| The quality of nutrients in plants is the most important factor that determines which and how much plants herbivores would choose to eat.The nutrients’ quality is affected by nutrients and secondary metabolites in plants.The phenomenon that the Giant Pandas in captivity like eating stems of semi-withered bamboo was first discovered in 2003 at China’s Wolong Conservation and Research Center.So,what is the change trend of nutrients and secondary metabolites in the stems of semi-withered bamboo with different storage time?And what are the changes of the factors compared with fresh bamboo?What are the main nutrients that may affect the bamboo stems which giant pandas love?In this thesis,Fargesia robusta from Wolong Conservation and Research Center was used as the experiment material.Six batches of samples were collected from September to November 2019.Then,after storage for 0d,15d,30d,45d,60d and 75d,the higher,middle and lower parts of bamboo stems were collected and the contents of nutrients(organic and inorganic)and secondary metabolites(total flavonoids,total alkaloids and total tannins)were detected,respectively.In order to provide a theoretical basis for feeding giant pandas with bamboo,this thesis compared the changing trend of bamboo nutrients and secondary metabolites with storage time and the effects of different storage time on the contents of nutrients and secondary metabolites in bamboo,and discussed the main factors that affect the food selection of Giant panda.The research content is as follows.Content 1 The effect of storage time on physical properties and smell of Bamboo.In this study,6 batches of bamboo were placed for 0d,15d,30d,45d,60d and 75d respectively.Then,the degree of stem luster,yellowing and bamboo leaf drop were judged by observation,and the change of smell of bamboo stem was also judged by smelling directly.In addition,the content of crude moisture was measured by atmospheric drying method.The results showed that with the extension of storage time,the bamboo stem gradually became dull and yellow,the leaves dropped slowly,and fragrance was released out and water content decreased.Bamboo stem luster:the luster began dimming at 15d,medium at 30d,relatively weak at 60d,and the luster almost disappeared after 75d.Yellowing of stems:The color changed rapidly in the early stage,with half of bamboo stems turning yellow at 15d;the change went slowly during 30-60d,and the yellowing degree reached more than 75%at 75d.Bamboo leaf drop situation:the leaves on the fresh bamboo stem almost did not drop.From the 15th day,the bamboo leaf drop rapidly reached about 40%in the early stage,and within 15-75d,the trend of bamboo leaf drop was slow,and at the last 75d,the drop degree reached more than 85%.Smell changes:The stems had no obvious smell change at 15d,but at 30d,bamboo stems had a slight aroma,which gradually became apparent from 30d to 60d,and could be sensed obviously at 60d.At 75d,most bamboo stems had obvious aroma.Water content change:water content decreases with the extension of storage time.At 15d,it decreased by one third,and during 15-75d,the water content decreased slowly,and at 75d,the water content decreased by nearly half.Content 2 Variation trend of organic nutrients in bamboo stem with storage timeIn this study,for the 6 batches of bamboo stems,dry matter,crude protein,crude ash,crude fat,crude fiber,soluble sugar and gross energy were detected by drying method,kjeldah method,Calcination method,Soxhlet extraction,Fiber analyzer method,Colorimetric method and Calculation method,respectively.To study the effects of different placement time on organic nutrients in stems(upper,middle and lower)of bamboo,and to explore the variation trend of these organic nutrients with placement time.The results showed that the crude protein content increased first and then decreased;the crude fiber and ash content decreased first and then increased,and the total energy,crude fat and soluble sugar content decreased gradually with the extension of time.Through curve fitting,on the basis of dry matter,the crude protein content of BSH,BSM and BSL reached the highest 2.38%at 49.73d,2.57%at 45.9d and 2.32%at 43.40d,respectively.The crude