Authors:ZHAO Peng1,YANG Shang1,ZHANG Huiling2,WEN Lunjun2,HU Xia2,SUN Haipeng2,CUI Zixue1,HOU Qirui2*
Affiliations: 1.Henan Sericulture Research Institute;2.Jiangsu University of Science and Technology
Introduction:Zhao Peng, male, from Nanzhao, Henan Province, assistant researcher, engaged in research on mulberry resource utilization. *Corresponding author, associate researcher, Ph.D., engaged in research on mulberry resource utilization.
Funds: Jiangsu Industry-University-Research Cooperation Project (BY2019259).
Source: Anhui Agricultural Sciences, Issue 6, 2024
Citation format: ZHAO Peng, YANG Shang, ZHANG Huiling, et al.Preparation and characterization of mulberry polyphenol microcapsules[J].Anhui Agricultural Sciences,2024,52(6):166-169.
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Morus alba L. is a perennial leaf cash crop, which has the characteristics of barrenness, drought tolerance and strong adaptability, and has a wide cultivation range in the mainland. It is estimated that the planting area of mulberry in mainland China is more than 10.6hm2, and the biomass yield of fresh mulberry leaves is 25~30t/hm2 per year, which is one of the highest yield tree species among woody leaf plants. Mulberry leaves have been used as fodder for silkworms for hundreds of years. Based on its antioxidant, antibacterial, and hypolipidemic properties, mulberry leaves are also used in Chinese herbal medicine. In recent years, people have a new understanding of the nutritional value and therapeutic efficacy of mulberry leaves, and mulberry leaves and their extracts are being widely used in feed and animal breeding, and have remarkable effects in improving animal production performance, feed conversion efficiency and animal product quality.
Polyphenols are phenolic secondary metabolites in plants, which are widely present in plant leaves, fruits, skins, and roots. Sanpolyphenols account for l%~3% of the dry weight of mulberry leaves, and have strong activities to scavenge hydroxyl radicals and oxygen radicals, which is a natural antioxidant of plants that needs to be developed urgently and contains a large amount in the mainland. There are multiple hydroxyl groups on the plant polyphenol benzene ring, which can undergo chemical reactions such as elimination, substitution, displacement and color development, which is highly unstable in nature, and the storage process will also be affected by oxidants, heat, light and enzyme reactions, reducing the bioavailability of polyphenolic compounds. Microencapsulation technology uses natural or synthetic polymer materials as wall materials, and the protected substances as the core materials, through microencapsulation, the core material is reduced from contact with the external environment, so that it is protected from light, temperature or oxide damage, and improves stability. Studies have shown that microencapsulation technology can significantly improve the stability and storage of polyphenols, and microcapsules have a sustained-release effect, which can prevent polyphenols from being destroyed by digestive juices and incomplete absorption. The wall materials commonly used in microencapsulation are maltodextrin, pullulan, rennet, sodium alginate, pectin, β-cyclodextrin, etc.
objective
Obtain better mulberry polyphenol microcapsule products to promote the development and utilization of mulberry leaf resources in food and feed additives.
way
Sanpolyphenol microcapsules were prepared by freeze-drying method with β-cyclodextrin as the wall material and mulberry extract as the core material, and their sustained-release characteristics, stability and antioxidant properties were tested. The ratio of Sanpolyphenol extract to β-cyclodextrin is shown in Table 1, and the standard curve of gallic acid is shown in Figure 1.
Fig.1 Standard curve of gallic acid
outcome
◆Embedding efficiency and microstructure of mulberry polyphenol microcapsules
The concentration of β-cyclodextrin in the wall material was optimized according to the concentration of the mulberry extract. As shown in Table 2, the embedding efficiency of Sanpolyphenol microcapsules increased with the increase of β-cyclodextrin (up to 76.97%), and the surface polyphenol content, total polyphenol content and embedding efficiency of Sanpolyphenol extract: β-cyclodextrin ≤ 1∶3 (T3~T6) tended to be stable. The increase in the concentration of wall material decreases the content of polyphenols per unit mass, so the content of polyphenols decreases relatively with the increase of β-cyclodextrin. Based on the data of embedding efficiency and total polyphenol content, the T4 combination was excellent.
