| Fresh waxy corn refers to the fresh ears picked at the milk ripening stage of waxy corn growth.At present,the quality evaluation system of fresh waxy corn is not perfect,and the research on the key factors affecting its edible quality is not deep enough,which leads to some restrictions on the development of fresh waxy corn industry.Starting from the construction of fresh waxy corn evaluation system,this paper analyzes the key factors affecting the edible quality of fresh waxy corn,and discusses the quality change law and influencing factors of fresh waxy corn at different harvest times.The main research contents include:Firstly,taking different varieties of fresh waxy corn as the research object and ordinary corn as the control,the sensory evaluation was carried out by using the standards of the Ministry of agriculture,and the physical and chemical indexes such as hardness,chewability,skin residue rate,viscosity and basic composition were analyzed.The results showed that there was a large difference in the scores of tender and sexy officials,but it had a poor correlation with the hardness value in the objective data,and had a significant positive correlation with the skin strength(P<0.05),indicating that the existing evaluation methods are difficult to closely connect with the key physical and chemical properties of waxy corn grains,and the evaluation system is not perfect.In the case of little difference in amylopectin content,Sukenuo 1505 with the lowest total starch content has the highest waxy sensory score,indicating that it is necessary to deeply study the influence of starch and its properties on edible quality.Secondly,fresh waxy corn starch was extracted,and its thermodynamic properties,gelatinization properties and starch structure properties were studied.The results showed that Sukenuo 1505(81.55%)and Sukenuo 1704(90.21%)with higher starch gelatinization degree had higher waxiness and tenderness scores.The results of correlation analysis showed that there was a significant positive correlation between waxiness and tenderness scores and starch gelatinization degree(P<0.05),and the correlation coefficients were 0.698 and 0.651respectively,indicating that the gelatinization degree of starch had a decisive effect on the edible quality of fresh waxy corn.At the same time,the amylopectin content,average chain length and M_w have little effect on the starch gelatinization behavior,while the water content and total starch content will affect the water absorption expansion in the starch gelatinization process,and then affect the starch gelatinization degree and the edible quality of fresh waxy corn.Thirdly,based on the current evaluation standards of the Ministry of agriculture,the evaluation system of fresh waxy corn is constructed,which is supported by quantitative description analysis and instrumental determination or content determination.In the evaluation system,according to the different attributes of fresh waxy corn,such as odor,color,waxiness,texture,sweetness and residue feeling,full two-dimensional gas chromatography high-resolution time-of-flight mass spectrometer,color difference instrument,rapid viscosity analyzer,texture analyzer and other instruments and total sugar,skin residue rate and other determination methods are selected for verification and determination.The results showed that the intensity values of color,sweetness,hardness,tenderness and dross in quantitative description analysis were significantly positively correlated with the brightness value,total sugar content measured by color difference instrument,hardness value measured by texture analyzer in full texture mode,chewability,skin strength and skin residue rate measured by texture analyzer in puncture mode(P<0.05),and the correlation coefficients were 0.868,0.928,0.928 and 0.952,0.929 and 0.941 respectively,It shows that the methods in the new evaluation system correspond well with the objective evaluation data;Hardness,chewability,skin strength,skin residue rate and other data can be introduced into the current standards of the Ministry of agriculture for objective data support.Finally,taking the fresh waxy corn"Sukenuo 11"as the research object,it was picked at different harvest periods(15d,17d,19d,21d and 23d after pollination),and its quality changes and starch properties were dynamically measured and analyzed.The results showed that with the extension of harvest time,the water content of samples decreased,the total starch content increased,and the hardness value and skin strength value of different samples increased;The sensory evaluation score increased first and then decreased.The samples picked 19 days after pollination had the best score,up to 80.18 points.Correlation analysis showed that there was no significant correlation between waxy fraction and total starch content,indicating that it was not that the higher the grain starch content,the better the waxy quality.Hardness was negatively correlated with water content(P<0.05),the correlation coefficient was-0.879,and positively correlated with total starch content(P<0.05),the correlation coefficient was 0.961.The results show that with the delay of harvest time,the decrease of water and the increase of total starch will continuously increase the hardness value of fresh waxy corn after cooking.When the hardness value exceeds a certain value,the tenderness score decreases,resulting in the deterioration of edible quality.Combined with the research results of gelatinization degree,in order to obtain the best edible taste,we should closely track the starch content and water content of fresh waxy corn during the harvest period,so as to ensure that the starch in the grain can be fully gelatinized in the cooking process,so as to obtain the best edible quality of fresh waxy corn. |
PDF Full Text Request