| Adding the monomer or pre-mixed various kinds of nutrient fortificants to certain kind of food carriers is called food fortification. Food fortification is the primary means of nutrition intervention. Fortification of powdery food or grainy food requires good homogeneity of fortificants distributed in food carrier. The production of powdery food is a complex process based on the mixing of powders which have different physical properties. It is very important to clarify the basic mixing mechanism and the main factors which may cause segregation of powder mixture, for it could establish essential technical foundation to produce high quality powdery nutrient fortified food. So we carried out a series of studies on physical properties of powder used in powder mixing.1.Determination of physical properties of mononer nutrient fortificants, adjuvants used in premix, and food carriers.Object A clear classification of physical properties affecting powder mixing was made. Physical properties of all kinds of experimental powder had been determined individually. Complete the query software for physical properties of monomer nutrients. Complete the query software for physical properties of nutrients monomer. Method Powdery nutrient fortificants monomer, adjuvants used in premix production and carriers used in food fortification were comprehensively collected, which based on GB14880-2012and industrial habits of micronutrients using. Physical properties including particle mesoscopic images, electron microscopy (sem) images, particle size distribution, particle effective density, Carr flowability index, Carr floodability index and hygroscopicity were determined and analyzed by effective methods, then a physical properties data query software of monomer nutrient fortificants was formed. Result There are126samples has been collected. By comparing the measured value of those physical properties indices, there had significantly differences between samples on the physical properties of the microstructure characteristics, flowability, floodability, hygroscopicity, etc. Based on these physical properties data, query software of monomer nutrient fortificants was developed after data sorting. Conclusion The fundamental reason affecting homogeneity of powder mixing was the physical properties differences of different powders.2.The creation of a empirical prediction formula for homogeneity after powder mixing Object Attempts to establish a quantity dependent relation between fractal dimension and the coefficient of variation in order to produce a empirical prediction formula for homogeneity. Method The fractal dimension was put forward to characterize the particle size distribution. After screening the powders of similar nature, the coefficient of variation of target contents which have different fractal dimensions after mixing was determined by atomic absorption spectrometry. After the data fitting calculation formula could be obtained. Result The result of data fitting showed there had a highly correlated relation between fractal dimensions and coefficient of variation(p<0.05). By which we got a empirical prediction formula for homogeneity, although it had a limited range of using it, which need to be revised further. Conclusion It had achieved initially that the homogeneity of powder mixture could be predicted by use of the data of size distribution.3.Orderly dry coating technique was used to improve the homogeneityObject Uniform distribution of nutrients in premix and fortified food achieved by using dry coating technique. Method Ultra-fine grinding experiments for some nutrients by using the airflow mill under the condition of different parameters were carried out. The grind results of different powder were evaluated by using the date of particle size distribution before and after crushing, and the grinding characteristics of different powder is discussed in this paper. After that, directly orderly dry coating experiments by Particle Composite System under the condition of different parameters were carried out, which fine nutrient monomer particles after ultra-fine grinding as guest particles, maltodextrin as host particles. The effectiveness of dry coating was evaluated by the electron microscopy (sem) images and size distribution data. The bonding intensity of guest particles and host particles was investigated through the dry mixing operation. By comparing coefficient of variation of target contents between the enriched flour separately fortified by nutrients particles and nutrients coated particles, the effectiveness of dry coating processing technology improving the homogeneity of micronutrient in fortified powdery food could be logically evaluated. Result The crushing effect was the best when the8Mpa was selected as jet mill’s air pressure, which through the results of ultrafine grinding of NaFeEDTA. After coating experiments in which ultrafine NaFeEDTA treated as guest particles, the guest particle addition amount was15%, Leaf blade rotation speed was40rpm, coating process time was10min, which were selected to be dry coating parameters. Under the selected conditions, the ultrafine grinding and dry coating experiments carried out separately on CaCO3, ZnO, VB1, VB2, niacinamide, folic acid. According to the results, the dry coating effect of mineral particles was better than vitaminic particles. The coated particles had favourable bonding intensity after dry coated by NaFeEDTA, CaCO3, ZnO. Loss of micronutrients in the coating process was small, so that recovery rate is over90%. By comparing coefficient of variation of target contents between the enriched flour separately fortified by nutrients particles and NaFeEDTA or CaCO3coated particles, there was a significantly reduction on the coefficient of variation, the degree of reduction was50%or more. Conclusions The orderly dry coating technique using ultrafine nutrients as guest particles can produce new stable particles, as guest particles got from ultrafine grinding by using jet mill. New coated particles as fortificants can improving homogeneity effectively in fortified food. |
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