The T4 group was selected for microstructure observation, and the results are shown in Figure 2. The adhesion of non-microencapsulated mulberry polyphenols was serious, and the dispersion was improved and fluffy after microencapsulation.
注:B.100 μm; C.300 μm; D.500 μm。
Fig.2 Scanning electron microscope (SEM) micrographs of unmicroencapsulated (A) and microencapsulated (B, C, D) sanpolyphenols
◆ Sanpolyphenol microcapsules release polyphenols in simulated gastric and intestinal fluids
Wrapping the smaller size of Sanpolyphenol with β-cyclodextrin can not only enhance its resistance to adverse environments, but also enable the rapid release of Sanpolyphenols in microcapsules under suitable conditions in the intestine, and significantly improve its effective absorption rate in the intestine. The dissolution of Sanpolyphenol microcapsules in artificial gastric and intestinal fluid in the T4 group is shown in Figure 3. In artificial gastric juice, the maximum polyphenol content is about 120 min (0.45 mg/mL), while in artificial intestinal fluid, the polyphenol content can quickly release polyphenols, and the polyphenol content rises rapidly to 1.18 mg/mL at 10 min, and the content is maintained at about 1.0 mg/mL in the next 2 hours (the maximum value is 1.19 mg/mL at 60 min). After being treated with artificial gastric juice, the mulberry microcapsules still maintained a granular state and the liquid was clear, but after entering the artificial intestinal juice, they became loose and gradually disintegrated, and the liquid was turbid, indicating that the obtained microcapsules had a good sustained release effect. The calculation showed that the maximum cumulative release degree of Sanpolyphenol microcapsules reached 88.37%.
Fig.3 Dilution curves of polyphenols in simulated intestinal and gastric juices of mulberry microcapsules
◆Stability test of Sanpolyphenol microcapsules
It can be seen from Figure 4 that with the extension of time, the overall polyphenol retention rate in Sanpolyphenol microcapsules and Sanpolyphenol samples showed a significant downward trend, and the polyphenol content in Sanpolyphenol samples decreased more sharply. The retention rate of polyphenols contained in Sanpolyphenol microcapsules was 86.22% after 20 days, while the retention rate of polyphenols in Sanpolyphenol samples was only 42.43%, indicating that the protection effect of microencapsulation on the internal core material was ideal, which could effectively improve the stability of Sanpolyphenols during storage.
Fig.4 Relationship between placement time and polyphenol retention
◆Detection of antioxidant activity of mulberry polyphenol microcapsules
Polyphenolic compounds generally have antioxidant activity, which can effectively scavenge harmful free radicals in the body and exert antioxidant damage effects. As can be seen from Figure 5, the antioxidant activity of Sanpolyphenol microcapsules is comparable to that of Sanpolyphenols. The ability of OH and O-2· showed an obvious dose-response relationship, and the ability to clear DPPH· showed a significant upward trend at low concentrations (≤0.5 mg/mL), and the clearance rate above 0.5 mg/mL did not change much. With the increase of sample concentration, the polyphenol content in the Sanpolyphenol microcapsule was lower than that in the Sanpolyphenol sample, so the ability of the Sanpolyphenol microcapsule to scavenge free radicals at high concentrations was slightly lower than that of Sanpolyphenol.
Fig.5 Sanpolyol microcapsules and the effects of Sanpolyphenol on · Clearance capacity of OH(a), DPPH·(b) and O-2·(c).
conclusion
The embedding efficiency of mulberry microcapsules increased with the increase of β-cyclodextrin, and the polyphenol content and embedding efficiency tended to be stable when the ratio of the two was ≤ 1∶3. The scavenging rates of OH, DPPH· and O-2· were comparable to those of Sanpolyphenols, indicating that microencapsulation did not affect their antioxidant activity.
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