Study On The Quality Of Dried Bamboo Shoots Of Chimonobambusa Utilis And Its Ultrafine Powder

Chimonobambusa utilis is one of the famous and precious bamboo species,belonging to subfamily bambusoideae.Chimonobambusa utilis bamboo shoots,as the bamboo resources of advanced characteristics in guizhou,is crisp and delicious.Chimonobambusa utilis bamboo shoots is rich in protein,dietary fiber,free amino acids,minerals,and active components(polyphenols,flavonoids,phytosterols and?-aminobutyric acid).However,the shooting cycle of bamboo shoots is short,the postharvest browning and lignification are easy to occur.Meantime,the traditional processing methods,including salty boiling,oven-drying and sun-drying,are easy to lead to the nutritional destruction,poor rehydration and darkening.Therefore,in this study,the nutritional and functional components of nine kinds of Chimonobambusa utilis bamboo shoots were analyzed.Then,the quality changes of bamboo shoots were investigated after dried by heat pump,vacuum microwave,vacuum microwave-heat pum combined,vacuum microwave-heat pum-vacuum microwave combined,Hot air drying and Salted boiling dry drying methods,respectively.Meanwhile,the effects of micronization treatment on the hydration characteristics,functional characteristics and organizational structure of dried bamboo shoots were explored,which could provide the scientific basis for new-type dried bamboo shoots and whole-flour functional food.The results are as follows:(1)The main nutritional and functional components of Chimonobambusa utilis bamboo shoots from different producing areas in Guizhou were analyzed and compared,and the principal component analysis was used to comprehensively evaluate their quality.The results showed that the dietary fiber content of 9 fresh bamboo shoots ranged from 17.87 to 38.11g/100g DW and the protein content ranged from 32.23 to 42.30 g/100 g DW.The total free amino acid(TFAA)content ranged from 821.27 to 568 3.72mg/100 g DW,and Q-1 had the highest ratio of EAA/TFAA(37.20%).Among the minerals,K content was the highest(3571.43 to 9620.00mg/100 g DW).The polyphenols content ranged from 602.83 to 854.07mg/100 g DW,and the flavonoids content ranged from 299.35 to 638.86mg/100 g DW.The contents of?-sitosterol and stigmasterol were 208.99-306.77mg/100 g DW and 81.89-130.36mg/100 g DW,respectively.The content of?-aminobutyric acid ranged from 70.06 to 704.94mg/100 g DW,and Q-1 was significantly higher than that of other fresh bamboo shoots(p<0.05).The polysaccharide content was 817.93?1798.31mg/100 g DW.According to the principal component analysis,six principal components were obtained,and the contribution rate of cumulative variance reached 93.377%.The top three bamboo shoots with high quality were Q-1,Q-5 and Q-3.(2)Comparing to other drying methods,microwave and heat-pump combined drying(MHD)and microwave drying(MD)had higher drying rate in the early stage,and reached the drying end point firstly with the drying time of 8 h.The drying models of 8 drying methods were fitted based on the water ratio(MR=(M_t-M_e)/(M₀-M_e)of bamboo shoots.The Page equation was the best drying model for hot air drying(HAD)and microwave-heat pump-microwave drying(CD),and the Diffusion approximation equation was the best drying model for salt pickling drying(SD).The optimal drying model for heat pump drying(HPD),MHD and MD was the Logistic equation.Therefore,the optimal drying model could be selected to fit the moisture ratio for different drying methods.(3)The results of the rehydration,texture characteristics and nutritional quality of dried bamboo shoots by different drying methods showed that the hardness of dried bamboo shoots by SD and HAD was higher than that of other samples,and the texture of bamboo shoots dried by HPD?MD?MHD and CD had no significant difference(p>0.05).Compared with FB(fresh bamboo shoots),the hardness of dried bamboo shoots by HPD?HAD?CD?MHD and BU was not significantly different after rehydration(p>0.05),which better maintained the original texture and had faster rehydration rate.The browning of BU and HAD samples was more serious.After rehydration,the color of HPD,MD,MHD and CD samples were close to FB.The contents of?-sitosterol,stigmasterol,polyphenols,flavonoids and GABA in HPD samples were highly preserved,while SD samples suffered the worst loss.According to the comprehensive evaluation of drying time,nutrient components retention and structure destruction,MHD is the best drying method for bamboo shoots.Notably,The loss rates of?-sitosterol and stigmasterol were less than 30%.But the mineral loss rate is higher(30?65%).The losses rates of polyphenols,flavonoids and GABA were more than 60%,After SWL and VD treatment,the contents of GABA,?-sitosterol and minerals(P,Cu,Zn and B)in VFD samples had no significant differences(p>0.05),and The retention rates of TFAA,EAA and K elements were about 65%.,while the contents of polyphenols,flavonoids,stigmastol,Ca,Mg,Fe and Mn increased with the retention rates of 113%?169%.(4)The whole powder of bamboo shoot was processed by drying ultrafine comminution,and the changes of the hydration,functional and structural characteristics were analyzed.The results showed that the particle size of the whole powder decreased gradually with the increase of grinding time.The ultrafine powder with the average particle size of 8.10?m was obtained at the grinding time of 8 min,the powder shape was small flakes or particles,the expansive force was significantly increased(up to 11.08mL/g),and the dispersion,hydraulic holding capacity and oil holding capacity were 2.51,7.13 and 3.82 g/g,respectively.The nitrite adsorption capacity of the whole bamboo shoots with different particle sizes had no significant difference at p H 2.0(p>0.05),but there was a significant negative correlation between the cholate adsorption capacity and particle size(p>0.05).In addition,compared to the 60 mesh bamboo shoot powder,the infrared spectral peak and quantity of the whole powder had no evident change,the chemical structure of the components was not destroyed,but the absorption peak strength increased with the extension of grinding time.