Jujube fruit: A potential nutritious fruit for the development of functional food products

Applying Cold Atmospheric Plasma to Preserve the Postharvest Qualities of Winter Jujube (Ziziphus jujuba Mill. cv. Dongzao) During Cold Storage

Winter jujube (Ziziphus jujuba Mill. cv. Dongzao) is a very popular horticultural fruit worldwide, which contains a high number of bioactive compounds. Nevertheless, jujube is perishable by microbial contamination and has a short shelf life under non-controlled conditions. Cold atmospheric plasma (CAP) presents a great potential for food sterilization, maintain postharvest quality, and prolonged storage time. Herein, this study investigated the potential effect of CAP with different exposure times (0, 5, 10, and 20 min) on the physicochemical and biochemical changes in jujube during 15-day storage at 4°C and 90% relative humidity (RH). The results showed that CAP treatment could obviously delay ripening, but displayed no effects on the speed of weight loss and moisture content. Meanwhile, the total native aerobic bacterial count in each jujube group was restrained during whole storage. However, CAP treatment showed a time-dependent manner to improve gene expression (PAL, 4CL, DFR, ANS, LAR, and ANR) related to phenolic biosynthesis. As compared to other groups, 20-min CAP treatment can keep or increase total phenolic content (TPC), maintain antioxidant activity, and reduce oxidative damage. Furthermore, the hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) content in jujube during middle storage were visibly reduced by 20-min CAP treatment. All in all, our findings concluded that appropriate CAP exposure time can be a promising candidate for the postharvest preservation of jujube.

The Inclusion of Jujube By-Products in Animal Feed: A Review

Given the increasing demands for the quality and safety of animal-derived foods and the strict regulations on the use of antibiotics in animal feed, the use of functional feed additives has attracted increasing research and development. Jujube fruit is an energy-rich food with antioxidant, antibacterial, and antidiarrheal properties. With the expanding areas of cultivation to jujube trees and the intensive processing of jujube in Asia, especially in China, a large number of jujube by-products are produced. These by-products are used widely in animal feed for pigs, chicken, cattle, goats, and fish, as they improve growth performance, promote digestive tract health, and enhance the quality of animal products. This article reviews the nutritional components and benefits of jujube by-products and their potential incorporation in animal feed. The aim of this review is to introduce jujube by-products as a novel supplement or partial dietary replacement in the animal feed industry.

The Effect of In Vitro Gastrointestinal Digestion on the Antioxidants, Antioxidant Activity, and Hypolipidemic Activity of Green Jujube Vinegar

Healthy fruit vinegar has been extensively favored in China in recent years. As a new type of fruit vinegar developed by our laboratory, green jujube vinegar has the characteristics of good taste and rich nutrition. To study the effect of in vitro gastrointestinal digestion on the antioxidant and hypolipidemic activity of green jujube vinegar, so as to provide basic data for research and the development of healthy food antioxidants, including the total phenolic content (TPC), total flavonoid content (TFC), total acid content, and volatile acid content, were measured. The antioxidant activity was measured by using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical scavenging methods and the ferric reducing antioxidant power assay (FRAP), and the hypolipidemic activity was measured by cholesterol adsorption and the sodium cholate adsorption capacities. The results show that gastric digestion significantly (p < 0.05) decreased the TPC, TFC, total acid content, and volatile acid content, for which the highest reductions were up to 54.17%, 72%, 88.83% and 82.35%, respectively. During intestinal digestion, the TFC remained at a high level and unchanged, and the TFC and volatile acid content significantly (p < 0.05) decreased by 72.66% and 89.05%, respectively. The volatile acid content did not significantly (p > 0.05) change within 2 h. The ABTS free radical scavenging ability and the reducing power free radical scavenging rate were correlated with the TPC, TFC, and total acid contents, and the DPPH free radical scavenging ability and cholesterol adsorption capacity were not. These findings suggest that green jujube vinegar can be a potential functional food for people’s use.

Preparation of Cellulose Nanocrystals from Jujube Cores by Fractional Purification

Jujube cores are fiber-rich industrial waste. Dewaxing, alkali treatment, bleaching, and sulfuric acid hydrolysis were used to generate cellulose nanocrystals (CNCs) from the jujube cores in this study. The morphological, structural, crystallinity, and thermal properties of the fibers were investigated using FE-SEM, TEM, AFM, FT-IR, XRD, and TGA under various processes. CNCs’ zeta (ζ) potential and water contact angle (WAC) were also investigated. The findings demonstrate that non-fibrous components were effectively removed, and the fiber particles shrunk over time because of many activities. CNCs had a rod-like shape, with a length of 205.7 ± 52.4 nm and a 20.5 aspect ratio. The crystal structure of cellulose Iβ was preserved by the CNCs, and the crystallinity was 72.36%. The temperature of the fibers’ thermal degradation lowered during the operations, although CNCs still had outstanding thermal stability (>200 °C). Aside from the CNCs, the aqueous suspension of CNCs was slightly agglomerated; thus, the zeta (ζ) potential of the CNCs’ suspension was −23.72 ± 1.7 mV, and the powder had high hydrophilicity. This research will be valuable to individuals who want to explore the possibility for CNCs made of jujube cores.

