Zizyphus Jujuba Mill Research Articles

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.

Fuzzy evaluation on the integrated benefit of regulated deficit irrigation for pear-jujube tree based on information entropy.

Based on the experimental data of regulated deficit irrigation at different growth stages on field pear-jujube tree (Zizyphus jujube Mill.) during 2005-2007 in Northwest China, the regulated deficit irrigation integrated benefits (RDIIB) with different water deficit treatments at different growth stages were evaluated and classified using a model. The results in 2005-2006 showed that the RDIIB under single-stage water deficit at fruit maturity stage were better than the other treatments, and the best RDIIB were gained under moderate (IVSD) or severe deficit (IVMD) at fruit maturity stage. The results in 2006-2007 also indicated that the four double-stage water deficit schemes have the better RDIIB, and the best scheme was severe water deficit at bud burst to leafing stage plus moderate water deficit at fruit maturity stage. The RDIIB evaluation model based on information entropy method provided the reliable technical guidance for the optimal RDI scheme of pear-jujube tree.

Glycine betaine inhibits postharvest softening and quality decline of winter jujube fruit by regulating energy and antioxidant metabolism

Winter jujube fruit easily softens after harvest. To investigate the effects of glycine betaine (N,N,N-trimethylglycine; GB) treatment on the quality of postharvest jujubes, fresh winter jujubes (Zizyphus jujuba Mill. cv. Dongzao) were immersed in 20 mmol·L−1 GB for 20 min. The results showed that GB application can effectively maintain cell wall component content by restraining gene expression and enzyme activities, including PG, CX, PME and β-Glu. Meanwhile, the activities of antioxidant enzymes (APX, CAT, SOD, POD) and the contents of nonenzymatic antioxidants (MDA, H2O2, ASA, GSH) were enhanced in treated jujubes, thereby reducing the content of ROS. In addition, energy metabolism enzyme activities (H+-ATPase, Ca2+-ATPase, SDH and CCO) and gene expression were also significantly increased, thus maintaining higher energy levels (ATP, ADP, AMP and EC). In summary, GB enhances ATP biosynthesis by increasing energy metabolism. It offers essential energy for the antioxidant metabolism, thus retarding the softening of postharvest jujubes.

A Homogalacturonan from Peel of Winter Jujube (Zizyphus jujuba Mill. cv. Dongzao): Characterization and Protective Effects against CCl4-Induced Liver Injury.

A homogalacturonan pectin (HG, designated as WJP-F80) was extracted from the peel of winter jujube (Zizyphus jujuba Mill. Cv. Dongzao) and separated via ethanol-graded precipitation. The structural and conformational features were elucidated through HPAEC-PAD, GC-MS, 2D NMR, and HPSEC-MALLS studies. In vivo assessments were carried out to evaluate the hepatoprotective effects of WJP-F80 against CCl4-induced injury of mice. Results showed that WJP-F80 was a linear 1,4-α-galacturonan with partially methyl-esterified at O-6 of GalpA and occasionally acetylation. The Mw of WJP-F80 was determined as 45.3 kDa, the polydispersity was calculated as 1.56, and the Rg was measured as 22.7 nm in 0.1 M NaNO3. The conformational analysis revealed that WJP-F80 exhibited as rigid stiff chain in low Mw range, while aggregation by self-assembly of HG chains lead to high Mw and random coil conformation. In vivo studies indicated that WJP-F80 can protect the livers of mice from acute injury induced via CCl4 by decreasing the serum biochemical markers of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) to normal levels. This work provides a theoretical basis for the value-added deep processing of winter jujube.

Effect of Soil Moisture and Calcium Deficiency on Incidence of New Branch Necrosis and Tip-Burn in Jujube (Zizyphus jujuba Mill.)

Jujube (Ziziphus jujuba Mill.) is the most important native species of Rhamnaceae, a large cosmopolitan family, and is one of the oldest cultivated fruit trees in the world. In recent years, consumption of fresh fruit and big fruit jujube has increased. The purpose of this study was to investigate the causes and its alleviation techniques of new branch necrosis and tip-burn, which occur in jujube during the new branch growth period. As a result of analyzing the inorganic component content of leaves, the calcium content was markedly 1.48% of abnormal samples compared to 1.90% of normal samples appeared low. Also, the calcium content in a necrotic new branch was also 0.14%, which was very low compared to 0.76% in the normal sample. In addition, the incidence rate of tip-burn at -30 kPa by soil at starting point of irrigation was 16.53%, higher than 7.22% at -10 kPa. The incidence of tip-burn by calcium foliar application was 0.6%, which was very low compared to control of 4.3%. Therefore, this study suggests that the symptoms of necrosis of new branch and tip-burn that occur during the new branch growth period of Jujube are related to the calcium content in the plant and lack of soil moisture and that calcium foliar application is effective in alleviating the occurrence of these abnormal symptoms.Alleviation effect of leaf tip-burn by Ca foliar application.

