SThe Effect Of Different Treatments On Water Status And The Yield Of Vitamin C In Broccoli

Extracting nutrients from plants is an important unit operation in the food and biological industries.There are two essential steps in nutrient extraction and measurements,which are:i)disruption of the cellular matrix,and ?)extraction of nutrients with proper solvent.Therefore,changing the microstructure of tissues,and increasing the permeability of adhesion membrane can significantly improve the release of nutrients.At the same time,it is essential to select proper solvent to ensure the stability of the nutrients.In the first part of this work,the degradation of the ascorbic acid in different solvents at room temperature and the effect of the different solvents with different pH on the yield of vitamin c in broccoli were determined.The degradation kinetics of ascorbic acid were best fitted by first-order reaction models.It was also found that the combination of metaphosphoric acid and other acid can significantly improve the yields of the vitamin C by comparing the common extractants.Afterwards,different teatments were operated on different parts of the broccoli(floret and stalk)to investigated their effects on tissue's microstrUcture and the release of the nutrient(vitamin C).The change of the microstructure of tissue was reflected by LF.NMR based on T2 shift,particle size distribution and microscopies.For mechanical treatments,the vitamin C yield of high pressure homogenization was increased 75.69%for floret and 28.84%for stalk respectively compared with that treated with homogenizations.The degradation of the vitamin C was observed by the longer ball mill grinding operations though the integrity of the tissues was similar with the high pressure homogenizations treated samples.This work confirms that the degree of the tissue damage has a positive correlation with the release of the nutrient(vitamin C)without considering the nutrients degradation.LF-NMR has been proved to be an effective method to compare different physical processes on their impact of broccoli stalk tissue's microstructure.For enzymatic treatments,compared to the blank group,pectinase can significantly destroy the microstructure of broccoli,and the yield of vitamin C was increased 81.1%for floret and 51.2%for stalk respectively.This part further verified the relationship between the change of microstructure and the release of the nutrient(vitamin C)and the reliability of reflecting the changes of plant's microstructure by LF-NMR based on T2 shift.