Development of Functional Pizza Base Enriched with Jujube (Ziziphus jujuba) Powder

Functional and enriched foods are increasingly in demand in the global market due to their benefits for human health and their prevention of several diseases. The aim of this work was to develop a functional pizza base, produced in the Neapolitan style, exploiting the beneficial properties of jujube. The jujube fruit is rich in phenolic compounds with high antioxidant activity and represents a good candidate for functional food development. The doughs were prepared by replacing the wheat flour with 2.5%, 5.0%, and 7.5% (w/w) of Ziziphus jujube powder (ZJP) and were subsequently cooked. Chemical analyses showed that both total phenolic compounds and antioxidant activity grew with the increase of ZJP. The addition of ZJP darkened the pizza base and raised its hardness, gumminess, and chewiness. However, no difference was found in the springiness and cohesiveness of the samples with or without ZJP. These results suggest that jujube powder can be successfully introduced into pizza dough as a functional ingredient.

Metabolite and Gene Expression Analysis Underlying Temporal and Spatial Accumulation of Pentacyclic Triterpenoids in Jujube

Jujube (Ziziphus jujuba Mill.) has attracted increasing attention because of its fruits’ high nutritional and medicinal value, which produce pentacyclic triterpenoids with valuable pharmacological activities beneficial to human health. However, the dynamic accumulation and metabolism pathway of triterpenoids remain unknown in jujube. Here, we performed metabolite assays of triterpenoids and expression analysis of genes involved in the corresponding metabolic processes on cultivated jujube (Z. jujuba cv. Junzao) and one type of wild jujube (Z. jujuba var. spinosa cv. Qingjiansuanzao). Our results showed that the triterpenoids accumulate predominantly in young leaves, annual stems, buds, and white-mature and beginning red stage fruit. Besides, the total triterpenoid content, ceanothic acid, oleanonic acid, and 3-ketoursolic acid were higher in ‘Qingjiansuanzao’ than in ‘Junzao’. Moreover, we found 23 genes involved in terpenoids metabolism were expressed in all organs, and the ZjSQS1, ZjCYP450/1, ZjCYP450/3, ZjOSC1, ZjFPS, and ZjAACT2 gene expression patterns were consistent with metabolites accumulation during fruit development. In addition, 100 μM MeJA induced ZjSQS1, ZjFPS, and ZjHMGR3 expression in leaves and enhanced triterpenoids accumulation. These findings will help understand the unique metabolism of terpenoids and will benefit further utilization and breeding of jujube as both edible fruit and functional food.

Development of energy-rich protein bars and in vitro determination of angiotensin I-converting enzyme inhibitory antihypertensive activities

Three energy-rich protein (ERP) bars were prepared to meet the daily recommended dietary allowance (RDA) for the protein of Pakistani athletes. The bars were developed using dates, cheddar cheese (CC), whey protein isolate (WPI), roasted chickpea flour, and rice flour in different proportions. Bar #1 contained 64 g dates, 16 g dried apricots, 12 g WPI, and 8 g ripened CC. Bar #2 contained the same proportion of these ingredients with an addition of 12.5 g roasted chickpea flour, while bar #3 contained 6.25 g roasted rice and 6.25 g roasted chickpea flour. All the ingredients were homogeneously mixed into paste to form bars weighing 100-110 g per serving size. These bars were studied for the compositional analysis (moisture, protein, and lipid content), protein characterization through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and in vitro determination of the angiotensin I-converting enzyme (ACE-I) antihypertensive activity. Moisture and lipid content in bars were 22% and 0.057%-0.313%, respectively, while protein, fiber, and ash contents varied from 22.3% to 23.6%, 6.66 to 5.81, and 2.12% to 2.44%, respectively. The minimum energy content was recorded (272.70 Kcal/100 g) in bar #1 while bar #3 showed the highest energy content 274.65 Kcal/110 g with the addition of (5%) roasted chickpea and rice flour, respectively. Electrophoresis analysis of proteins in bar # 1 (cheese +WPI) showed the four bands at 62, 24, 20, and 12 kDa. Bar #2 (10% roasted chickpea flour) showed some additional bands at 40, 36, 34, and 28 kDa while relatively lower antihypertensive activity than bars #1 and 3. The study revealed that adding 10% roasted chickpea flour (bar #2) increased the protein content and diversity in proteins. It provided 40% proteins to athletes and could be helpful to meet their R.D.A. by consuming two bars/day.

