Fresh Jujube Research Articles

Effect of harvest, drying and storage on the bitterness, moisture, sugars, free amino acids and phenolic compounds of jujube fruit (Zizyphus jujuba cv. Junzao).

The taste of dried jujube fruit when compared with fresh ones is less palatable, as it develops bitterness during drying and storage. Therefore, identifying the methods by which bitterness occurs is essential for developing strategies for processing and storage. Bitterness in fresh jujube fruit was negligible; however, it increased by 0.9-, 1.5- and 1.8-fold during drying and storage over 6 and 12 months. The moisture significantly decreased during harvesting and drying. Free amino acids, except proline and tyrosine, significantly decreased during drying and storage. Fructose, glucose and sucrose hardly changed during harvest, drying and storage. Titratable acidity, total phenolic and total flavonoids contents were stable during harvest and drying, but increased upon storage. Additionally, protocatechuic and ellagic acids were not detected in fresh jujube fruit, however, were found to increase during drying and storage. Bitterness in fresh jujube fruit tasted negligible because of meagre amount of phytochemicals, while the condensation effect of moisture reduction, the loss of free amino acids, and the formation of protocatechuic and ellagic acids could aggravate the bitterness of jujube fruit during drying and storage. © 2017 Society of Chemical Industry.

Selenium enrichment, fruit quality and yield of winter jujube as affected by addition of sodium selenite

Winter jujube (Zizyphus jujuba Mill.) is a kind of high quality, fresh jujube fruit originated from China. Selenium (Se) affects the chemical composition and antioxidative properties in plants. At appropriate concentrations, Se acts as an antioxidant or activates mechanisms that can alleviate oxidative stress in the chloroplast, and enhances plant growth. Although the addition of Se is known to increase Se uptake in crops, it is unclear whether exogenous Se affects nutritional and functional components in winter jujube. Winter jujube trees were sprayed with selenium (as sodium selenite) at five concentrations (0, 25, 50, 100, or 200mg/L of Se) three times at the fruitlet stage between July and August. The Se content, ratio of organic Se to total Se in leaves and fruits, fruit quality, and yield were measured. At Se concentrations of 50mg/L or higher, total Se content increased rapidly whereas the ratio increased initially and decreased later. Different Se concentrations affected the quality of fruits differently: at 50mg/L, compared to their values in the unsprayed control trees, vitamin C content was greater by 20.94%; soluble sugars, 29.48%; total flavonoids, 43.48%; and the sugar: acid ratio, 41.81%. Along with the increase of Se addition, average fruit weight and yield of winter jujube presented a trend of increasing up to 50mgL−1 and decreasing thereafter. Thus, the foliar spray of sodium selenite at Se concentration of 50mg/L is recommended during the fruitlet stage of Zhanhua winter jujube.

The Jujube Genome Provides Insights into Genome Evolution and the Domestication of Sweetness/Acidity Taste in Fruit Trees.

Jujube (Ziziphus jujuba Mill.) belongs to the Rhamnaceae family and is a popular fruit tree species with immense economic and nutritional value. Here, we report a draft genome of the dry jujube cultivar ‘Junzao’ and the genome resequencing of 31 geographically diverse accessions of cultivated and wild jujubes (Ziziphus jujuba var. spinosa). Comparative analysis revealed that the genome of ‘Dongzao’, a fresh jujube, was ~86.5 Mb larger than that of the ‘Junzao’, partially due to the recent insertions of transposable elements in the ‘Dongzao’ genome. We constructed eight proto-chromosomes of the common ancestor of Rhamnaceae and Rosaceae, two sister families in the order Rosales, and elucidated the evolutionary processes that have shaped the genome structures of modern jujubes. Population structure analysis revealed the complex genetic background of jujubes resulting from extensive hybridizations between jujube and its wild relatives. Notably, several key genes that control fruit organic acid metabolism and sugar content were identified in the selective sweep regions. We also identified S-locus genes controlling gametophytic self-incompatibility and investigated haplotype patterns of the S locus in the jujube genomes, which would provide a guideline for parent selection for jujube crossbreeding. This study provides valuable genomic resources for jujube improvement, and offers insights into jujube genome evolution and its population structure and domestication.

