Study On Effects Of Different Enzymes On The Quality Of Flue-Cured Tobacco

As a special hobby products in people's daily life,the quality of tobacco(Nicotiana tabacum L.)affects the health of human body directly.To provide a scientific basis for improving the quality of flue-cured tobacco,this study was focused on the impacts of different enzyme treatments on general chemical index,aroma,sensory quality,color,surface micromorphology and combustion properties of flue-cured tobacco,by spraying a certain amount of enzyme solution(neutral protease,papain,flavor protease,cellulase,pectinase,glucoamylase and alpha amylase)on tobacco leaves before baking,YN99 which is the main variety in Qinling Mountains tobacco area were analyzed.The main results were as follows:(1)Enzyme treatments could effectively increase the sugar content,while decrease total alkaloid,total nitrogen and starch content in tobacco leaves.Considering economical practicability of enzyme in the actual production,the enzyme concentration of 50 U/g was optimal to improve sugar content of tobacco leaves.The total alkaloid content in tobacco leaves through enzyme treatment was much lower than that of control group,and the ratio of sugar to nicotine was generally high.Total nitrogen content and potassium content in flue-cured tobacco samples were generally at a low level,and chlorine content was relatively suitable(except flavor protease).Considering potassium,chlorine and the ratio of potassium to chlorine,the three indexes were most suitable for tobacco leaves treated with 50 U/g neutral protease.The starch content of tobacco leaves treated with pectinase was the lowest,and the degradation effect was the best.Secondly,the degradation effect was followed by cellulase and neutral protease.Grey correlation analysis results showed that chemical quality and coordination of tobacco leaves treated with 50 U/g,120 U/g and 160 U/g pectinase,50U/g neutral protease and 120 U/g glucoamylase were the best.(2)63 kinds of volatile aroma compounds were detected in the samples,and they could be divided into alcohols(9 kinds),acids(2 kinds),ketone(16 kinds),aldehydes(8 kinds),esters(5 kinds),alkanes(19 kinds),alkenes(3kinds)and N-heterocycle(1 kind)according to the chemical structure of aroma.The main aroma of tobacco was made up of olefinic hydrocarbons(neophytadiene),alcohols,ketones and alkanes.The total aroma quality of tobacco leaves treated with 120 U/g and 160 U/g pectinase were the best.The cluster analysis showed that 42 tobacco samples could be divided into 4 categories,and the results wereconsistent with the rank order of principal component analysis.The aroma style of tobacco treated with the same enzyme was similar.The result of correlation analysis showed that the total nitrogen,total alkaloid and starch had maximum effect on tobacco aroma,and the aroma quality can be improved by coordinating the chemical components in tobacco leaves.(3)The middle flavor type of flue-cured tobacco was slightly to still significant.The fragrant rhyme was based on sweet and hay flavor,with refresh sweet,burnt-sweet,green,woody fragrance,toasty and spicy.The aroma state was suspended.The smoke concentration,strength,aroma quality and quantity were upper middle,and the aroma permeability was good,accompanied by a little offensive flavor.There were quite a few differences of tobacco smoke and taste characteristics between different treatments.Among them,the flavor type,aroma state,aroma quality and quantity,smoke characteristics of tobacco leaves treated with 120U/g and 160 U/g pectinase scored higher and their sweet,fresh sweet and hay flavor was outstanding.Smoke concentration was large.The strength was moderate.The aroma permeability was good,and the irritation and aftertaste scores were relatively moderate,and the sense of dryness was the lowest,thus the sensory quality of tobacco treated with 120 U/g and 160 U/g pectinase was best in all treatments.While the sensory quality of flue-cured tobacco treated with 50 U/g and 75U/g neutral protease,25 U/g flavor protease was worse.(4)Different enzyme treatment had effects on the color,surface morphology and pyrolysis characteristics of tobacco leaves.The brightness and color saturation and intensity of tobacco leaves treated with papain were better.It could improve the appearance quality of tobacco leaves by increasing the content of sugar and potassium and reducing starch content in flue-cured tobacco leaves.The positive epidermal cells of the tobacco leaf had different degrees of loose deformation,and the abaxial epidermal cells appeared to fold.The action mechanism of different enzymes was different,neutral protease and cellulase mainly act on the gap of epidermal cells,so that separating the cells.Positive epidermal cells of tobacco leaves treated with other enzymes had smaller clearance and the surface became loose and smooth.Among them,the changes of the front and back of the tobacco leaves treated with glucoamylase and alpha amylase were the most obvious.The pyrolysis process of tobacco leaves was divided into 4 thermal weight loss stages.Among them,the second and the third stage had the highest thermal weight loss rate,and the most significant contribution to volatile aroma components.The maximum thermal weight loss rate of the tobacco leaves treated with pectinase was the highest at the two stages,and the final residual rate was the lowest.