Preparation Of Bacterial Cellulose Nanocrystals Based On Vortex Fluid Technology And Its Application In Food Oil Reduction And Packagin

Bacterial cellulose(BC)as a new functional material,has attracted much attention.It is a kind of polymer material with three-dimensional network structure,excellent mechanical and thermal properties.Cellulose nanocrystals(BCNC)extracted from BC are a kind of biological based nanomaterials with unique structural characteristics and physical and chemical properties.At present,developing new resources,new extraction methods and new processing methods,BCNC is a promising application material in biomedicine,pharmaceutical,electronics,nanocomposites,membranes,super capacitors and other fields.Nowadays,the main extraction methods are acid hydrolysis,mechanical treatment and enzyme hydrolysis.Vortex fluid device(VFD)is a recently emerging continuous flow thin film microfluidic platform that utilizes high shear forces,strong micro-mixing,and high heat and mass transfer to overcome the mixing and heat transfer limitations of traditional batch processing.In this study,cellulose nanocrystals were prepared by enzymolizing bacterial cellulose,and then modified by vortex fluid technology to obtain a kind of cellulose nanocrystals with different forms.The obtained cellulose nanocrystals and BC were applied to determine the oil content and its related properties in doughnuts,which provided a new possibility for the method of oil reduction in fried food.Then it was applied to food packaging film to measure its mechanical properties and other properties.It was found that the mechanical strength of the biodegradable film produced by the VFD-treated bacterial cellulose hydrolysate was enhanced,which provided a new way for the production of biodegradable film and had potential applications in the food and agricultural industry.The specific research content is as follows:(1)Cellulose nanocrystals were extracted from bacterial cellulose by enzymatic hydrolysis using neutral cellulase.The cellulose nanocrystals were modified by continuous mode of VFD(flow rate 0.3m L/min,rotation speed 6000 rpm,inclination Angle 45°)and restricted mode(quartz tube 2m L,rotation speed 6000rpm).Then the structure was characterized by DLS,SEM,AFM,FT-IR,TGA and XRD.The results show that The VFD operating in continuous mode and confined mode aggregated <10um rock-type bacterial cellulose into large particles >30um,resulting in aggregation effect.The large particles were then fragmented,and the morphology changed from rough surface to smooth surface and round egg shape.XRD,TGA and FTIR analysis showed that the results of the three bacterial cellulose hydrolysates were significantly higher than those of the unhydrolyzed bacterial cellulose,although the morphology difference had no significant effect on the crystallinity and thermal stability of the three samples.A new and most advanced method,VFD technology,can change the morphology of cellulose based materials and has great potential for practical application.(2)Bacterial cellulose,enzymatic hydrolysis of bacterial cellulose hydrolysate and microwave-assisted enzymatic hydrolysis of bacterial cellulose hydrolysate were added to the doughnuts to compare and characterize the oil content and structure characteristics.Oil content,water content,in vitro digestion experiment,TPA and SEM were measured to compare the differences.The oil reduction mechanism of doughnuts was also understood by measuring BC,enzymatic hydrolysis of BC and microwaveassisted enzymatic hydrolysis of BC.The results showed that the water holding capacity and oil holding capacity of bacterial cellulose hydrolysate produced by enzymolysis and microwave-assisted enzymelysis were higher and lower than those of untreated bacterial cellulose.In the production of fried doughnuts,the oil content of fried doughnuts can be significantly reduced from about 28 % to 15 % by replacing 2 % flour with 2 % bacterial cellulose hydrolysate.The results of texture profile analysis showed that there was no significant difference between different samples of fried doughnuts,and SEM analysis found that the internal microstructure of different samples was similar.In vitro digestion tests did not change the release of reducing sugars from different samples,so adding bacterial cellulose hydrolysates to fried donuts does not have adverse health effects,so it is an effective and feasible way to reduce oil.(3)Bacterial cellulose,hydrolyzed bacterial cellulose hydrolysate and VFD modified hydrolyzed bacterial cellulose hydrolysate were added to the raw material of biodegradable film.The internal structure and properties of different raw material samples were analyzed by SEM,AFM,FT-IR,mechanical strength,contact Angle and biodegradability.The results showed that the mechanical strength of the biodegradable film was improved without reducing its biodegradability by using the bacterial cellulose hydrolysate modified by VFD.It was observed by SEM that more uniform and unidirectional bacterial cellulose hydrolysates were integrated into the internal structure of the membrane prepared by VFD-treated bacterial cellulose hydrolysates compared with other non-VFD-treated samples.FTIR spectroscopy shows no chemical differences between the films.AFM shows the roughness of the film surface.