Fate of triadimefon and its metabolite triadimenol in jujube samples during jujube wine and vinegar processing

Chinese jujube (Zizyphus jujuba Miller) is an indigenous fruit with Chinese characteristics in China which is widely used in traditional medicines and also consumed as a food material. Chinese jujube is subjected to wide varieties of pesticides like triadimefon which are harmful to humans. In present study, the fate of triadimefon and its metabolite triadimenol during jujube wine and vinegar fermentation processing was assessed. Jujube samples collected from plants sprayed with triadimefon from field trials. The analysis of triadimefon and triadimenol residues were carried out by gas chromatography–mass spectrometry (GC-MS) at different steps of the fermentation i.e fresh jujube, first and second jujube juice and pomace, jujube wine, and jujube vinegar. Processing factors (Pfs), which is defined as the ratio of pesticide residues in jujube sample to that in jujube wine or vinegar samples, were lower than 1 for triadimefon, indicating that food processing could reduce the pesticide level. But triadimefon was metabolised to triadimenol during this process with the Pfs of triadimenol in jujube wine and vinegar were 1.38 and 1.13, respectively, indicating that more attention is needed towards the metabolites during the processing. The study indicates the level of safety towards triadimefon in jujube beverage processing and allows the refining of the dietary risk analysis.

Tea polyphenols incorporated into alginate-based edible coating for quality maintenance of Chinese winter jujube under ambient temperature

The effects of different concentrations (1 g/L, 3 g/L and 5 g/L) of tea polyphenols incorporated into alginate-based (sodium alginate 1 g/L, glycerol 11.6 g/L and sunflower oil 0.25 g/L) edible coating on the respiration intensity, physicochemical properties, and activities of antioxidant enzymes of fresh winter jujube during 8 days storage under ambient temperature were evaluated. Coated jujube without tea polyphenols and uncoated jujube were stored under the same conditions and served as the controls. The alginate-based edible coating with 1 g/L tea polyphenols significantly reduced red indices, total chlorophylls content, respiration rate, electrolyte leakage and malonaldehyde content while maintaining the ascorbic acid content, total phenol content and the activities of antioxidant enzymes. However, the alginate-based edible coating incorporated with tea polyphenols, whichever their concentrations, had no significant effect on firmness. Alginate-based edible coating with 1 g/L tea polyphenols has a potential to maintain the quality of fresh jujube under ambient temperature.

A randomized controlled trial on the effects of jujube fruit on the concentrations of some toxic trace elements in human milk.

Background:This study aims to investigate the concentrations of lead, cadmium, and arsenic in the human milk, and to assess the effect of jujube fruit consumption by lactating mothers in reducing the concentration of these heavy metals in their milk.Materials and Methods:This randomized controlled trial was conducted in 2014 among forty postpartum mothers in Isfahan, the second largest and polluted city in Iran. Mothers were randomized into two groups; the intervention group received 15 g/day of fresh jujube fruit, and the controls received routine care for 8 weeks.Results:In the beginning, the concentrations of lead, cadmium, and arsenic were high, without significant difference between groups. The mean (standard deviation) concentrations of lead, cadmium, and arsenic were 29.49 (16.6), 4.65 (3.51), and 1.23 (0.63) μg/L, respectively. The smoothed empirical distribution of environmental pollutants showed that in both groups the mean values and variance of toxic metals decreased after 8 weeks, with a sharper decline in the intervention group. Quantile regression analysis showed that in the intervention group, lead concentration decreased by 2.54 μg/L at the 90th quintile, and cadmium decreased by 0.19 μg/Lat 75th quintile; without significant change in arsenic level. The corresponding figures were not significant in the control group.Conclusion:The concentrations of heavy metals were high in human milk, and the consumption of jujube fruit had some beneficial effects in reducing these harmful elements. Pregnant and lactating mothers should be advised to reduce their exposure to environmental pollutants, and consumption of some natural medicinal foods can be useful in reducing the concentration of pollutants in human milk. Because of numerous benefits of breast milk, in spite of the existence of some toxic trace elements, breastfeeding must be encouraged because such contaminants are also found in water and formula. The impact of the current findings on the primary prevention of chronic disease should be determined in future longitudinal studies.