ash content of BSH,BSM and BSL reached the lowest 1.874%at 26.7d,1.55%at 32.8d and 1.50%at 28.3d,respectively.Crude fiber:the content of BSH,BSM and BSL reached lowest 39.31%,39.11%and 39.14%at 46.95d,23.45d and 21.58d,respectively.Crude fat:the maximum content of each part is BSHfre 5.95%,BSHfre 6.58%,BSLfre 6.00%.The maximum content of soluble sugar in each part was BSHfre 37.708%,BSMre 43.16%,BSLfre41.959%.Total energy:the minimum value of BSH and BSM is 664.87kJ and 576.91kJ at 57.3d and 136.09d,respectively;the maximum value of BSL is 920.83g/kJ at 0d.Content 3 Variation trend of inorganic mineral elements in stem of Fargesia robusta with storage timeIn this study,6 batches of bamboo were placed for 0d,15d,30d,45d,60d and 75d respectively.Then,major inorganic mineral elements(Ca,P,Na,K and Mg)and trace mineral elements(Mn,Fe,Zn and Cu)were detected to study the effects of different storage time on inorganic nutrients in bamboo stem of three parts,and to explore the variation trend of inorganic nutrients with storage time.Calcium was detected by titrimetry,phosphorus by ultraviolet spectrophotometer,and Na,K,Mg,Mn,Fe,Zn and Cu were detected by ICPMS.The results show that there is no obvious correlation between the contents of inorganic mineral elements and storage time.For Ca,the variation range of BSH,BSM and BSL is 166.19-299.74 μg/g,126.65-342.67 μg/g and 201.81324.41μg/g,respectively.For P,the variation range of BSH,BSM and BSL is 341.11365.57μg/g,340.22-369.86μg/g and 338.60-373.41μg/g,respectively.For Zn,the variation range of BSH,BSM and BSL is 11.69-19.98μg/g,7.80-17.29μg/g and 7.2516.07μg/g,respectively.For Mg,the variation range of BSH,BSM and BSL is 62.57132.97μg/g,78.75-97.23μg/g and 80.18-97.20μg/g,respectively.For Mn,the variation range of BSH,BSM and BSL is5.37-19.60μg/g,1.23-16.43μg/g and 1.23-16.33μg/g,respectively.For K,the variation range of BSH,BSM and BSL is 1318.53-1411.76μg/g,1220.25-1347.02μg/g and 1359.04-1458.43μg/g,respectively.For Cu,the variation range of BSH,BSM and BSL is 1.46-3.48μg/g,0.92-3.11 μg/g and 0.91-3.47μg/g,respectively.For Fe,the variation range of BSH,BSM and BSL is 76.56-134.70μg/g,84.10164.50μg/g and 72.98-153.19μg/g,respectively.For Na,the variation range of BSH,BSM and BSL is 320.83-392.82μg/g,357.47-396.96μg/g and 360.54-421.59μg/g,respectively.Content 4 Variation trend of secondary metabolites in stem of Fargesia robusta with storage timeIn this study,6 batches of bamboo were placed for 0d,15d,30d,45d,60d and 75d respectively.Then,the total alkaloids were detected by Reisberg salt colorimetry;total tannin and flavonoids were detected by ultraviolet spectrophotometer.The results showed that the total alkaloid content increased slightly at first and then decreased with the extension of time,with the maximum content of BSH,BSM and BSL being 7.53g/kg at 18.2d,7.44g/kg at 5.5d and 7.30g/kg at 8.6d,respectively.The total flavonoids content decreases with the extension of storage time,with the highest value of BSH,BSM and BSL being 0.40%,0.38%and 0.37%,respectively,at 0d for all.The total tannin content decreased first and then increased with the storage time,with the minimum content of BSH,BSM and BSL being 4.84g/kg at 47.63d,5.326g/kg at 43.13d,and 4.994g/kg at 81.11 d,respectively.Content 5 Evaluation of palatability of Fargesia robustaNormalized the experiment data to make them dimensionally consistent.Regression analysis and fitting curve were performed on the data,and the relationship between the optimum palatability and storage time was analysed.The results showed that the palatability of BSH was the best when it was placed for 49d,BSM for 23d,and BSL for 21d.In conclusion,with the increase of storage time,Fargesia robusta has significant changes in physical properties,smell,nutrients and secondary metabolites.After storage,the stem released fragrant smell;most of the nutrients(organic and inorganic nutrients)content increased;the secondary metabolites content decreased,and thus the palatability improved significantly.The experiment results can provide scientific basis for rational utilization of Fargesia robusta resources and guide the determination of feeding for wild training giant pandas. |
