retention of nutrients and innovation of flavor. Fermentation is the main deep-processing method with broad development potential. In the future, chemical components and toxicological evaluation need to be combined with research to bring consumers higher quality functional jujube products and ensure the sustainable development of the jujube industry.

A grader for fresh jujube with electromagnetic synchronous actuator assembly

AbstractIn recent years, the post‐harvest commercialization of fresh jujube sorting technology is backward, the efficiency of manual grading is low, and the application of machine vision technology in fruit grading has been a research hotspot. To improve the grading accuracy and speed of the fresh jujube machine vision grading machine, this study designs a method of fresh jujube machine vision grading using an electromagnetic synchronous actuator. The grading machine consists of an automatic distribution and arrangement system, an image acquisition and processing system, and a synchronous actuator assembly, which uses a sensitive electromagnet to adsorb a silicon steel switching buckling plate to execute the action. The image processing process includes an image color component, Sobel operator filtering, Otsu method binarization, and ellipse fitting to extract the color and size eigenvalues. The experimental results show that the date images can be acquired quickly and processed accurately with a processing speed of 50 ms per frame. In addition, the proposed actuator can be sensitively triggered with a response time of 40 ms. The grader successfully classified jujube into five size classes and one color class. The grading accuracy and non‐destructive rate reached 93.7% and 100%, respectively. The grading efficiency is 20 jujubes per second, with a maximum production rate of 1400 kilograms per hour. This grading machine realizes the requirements of high accuracy, high speed, and non‐destructive grading of fresh jujube and provides an important technical and theoretical basis for the development of machine vision jujube rapid grading technology.Practical applicationsIn recent years, sorting technology in the post‐harvest commercialization of fruits has been outdated, and manual grading has been inefficient. The application of machine vision technology in fruit grading has been a research hotspot in recent years. This study designs a machine vision grading of fresh dates with an electromagnetic synchronous actuator. The grader was composed of a roller conveyor, synchronous actuator assembly, image main processor, and actuator controlling co‐processor. Experimental results indicated that jujube images could be acquired rapidly and processed accurately, with a processing speed of 50 ms per frame. In addition, the proposed actuator could be sensitively triggered with a response time of 40 ms. Finally, the grader successfully sorted jujubes into five size classes and one color class. The grading accuracy rate and non‐destructive rate reached 93.7% and 100%, respectively. The grading efficiency was 20 jujubes per second, and the maximum productivity was 1400 kg/h.

Detection of dried jujube from fresh jujube with different variety and maturity after hot air drying based on hyperspectral imaging technology

The consistent quality of dried jujube has a significant impact on its economic value and consumer acceptance. Currently, the evaluation of dried jujube quality heavily relies on agricultural experts and advanced instrument analysis, which is time costly and is limited by many uncertainties. This study aims to develop a rapid and accurate method for classifying dried jujube produced from fresh jujube at different stages of maturity using hyperspectral imaging. Dried jujube samples were collected from two varieties (Zhongyang Muzao jujube and Yuanling jujube) in Hebei Province, representing two maturity stages: Kimri and Rutab. Linear partial least squares-discriminant analysis (PLS-DA), K-Nearest Neighbor (KNN) and support vector machine (SVM)algorithms were combined with six pre-processing methods. the pretreatment spectra of Area Naturalization (AN), Baseline and Multiple scattering correction (MSC) were selected for further analysis. Successive projections algorithm (SPA), Competitive adaptive reweighted sampling （CARS）and Uninformative Variables Elimination (UVE)were combined to select characteristic variables. A total of 16 characteristic variables were selected by AN-UVE-SPA-SVM model. This model achieved the highest accuracies of 96.0 % and 93.1 % in the final discriminant accuracy for the calibration and Validation sets, respectively. The hardness, soluble solid content (SSC), and moisture of two categories of dried jujube derived from fresh jujube at various stages of maturity were analyzed. The results showed that dried jujube produced from fresh jujubes at the Rutab stage were more likely to exhibit characteristics of high SSC and low hardness' compared to those produced at the Kimri stage. The partial least squares regression (PLSR) model established based on characteristic wavelengths extracted by AN-UVE-SPA showed the best results in predicting SSC and moisture. This study showcased the feasibility of identifying and classifying dried jujube using hyperspectral imaging technology, laying a solid foundation for further research in the rapid non-destructive testing of dried fruits and vegetables through the application of hyperspectral technology.