Analysis of Volatile Flavor Compounds of Jujube Brandy by GC-MS and GC-O Combined with SPME

To identify the unique flavor compounds in jujube brandy and changes in flavor compounds in the process of aging, Gas Chromatography-Mass Spectrometry (GC-MS) and GC-Olfactometry (GC-O) combined with solid-phase micro-extraction were used for the analysis of the volatile flavor compounds of fresh and aged jujube brandy. The equilibrium of the flavor compounds required divinylbenzene/carboxen/polydimethylsiloxane fiber for 40 min at 40°C. A total of 72 compounds were positively or tentatively identified by GC-MS, including 34 esters, 12 alcohols, 2 acids, 7 hydrocarbons, 3 aldehydes, 3 ketones and 8 terpenes in jujube brandy. Among them, ethyl laurate, ethyl caproate, ethylbenzoate and ethyl hexanoate were the main components. The flavor components of jujube brandy were identified by GC-O and 47 flavors were detected. Among them, orange-like (ethyl acetate), apple-like (butanoic acid, ethyl ester), fermented (hexanoic acid, ethyl ester), chocolate-like (nonanoic acid, ethyl ester) and red date-like (dodecanoic acid, ethyl ester) were strongly sensed. Changes in the flavor compounds in the process of aging were detected. During the period of aging, the contents of alcohols, aldehydes and ketones generally decreased, whereas those of esters and acids increased.

충북 보은지역 대추재배 토양의 화학적 특성 조사

BACKGROUND: Recently, as the consumption of fresh jujube is increased, fertilizer in jujube cultivation is excessively used to supply nutrient for large fruit produce. This study was conducted to obtain the useful data related to optimum nutrient management technique for fresh jujube cultivation. METHODS AND RESULTS: Nutrient contents of the jujube orchard soils were investigated at 30 different jujube orchards in Boeun, Chungbuk. Soil samples were collected from the different orchards in June, both 2012 and 2013. Soil chemical properties such as pH, organic matter, available phosphate, and exchangeable potassium, calcium, and magnesium were analyzed. Soil available phosphates in optimum level for jujube cultivation were 7% and 13% of total samples in the 2011 and 2012 respectively, and 73% and 57% were higher than optimum level. In Exchangeable K, 37%, 30% were optimum level, 63%, 67% were higher in the year 2011 and 2012 respectively. CONCLUSION: These results showed that nutrient contents of soils were accumulated in jujube orchard of Boeun area. Especially, available phosphate and exchangeable potassium were greatly higher than their optimum level for jujube cultivation respectively.

Effect of processing and concentration method on physicochemical and sensory characteristics of jujube

Jujube is used as an herbal remedy to treat various diseases because of its associated health effects such as antimicrobial activity and its bioactive phenolic and flavonoid compounds. In addition to biologically active substances, jujube also contains nutrients and micronutrients and can be used as a food additive. Jujube concentrate, a combination of relatively transparent contains the qualitative and quantitative properties of jujube and has particular applicability in the food industry as a flavorant, nutritional and pharmaceutical additive, natural color and sweetener. In this study, we researched the formulation of concentrates on four processing methods of fresh and dried jujube by using methods of doping concentration under vacuum rotary evaporator and atmospheric pressure. To investigate its physicochemical properties, tests including the measurement of pH, ash, total solids, sugar, colorimetric and sensor tests based on a completely randomized factorial design were performed. Based on the results of the organoleptic analysis, the total sugar of dried concentrated jujube under vacuum was considered the best treatment. On the other hand samples of fresh jujube concentrated under vacuum recovery only in terms of flavor and sugar and high pH located in lower level. Adding citric acid was necessary in this case. All treatments were ranked higher when they were vacuumcondensed.

Effect of ultraviolet irradiation combined with chitosan coating on preservation of jujube under ambient temperature

The effect of ultraviolet irradiation combined with chitosan coating on fresh jujube under ambient temperature was investigated. In the first period, the jujubes were irradiated for 4, 6, 8, 10 min at 253.7 nm ultraviolet, or coated with 1%, 1.5%, 2% and 2.5% of chitosan, respectively. In the second period, the jujubes were firstly irradiated 6 min, and then coated with 1.5% of chitosan. The result showed that combined treatment could reduce decay incidence of jujubes and restrain increase of respiration rate, weight loss, malonaldehyde content and electrolyte leakage of jujubes. Furthermore, the activities of superoxide dismutase, peroxidase, and catalase were maintained at higher level, and the decrease of ascorbic acid and chlorophyll was restricted. The present data indicated that treating post-harvest jujubes with ultraviolet irradiation combined with chitosan coating was an effective method, and might be considered in commercial application for preservation of postharvest fruit.

