SHU GAOFENG

殳 高峰

Tsukuba Repository

Preparation and Characterization of
Ergocalciferol-Loaded Nanodispersions
Stabilized by Different Emulsifiers
著者 SHU GAOFENG
year 2018
その他のタイトル 異なる乳化剤を利用したエルゴカルシフェロール内
包化ナノ分散系の調製及び特性評価
学位授与大学 筑波大学 (University of Tsukuba)
学位授与年度 2018
報告番号 12102甲第8854号
URL http://hdl.handle.net/2241/00153918
  
氏     名 SHU GAOFENG 
学 位 の 種 類       EA 博士（食料革新学） 
A学 位 記 番 号       EA 博 甲第   ８８５４   号 
A学位授与年月       EA 平成 ３０年 ９月 ２５日 
A学位授与の要件       EA 学位規則 第４条第１項該当（昭和２８年４月１日文部省令第９号） 
審 査 組 織 グローバル教育院 
学位論文題目  Preparation and Characterizat ion of Ergocalciferol-Loaded  
Nanodispersions Stabil ized by Different Emulsif iers（異なる乳化剤を利用  
したエルゴカルシフェロール内包化ナノ分散系の調製及び特性評価）  
 （職名） （学位） （氏名） 
主査 筑波大学教授 博士（工学） 市川 創作 
副査 筑波大学教授 工学博士 中嶋 光敏 
副査 
筑波大学准教授 
（協働大学院） 
博士（農学） 小林 功 
副査 筑波大学准教授 博士（農学） Marcos Antonio das NEVES 
 
 
Abstract of thesis 
Vitamin D is one of the essential bioactive compounds for human being, due to its special health-promoting 
functionality. Previous studies have demonstrated that this substance contributes to the development of bone, teeth 
and cartilage. Moreover, it also prevents cancer, and enhances the heart and immune system. Ergocalciferol is a type 
of plant-based vitamin D, which is naturally present in a low amount in wild mushrooms, whereas another type called 
cholecalciferol can be produced in the human skin via the exposure of sunlight. However, there is still an estimated 
one billion people worldwide who either have vitamin D deficiency or insufficiency due to limited sun exposure, 
extensive UV-protecting sun cream usage, or poor dietary intake. For these above-mentioned reasons, fortified food 
and beverage products with vitamin D are gaining attention in food industry nowadays. However, vitamin D has poor 
water-solubility, chemical instability towards environmental stresses and variable oral bioavailability, which strongly 
limit the application of this vitamin as a functional ingredient to be incorporated into aqueous-based food products. 
Encapsulation of vitamin D in nanodispersion-based delivery systems could be an attractive strategy to overcome 
these limitations. Selection of an appropriate emulsifier is extremely important to prepare a stable and efficient 
nanodispersion. The author therefore aimed to formulate and characterize ergocalciferol-loaded nanodispersions 
stabilized by different emulsifiers.  
 Firstly, the author prepared ergocalciferol-loaded nanoemulsions by using high-pressure homogenization method. 
The effects of emulsifier type and concentration, oil type and concentration, and homogenization pressure on the 
droplet characteristics of nanoemulsions produced by high-pressure homogenizer were investigated. The results 
showed that the average size of emulsified droplets decreased with increasing operating pressure and emulsifier 
concentration. Nano-sized droplets (d4,3 < 150 nm) could be successfully formed using soybean oil, perilla oil and 
medium chain triglyceride (MCT). The nanoemulsions stabilized by modified lecithin (ML), sodium caseinate (SC) 
or decaglycerol monooleate (MO7S) showed similar droplet size and size distribution.  
Secondly, the author investigated the effect of emulsifier type on the stability of ergocalciferol-loaded 
nanoemulsions. The stability of resulting nanoemulsions was evaluated when they exposed to different environmental 
stresses and during 30 days of storage at 25 and 55 ᵒC. Results showed that the emulsions prepared by MO-7S or ML 
were stable against a wide range of pH (2-8), while SC-stabilized emulsions showed instability with extensive droplet 
aggregation at pH 4 and 5. Only ML-stabilized emulsions showed droplet growth due to coalescence when treated at 
high NaCl concentration (300-500 mM). In the absence of glucose, SC-stabilized O/W emulsions showed better 
freeze-thaw stability, in comparison to those formed with ML or MO-7S emulsifiers. The emulsion produced by ML 
was found to be stable to droplet aggregation at high temperatures (80-120 ᵒC) for 1 h. All the O/W emulsions stored 
at 25 ᵒC showed good physical and chemical stabilities. However, the chemical stability of ergocalciferol in emulsion 
system decreased in order of ML > MO-7S >> SC during storage at 55 ᵒC for a period of 30 days. 
Thirdly, the author examined the effect of emulsifier type on the in vitro bioaccessibility of ergocalciferol-loaded 
nanoemulsions (mouth, stomach and small intestinal phases). Results indicated that the droplet size, size distribution, 
ζ-potential and microstructure of nanoemulsions during digestion depended on the emulsifier type. The fate of lipid 
in the small intestinal phase also relied on the emulsifier type, with the free fatty acids release rate decreasing in the 
following order: MO7S > ML-MO7S > ML > SC. The bioaccessibility of ergocalciferol in nanoemulsions prepared 
using MO7S, ML, and ML-MO7S was 62%, 64%, 65%, respectively, which was higher than that stabilized by SC, 
12%. No significant loss of ergocalciferol was observed in all nanoemulsions after full digestion; they were 
chemically stable against digestion conditions, regardless of the emulsifier type. 
Lastly, the author investigated the formulation, stability and bioaccessibility of ergocalciferol nanodispersions 
stabilized by ML and SC as natural emulsifiers. The mean particle size of nanodispersions stabilized by ML, 56 nm, 
was much smaller than those stabilized by SC, 112 nm. The ML-stabilized nanodispersions were stable over a wide 
range of pH, NaCl concentrations and heating, but became unstable with slight increase in particle size when exposed 
to CaCl2 solution. In comparison, SC-stabilized nanodispersions were relatively unstable, becoming aggregation 
under the conditions of pH 4-5, CaCl2 addition and heating. Long-term stability for ergocalciferol were observed in 
both ML- and SC-stabilized nanodispersions. The bioaccessibility of ergocalciferol was strongly dependent on the 
emulsifier type, with ML providing much higher bioaccessibility than SC. 
The author has found that modified lecithin is a promising natural emulsifier for preparing ergocalciferol 
nanoemulsions/nanodispersions with excellent stability and ergocalciferol bioaccessibility. Comparing with 
nanoemulsions, ergocalciferol nanodispersions could be prepared using much lower level of emulsifier, which seems 
to be more practical in food production.                
 
