| Xinjiang gray jujube is rich in nutrients and belongs to the excellent food of medicine and food.However,the current primary processing of jujube is mainly based on drying,which is a single product and not conducive to the efficient development of the industry.The extraction and application of jujube polysaccharides with strong antioxidant activity can significantly increase the local economic benefits.In this paper,hot water extraction,ultrasound-assisted,enzyme-assisted and multi-mode ultrasound-assisted enzymatic methods were used to extract the polysaccharides from jujube and characterize their physicochemical properties,structural properties and antioxidant activity;The best extraction method was screened out and applied to the pilot scale for scale-up,which provided theoretical basis and data support for the research of jujube polysaccharide from laboratory level to industrial production.At the same time,the development of jujube polysaccharide-peptide composite functional beverage products is carried out to increase its industrial benefits.The main contents and conclusions of the study are as follows:(1)Study on the extraction process of jujube polysaccharide by multi-mode ultrasound-assisted enzymatic method.The extraction of jujube polysaccharides(JPS)was carried out using a combined extraction method with multiple frequency modes(single-frequency,dual-frequency and triple-frequency)of ultrasound-assisted enzymatic methods,and hot water extraction(HWE),ultrasound-assisted(UAE)and enzyme-assisted extraction(EAE)were used as controls,and the extraction rate,extraction time and antioxidant activity(DPPH radical scavenging capacity,ABTS radical scavenging capacity,hydroxyl radical scavenging capacity and total reducing power)were used as indicators for the screening of the best extraction method by using a comprehensive score.The results showed that compared with the traditional extraction method,ultrasonic-assisted enzymatic extraction could significantly improve the yield of jujube polysaccharide by about 12.62-24.19%,among which the highest yield was obtained by JPS-22 k Hz+E.The 22/33 k Hz dual-frequency ultrasound-assisted enzymatic method,which possessed higher yield with better maintenance of antioxidant activity.According to the results of antioxidant activity before and after gastrointestinal digestion simulation,the DPPH and ABTS radical scavenging ability of jujube polysaccharide were significantly increased after gastrointestinal digestion,and this conclusion can provide a scientific basis for the oral consumption of jujube polysaccharide as an antioxidant food.(2)Physicochemical properties and structural characterization of jujube polysaccharides extracted by multimodal ultrasound-assisted enzymatic method.The polysaccharides obtained by different extraction methods were separated and purified by decolorization,degreasing,deproteinization with Sevage reagent and dialysis,and the purified jujube polysaccharides were subsequently used to characterize the glycosidic bond type,monosaccharide composition,molecular weight,rheological properties,thermal stability,microscopic morphology and spatial structure of jujube polysaccharides by infrared spectroscopy,ultraviolet spectroscopy,high performance size exclusion chromatography,particle size analyzer,thermal analyzer,rheometer,scanning electron microscopy and atomic force microscopy,The results showed that the ultrasonic-assisted enzymatic method was effective in the analysis of the glycosidic bond type,monosaccharide composition,molecular weight,rheological properties,thermal stability,microscopic morphology and spatial structure of the date palm.The results showed that the ultrasonic-assisted enzymatic method did not have any significant effect on the monosaccharide composition of jujube polysaccharides,and all the seven tested monosaccharides and one glyoxalate could be detected,but there was a significant effect on the monosaccharide content,with maltose(Mal)predominating and galactose(Gal)and arabinose(Ara)following.The molecular weight of the polysaccharides obtained by ultrasound-assisted enzymatic extraction was significantly lower than that of the traditional extraction method,and the heavy average molecular weight(Mw)decreased from 7.46×105 Da to 0.93×105Da-1.94×105 Da.The molecular weight results were consistent with the particle size,and the small molecular weight polysaccharides showed better antioxidant activity.SEM showed that the ultrasound-assisted enzyme method effectively broke the glycosidic bonds of the polysaccharides,furthermore,the lamellar structure of the polysaccharides was broken into small flakes,and contained filamentous branches and showed a loose mesh-like morphology,and the chain structure of the polysaccharides extracted by ultrasound-assisted enzyme method under AFM became shorter and the side chains were broken,more disordered,and the molecular height decreased significantly,and there was no obvious aggregation.There was no obvious aggregation.(3)The best process obtained is carried out in pilot scale-up test research,and material consumption,energy consumption,water consumption,etc.are calculated respectively to provide a theoretical basis for industrial production.The results showed that the 22/33 k Hz dual-frequency ultrasonic auxiliary enzyme method could extract jujube polysaccharides well,and the extraction rate could reach 64.96%,and it was found that 25 kg of fresh jujube raw materials consumed a total of 1000.64 k W·h in the pilot amplification test of polysaccharide extraction,the water consumption was6500 L,and the consumption cost reached 894.59 yuan,which provided a theoretical basis for the actual industrial production.Taking the pilot production final product as raw material,the development of polysaccharide-peptide composite functional beverage was carried out,and the response surface optimization test was carried out on the basis of single factors,and it was found that the best formula process was:45.77%(v/v)of jujube polysaccharide concentrate,2.10% collagen peptide,1.06%maltodextrin and 0.018% of citric acid added,at this time,the comprehensive score of the obtained product was the highest,and the sensory indexes,physical and chemical indexes and microbiological indicators of the product met the requirements of relevant national standards.In summary,according to the laboratory level and pilot magnification test results,ultrasonic assisted enzymatic method can be used as a good extraction method of jujube polysaccharides,which not only significantly improves the extraction rate of polysaccharides,but also enhances its biological activity by changing the basic structure of polysaccharides,so that the obtained polysaccharides can be better used in industrial production,thereby significantly increasing local industrialization benefits. |
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