Identification of crack features in fresh jujube using Vis/NIR hyperspectral imaging combined with image processing

Detection of crack defect in fresh jujube is a critical process to guarantee jujube quality and meet processing demands of fresh jujube fruit. This study presented a novel method for identification of fresh jujube crack feature using hyperspectral imaging in visible and near infrared (Vis/NIR) region (380–1030nm) combined with image processing. Hyperspectral image data of samples were used to extract the characteristic wavebands by chemometrics, which integrated the method of partial least squares regression (PLSR), principal component analysis (PCA) of spatial hyperspectral image (SPCA) and independent component analysis (ICA) of spatial hyperspectral image (SICA). On the basis of the selected wavebands, least-squares support vector machine (LS-SVM) discrimination models were established to correctly distinguish between cracked and sound fresh jujube. The performance of discriminating model was evaluated using receiver operating characteristics (ROC) curve analysis. The results demonstrated that PLSR–LS-SVM discrimination model with a high accuracy of 100% had the optimal performance of “area”=1 and “std”=0. For acquiring rich crack feature information, SPCA was also carried on images at the five characteristic wavebands (467, 544, 639, 673 and 682nm) selected by PLSR. Finally, the SPC-4 image was explored to identify the location and area of crack feature through a developed image processing algorithm. The results revealed that hyperspectral imaging combined with image processing technique could achieve the rapid identification of crack features in fresh jujube.

Building Kinetic Models for Determining Vitamin C Content in Fresh Jujube and Predicting Its Shelf Life Based on Near-Infrared Spectroscopy

Fresh jujube (Ziziphus jujube) is rich in vitamin C, which is an important quality index and generally decreases with storage time. The aim of this study was to build kinetic models for determining the vitamin C content, thus predicting the quality characteristics and shelf life of fresh jujube. The quality changes of the jujube stored at room temperature (20 °C) were analyzed using near-infrared spectroscopy. The significant spectra were determined and a calibration model for vitamin C content was developed. The results showed that vitamin C content could be described by the zero-order kinetics model based on the regressions. In addition, the shelf life of the jujube at room temperature was calculated according to the regression model.

Effects of carbon monoxide on quality, nutrients and antioxidant activity of post‐harvest jujube

To effectively extend the shelf life of fresh jujube, carbon monoxide (CO), as a small molecular gas, was applied to fumigate fresh jujube. The quality and antioxidant activity of jujubes fumigated with carbon monoxide at concentrations of 0 (control), 5, 10, 20 and 40 µmol L⁻¹ for 1 h under ambient temperature were investigated. The jujube fumigated with 10 µmol L⁻¹ CO showed the best preserving effect amongst all samples. At 30 days, the decay incidence of jujube fumigated with 10 µmol L⁻¹ CO is only two-thirds of that of control sample; its red index and weight loss rate were 22.8% and 19.4% lower, and its firmness, soluble solids content (SSC) and acidity were 18.7%, 5.4% and 12.2% higher than that of control samples, respectively. Its vitamin C and total flavonoid contents were also the highest. However, no significant difference in total polyphenol content was found. The jujubes treated with 10 µmol L⁻¹ CO exhibited the highest antioxidant activity in terms of reducing power and 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical scavenging activity. However, the jujubes fumigated with 40 µmol L⁻¹ CO showed inferior characteristics compared with the control sample. Fumigating jujubes with proper concentration of CO probably is a potential novel method for post-harvest jujube preservation in the future.

농가에서 활용가능한 생대추의 저장조건 연구

생대추의 저장기간을 연장하기 위하여 그리고 농가에서 직접 활용 가능한 효과적인 저장방법을 찾기 위하여 70% 숙기를 가진 생대추를 0°C 온도와 80~90% 습도로 조절하고 에틸렌제거 장치가 설치된 저온저장고에서 플라스틱상자와 종이상자를 저장용기로 사용하고 한지와 기능성필름을 포장방법으로 사용하여 9주까지 저장하면서 이미지, 수분함량, 부패율, 경도, 색도 및 당도를 측정하였다. 대조군 시료의 경우 수분함량이 저장 전 69.2%에서 9주 저장 후에는 66.1%로 감소하였으며 기능성필름으로 포장한 시료의 경우 저장기간 동안 큰 변화를 나타내지 않았다. 부패과는 6주까지는 나타나지 않았으나 그 이후로는 지속적으로 증가하는 경향을 보였다. 대조군 시료의 경도는 지속적으로 감소하는 경향을 보였으나 종이상자에 기능성필름으로 포장한 시료의 경우 저장 기간 동안 큰 변화가 없었다. 저장 기간 동안 적색도는 대부분의 시료에서는 천천히 증가하는 경향을 나타냈으며 당도는 다소 감소하는 경향을 나타냈다. 본 연구결과 70% 숙기를 가진 생대추를 9주까지 품질의 변화 없이 저장하기 위해 가장 효과적인 저장방법으로는 저장용기로 플라스틱상자보다는 표면에 노출되는 대추의 양을 줄일 수 있는 종이상자를 사용하는 것이 포장방법으로 한지보다는 기능성필름을 사용하는 것이었다. 결론적으로 농가에서 활용가능한 생대추의 저장방법으로 온도, 습도, 에틸렌이 조절된 저온저장고에서 종이상자와 기능성필름을 가볍게 덮은 조건에서 생대추의 저장을 9주까지 품질을 유지하면서 저장할 수 있었다.