A Combination of Rosa Multiflora and Zizyphus Jujuba Enhance Sleep Quality in Anesthesia-Induced Mice.

Sleep is an essential component of quality of life. The majority of people experience sleep problems that impact their quality of life. Melatonin is currently a representative sleep aid. However, it is classified as a prescription drug in most countries, and consumers cannot purchase it to improve their sleep. This sleep induction experiment in mice aimed to identify a natural combination product (NCP) that can create synergistic sleep-promoting effects. Based on the mechanism of action of sleep, we investigated whether phenomenological indicators of sleep quality change according to the intake of NCP. The sleep onset and sleep time of the mice that consumed the NCP found by this study were improved compared to the existing sleep aids. The mean melatonin level in the blood increased by 197% compared to the control. To our knowledge, this is the first study to demonstrate that Rosa multiflora Thunb. (Yeongsil) can promote sleep similarly to Zizyphus jujuba Miller (Sanjoin). The results indicate a preclinical study of NCPs containing Rosa multiflora Thunb and Zizyphus jujuba Miller developed by us showed significant differences in sleep incubation and duration depending on melatonin concentrations. Our results also suggest that increased melatonin concentrations in the blood are likely to improve sleep quality, especially regarding incubation periods.

The insecticidal potential of Bacillus velezensis CE 100 against Dasineura jujubifolia Jiao & Bu (Diptera: Cecidomyiidae) larvae infestation and its role in the enhancement of yield and fruit quality of jujube (Zizyphus jujuba Miller var. inermis Rehder)

Jujube (Zizyphus jujuba Miller var. inermis Rehder) is highly susceptible to jujube gall midge (Dasineura jujubifolia Jiao & Bu) larvae infestation, which causes rolled leaf damage, leaf galls, discoloration, and a decline in fruit yield. In this study, we demonstrate the larvicidal potential of cuticle-degrading chitinase and protease produced by Bacillus velezensis CE 100 against jujube gall midge larvae and the plant growth-promoting effect on jujube fruit yield. The laboratory insecticidal assay involving bacterial broth culture and crude enzymes of B. velezensis CE 100 revealed that both treatments caused gall midge larvae mortality rates of up to 85.5% and 96.7%, respectively. Both treatments caused severe degradation of the larvae cuticle, such as deformation of the exoskeleton and loss of sensilla. Foliar application of the bacterial broth culture in the jujube field reduced the rate of rolled leaf damage by 3.8-fold more than that in the control group. In addition, B. velezensis CE 100 produced indole-3-acetic acid (IAA) up to 3.5 mg/mL, which improved root development, and exhibited the potential for nitrogen-fixation and phosphate solubilization to improve nutrient availability and uptake. Compared to the control, applying the bacterial treatment in the jujube field increased the leaf chlorophyll content by 1.3-fold and improved the fruit yield by 2.4-fold. For the first time, we demonstrate the dual larvicidal and bio-stimulation potential of entomopathogenic B. velezensis CE 100 in managing gall midge larvae and the improvement of jujube fruit production, respectively.

Transcriptomics analysis and candidate genes associated with Xinjiang jujube fruits in response to Alternaria alternata infection

Black spot disease, caused by Alternaria alternata, is one of the most destructive diseases of jujube worldwide. To better understand the resistance mechanisms of jujube to A. alternata infection, two different cultivars, Zizyphus jujuba Mill. var. Junzao (susceptible) and Zizyphus jujuba Mill. var. Huizao (resistant) were tested. In this study, we identified 2235 differentially expressed genes (DEGs) in the disease-resistant cultivar and 4958 in the susceptible cultivar. Most were associated with plant phytohormone synthesis and signal transduction, flavonoid synthesis, and glutathione metabolism. The expression of six DEGs associated with disease resistance was detected by real-time quantitative polymerase chain reaction (RT-qPCR), consistent with the results of Illumina transcriptome sequencing. Moreover, the distinct expression level of the six DEGs in Jun jujube and Hui jujube, verified that these are defense response factors. The present study identified several candidate resistance genes and signal transduction pathways that may contribute to black spot disease resistance in jujube, which will assist the investigation of resistance mechanisms in the response of jujube to A. alternata infection.

