| Objective:In recent years,selenium as an essential trace element for human body has been widely studied,and a variety of selenium rich foods have appeared on the market.The nutritional value of food can be seen as two parts,one is the content of nutritional elements in food itself,the other is the retention of nutrients in the process of processing.Therefore,in this study,selenium rich corn in selenium rich areas was used as raw material to explore the effects of the existing parts of selenium in corn grains and different processing methods on selenium content and its bioavailability;The structure and physical properties of selenium rich corn starch,waxy corn starch and common corn starch were studied.It can lay a foundation for the deep processing of selenium rich corn and provide a reference for the development of other selenium rich agricultural products.Methods:The content of selenium in corn kernel was determined by hydride generation atomic fluorescence spectrometry;Corn was processed by steaming,frying and fermentation,and then the effect of processing methods on selenium content was determined;The dissolution of selenium in gastric and intestinal juice was determined by simulating gastrointestinal digestion in vitro;The structure and physicochemical properties of three kinds of corn starch were determined.Results:The selenium content in the embryo,endosperm and seed coat was determined to determine the location of selenium in the corn kernel.The distribution position of selenium in the corn kernel was embryo>seed coat>endosperm,and the highest selenium content in corn germ was 24.62 ?g/g Moreover,the gliadin selenium content in corn is higher than the starch selenium content.The organic selenium content is calculated to account for more than 80% of the total selenium.Combined with the percentage of selenium in the seed coat,embryo,and endosperm,it can be calculated separately The total amount of selenium in the seed coat,embryo and endosperm is 1168.58 ?g,1703.24 ?g and 2345.15 ?g.When measuring the influence of the crushed particle size on the selenium content of corn,it was found that the total selenium and organic selenium gradually decreased after sieving through the sieving sieves with different apertures,which indicated that selenium was distributed in corn flour of different crushed particle sizes.The processing methods have an effect on the selenium content,and both show a downward trend.The steaming and frying treatments have the greatest impact on the selenium content.After 30 minutes of treatment,it decreases by 0.85 ?g/g and 0.52 ?g/g,respectively,while the lactic acid bacteria and yeast treatments decrease slowly.The in vitro simulated gastrointestinal digestion was used to determine the release of selenium in the gastric juice and intestinal juice.The results showed that the release of selenium showed an upward trend in the digestion stages of the stomach and intestines,and the upward trend in the intestinal digestion stage was greater than that in the gastric digestion stage.At the same time,through the determination of X-ray diffraction,infrared spectrum scanning,polarized light cross,thermal properties and the freeze-thaw stability and rheological properties of three different types of corn starch,it was found that all three types of corn starch There is a very obvious polarized cross phenomenon,and it presents a standard "cross" shape;the crystallinity of the three corn starches in descending order is: waxy corn starch 30.48%> ordinary corn starch 29.88%> selenium-enriched corn starch 26.23 %.Thermal analysis showed that the initial gelatinization temperature of the three types of corn starch was different.The initial gelatinization temperature of starch was 67.6?,selenium-enriched corn starch 55.2?,and waxy corn starch 47.2? from high to low.The gel strength analysis showed that the gel strength of waxy corn starch paste was the smallest,and the gel strength of selenium-enriched corn starch was in the middle.Moreover,the transparency of selenium-enriched corn starch is also in the middle;a large amount of supernatant is precipitated after thawing of waxy corn starch after being frozen for 72 hours,and its freeze-thaw stability is not very good,and ordinary corn starch has the best freeze-thaw stability;in static rheological research Among them,the three kinds of corn starches are pseudoplastic fluids.In the static rheological upward line,when the shear rate increases,the shear stress also increases;in the dynamic rheological study,the elastic moduli of the three corn starches are all Greater than the viscous modulus,the loss tangent(tan?)is less than 1,G'and G'increase with the increase of angular frequency,indicating that 5% starch paste exhibits a typical weak gel characteristic. |
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