Volatile Profile Characterization of Jujube Fruit via HS-SPME-GC/MS and Sensory Evaluation.

Current research does not fully elucidate the key compounds and their mechanisms that define the aroma profile of fresh jujube fruits. Therefore, this study conducted a comprehensive analysis of both free and glycosidically bound aroma compounds in fresh jujube fruits of ten cultivars. Utilizing gas chromatography-mass spectrometry (GC-MS), we identified 76 volatile free aroma compounds and 19 glycosidically bound volatile compounds, with esters, aldehydes, and ketones emerging as the predominant volatile compounds in the jujube fruits. Odor activity value (OAV) analysis revealed that the primary aroma profile of the jujubes is characterized by fruity and fatty odors, with β-damascenone being a key contributor to the fruity aroma, and (E)-2-oct-en-1-al and nonanal significantly influencing the fatty aroma. Moreover, the integration of sensory evaluation and partial least squares regression (PLSR) analysis pinpointed octanal, (E)-2-oct-en-1-al, nonanal, β-damascenone, and pentanal as significant contributors to the jujube's characteristic aroma, while isoamyl acetate was identified as significantly influencing the fatty acid taste. This study not only underscores the complexity of the jujube aroma composition but also highlights the impact of environmental factors on aroma profiles, offering valuable insights into the sensory characteristics of jujube fruits.

基于可见/近红外光谱的鲜枣可溶性固形物在线检测

Soluble solid content (SSC) is one of the important evaluation indexes of the internal quality and taste of fresh jujube. In order to realize the online nondestructive detection of SSC of fresh jujube, this paper took Huping jujube as the research object, adopted self-constructed nondestructive online testing system to collect the spectral information of jujubes (350~2500 nm), and studied the influence of the rotational speed of 4 r/min on the online prediction model of SSC of jujube. Kennard-Stone (KS) algorithm was used to divide the sample into correction set and prediction set. Six commonly used preprocessing methods such as SG smoothing (S-G), multiplicative scatter correction (MSC), standard normal variate (SNV), orthogonal signal correction (OSC), first derivative (FD), and second derivative (SD) were applied to the spectral data, and the regression coefficient (RC) algorithm and the successive projections algorithm (SPA) were utilized to select informative wavelengths, and a quantitative prediction model for the SSC of Huping jujube was established using partial least squares regression (PLSR). The results indicate that the PLSR prediction model established by preprocessing the original spectrum with OSC and combining it with RC algorithm to select characteristic wavelengths was optimal. Therefore, when predicting the SSC of Huping jujube, the optimal model was OSC-RC-PLSR, and the correlation coefficients of the correction set and prediction set were 0.846 and 0.782, respectively, and the corrected root mean square error (RMSEC) and predicted root mean square error (RMSEP) were 1.962 and 2.247, respectively. The results show that non-destructive detection of soluble solid content of jujube can be achieved by combining visible-near-infrared spectroscopy and appropriate regression model, which provides an innovative way for online sorting and identifying fresh jujube.

