| Nanfeng tangerine(Citrus reticulita Blanco cv Nanfeng tangerine), an ancient speciesof tangerine, is famous at all times and in all countries for its thin skin, little nuclear,juiciness, mastication, golden color, good taste and rich nutrition. However, consumersnowadays generally believe that Nanfeng tangerine fruit quality is not good as before,especially in slag pulp, seriously affecting the Nanfeng tangerine’s commodityperformance and economic value, which will restrict the further development of Nanfengtangerine industry. This topic, compared with the shatangju mandarin, covers from thephysiological and biochemical research on Nanfeng tangerine pulp residue sex of pecticsubstances and the characteristics of the metabolism related enzyme activity changes toNanfeng tangerine, on the basis of predecessors’ work, then improve research methods andfurther the research content, therefore to know the reason of no slag and its possibleregulation mechanism, and to provide theoretical basis and technical measures to maintainthe good quality and improvement of Nanfeng tangerine. The main results are as followed:(1) Using the development process of early-ripe Nanfeng tangerine as theclassification standard and during the development process, according to the importantindicators of the single fruit weight, fruit transverse and longitudinal length and fruit color,we divide the fruits of the early-ripe Nanfeng tangerine97-1, small-fruit Nanfeng tangerine97-2and shatangju mandarin into earlier-stage fruit expansion, medium-stage fruitexpansion, later-stage fruit expansion, fruit veraison and fruit ripening. And the date of theshatangju mandarin’s earlier stage of fruit expansion to medium stage is from July23thtoSeptember26th, while the date of small-fruit Nanfeng tangerine97-2’s later stage to fruitveraison if from September24thto November2nd.(2) The fiber strength, fiber ductility, fiber tenacity of sugar tangerine fruit are lowerthan those of early-ripe Nanfeng tangerine97-1and small-fruit Nanfeng tangerine97-2during the whole fruit ripening process. In the fruit ripening stage, early-ripe Nanfengtangerine97-1has the highest fiber strength and fiber ductility, which is remarkably higherthan those of the small-fruit Nanfeng tangerine97-2and shatangju mandarin, the latter ofwhich has the lowest fiber strength and fiber ductility. The early-ripe Nanfeng tangerine97-1has the highest fiber tenacity, which is remarkably higher than the small-fruit Nanfengtangerine97-2and the sugar tangerine. Though the sugar tangerine has the lowest fibertenacity, it is not remarkably different from that of the small-fruit Nanfeng tangerine97-2.The shear force of the early-ripe Nanfeng tangerine97-1is the highest, which is a littlehigher than that of the small-fruit Nanfeng tangerine but significantly higher than that ofthe shatangju mandarin. The chewiness and the fruit firmness of the early-ripe Nanfengtangerine97-1, the small-fruit Nanfeng tangerine97-2and the shatangju mandarin aresimilar. To sum up, we could use fiber strength, fiber ductility, fiber tenacity, shear force as the secondary indicators for mastication and the lower the indicators, the better themastication is.(3) When using colorimetry of carbazole to measure the pectin, the response time andresponse temperature are the key factors. The optimal put1.0mL pectin extract in25mLbrown plug calibration tube, then carefully put6mL concentrated sulfuric acid along thewall into it and add0.2mL1.5mol/L carbazole-ethanol solution, shake well, and heat it inboiling water for20min. Taking it out after cooling down to room temperature, and thenmeasure the absorbance values of the reaction liquid in the wavelength of530nm.(4)The water soluble pectin of Shatangju mandarin, early-ripe Nanfeng tangerine97-1and small-fruit Nanfeng tangerine97-2firstly decline and then increase from the fruitexpansion stage to the fruit ripening stage. The protopectin of the shatangju mandarinduring the veraison stage is the highest and lowest in the fruit expansion during themedium-term and the later period. The protopectin of the early-ripe Nanfeng tangerine97-2is the highest during the fruit expansion medium-term and is the lowest during thefruit expansion later period and the veraison period. The protopectin of the small-fruitNanfeng tangerine97-2changes dramatically during the whole fruit ripening because it isthe highest in the fruit expansion later period and is the lowest in the fruit expansion earlierstage. And the trend of change of the overall pectin is the same as the protopectin. Duringthe fruit ripening stage, the protopectin and overall pectin of the shatangju mandarin areboth lower than those of the early-ripe Nanfeng tangerine97-1and the small-fruit Nanfengtangerine97-2. The effect of protopectin on the overall pectin is larger water solublepectin.