X-rays irradiation affects flavonoid synthesis and delays reddening of winter jujube (Zizyphus jujuba Mill. cv. Dalidongzao) during cold storage

This study investigated the color and pigment content changes, the activities of flavonoid biosynthesis related enzymes and relative expression of genes of irradiated winter jujubes during cold storage at 0 ± 1 ℃ for 70 d. The results showed that 0.3 kGy X-rays could maintain the lightness and superior appearance of winter jujube while suppressing the decay. In addition, the activities of phenylalanine ammonia-lyase (PAL) and dihydroflavonol reductase (DFR) were restricted in 0.3 kGy X-rays treated jujubes, and the relative expression of MYB transcription factors (LOC107415776 and LOC107404478) and bHLH transcription factors (LOC107407443, LOC107423582 and LOC107423649) were down-regulated, causing the reduced anthocyanin and quercetin content. Together with the alleviated chlorophyll degradation levels delayed the reddening of irradiated jujube. This research demonstrates the potential of 0.3 kGy X-rays in delaying winter jujube reddening, which can provide a solid theoretical reference for the mechanism study.

Incorporation of 1-methylcyclopropene and salicylic acid improves quality and shelf life of winter jujube (Zizyphus jujuba Mill. cv. Dongzao) through regulating reactive oxygen species metabolism.

Winter jujube fruit is susceptible to aging, peel reddening, dehydration, shrinkage, and tissue softening during shelf life after it is removed from the cold storage conditions. In this study, the effects of 1-methylcyclopropene (1-MCP) and salicylic acid (SA) on the quality of winter jujube fruit during shelf life were investigated by measuring physiological indexes and the activities of antioxidant enzymes and enzymes related to reactive oxygen species (ROS) metabolism of winter jujube fruit. The results showed that 1-MCP treatment and SA treatment suppressed weight loss, respiratory rate, malondialdehyde (MDA) content, H2O2 content, and production rate, but improved firmness, color difference (ΔE), soluble solid content (SSC), titratable acidity (TA), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), phenylalanine ammonia-lyase (PAL) activities, ascorbic acid content, glutathione content, total phenolic content, and total flavonoid content in comparison with the control. Particularly, the combined treatment of 1-MCP and SA (1-MCP+SA treatment) showed the maximum efficacy compared to the 1-MCP treatment and SA treatment alone. 1-MCP+SA treatment exhibited the best preservation effect, followed by SA treatment and 1-MCP treatment. Thus, the combined treatment of 1-MCP and SA is an effective approach to maintain the postharvest quality of winter jujube fruit and extend the shelf life.

Microclimate, yield, and income of a jujube–cotton agroforestry system in Xinjiang, China

The purpose of this study was to establish a jujube (Zizyphus jujuba Mill.)–cotton (Gossypium hirsutum Linn.) intercropping agroforestry system in the south and north of Xinjiang Uygur Autonomous Region and to determine the impact of intercropping systems on microclimate, yield, and income compared with sole-cropping planting. Therefore, a two-year field experiment was carried out in the Hotan and Shihezi areas to measure photosynthetically active radiation (PAR) on the space-time scale, air temperature on the time scale, wind speed and windproof efficiency on the time scale, and yield and income. Through correlation analysis, the relationship between intercropping microclimate and intercropping yield were revealed. Compared with corresponding sole-cropping cotton, the PAR of intercropping in Hotan and Shihezi was 13.04% and 12.75% lower, respectively, and the closer to the tree alley, the smaller it was. Intercropping changed the daily dynamics of air temperature, especially at high temperatures, under which the decrease range was significant. Intercropping has buffer effect and latent heat release on air temperature and the maximum temperature in Hotan and Shihezi intercropping was 13.57% and 6.49 lower than that in sole-cropping, respectively. Intercropping reduced the wind speed, the greater the wind speed in a certain range, the stronger the windproof efficiency. The maximum windproof efficiency of Hotan intercropping was 50.92%, and that of Shihezi was 48.56%. The intercropping system had advantages in land equivalent ratio (LER), yield, and income. The income of intercropping was 11622.38–12528.55 USD·hm−2, 55.41–61.91% higher than that of sole-cropping cotton and 19.19–20.37% higher than that of sole-cropping jujube. The results showed that the development of jujube-cotton intercropping could protect the growing environment of cotton and increase farmers' economic income by improving the field microclimate.