Xanthan gum coating delays ripening and softening of jujube fruit by reducing oxidative stress and suppressing cell wall polysaccharides disassembly

Harvested jujube fruit are prone to rapid ripening and softening during postharvest storage. In this work, jujube fruit were coated with xanthan gum (0.3%) and compared with uncoated control during storage at 20 ± 1 ºC for 15 d. Xanthan gum coating suppressed disease incidence (DI) and reduced fruit weight loss (FWL) of coated jujubes. Similarly, coating delayed reddening index development and suppressed relative ion leakage (RIL), malondialdehyde (MDA), superoxide anion (O2–•) and hydrogen peroxide (H2O2) concentrations. The coated jujubes exhibited suppressed respiration and ethylene production rates along with higher antioxidative enzymes activity. On the other side, xanthan gum coating preserved higher firmness and showed lower water-soluble pectin (WSP) along with conserved concentrations of Na2CO3-soluble pectin (SSP), cellulose (CS), hemicellulose (HCS) and chelate-soluble pectin components (CSP) owing to suppressed activities of polygalacturonase (PG), cellulase (CX), pectin methylesterase (PME) and β-galactosidase (β-gal) enzymes. The coated jujubes showed reduced total soluble solids increase and exhibited higher ascorbic acid content. So, xanthan gum coating could be applied as an eco-friendly postharvest treatment for the quality preservation of fresh jujube fruit.

Analysis of the changes in quality and characteristics of hot air drying of Xinjiang jujube (Zizyphus jujuba Mill. cv. Junzao) following a delayed harvest

Dry processing is ineffective in preserving fresh jujubes (Zizyphus jujuba Mill.), contributing largely to the delayed jujube harvest in Xinjiang. However, no studies have evaluated the impact of delayed harvest periods on processing quality. Therefore, the present study investigated the effects of different delayed harvest periods on the characteristics of the quality of jujubes in Xinjiang after hot air drying. Six batches (S1–S6) were sampled over a 7-d period. Various indicators of jujubes changed significantly during the extended harvest period (P < 0.05). The water content of the fruit decreased progressively. While the percentages of soluble solids, total sugars, and reducing sugars increased continuously, the total weight of these parameters in a single jujube fruit decreased continuously. The proportion of ascorbic acid, total weight, and drying time decreased steadily. The fruit had the highest ascorbic acid content at the S4 stage after hot air drying (87.14 mg 100 g−1). Fewer color differences were recorded in hot air-dried fruits as compared with fresh jujubes; the cracking rate decreased after hot air drying, but the fruit could be rehydrated more effectively. A comprehensive evaluation revealed that jujubes harvested in the S4 stage were better suited for dry processing.

Effects of postharvest chitosan and potassium sorbate coating on the storage quality and fungal community of fresh jujube

Fresh jujube fruit are confronted with serious quality deterioration after harvest. This study explored the effects of chitosan and potassium sorbate coatings on the physicochemical quality and fungal community of jujube during cold storage. Microscopic observation showed that chitosan can uniformly distribute potassium sorbate on the surface of jujube. Chitosan coating inhibited the increase in respiration rate and total soluble solids and the decrease in titratable acidity and firmness. Jujube fruit treated with chitosan and potassium sorbate showed the lowest decay rate (2.67%) after 35 d of storage. High-throughput sequencing analysis indicated that the largest number of fungal amplicon sequence variants (ASVs) was detected in jujube treated with chitosan and potassium sorbate, exhibiting higher Chao1, Shannon and Simpson diversity indices. Treatment with chitosan or potassium sorbate alone reduced the relative abundance of Cladosporium in jujube fruit. Jujube treated with chitosan and potassium sorbate had the lowest total relative abundance of all potential pathogenic fungi (Cladosporium, Alternaria and Diaporthe). FUNGuild analysis showed that chitosan and potassium sorbate treatment could inhibit the relative abundance of plant pathogenic fungi. As a result, chitosan maintained the physicochemical properties of jujube by inhibiting the respiration rate, and the combination of chitosan and potassium sorbate reduced the decay rate of jujube by inhibiting pathogenic fungi. Therefore, chitosan and potassium sorbate coating is a promising approach to improve the storage quality and delay the decay of jujube fruit after harvest.

Combined Treatment of Acidic Electrolyzed Water and High-Voltage Electrostatic Field Improves the Storage Quality of Huping Jujube (Ziziphus jujuba Mill. cv. Huping).