 
 Abstract of assessment result 
【Review】 
Vitamin D deficiency is prevalent in many populations, which leads to adverse health effects. Thus, it is important 
to develop foods and beverages with this water-insoluble micronutrient. This work therefore aimed at developing 
effective dispersion systems for delivering ergocalciferol (vitamin D2). In order to produce O/W nanoemulsions with 
relatively small droplets, the author investigated and optimized the operating parameters of high-pressure 
homogenization method. The factors influencing the physiochemical stability of the resulting nanoemulsions were 
then systematically investigated, and the corresponding mechanisms were well clarified. In addition, the author 
elucidated the relationship between emulsifier type and ergocalciferol bioaccessibility of nanoemulsions via in vitro 
digestion model. Lastly, the author clarified that effective ergocalciferol nanodispersions with high stability and 
bioaccessibility could successfully formulated via solvent displacement method using natural emulsifiers such as 
enzymatically modified lecithin. A variety of food products (e.g., soups and beverages) could be fortified with 
ergocalciferol-enriched nanoemulsions/nanodispersions, which may solve vitamin D deficiency prevalent in many 
people. Overall, the results obtained by the author in this study would contribute to a food innovation through the 
development and efficient design of nano-delivery systems for vitamin D.   
 
【Result】 
The final examination committee conducted a meeting as a final examination on 18 June, 2018. The applicant 
provided an overview of dissertation, addressed questions and comments raised during Q&A session. All of the 
committee members reached a final decision that the applicant has passed the final examination. 
 
【Conclusion】 
Therefore, the final examination committee approved that the applicant is qualified to be awarded Doctor of Food 
Innovation of Life Science Innovation Program. 


異なる乳化剤を利用したエルゴカルシフェロール内包化ナノ分散系の調製及び特性評価

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異なる乳化剤を利用したエルゴカルシフェロール内包化ナノ分散系の調製及び特性評価

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