Inhibitory effects of a water-soluble jujube polysaccharide against biofilm-forming oral pathogenic bacteria

Oral diseases caused by infectious pathogens raises significant concerns in public health. In the light of side effects of current antibiotics therapy and growing drug resistance of pathogenic bacteria, natural products have become attractive alternatives for antibiotics agents in dental practice. This current study investigated the effects of polysaccharides extracted from Zizyphus jujuba Mill. on three major oral biofilm-forming pathogenic bacteria including caries-inducing Streptococcus mutans, lesions-causing MRSA, and periodontitis-related Porphyromonas gingivalis, as well as general oral microbiota. Our results demonstrated that jujube polysaccharide prepared in this study was mainly composed by galacturonic acid with an average molecular weight 242 kDa, which were further characterized for structural features by FT-IR spectra and NMR spectroscopy analysis. This jujube polysaccharide was shown to exhibit remarkable inhibitory effects against all the tested oral bacterial pathogens through various mechanisms including growth inhibition, biofilm prevention and disruption, intervention of bacterial infection (adhesion and invasion), attenuation of cytotoxicity, modulation of excessive inflammatory response of LPS-stimulated and MRSA-infected macrophages as well as positive regulation of oral microbiota. The present study paves the way to explore jujube polysaccharides for the prevention and treatment of oral infectious diseases.Graphic Abstract.

Prophylactic efficacy of Unani herbal and herbo-mineral preparations in population at risk of COVID-19 – A randomised controlled prospective field trial

Present study was aimed to evaluate the efficacy of Unani poly-herbal decoction and Khamira Marvareed (herbo-mineral preparation) in COVID-19 susceptible population. This study was conducted as prospective, open label, randomized Controlled, prophylactic Community-based clinical trial. Four thousand five hundred healthy adults from containment zone were allocated randomly into intervention (n=2250) and control group (n=2250). The intervention group was given a combination of herbal drugs namely Unnab ( Zizyphus jujube Mill.), 5 pieces; Sapistan ( Cordia myxa L . ), 9 pieces; Behidana ( Cydonia oblonga Mill.), 3gms in decoction form and Khameera Marwareed , 5gms as semisolid preparation, orally once daily in the morning for 20 days. No drug was given in the control group. The subjects were assessed on 0, 20 th and 35 th day. The prophylactic effect of the Unani intervention was evaluated on the basis of difference of COVID-19 incidence between the groups, COVID-19 like symptoms, scores of immunity status questionnaire and WHOQOL-BREF scale after completion of 35 th day of study. The study remained inconclusive to find any difference in COVID-19 incidence, but showed highly significant result (p<0.001) in favour of Unani intervention in containing all COVID-19 like symptoms except cough; highly significant results (p<0.001) in score of immunity status questionnaire and highly significant results (p<0.001) in scores of physical and psychological domains of WHOQOL-BREF scale. The highly significant results in almost all secondary outcomes suggest the efficacy of the Unani intervention in control of COVID-19 like symptoms and may be beneficial in prevention of COVID-19 infection.

Propyl Gallate Treatment Improves the Postharvest Quality of Winter Jujube (Zizyphus jujuba Mill. cv. Dongzao) by Regulating Antioxidant Metabolism and Maintaining the Structure of Peel

The quality and color of winter jujube fruits are easy to change after harvest. We studied the regulation mechanism of propyl gallate (PG) on post-harvest physiological quality of winter jujube, from the perspective of antioxidant metabolism and peel structure. In our research, winter jujube fruits were treated with 0.001 mol L−1 PG solution for 20 min. Our results showed that PG delayed the development of peel color, and improved the firmness, total soluble solids (TSS), and titratable acid (TA) of winter jujube. Meanwhile, the PG treatment had higher content of total phenols, total flavonoids, ascorbic acid (AsA), and reduced glutathione (GSH), and kept the enzyme activity including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) at a higher level. PG treatment reduced membrane oxidative damage and maintained the integrity of pericarp structure by reducing electrolyte leakage (EL), lipoxygenase activity (LOX), hydrogen peroxide (H2O2), and malondialdehyde (MDA) content in the peel. Accordingly, PG improved the postharvest quality of jujube fruits by regulating antioxidant metabolism and maintaining the structure of peel. The appropriate concentration of PG has good application potential in the storage and preservation of fresh fruits such as winter jujube.