Fresh jujube is prone to rapid deterioration after harvest due to its active metabolism and rich nutrients. This study aimed to investigate the effects of acidic electrolyzed water (AEW), a high-voltage electrostatic field (HVEF) and a combination of AEW and HVEF (AEW + HVEF) treatments on the storage quality of Huping jujube (Ziziphus jujuba Mill. cv. Huping) stored at 0 ± 1 °C for 90 days. The results showed that the fruits treated with AEW + HVEF exhibited better storage quality than those treated with either AEW or HVEF alone. Specifically, the fruits treated with AEW + HVEF maintained higher levels of nutrients and taste compounds, including total soluble solid (TSS), total soluble sugar, reducing sugar and titratable acidity (TA), as well as lower respiration rate, weight loss, decay index and TSS/TA ratio. Additionally, the AEW + HVEF treatment could delay the increase in reddening index, a* and color change (ΔE) values, and the decrease in L* and b* values, by retarding the degradation of chlorophyll and accumulation of carotenoids and flavonoids, thereby preserving the more desirable appearance color. Furthermore, the combined treatment could enhance the glutathione reductase (GR) activity and 2,2'-azino-bis-(3-ethylbenzothizoline)-6-sulfonic acid (ABTS) +-scavenging ability. Thus, the AEW + HVEF treatment is a potential method for Huping jujube preservation.

The Key Metabolic Network and Genes Regulating the Fresh Fruit Texture of Jujube (Ziziphus jujuba Mill.) Revealed via Metabolomic and Transcriptomic Analysis.

The texture of fresh jujube fruit is related to its popularity and commercial value. The metabolic networks and essential genes that regulate the texture of jujube (Ziziphus jujuba) fruit are still unknown. In this study, two jujube cultivars with significantly different textures were selected by a texture analyzer. The four developmental stages of the exocarp and mesocarp of jujube fruit were studied separately using metabolomic and transcriptomic analyses. Differentially accumulated metabolites were enriched in several critical pathways related to cell wall substance synthesis and metabolism. Transcriptome analysis confirmed this by finding enriched differential expression genes in these pathways. Combined analysis showed that 'Galactose metabolism' was the most overlapping pathway in two omics. Genes such as β-Gal, MYB and DOF may affect fruit texture by regulating cell wall substances. Overall, this study provides an essential reference for the establishment of texture-related metabolic and gene networks of jujube fruit.

Effects of four disease-controlling agents (chlorothalonil, CuCl2, harpin, and melatonin) on postharvest jujube fruit quality

Postharvest senescence and disease development can reduce the nutritional value of fresh jujube fruit. Herein, four different disease-controlling agents (chlorothalonil, CuCl2, harpin and melatonin) were separately applied to fresh jujube fruit, and all improved postharvest quality (evaluated by disease severity, antioxidant accumulation and senescence) relative to controls. Disease severity was drastically inhibited by these agents, in the order chlorothalonil > CuCl2 > harpin > melatonin. However, chlorothalonil residues were detected even after storage for 4 weeks. These agents increased the activities of defense enzymes including phenylalanine ammonia-lyase, polyphenol oxidase, glutathione reductase and glutathione S-transferase, as well as accumulation of antioxidant compounds such as ascorbic acid, glutathione, flavonoids and phenolics, in postharvest jujube fruit. The enhanced antioxidant content and antioxidant capacity (evaluated by Fe3+ reducing power) was ordered melatonin > harpin > CuCl2 > chlorothalonil. All four agents significantly delayed senescence (evaluated by weight loss, respiration rate and firmness), with the effect ordered CuCl2 > melatonin > harpin > chlorothalonil. Moreover, treatment with CuCl2 also increased copper accumulation ~ threefold in postharvest jujube fruit. Among the four agents, postharvest treatment with CuCl2 could be considered most appropriate for improving postharvest jujube fruit quality under low temperature conditions without sterilization.

Combined LC-MS-based metabolomics and GC-IMS analysis reveal changes in chemical components and aroma components of Jujube leaf tea during processing.

