ABSTRACT
Astaxanthin (AX) is one of the major bioactives that has been found to have strong antioxidant properties. However, AX tends to degrade due to its highly unsaturated structure. To overcome this problem, a Pickering O/W emulsion using nanofibrillated cellulose (NFC) as an emulsifier was investigated. NFC was used because it is renewable, biodegradable, and nontoxic. The 10 wt% O/W emulsions with 0.05 wt% AX were prepared with different concentrations of NFC (0.3-0.7 wt%). After 30 days of storage, droplet size, ζ-potential values, viscosity, encapsulation efficiency (EE), and color were determined. The results show that more stable emulsions are formed with increasing NFC concentrations, which can be attributed to the formulation of the NFC network in the aqueous phase. Notably, the stability of the 0.7 wt% NFC-stabilized emulsion was high, indicating that NFC can improve the emulsion's stability. Moreover, it was found that fat digestibility and AX bioaccessibility decreased with increasing NFC concentrations, which was due to the limitation of lipase accessibility. In contrast, the stability of AX increased with increasing NFC concentrations, which was due to the formation of an NFC layer that acted as a barrier and prevented the degradation of AX during in vitro digestion. Therefore, high concentrations of NFC are useful for functional foods delivering satiety instead of oil-soluble bioactives.
ABSTRACT
The objective of this study was to explore the influence of nanocellulose type (nanocrystalline cellulose (NCC) and nanofibrillated cellulose (NFC)) and concentrations (0.05-0.20%, w/w) on the physicochemical properties, microstructure, and in vitro digestion of ß-carotene loaded emulsions and ß-carotene bioaccessibility. The optimum conditions for the formation of stable ß-carotene loaded emulsions were found when NCC was used as a stabilizer at a concentration of 0.2% w/w. This was due to the rod-shaped structure of NCC, which led to more stable emulsions with smaller droplet size and reduced flocculation. During the in vitro gastrointestinal digestion, NFC emulsions at increased concentrations were found to retard free fatty acid (FFA) release from the emulsions and reduce the bioaccessibility of ß-carotene. On the other hand, NCC emulsions at concentrations of 0.2% w/w promoted lipolysis and demonstrated highest ß-carotene bioavailability. Hence, these emulsions could be used for the delivery of ß-carotene with potential applications in the development of functional foods and nutraceuticals.
ABSTRACT
The pretreatment process is an essential step for nanofibrillated cellulose production as it enhances size reduction efficiency, reduces production cost, and decreases energy consumption. In this study, nanofibrillated cellulose (NFC) was prepared using various pretreatment processes, either chemical (i.e., acid, basic, and bleach) or hydrothermal (i.e., microwave and autoclave), followed by disintegration using high pressure homogenization from oat bran fibers. The obtained NFC were used as an emulsifier to prepare 10% oil-in-water emulsions. The emulsion containing chemically pretreated NFC exhibited the smallest oil droplet diameter (d32) at 3.76 µm, while those containing NFC using other pretreatments exhibited d32 values > 5 µm. The colors of the emulsions were mainly influenced by oil droplet size rather than the color of the fiber itself. Both NFC suspensions and NFC emulsions showed a storage modulus (G') higher than the loss modulus (Gâ³) without crossing over, indicating gel-like behavior. For emulsion stability, microwave pretreatment effectively minimized gravitational separation, and the creaming indices of all NFC-emulsions were lower than 6% for the entire storage period. In conclusion, chemical pretreatment was an effective method for nanofiber extraction with good emulsion capacity. However, the microwave with bleaching pretreatment was an alternative method for extracting nanofibers and needs further study to improve the efficiency.