(5) The activity of pectin methylesterase of the small-fruit Nanfeng tangerine97-2,the early-ripe Nanfeng tangerine97-1and shatangju mandarin is the highest during theearlier stage of fruit expansion. The activity of pectin methylesterase of the shatangjumandarin and early-ripe Nanfeng tangerine97-1is the lowest during the fruit veraisonperiod. And the activity of pectin methylesterase does not change significantly during thefruit expansion medium term, later period, veraison period and ripe period. During the fruitripening period, the PE activity of the early-ripe Nanfeng tangerine97-1is the highest andthat of the small-fruit Nanfeng tangerine97-2ranks second while that of the shatangjumandarin is the lowest but the differences are not evident.(6) The changes of the activity of polygalacturonase of the early-ripe Nanfengtangerine97-1and that of the shatangju mandarin are basically the same, which experiencedecrease, increase and decrease again. The activity of polygalacturonase of the small-fruitNanfeng tangerine97-2firstly increases and then decreases. The activity of the polygalacturonase of the early-ripe Nanfeng tangerine97-1and shatangju is the lowestduring the fruit ripening period and the activity of the small-fruit Nanfeng tangerine97-2isthe lowest during the fruit expansion earlier stage. And the polygalacturonase of all kindsof tangerines is highest during the veraison period. In the ripening period, the activity ofpolygalacturonase of the small-fruit Nanfeng tangerine97-2is the highest, which isdistinctly higher than that of the early-ripe Nanfeng tangerine97-1and shatangju mandarin.Meanwhile, the differences of the polygalacturonase activity between the early-ripeNanfeng tangerine97-1and shatangju mandarin are not remarkable.(7) The edible part of membrane is positively correlated with the water solublepectin, protopectin and overall pectin but not closely correlated. The fiber strength, fiberductility, fiber tenacity, shear force, firmness and chewiness are all negatively correlatedwith water soluble pectin and are positively correlated with protopectin and overallpectin. The fiber ductility has closely positive correlation with protopectin and overallpectin. The shear force is negatively correlated with water soluble pectin. The firmness ispositively correlated with protopectin and overall pectin. The protopectin and overallpectin have significantly positive correlation, the correlation index of which is larger thanthat of the water soluble pectin and the overall pectin. The influence of the protopectin onthe overall pectin is larger than that of water soluble pectin. The pectin methylesteraseactivity is negatively correlated with protopectin and overall pectin and is positivelycorrelated with water soluble pectin, which means that when the pectin methylesteraseactivity is high, the protopectin is low and the water soluble pectin is high.(8) Different citrus varieties of sensory evaluation of mastication rank like this:Weizhang> Gonggan> October Red> Tiancao>Penggan>Zaoshu Nanfeng orange97-1,which is basically consistent with the protopectin content determination. Correlationanalysis show that the soluble pectin content of ripe citrus fruit and the total pectincontent are significantly and positively correlated, negatively related with the originalpectin content, and the activity of PE is significantly in positive correlation with theactivity of PG enzyme positive correlation, but the correlation is not significant; citrusfruit maturity pectin content and activity of PE enzyme electrode a significant negativecorrelation with PG activity, but the correlation was not significant negative correlation.Citrus fruit mature period of slag is mainly determined by the difference between theoriginal pectin content, and the correlation between PE activity is higher than that of PGactivity. |