Haplotype Analysis of Chloroplast Genomes for Jujube Breeding

Jujube (family Rhamnaceae) is an important economic fruit tree in China. In this study, we reported 26 chloroplast (cp) sequences of jujube using Illumina paired-end sequencing. The sequence length of cp genome was 161, 367-161, 849 bp, which was composed of a large single-copy region (89053-89437 bp) and a small single-copy region (19356-19362 bp) separated by a pair of reverse repeat regions (26478-26533 bp). Each cp genome encodes the same 130 genes, including 112 unique genes, being quite conserved in genome structure and gene sequence. A total of 118 single base substitutions (SNPs) and 130 InDels were detected in 65 jujube accessions. Phylogenetic and haplotype network construction methods were used to analyze the origin and evolution of jujube and its sour-tasting relatives. We detected 32 effective haplotypes, consisting of 20 unique jujube haplotypes and 9 unique sour-jujube haplotypes. Compared with sour-jujube, jujube showed greater haplotype diversity at the chloroplast DNA level. To cultivate crisp and sweet fruit varieties featuring strong resistance, by combining the characteristics of sour-jujube and cultivated jujube, three hybrid combinations were suggested for reciprocal crosses: "Dongzao" × "Jingzao39," "Dongzao" × "Jingzao60," "Dongzao" × "Jingzao28." This study provides the basis for jujube species' identification and breeding, and lays the foundation for future research.

Investigation of the Volatile Profile of Red Jujube by Using GC-IMS, Multivariate Data Analysis, and Descriptive Sensory Analysis

The aroma characteristics of six red jujube cultivars (Jinchang-'JC', Junzao-'JZ', Huizao-'HZ', Qiyuexian-'QYX', Hetiandazao-'HTDZ', and Yuanzao-'YZ'), cultivated in Xinjiang Province, China, were studied by E-nose and GC-IMS. The presence of acetoin, E-2-hexanol, hexanal, acetic acid, and ethyl acetate played an important role in the classification results. JC, JZ, HZ, and YZ were different from others, while QYX and HTDZ were similar to each other. HZ had the most abundant specific VOCs, including linalool, nonanoic acid, methyl myristoleate, 2-acetylfuran, 1-octen-3-one, E-2-heptenal, 2-heptenone, 7-octenoic acid, and 2-pentanone. HZ had higher intensity in jujube ID, floral, sweet, and fruity attributes. Correlation analysis showed that jujube ID (identity) might be related to phenylacetaldehyde and isobutanoic acid that formed by the transamination or dehydrogenation of amino acids; meanwhile, the sweet attribute was correlated with amino acids, including threonine, glutamic acid, glycine, alanine, valine, leucine, tyrosine, phenylalanine, lysine, histidine, and arginine.

Hydrogen sulfide treatment increases the antioxidant capacity of fresh Lingwu Long Jujube (Ziziphus jujuba cv. Mill) fruit during storage

Hydrogen sulfide (H₂S) has been identified as an important gaseous signal molecule in plants. Here, we investigated the effects of H₂S on postharvest senescence and antioxidant metabolism of Lingwu Long Jujube (Ziziphus jujuba cv. Mill) fruits (LLJF). Fumigation of Jujube fruits with H₂S released from 0.4 mm NaHS could significantly prolong the postharvest shelf life of jujube fruits, reduce the decay rate of fruit, the weight loss of fruit, and inhibit the fruit loss, hardness, color, soluble solids, and titratable acidity. Compared with the control group, exogenous H₂S fumigation significantly decreased the loss of chlorophyll, carotenoids, soluble protein, ascorbic acid, phenols, and flavonoids in jujube fruits during post-harvest storage. At the same time, H₂S could significantly delay the accumulation of malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and superoxide anion (O₂^∙−) and promote catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD) activity, and inhibit polyphenol oxidase (PPO) activity. To summarize, H₂S can effectively alleviate postharvest senescence and decay of jujube fruits by regulating the ROS accumulation and antioxidant enzymes, and prolong the storage period of postharvest.

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H₂S treatment could significantly prolong the postharvest shelf life of jujube fruits.

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H₂S could significantly delay the accumulation of MDA, H₂O₂ and O₂^∙− during storage of jujube fruits.

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H₂S treatment promote CAT, SOD, APX, POD activity, and inhibit PPO activity during storage of jujube fruits.

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Provides a new method for storage of post-harvest jujube fruits.