Making tea from jujube leaves changed the chemical composition and aroma composition of jujube leaves. Here, Through LC-MS, GC-IMS, and GC-MS technology, we have revealed the effect of jujube leaf processing changes on metabolites. LC-MS identified 468 non-volatile metabolites, while GC-IMS and GC-MS detected 52 and 24 volatile metabolites, respectively. 109 non-volatile metabolites exhibiting more pronounced differences were screened. Most lipids and lipid-like molecules, organic acids, amino acids, and flavonoids increased significantly after processing. GC-IMS and GC-MS analysis revealed that the contents of aldehydes and ketones were significantly increased, while esters and partial alcohols were decreased after processing into jujube leaf tea. The main flavor substances of fresh jujube leaf and jujube leaf tea were eugenol and (E) - 2-Hexenal, respectively. Furthermore, amino acids and lipids were closely linked to the formation of volatile metabolites. Our study provided new insights into the changes in metabolites of jujube leaves processed into jujube leaf tea, and had great potential for industrial application. It laid a foundation for further research on fruit tree leaf tea.

Preservation of Phenols, Antioxidant Activity, and Cyclic Adenosine Monophosphate in Jujube (Ziziphus jujuba Mill.) Fruits with Different Drying Methods.

Jujube, commonly known as the Chinese date, is a nutritious fruit with medicinal importance. Fresh jujube fruits have a shelf life of about ten days in ambient conditions that can be extended by drying. However, nutrition preservation varies with the drying method and parameters selected. We studied total phenolic content (TPC), proanthocyanidins (PA), vitamin C, cyclic adenosine monophosphate (cAMP), and antioxidant activities in jujube fruits dried with freeze-drying (FD), convective oven drying (OD) at 50 °C, 60 °C, and 75 °C, and sun drying (SD) with FD as a control. The cultivars used for this study were 'Capri' and 'Xiang' from Las Cruces in 2019, and 'Sugarcane', 'Lang', and 'Sherwood' from Las Cruces and Los Lunas, New Mexico, in 2020. Freeze-drying had the highest of all nutrient components tested, the best estimates of mature jujube fruits' nutrient contents. Compared with FD, the majority of PA (96-99%) and vitamin C (90-93%) was lost during SD or OD processes. The retention rates of antioxidant activities: DPPH and FRAP were higher in OD at 50/60 °C than SD. SD retained a higher cAMP level than OD at 50/60 °C in both years. The increase in oven drying temperature from 60 °C to 75 °C significantly decreased TPC, PA, antioxidant activities, and cAMP.

Ultrasound-assisted ascorbic acid solution pretreated hot-air drying improves drying characteristics and quality of jujube slices.

The effective hot-air drying of foods such as jujube requires an effective green pretreatment alternative to chemical pretreatments. Jujube slices were pretreated using 5 and 10 mg mL-1 ultrasound-assisted vitamin C (UVC) for 10, 20, and 30 min, followed by hot-air drying. Ultrasound-assisted vitamin C pretreatment for 10, 20, and 30 min modulated the characteristics of fresh jujube slices such as water loss (from -28.25% to -25.52% after 30 min of UVC pretreatment), solid gain (from -31.68% to -26.82% after 30 min of UVC pretreatment), loss of total and reducing sugars (from 200.25 mg and 34.88 mg to 287.14 mg and 4.71 mg, respectively, after 30 min of UVC pretreatment), total soluble solids (from 76.32 o Brix to 82.08 o Brix), and water diffusivity (from 9.01 × 10-10 m2 s-1 to 6.71 × 10-10 m2 s-1 ). These characteristics were associated with altered surface morphology and improved drying characteristics. The UVC pretreatment preserved an acceptable reddish-yellow or orange-like color during hot-air drying and reduced the browning index from 26.3 optical density (OD)/g DM to 23.25 OD/g dry mass basis (DM), which was connected with reduced 5-hydroxymethylfurfural (HMF) content. On the other hand, the proportions of bioactive components such as vitamin C increased from 1.05 mg g-1 DM to 9.02 mg g-1 DM, phenolics increased from 12.8 mg gallic acid equivalent (GAE)/g DM to 17.5 mg GAE/g DM, flavonoids increased from 4.0 mg rutin equivalent (RE)/g DM to 4.4 mg RE/g DM, and procyanidin content increased from 2.0 mg catechin equivalents (CE)/g DM to 2.9 mg CE/g DM in UVC pretreated jujube slices, which had a positive association with increased antioxidant activity - for example, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid(ABTS) increased from IC50 22.5 mg DM/mL to 8.0 mg DM/mL, 2,2-diphenyl-1-picrylhydrazyl (DPPH) changed from IC50 36.5 mg DM/mL to 9.5 mg DM/mL, and ferric reducing antioxidant power (FRAP) increased from 2.0 mg vitamin C equivalent (VCE)/g DM to 11.9 mg VCE/g DM). The data indicated that UVC can be used as a promising pretreatment method for improving the hot-air drying characteristics and the quality of jujube slices. © 2023 Society of Chemical Industry.