Effects of Different Irrigation Water Salinity on the Soil Water-Salt, Photosynthesis, Yield and Quality of Winter Jujube (Zizyphus Jujuba Mill. “Dongzao”) Under Drip Irrigation in the Yellow River Delta of China

Effects of Different Irrigation Water Salinity on the Soil Water-Salt, Photosynthesis, Yield and Quality of Winter Jujube (Zizyphus Jujuba Mill. “Dongzao”) Under Drip Irrigation in the Yellow River Delta of China

Effects of ultrasound-assisted low-concentration chlorine washing on ready-to-eat winter jujube (Zizyphus jujuba Mill. cv. Dongzao): Cross-contamination prevention, decontamination efficacy, and fruit quality

Wash water is circulated for use in the minimal processing industry, and inefficient disinfection methods can lead to pathogen cross-contamination. Moreover, few disinfection strategies are available for ready-to-eat fruits that do not need to be cut. In this study, the use of chlorine and ultrasound, two low-cost disinfection methods, were evaluated to disinfect winter jujube, a delicious, nutritious, and widely sold fruit in China. Ultrasound treatment (28 kHz) alone could not decrease the cross-contamination incidence of Escherichia coli O157:H7, non-O157 E. coli, and Salmonella Typhimurium, and free chlorine treatment at 10 ppm decreased the incidence from 55.00% to 5.00% for E. coli O157:H7, 65.00% to 6.67% for non-157 E. coli, and 70.00% to 6.67% for S. Typhimurium. The cross-contamination incidence was completely reduced (pathogens were not detected in sample) when the treatments were combined. The counts of aerobic mesophiles, aerobic psychrophiles, molds, yeasts, and three pathogens in the group subjected to combination treatment (28 kHz ultrasound + 10 ppm free chlorine) were significantly lower than those in the control, chlorine-treated, and ultrasound-treated groups during storage (0–7 d at 4 °C). Analysis of weight loss, sensory quality (crispness, color, and flavor), instrument color (a*/b*), soluble matter contents (total soluble solids, reducing sugar, total soluble sugar, and titratable acid), and nutritional properties (ascorbic acid and polyphenolic contents) indicated that treatment with ultrasound, chlorine, and their combination did not lead to additional quality loss compared with properties of the control. Additionally, the activities of phenylalanine ammonia-lyase and polyphenol oxidase were not significantly increased in the treatment group, consistent with the quality analysis results. These findings provide insights into disinfection of uncut ready-to-eat fruits using a minimum dose of disinfectant for cross-contamination prevention under ultrasonication. The use of ultrasound alone to decontaminate fresh produce is accompanied by a high risk of pathogen contamination, and the use of sanitizers to decrease cross-contamination incidence is recommended.

Influences of low temperature on the postharvest quality and antioxidant capacity of winter jujube (Zizyphus jujuba Mill. cv. Dongzao)

Winter jujube inevitably suffers from rapid oxidation after harvest, leading to quality deterioration. Temperature plays an important role in the ripening and senescence of fruit. This study aimed to investigate the effect of different temperatures on the quality parameters, antioxidant enzyme activities, and antioxidant enzyme-related gene expressions of winter jujube. Jujube fruit were stored at room temperature (RT: 25 °C) and low temperature (LT: 0 °C) for 35 days, respectively. Compared with RT, LT maintained higher firmness and lower respiratory rate, inhibited the increase of weight loss, decay rate, total soluble solids (TSS) and reddening rate, delayed the decrease of titratable acid (TA) and ascorbic acid (AsA) content. LT-stored jujube fruit also showed higher antioxidant enzyme activities and related gene expression (Mn-SOD, APX, and GR, except CAT). We observed a significant correlation between fruit quality parameters and antioxidant enzymes, suggesting that fruit senescence is closely related to antioxidant ability. In short, LT delayed the ripening rate by inducing a series of physiological and molecular reactions, thereby improving antioxidant levels and storage quality.