Purification and antioxidant properties of triterpenic acids from blackened jujube (Ziziphus jujuba Mill.) by macroporous resins

In order to investigate the purification process and antioxidant activity of triterpenic acids from blackened jujube, the macroporous resin was applied to purify the crude extract from blackened jujube. The adsorption and desorption characterizations of five different macroporous adsorption resins (AB-8, D-101, X-5, HPD-100, S-8) for triterpenic acids of blackened jujube were compared, the optimum purification resins were screened, and the purification parameters were optimized. The antioxidant activity of crude extracts and purified products from blackened jujube was analyzed. The results showed that D-101 resin possessed the best effect on the purification of blackened jujube triterpenic acids. The optimum purification parameters were as follows: sample concentration 25.5 μg/ml, 130 ml of the sample volume was with a flow rate of 2.0 ml/min, eluted with 95% ethanol, and speed flow was 1.0 ml/min. The purity of triterpenic acids was increased by 2.49 times after purification with a recovery rate of (78.58 ± 0.67)%. Furthermore, the IC50 values of hydroxyl radical scavenging capacity from triterpenic acids crude extract and purified substances were 0.900 and 0.850 mg/ml, respectively, and the IC50 values of superoxide anion radical were 0.745 and 0.594 mg/ml, respectively, indicating that the antioxidative capacity of the purified product was stronger than the crude extract. The purified triterpenic acids (PTA) groups at different doses had excellent protective effects on H2O2-induced damage HUVEC cells. Results have revealed that triterpenic acids of blackened jujube have good antioxidant function and utilization and development prospects.

Flavonoid Glycosides from Ziziphus jujuba var. inermis (Bunge) Rehder Seeds Inhibit α-Melanocyte-Stimulating Hormone-Mediated Melanogenesis

Ziziphus jujuba extracts possess a broad spectrum of biological activities, such as antioxidant and anticancer activities in melanoma cancers. Nevertheless, the compounds contain high antioxidant capacities and anticancer activities in melanoma cells, shown to be effective in hyperpigmentation disorders, but whether flavonoid glycosides from Z. jujuba regulate anti-melanogenesis remains unclear. In this study, we evaluated the anti-melanogenic activity of five flavonoid glycosides from Z. jujuba var. inermis (Bunge) Rehder seeds, including jujuboside A (JUA), jujuboside B (JUB), epiceanothic acid (EPA), betulin (BTL), and 6’’’-feruloylspinosin (FRS), in B16F10 melanoma cells and zebrafish larvae. According to our results, JUB, EPA, and FRS potently inhibited α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis and prevented hyperpigmentation in zebrafish larvae. In particular, under α-MSH-stimulated conditions, FRS most significantly inhibited α-MSH-induced intracellular and extracellular melanin content in B16F10 melanoma cells. Additionally, JUB, EPS, and FRS remarkably downregulated melanogenesis in α-MSH-treated zebrafish larvae, with no significant change in heart rate. Neither JUA nor BTA were effective in downregulating melanogenesis in B16F10 melanoma cells and zebrafish larvae. Furthermore, JUB, EPA, and FRS directly inhibited in vitro mushroom tyrosinase enzyme activity. JUB, EPA, and FRS also downregulated cyclic adenosine monophosphate (cAMP) levels and the phosphorylation of cAMP-response element-binding protein (CREB), and subsequent microphthalmia transcription factor (MITF) and tyrosinase expression. In conclusion, this study demonstrated that JUB, EPA, and FRS isolated from Z. jujuba var. inermis (Bunge) Rehder seeds exhibit potent anti-melanogenic properties by inhibition of the cAMP-CERB-MITF axis and consequent tyrosinase activity.

Research advances in bioactive components and health benefits of jujube (Ziziphus jujuba Mill.) fruit

Jujube (Ziziphus jujuba Mill.), a highly nutritious and functional fruit, is reported to have various health benefits and has been extensively planted worldwide, especially in China. Many studies have shown that bioactive components derived from jujube fruit have significant nutritional and potential biological effects. In this paper, the latest progress in research on major bioactive compounds obtained from jujube is reviewed, and the potential biological functions of jujube fruit resources are discussed. As a dietary supplement, jujube fruit is well recognized as a healthy food which contains a variety of bioactive substances, such as polysaccharides, polyphenols, amino acids, nucleotides, fatty acids, dietary fiber, alkaloids, and other nutrients. These nutrients and non-nutritive phytochemicals obtained from jujube fruit have physiological functions including anticancer, antioxidant, anti-inflammatory, anti-hyperlipidemic, anti-hyperglycemic, immunoregulatory, neuroprotective, sedative, and antiviral functions. Of note is that new constituents, including alkaloids, dietary fiber, and other bioactive substances, as well as the antiviral, hypoglycemic, lipid-lowering, and neuroprotective effects of jujube fruit, are systematically reviewed here for the first time. Meanwhile, problems affecting the exploitation of jujube fruit resources are discussed and further research directions proposed. Therefore, this review provides a useful bibliography for the future development of jujube-based products and the utilization of jujube nutritional components in functional foods.