| The aim of this study is to study the effect of heat treatment on wheat physiological quality,to master the change rules of wheat quality and the occurrence rules of pests and mold during storage.To grasp the rules of wheat quality change during storage and provide data reference for heat treatment grain storage,in order to obtain a safe and green method of grain storage.In this experiment,the harvested wheat in 2019 was selected as the research material.And the 12.5%?14.0% moisture content wheat which contain insects and mold was treated with three heat treatment methods of hot air treatment,microwave treatment and superheated steam treatment,respectively.To select the factor that heat treatment have no significant effect on the physiological quality of wheat and achieve the maximum effect of killing pests and mold.And the effect of heat treatment on wheat in the later storage was discussed,containing physiological quality,eating quality of the wheat.Based on the comprehensive score of quality changes,compare the effects of the three heat treatment methods.The results show that:(1)With the increase of heat treatment temperature and treatment time,the death rate of insect pests in wheat increased,the amount of mold decreased,and the germination rate and viability of wheat decreased.It was found that the three heat treatments were not suitable for the seed grain heat treatment,but could be used for the stored grain.The factor of heat treatment which had no significant effect on wheat viability and achieved the maximum effect of killing pests and mold as follows: hot air treatment at 60?/20 min and 65?/10 min for 12.5% and 14.0% moisture content wheat respectively;microwave treatment at 385w/80 s for 12.5% and 14.0% moisture content wheat respectively;superheated steam treatment at 130?/40 s for 12.5% and 14.0% moisture content wheat respectively.(2)The effect of heat treatment on the storage quality of wheat during storage showed that:the degree of infection on untreated wheat and 14.0% moisture content wheat of hot air treatment were more serious than that wheat of microwave treatment and superheated steam treatment,and the wheat of superheated steam treatment and 12.5% moisture content wheat with microwave treatment was basically not eroded by pests.When stored for 1-3 months,the water content of all wheat samples was relatively stable;when stored for 3-8 months,the water content of untreated wheat with 2 water contents,wheat with 14.0% moisture content and hot air treatment showed an overall upward trend;the water content of wheat treated with 12.5% moisture content microwave and wheat treated with superheated steam treatment showed a gentle change,and the water content of wheat in the later stage rose slightly.There was no significant change viability of the wheat after three treatments,but the conductivity and fatty acid value increased slightly,and mold decreased.During the whole storage period,the viability decreased,the conductivity and fatty acid value increased gradually of all wheat samples,but the untreated wheat has a bigger change.But the change range of untreated wheat and 14.0% moisture content hot air treatment wheat was larger,while the change range of microwave treatment group and superheated steam treatment group was lower.The mold amount of untreated wheat and high moisture hot air treated wheat increased as a whole,while that of other samples did not change much during the whole storage period.(3)The results of eating quality of heat-treated wheat during storage showed that: After heat treatment,the evaluation of steamed bread characters decreased,except for the wheat with superheated steam treatment.The hardness and chewiness of steamed bread increased slightly,while other parameters changed little.With the extension of storage time,the evaluation of steamed bread characters showed a downward trend,and the specific volume,surface color,springiness,smell,taste,toughness and viscosity also showed a downward trend.But for the untreated group and the 14.0% moisture content hot air treatment,the decrease of the taste score of the steamed bread was larger than that of the microwave treatment group and the superheated steam treatment group.Among them,the taste score of the superheated steam treatment group and the 12.5% moisture content microwave treatment wheat had a gentle change.The hardness and chewiness of steamed bread increased,while the springiness,cohesiveness and resilience decreased as a whole.At the end of storage,the hardness and chewiness of untreated group wheat and 14.0% moisture hot air treated wheat were significantly higher than other samples,the springiness,cohesiveness and resilience were lower.The superheated steam treatment group and the 12.5% moisture content microwave treatment wheat better than untreated wheat group.The results of steamed bread and texture characteristics showed that the eating quality of untreated wheat and 14.0% moisture hot air treated wheat was significantly worse than that of other heat-treated wheat.(4)The main volatile substances in wheat were alkanes,alcohols,aldehydes and ketones,among which alkanes were the main ones.95 volatile compounds were detected in wheat before and after heat treatment.After heat treatment,the variety of volatile substances in wheat increased,in which ketone and aldehyde content increased slightly,alkane type and content decreased slightly,alkene content decreased slightly,alcohol and other volatile substances had no obvious regularity.Compared with the initial stage of storage,the relative percentage of alkanes in wheat samples decreased,while the relative percentage of alkenes increased at the end of storage.The change range of wheat with untreated group was larger than that wheat group with superheated steam.The aldehydes content of untreated wheat group and the hot air treatment group decreased,and the relative percentage content of other volatile substances increased.There was no obvious change of alcohols and ketones among the samples.Compared with the volatile substances content of wheat at the beginning of storage,the volatile matter content of superheated steam group was more stable.(5)After three treatments,the wet gluten decreased slightly except for the 12.5% moisture content wheat with superheated steam treatment,and the moisture absorption of gluten did not change much.The aggregation characteristics of gluten was no obvious change.At the beginning of storage,the results show that the microstructure of untreated wheat gluten protein is compact,the surface is smooth and meticulous,and the arrangement of gluten protein is regular.After hot air treatment and microwave treatment,the microstructure of gluten became irregular,and the wheat with superheated steam treatment,the microstructure of gluten did not change obviously.With the extension of storage time,the wet gluten content and moisture content of gluten decreased continuously.Among them,the moisture content of gluten of untreated wheat and 14.0% moisture content wheat treated by hot air decreased the most,the moisture content of wheat gluten was less than 180 after 3 months of storage.It has been shown that it is unsuitable for storage slightly.At the end of storage,the dry gluten of wheat samples had little change compared with that at the beginning.The focusing aggregation characteristics of gluten of untreated wheat group showed that obviously gluten aggregation characteristics deterioration at the end of storage.The focused aggregation properties of wheat gluten treated by microwave and superheated steam degree of decline was the second,and the quality of gluten was better than that of the control group.When stored for 8 months,the microstructure of gluten protein of the wheats changed in different degrees.Compared with the initial stage,the microstructure of gluten protein of the untreated wheat changed obviously.The surface of gluten became rough,broken,scattered and loose,which indicated that the protein structure of those wheat samples had been changed.The microstructure of wheat gluten treated by hot air treatment group and the 14.0% moisture content with microwave treatment showing roughness and irregularity.The gluten structure change of the wheat treated by superheated steam only part of the structure is irregular.(6)According to the comprehensive quality scores of heat-treated wheat stored for the eighth months,heat-treated wheat has advantage to delay the deterioration of storage quality of wheat.For the wheat with the same initial moisture content,the comprehensive score and quality of the wheat treated by superheated steam were the highest at the end of storage,followed by the wheat treated by microwave and hot air,and the wheat untreated had the lowest comprehensive score and the worst quality.Under the same treatment,the quality score of wheat with high original water content was lower than that of wheat with low original water content at the end of storage.The three heat treatment methods have different advantages in slowing down the deterioration of wheat quality during storage,among which the hot air treatment is not as obvious as the superheated steam treatment and microwave treatment.The results of systematic clustering show that the quality of wheat treated with superheated steam and wheat treated with microwave at 12.5% moisture content is excellent,the quality of untreated wheat and wheat treated with hot air at 14.0% moisture content is poor,and the quality of other wheat is good. |
PDF Full Text Request