CULTIVATION PRACTICES OF TABLE CULTIVAR OF CHINESE JUJUBE IN THE COLD NORTH XINJIANG

North Xinjiang belongs to an alpine region with high altitude. Almost no Chinese jujube was grown 10 years ago in this severely-cold area. However, scientists have developed cultivars of Chinese jujube suitable for this region. As a consequence, the Chinese jujube cultivation increased very fast in recent years and high quality fresh jujube was successfully produced there. The present article reported the growing history and current situation of Chinese jujube industry in Xinjiang, and the practical cultivation techniques for Chinese jujube in North Xinjiang.

Rheological Properties of Fresh Jujube Pulp

The rheological behavior of fresh jujube pulp with different concentration (30%-50%) was studied at a wide range of temperature (20°C-60°C) and homogenization pressure (0M-25MPa)in this paper. The result shown particle of fresh jujube pulp decreases with homogenization pressure, viscosity increased with concentration increase but decreases with temperature increase. Besides, the viscosity of fresh jujube correlated remarkably with its soluble solids content and pulp particles size.

Kinetic model of mold contamination in fresh jujube stored at room temperature based on near-infrared spectroscopy.

Kinetic model of mold contamination in fresh jujube stored at room temperature based on near-infrared spectroscopy.

Robust model of fresh jujube soluble solids content with near-infrared (NIR) spectroscopy

model with samples harvested in 2009, respectively. The established PLS models obtained Rc with the range of 0.8846 to 0.8893 and RMSEC with the range of 1.0248 to 0.9645 °Brix. The obtained results were better than the result of the model which was established only with samples harvested in 2009. Moreover, the models established using different numbers of added samples had similar results. Therefore, it was concluded that adding samples from another harvest year could improve the accuracy and robustness of the model for SSC prediction of fresh jujube. The overall results proved that the consideration of samples from different harvest places and years would be useful for establishing an accuracy and robustness spectral model.

A simple identification model for subtle bruises on the fresh jujube based on NIR spectroscopy

Visible–near infrared reflectance (NIR) spectroscopy was applied to identify the subtle bruise of fresh jujube. In this paper, 70 samples were selected randomly as a calibration set and 30 samples were selected as a prediction set. Multiplicative scatter calibration (MSC) was used to pre-process the spectra, 9 characteristic wavelengths were selected by successive projection algorithm (SPA) in the end. On the basis of spectroscopy theoretical analysis, the principal component analysis (PCA) was performed to analyze the spectral data of the characteristic wavelengths, and 4 principal components (PCs) data which were used as the input variables for the Least squares support vector machine (LS–SVM) model for identifying the subtle bruise of fresh Jujube fruits were picked up. Intact jujubes and bruise jujubes in prediction with code 1 and 2 respectively could be considered as the outputs. The identification accuracy rate of the MSC–SPA–PCA–LS–SVM model for subtle bruises of fresh jujube fruits could reach 100%, proving that the key information in spectral data could be effectively picked up by SPA and PCA combination methods. It is feasible to identify the subtle bruise of fresh jujube using visible–near infrared reflectance (NIR) spectroscopy.

Studies on the Fermentation Technics of Dry Wild Jujube Wine

In this study, we tried to utilize wild jujube as the raw material to produce fruit wine. Grape wine active dry yeast was used for fermentation. The effects of initial sugar content, inoculation concentration of yeast, fermentation temperature and pH were investigated. Fermentation conditions were optimized by orthogonal test. The resulted optimum fermentation conditions were as the following: initial sugar content: 18%, pH value: 4.0, fermentation temperature: 24°C, and inoculum concentration of dry yeast: 0.3%. The produced wine was amber, clear and transparent, fresh jujube fruit aroma, and had mellow and harmonious taste. Its alcohol content was 12.6% vol, the content of residual sugar was 1.5 g/L, vc content was 350 mg/L and total acid were 4.0 g/L.