Compositional Changes of the Jujube Fruit During Solar and Tray Drying

In this study, jujube fruit (Zizyphus jujuba Mill.) was used as material. Jujube fruits were obtained from producer in Çivril-Denizli regions. Firstly, total solube solids, dry matter, titratable acidity, pH, total phenolic content, organic acid (malic, citric, succinic, and tartaric acid), sugars (glucose, fructose, and sucrose), and water-soluble vitamins (ascorbic acid, riboflavin, niacin, pyridoxine, and thiamine) in fresh jujube fruit were analyzed. Secondly, fresh jujube fruits were dried in a solar and tray dryer (50, 60, and 70 °C). Total phenolic content was determined by the spectrophotometric method. Sugars, organic acids, and water-soluble vitamins content were determined using a high-performance liquid chromatography (HPLC) instrument. By solar drying the jujube fruit, the glucose and sucrose content of the fruit decreased, while the fructose content increased. While the initial fructose content was 242.6±4.3, solar drying increased to 256.9±4.0. There was a decrease in glucose, fructose and sucrose contents in jujube fruits dried by tray drying process. It was determined that the organic acid and water-soluble vitamin content of jujube fruit decreased in both solar and tray drying processes. Among the water-soluble vitamins, the highest loss was observed in ascorbic acid and pyridoxine. It was determined that the jujube fruit, whose initial ascorbic acid content was 71.2±0.5, decreased to 9.6±0.1 and 12.1±0.2 values as a result of drying in the solar and on the tray, respectively. On the other hand, solar drying resulted in a greater reduction in vitamin content compared to tray drying.

Evaluation of maturity and moisture content in fresh jujube using fractal theory and tissue images

This study proposes a novel method for jujube maturity and water content determination incorporating fractal theory. Firstly, the tissue section images of winter jujube at different maturity and tissue section image images of winter jujube with different moisture content were preprocessed by grayscale, median filter, histogram equalization and binarization. Secondly, the fractal dimension of jujube tissue section images of jujube at different maturity, and the fractal dimension of tissue slice images of jujube with different moisture content were calculated based on the box dimension algorithm. Finally, the relationships of the fractal dimension-maturity and fractal dimension-moisture content were explored. The results showed that the fractal features had good discrimination performance, the fractal dimension decreased with the increase of maturity, and the fractal dimension decreased with the increase of moisture content. This study provides a new way of thinking about the detection of physical and chemical indicators of winter jujube and other fruits.

