Encapsulation Of Vitamins In Glassy Carbohydrates Employing Extrusion

L-Ascorbic acid (AA) commonly known as Vitamin C is a physiologically and biochemically essential water soluble bioactive compound required for the normal regulatory functions. AA has been extensively used in variety of food formulations and acts as an antioxidant agent besides its nutritional role in the human body. It is established that AA helps in the absorption of inorganic Fe and inhibits the formulation of carcinogenic compounds in the body. It also acts as co-factor for enzymes, involves in the biosynthesis of carnitine, stimulates collagen synthesis, modulates neurotransmitter systems and offers improved immunity against diseases. Its possible role in minimizing the risk of serious diseases such as heart diseases and cancer is very interesting. With the improved knowledge of functional properties of this vital food ingredient, the trend to incorporate it into different food systems is increasing. Due to the highly unstable nature, AA is prone to be degradation and also destabilize the whole food system. Therefore, it is important to stabilize AA prior to its application.The technique of the encapsulation of vitamins (AA and vitamin E) in glassy carbohydrates employing extrusion was investigated. The processes and formulations of the technique were studied. And the characteristics of the extrudated products were analysised. Major contents of this paper are as following:1. AA was encapsulated in glassy low dextrose equivalent (DE) maltodextrin (DE 8-10) matrix by extrusion. The effects of formulation parameters i.e., core-matrix ratio and moisture content were mainly investigated on glass transition temperature (Tg) of extrudates. The AA yield, AA content and moisture of the products together with extrusion parameters were also measured and compared for different formulations. Both the water content and AA content have a great effect on Tg. The Tg of extrudates containing water content from 7.860% to 10.430% decreased from 43.17℃to 27.48℃and The Tg of extrudates which core to matrix from 1:4 to 1:8 increased from 35.79℃to 41.64℃. AA yield of all samples is above 96% and with increasing water content there was a small decrease in the AA yield. The increased water level and core-matrix ratio reduce specific mechanical energy and die head pressure. From X-ray diffraction result, AA was most likely molecularly dispersed within the maltodextrin matrix.2. Extrusion was used to produce capsules of AA in a glassy high DE maltodextrin (DE 10-15) matrix. Barrel temperature, screw speed and feed speed were selected as variables and motor torque (motor torque percent) and die head pressure during extrusion were studied. The AA loading capacity, yield and Tg of the extruded products were also investigated. The results showed that high barrel temperature, high screw speed or low feed speed could make motor torque and die head pressure decrease. The optimum barrel temperature, screw speed and feed speed were middle temperature (85℃-105℃-120℃-105℃),60 rpm and 1.1 kg h-1. Encapsulation of AA in the low water content/solid/glassy-state carbohydrate matrix was developed according on the optimum condition. Maltodextrin (DE 10-15), trehalose and gum arabic were used in the formulation as film forming materials. Glass phase characteristics of AA in the encapsulating matrix were assessed. The method could allow the AA content in final extrudates (payload) of three formulations more than 15.67 g/100 g extrudates while the AA yield were above 97%. The Tg of the extrudates were above 40℃. The incorporation of trehalose and gum arabic reduced the Tg and the expansion ratio of the extrudates, respectively. The results of scanning electron microscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy indicated that the formulated feed materials became a glassy solid solution, where the AA were dispersed in the matrix of carbohydrates. Milled extrudates (20～40 mesh) of three formulations showed a fast dissolution rate, and AA in milled extrudates were completely dissolved within 10 minutes. The rate was controlled by the carbohydrates matrix. The extruded products were applied to the formula milk powder and the AA loss decreased obviously which indicated that the encapsulated AA in the glassy carbohydrates matrix may decrease the reactions between AA and other ingredients in the food system. AA could be well protected.3. AA was encapsulated in the glassy isomalto-oligosaccharides by extrusion. Two formulations which had 10% and 16% AA content were prepared. The measuring feeder was set to obtain a flow rate of 1 kg h-1 of premixed material and screw speed was maintained at 60 rpm for all the experimental runs. Three barrel temperatures were studied. The parameters such as torque and die head pressure during extrusion were investigated. X-ray diffraction and differential scanning calorimeter were used to investigate the characteristics of products. The AA yield, loading capacity and moisture content of the products were also measured. The results showed that high barrel temperature could make motor torque and die head pressure decrease. At middle and low barrel temperature, torque decreased with increased AA. AA could be encapsulated successfully. The Tg was decreased with increased AA.The result of X-ray diffraction indicated that the formulation was a glassy solid solution. The extrudated products were applied to the formula milk powder and the AA retention rate were improved greatly.4. Vitamin E (VE) was encapsulated in glassy carbohydrates by extrusion. Four typical formulations were prepared in order to have 5% and 8% VE added to each 20% and 30% modified starch containing feed material, all four formulations contained soya lecithin at 1% level as an emulsifier. The measuring feeder was set to obtain a flow rate of 1.2 kg h-1 of premixed material, the barrel temperatures were set to T1 (65℃), T2 (95℃), T3 (115℃), T4 (105℃) and screw speed was maintained at 60 rpm for all the experimental runs.The parameters such as torque, specific mechanical energy and die head pressure during extrusion were monitored. The physico-chemical properties of glassy extruded products were investigated. The results showed that high VE content and low modified starch could make motor torque, SME and die head pressure decrease. It is very important to use the modified stach with the emulsification properties for encapsulating the oil soluble materials. The VE retention rates were above 93% after extrusion. The VE oil could be dispersed as the small oil droplets throughout the carbohydrate matrix by using the high HLB emulsifier and modified starch. The size and distribution of the VE oil droplets were uniform. There was a slight loss for VE during the storage, while the VE retention rate of encapsulated VE was much higher than unencapsulated VE significantly. The VE could be encapsulated successfully. The Tg of the extrudates were above 30℃and Tg could be a good predictor of caking properties at elevated temperatures.