Effect Of Microwave Heating On Gluten Structure Property And Nutrition Changes And Food Safety

Gluten is one of the most important sources of daily food protein.As one of the widely used food heating methods,microwave heating has been associated with the NFCs(Neoformed contaminants)formation due to microwave accelerate organic chemical reaction,which has become a great concern.In this study,gluten was used as raw material and treated with microwave.The basic composition,structure,conformational changes of gluten before and after microwave treatment,as well as its digestibility,structure,basic composition and conformational changes during in vitro digestion were studied.In addition,the nutritional safety was analysised based at the normal microwave home cooking mode.The protein content of the gluten used was about 23.47% whlie the hydrocarbon content is about 11.09%,and it only contains small percentages of fat and ash.With the increase of microwave power and microwave treating time,the water loss rate increased,so did the gluten's mass loss;the gluten color also changed obviously,and with the increase of microwave power and heating time,the color evaluation index E reduced.The content of hydrophobic amino acid of the gluten protein increased,and the content of amino acids including glutathione,arginine and lysine decreased obviously.The secondary structures in gluten protein changed after microwave treatment.The formation of ?-helix and ?-turn were promoted,and the expansion of the structure and intermolecular ?-fold was significantly reduced.The results of DSC and SEM show that microwave treatment could promote the polymerization of the gluten.And when the microwave power exposure increases to a certain extent,the mass loss does not change any more,when the microwave power changed from 200 W to 400 W,the mass loss and the color changes were not significantly different.The digestibility of the gluten and the free amino groups of gluten digests increased with the increase of the degree of enzymatic hydrolysis.In the course of in vitro pepsin treatment,there was little difference of free amino groups and digestibility among 200 W,1min;200W,5min;and 1000 W,1min.However,after in vitro trypsin digestion,the digestibility of the gluten treated with microwave,especially after high-power and long-time treatment,was significantly lowered.The particle size of the gluten digests decreased with the increase of enzymolysis intensity,but increased with the increase in microwave energy exposure.The fluorescence intensity of gluten digests decreased at 2 h after enzymolysis,and decreased with the increase of microwave power used.Moreover,the emission wavelength of gluten digests continued to shift to the red with the increase of microwave energy exposure.After digestion of gluten protein,the molecular weight of the digested gluten protein was mainly below 1000 Da,and with the microwave energy exposure increased,the proportion of molecular weight which was above 1000 Da also increased,especially when the microwave treatment was at 1000 W for 5 minutes with the weight of gluten about 60 g.The content of the flavor amino acid in the digests of the gluten after microwave treatment was improved.The digests ware analyzed by MALAI-TOF / TOF-MS,and the amino acid sequence was accurately determined.A small amount of melanoidin,acrylamide and fructosamine were detected in raw gluten.After microwave treatment,there was still no hydroxymethyl furfural detected.With the increase of microwave energy exposure,the contents of melanoidin,acrylamide and fructosamine increased gradually.With normal home microwave cooking methods,the contents of melanoidin and fructosamine were more than those produced by traditional non-micorwave cooking method.What's more,the addition of edible oil and vinegar increased the content of melanoidin,however,there was a certain inhibitory effect in increasing of fructosamine with the addition of vinegar,while the addition of sucrose promoted the frucsosamine formation under microwave treatment.When the combination of edible oil and salt or sugar was added,there was still no hydroxymethylfurfural formed in the product treated by traditional cooking method,while there were just a small amount formed when treated by microwave.The content of hydroxymethylfurfural was obviously increased after adding edible oil and vinegar simultaneously.Furthermore,the addition of edible salt or sucrose after adding edible oil and vinegar,the content of hydroxymethylfurfural in the sample was almost unchanged when treated by traditional cooking method,but the content of hydroxymethyl furfural was almost doubled that of the regular retort treatment when treated by microwave.In the simulation of traditional home cooking method,acrylamide was released in varying degrees after cooking with the addition of different condiment.However,the acrylamide content was significantly increased when adding sucrose and trated by microwave,and vinegar had a certain inhibitory effect in producing acrylamide.