Adapting Root Distribution and Improving Water Use Efficiency via Drip Irrigation in a Jujube (Zizyphus jujube Mill.) Orchard after Long-Term Flood Irrigation

Jujube tree yields in dryland saline soils are restricted by water shortages and soil salinity. Converting traditional flood irrigation to drip irrigation would solve water deficit and salt stress. The root distribution reacts primarily to the availability of water and nutrients. However, there is little information about the response of jujube roots to the change from flood irrigation to drip irrigation. In this context, a two–year experiment was carried out to reveal the effects of the change from long–term flood irrigation to drip irrigation on soil water, root distribution, fruit yield, and water use efficiency (WUE) of jujube trees. In this study, drip irrigation amounts were designed with three levels, i.e., 880 mm (W1), 660 mm (W2), 440 mm (W3), and the flood irrigation of 1100 mm was designed as the control (CK). The results showed that replacing flood irrigation with drip irrigation significantly altered soil water distribution and increased soil moisture in the topsoil (0–40 cm). In the drip irrigation treatments with high levels, soil water storage in the 0–60 cm soil layer at the flowering and fruit setting, and fruit swelling stages of jujube trees increased significantly compared with the flood irrigation. After two consecutive years of drip irrigation, the treatments with higher irrigation levels increased root length density (RLD) in 0–60 cm soil depth but decreased that in the 60–100 cm depth. In the horizontal direction, higher irrigation levels increased RLD in the distance of 0–50 cm, while reducing RLD in the distance of 50–100 cm. However, the opposite conclusion was obtained in W3 treatment. Additionally, in the second year of drip irrigation, W2 treatment (660 mm) significantly improved yield and WUE, with an increasing of 7.6% for yield and 60.3% for WUE compared to the flood irrigation. In summary, converting flood irrigation to drip irrigation is useful in regulating root distribution and improving WUE, which would be a promising method in jujube cultivation in arid regions.

MORPHOLOGICAL AND CHEMICAL ANALYSIS OF ZIZYPHUS JUJUBA MILL. FRUITS FROM TIMIȘOARA BOTANICAL PARK

Zizyphus jujuba Mill. belongs to the Rhamnales order, Rhamnaceae family, Rhamnus genus. The genus includes about 40 species native to tropical and subtropical regions of both hemispheres, as well as the Mediterranean region. Species Zizyphus jujuba Mill. it is native to SW Asia, has ornamental features and is found spontaneously on the Danube coast. The first cultivated varieties were introduced at the Faculty of Horticulture in Bucharest in Shanxi Province, China in a joint research project in 1997. In our study, the fruits were harvested from two genotypes in the Botanical Park of Timisoara. For the harvested fruits were analyzed: fruit weight (g), seed weight (g), fruit length (mm), fruit width (mm) and chemical analyses were performed: soluble dry matter (%), C vitamin (mg 100 g-1), total potassium content (mg 100 g-1) and protein (%). In the analyzed fruits, the soluble dry matter varied between 28.3-29.81%, C vitamin between 247.97-288.17 mg 100g-1, proteins between 4.84-5.63% and potassium between 79.53 -79.63 mg 100 g-1.

Numerical analysis of heat and mass transfers during intermittent microwave drying of Chinese jujube (Zizyphus jujuba Miller)

A 3-D coupled electromagnetics, heat transfer, and mass transfer model for intermittent microwave drying of jujube fruit was developed to understand and optimize the effect of duty cycle (power level) and initial moisture on the temperature and moisture distributions and the rate of drying. The model was validated using measured temperature, pressure, and moisture content histories. A comprehensive understanding of the spatial and time evolutions of temperature, moisture, pressure, microwave power absorption, and evaporation rate were obtained. A uniformity index for temperature and moisture, that more closely relates to quality, was computed as drying progressed, providing unique insight into how the power level can affect quality in such a complex drying process. The effect of duty cycling was clearly seen, showing a sharp increase in temperatures, evaporation rate and pressure during the ON-phase, followed by decrease during the OFF-phase. Moisture profiles tracked the temperature cycling. Low moisture samples heated more spatially uniformly at relatively lower temperatures and with more uniform moisture profiles. Lower duty cycles (effectively lower power) reduced both the rate of temperature rise and the moisture loss, while improving the uniformity of temperature and moisture. The model provided a comprehensive mechanistic insight into the complex microwave drying process that would greatly reduce the time and resources in the design of product, process, and equipment.