Impact Of Light On Bitterness And Astringency And Tannin Content,Morphology And Distribution Of Dendrocalamus Latiflorus

It was especially important to research main substance which caused the bitterness and astringency of bamboo shoot and how to take off it,because the majority of bamboo shoots have an universal disadvantage,they taste much more bitter and astringent when they are emerged out of ground and exposed to the sunlight,which awfully downgrades their overall sensory flavor and declines their market sale value,and it was absolutely regarded as one of major bottlenecks threatening their production,processing and trade particularly.This paper takes heavy bitter Ma bamboo(Dendrocalamus latiflorus)as the research object,three aspects of test respectively were carried out:1.The experiment of bamboo shoot in water boiling.Based on the preliminary test in which bamboo shoots had no bitter and astringent taste after being boiled at 100°C for 420 s,hence,the experiment boiling time was set at 0s,30 s,90s,150 s and 420 s in a 150 mL water.The boiled bamboo shoot residues and bamboo shoot soups were measured for soluble tannin,oxalate acid and free bitter amino acids(Phe,Val,Arg,Met and Leu)by Contents Phosphato-tungstic acid colorimetry,Reversed-phase high-performance liquid chromato graphy and Automatic amino acids analyzer.The results as follows:The bitter and astringent flavor of bamboo shoots was overwhelmingly caused by soluble tannin,the relationship between bamboo shoots bitterness and astringency and tannin was highly significant,and the correlation coefficient were0.896 and 0.867 respectively;The relationship between bamboo shoots astringency and oxalate was significant,and the correlation coefficient was 0.448,but it was no significant relationship between bamboo shoots bitterness and oxalate;It was no significant relationship between bamboo shoots bitterness and astringency and free bitter amino acids.The tannin functions were used to discover the mysteries of heavy bitterness and astringency of bamboo shoots.2.Sensory evaluation.The characteristic curves quantitative function describing the corresponding relationship between food-class standard tannin and oxalate and their mixture solution concentration and each of taste intensity were set up and the boiled bamboo shoot residues,bamboo shoot soups,fresh Dendrocalamus latiflorus and Phyllostachys edulis were sensory evaluated for bitter and astringent intensity by panelists.The results as follows: The result showed the standard Tannin solution featured two kinds of taste,bitterness and astringency and oxalate solutions presented two kinds of taste,sourness and astringency.Oxalate itself was not bitter,but it could enhance the bitter and astringent taste of tannin.Meanwhile,it was found that the astringent intensity of the mixture solution was higher than that of a single compound,but lower than the sum of two compounds,which hinted the astringent taste of the mixture solutions was a result of overlapping effect of these two compounds.The results from the quantification of tannin functions of 9 samples showed that the tannin characteristic curve could give the explanation(Explanation=calculation scores/sensory evaluation scores × 100%,the difference between calculation scores and sensory evaluation scores will be small if the explanation is close to 100%)of 70.7 to 132.0 percents to the bitterness and 70.4 to 136.4 percents for astringency,so the result demonstrated that tannin functions could forecast the bitterness and astringency intensity of Dendrocalamus latiflorus.The sensory evaluation result was highly significance between Dendrocalamus latiflorus and Phyllostachys edulis.There was no significant difference between the calculation value by tannin characteristic curve and the sensory evaluation scores by sensory specialists of free Dendrocalamus latiflorus,and the bitterness and astringency was gradually increasing from base to top of Dendrocalamus latiflorus.However,the taste of Phyllostachys pubescen was sharp which different from bitterness and astringency,so it was need be further study to find the substances which cased the sharp taste of Phyllostachys edulis.3.The distribution and morphology of the cells with tannin(CWT)as well as the quality,concentration of tannin,carbohydrate in bamboo shoot of Dendrocalamus latiflorus were investigated on the three treatments of Mulching with soil(EP),Double-layer light-proof bagging(CLPB),and Natural growth(CK)by means of sensory evaluation,optical microscopy,transmission electron microscopy(TEM)and phosphotungstic acid-sodium tungstate colorimetry,Reversed-phase high-performance liquid chromatography and automatic amino acids analyzer.The results as follows:(1)The test of three cultural patterns were all not only bitterness and astringency,but also the intensity of bitterness and astringency was increasingly enhanced from base to top of bamboo shoot and the intensity of bitterness and astringency of three treatments was: CK> CLPB > EP.the order of tannin content and CWT distribution density of three treatments was: CK > CLPB > EP,both the order of tannin content and CWT of three treatments in different parts were : top > middle > bottom.The result showed the Dendrocalamus latiflorus only featured two kinds of carbohydrates,glucose and fructose,non-sucrose,and there was no significant to carbohydrate of three treatments.The tannin content,CWT density and test intensity of bamboo shoots had an negative relationship with light-proof,so such light-proof measures as EP and CLPB significantly reduced the tannin content of bamboo shoot,improved its edible taste quality,therefore had a great theoretical and productive significance.(2)The tannin cells of Dendracalamus Latiforus appeared colorless,but black by 2% FeCl2 Solution method which made a clear distinguishing between CWT and non-CWT and proved to be effective.Most of the tannin was distributed inside parenchyma cells,a little found in fiber cells.Tannin was mainly flocculent in the top and middle parts of bamboo shoot,and granular in the basal parts.So the CWT shape was just closely related to the position of bamboo shoot.(3)The sensory evaluation result of CK by the test forecast model of tannin:The tannin characteristic curve could give the explanation(Explanation = calculation scores/sensory evaluation scores×100%,the difference between calculation scores and sensory evaluation scores will be small if the explanation is close to 100%)of 68.7 to 138.9 percents to the bitterness and 69.1 to 125.7 percents to astringency;CLPB:the tannin characteristic curve curve could give the explanation of 72.7 to 137.3 percents to the bitterness and 66.2 to 109.4 percents to astringency;EP:The tannin characteristic curve could give the explanation of 67.1 to 136.2 percents to the bitterness and 67.1 to 138.4 percents to astringency.It could be widely used as a taste quality grading standard of bamboo shoot in its production,processing and marketing,and a guidance for selecting or breeding good flavor bamboo shoot species for production cultivation,to predict and evaluate bitter and astringent intensity of bamboo shoot by analysis of its tannin content.