Comparative Evaluation of Physicochemical Properties, Microstructure, and Antioxidant Activity of Jujube Polysaccharides Subjected to Hot Air, Infrared, Radio Frequency, and Freeze Drying

In this study, we used four drying methods (hot air, freezing, infrared, and radio frequency) to dry fresh jujube and its polysaccharide extracts by a two-step drying method, and the effects of the drying methods on the physical and chemical properties, structural properties, and antioxidant activity of jujube polysaccharides were studied. The results showed significant differences in the yield, drying time, monosaccharide content, molecular weight, apparent viscosity, thermal stability, and microstructure of the polysaccharides treated under the different drying methods. In contrast, no significant differences in the monosaccharide composition and functional groups of the polysaccharide samples obtained from the different drying methods were observed. Among all the tested methods, the freeze-drying extraction rate was the highest, reaching 4.52 ± 0.19%, while its drying time was the longest. Although the extraction rate of radio frequency drying was only 3.55 ± 0.21%, the drying time was the shortest, compared with hot air drying, the drying time was reduced by 76.67–83.29%, and the obtained polysaccharides exerted good antioxidant activity. Therefore, radio frequency drying is a potential polysaccharide extraction and drying technique, and this study can provide a theoretical basis for its industrial production.

A novel postharvest preservation technology of fruit—Intermittent high oxygen treatment: A case study on “Lingwu” long jujube

Fresh “Lingwu” long jujube (Ziziphus jujuba cv. Mill) fruit is susceptible to softening, water loss, and flavor change during storage. The effect of intermittent high oxygen treatment (IHOT) on the quality of jujube was investigated, which was immersed in the oxygen concentration of 50% and 90% for 30 min every week along with 8 weeks of storage at 0 ± 1°C. Significantly, the firmness, weight loss, soluble solids content (SSC), and membrane integrity were significantly retarded in 50% and 90% IHOT. Meanwhile, the activities of peroxidase (POD) were maintained a higher level after 35 d storage in 50% IHOT. And the activities of alcohol dehydrogenase (ADH) were significantly inhibited, and the peak was delayed by 50% IHOT. Furthermore, polyphenol oxidase (PPO) activity was barely changed during the first 28 days of storage, and the lowest enzymatic activity was shown later in the 50% IHOT. These results indicated that the short-term HOIT with appropriate concentration (50%) delayed the softening, maintained the moisture content and membrane integrity, and modulated key metabolic pathways of jujube fruit. As a whole, the applicability of IHOT could prolonged the shelf life of fresh jujube, which shows a great potential, in the application of fruit preservation. Practical applications Evaluation of different oxygen concentrations and treated models on jujube fruit helps the development of preservation technology for extending the shelf life of fruits. The application of intermittent high oxygen treatment to the fruits and vegetables was helpful to a novel postharvest preservation technology and the development of the fresh jujube fruit market.

Detection of Soluble Solids Content in Different Cultivated Fresh Jujubes Based on Variable Optimization and Model Update.

To solve the failure problem of the visible/near infrared (VIS/NIR) spectroscopy model, soluble solids content (SSC) detection for fresh jujubes cultivated in different modes was carried out based on the method of variable optimization and model update. Iteratively retained informative variables (IRIV) and successive projections algorithm (SPA) algorithms were used to extract characteristic wavelengths, and least square support vector machine (LS-SVM) was used to establish detection models. Compared with IRIV, IRIV-SPA achieved better performance. Combined with the offset properties of the wavelength, repeated wavelengths were removed, and wavelength recombination was carried out to create a new combination of variables. Using these fused wavelengths, the model was recalibrated based on the Euclidean distance between samples. The LS-SVM detection model of SSC was established using the update method of wavelength fusion-Euclidean distance. Good prediction results were achieved using the proposed model. The determination coefficient (R2), root mean square error (RMSE), and residual predictive deviation (RPD) of the test set on SSC of fresh jujubes cultivated in the open field were 0.82, 1.49%, and 2.18, respectively. The R2, RMSE, and RPD of the test set on SSC of fresh jujubes cultivated in the rain shelter were 0.81, 1.44%, and 2.17, respectively. This study realized the SSC detection of fresh jujubes with different cultivation and provided a method for the establishment of a robust VIS/NIR detection model for fruit quality, effectively addressing the industry need for identifying jujubes grown in the open field.