| Pueraria DC. plants, classified into Leguminosae family, were mainly distributed in China. Among the 18 species, Pueraria lobata (Willd.) Ohwi and P.thomsonii Benth were commonly seen. In the present study, the nutrition and phytochemicals changes of two species of P.thomsonii Benth during whole power processing and soup-cooking were systematically studied and the main conclusions were listed as follows:1. Nutrients and bioactive components of P.thomsonii Benth in different growth periods were investigated, and HPLC method was taken to qualitatively and quantitatively analyse the isoflavones in the pueraria lobate.In this study 8 isoflavones from total isoflavones were identified with HPLC, and puerarin was the largest proportion. The total isoflavones of Dayezi cultivar was significantly higher than that of Cangwuxiye cultivar during the growth period. Cangwuxiye cultivar was a suitable material for starch preparation. With the extending of the growth period, the isoflavones content of the two species of pueraria lobate increased significantly. Particularly, from August to the January of second year, the content of puerarin in Cangwuxieye variety and Dayezi variety increased by 44% and 52%, respectively. While the content of daidzin increased 145% and 202%, especially, the content of total isoflavones of Dayezi variety increased by 53%. Dayezi variety showed a higher in vitro antioxidant activity than that of Cangwuxieye variety, which might attribute to the higher content of total isoflavones. In December, the isoflavones content in Cangwuxiye and Dayezi variety accumulated to the maximum, and then the isoflavones content no longer changed with the extending of growth period, and December was considered as a suitable time for its harvest.2. The processing characteristics of uncooked pueraria whole powder and the cooked whole powder were studied.The cell integrity, sensory attributes and water binding capacity of the raw pueraria whole powder were better than that of the cooked, which attributed to application of the high temperature gas steam during the processing of cooked power. Starch gelatinization and protein denaturation of cooked powder induced a higher solubility, but at the same time, curing also led to the increase of free starch. When the pH value was 3, the freeze-thaw stability was the optimum, and the addition of NaCl or sucrose could increase the freezing thawing stability of raw whole powder, and the best additive of NaCl concentration was 5%.The temperature of pueraria cooked whole powder was higher than that of the raw. The breakdown value of uncooked whole powder was smaller, which showed the intensity of starch granule was relatively large in the process of swelling. But cooked powder showed larger breakdown value and the stability of its hot paste was poor. According to SPME-GC-MS analysis,89 kinds of volatile substances were identified, which were mainly classified into esters, ketones, olefins, acids and hydrocarbons.14 species of the components were common to the both, and the components which accounted higher content mainly were hexanal, (E)-2-octene aldehyde, nonanal, decanal, 3-octene 2-one and 2,2-dimethyl butyric acid vinyl ester.3. The orthogonal optimization of the processing technology of Puerariae cooked powder was studied. Based on the single factor analysis, the concentration of leaching calcium and condition of gas-steaming treatment affected the quality of powder.Based on an overall consideration of the effects of both the iodine blue value and total isoflavones content, the comprehensive index value of different drying combination process was calculated. The results showed that the main factors were as follows:gas-steaming time> leaching calcium concentration> drying temperature. Besides, the factors which determined the optimum technological conditions were:the gas steam time of 8min, the concentration of calcium concentration of 32μg/mg, and the drying temperature of 80℃.4. The cooking time and temperatures had a big effect on the nutritional quality and functional ingredients of pueraria lobate soup.Different cooking time had certain effect on the nutritional quality of Radix Puerariae. As the cooking time increased, water soluble substances precipitated gradually and transferred to the soup, the content of total sugar and reducing sugar decreased significantly, and in 3.5h reached the lowest level. Besides, the total content of amino acids and total free amino acids in the soup reached the highest value at 1h. The content of total isoflavones in Radix Puerariae decreased significantly after 1.5h, while the content of isoflavones in soup in 1.5h was the highest. With the increase of cooking time, isoflavones composes such as puerarin and daidzein in the soup showed a significant decreasing while the contents of daidzein、biochanin A and isoliquiritigenin in the soup significantly increased. Therefore, the suitable cooking time should be not more than 1.5h.As the cooking temperature of the soup increased, total sugar and reducing sugar content of pueraria lobate decreased, while the soup showed a trend of increase. The total content of amino acids and total free amino acids in the soup was indistinctive from that of the control group. The total isoflavones content in Radix puerarin decreased and reached the lowest level at 100℃, and reached the highest level at 70℃. With the increase of temperature, the content of major isoflavones such as puerarin and daidzin decreased significantly, and isoflavones content in the soup gradually increased. So 70℃ was recommended as the cooking time. |
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