Influence of non-cellulose structural carbohydrate composition on plant material decomposition in soil

The C mineralisation pattern during the early stage of decomposition of plant materials is largely determined by their content of different carbohydrates. This study investigated whether detailed plant analysis could provide a better prediction of C mineralisation during decomposition than proximate analysis [neutral detergent solution (NDF)/acid detergent solution (ADF)]. The detailed analysis included sugars, fructans, starch, pectin, cellulose, lignin and organic N. To determine whether differences in decomposition rate were related to differences in hemicellulose composition, the analysis particularly emphasised the concentrations of arabinose and xylose in hemicelluloses. Carbon dioxide evolution was monitored hourly in soil amended with ten different plant materials. Principal component and regression analysis showed that C mineralisation during day 1 was closely related to free sugars, fructans and soluble organic N components (R ² = 0.83). The sum of non-cellulose structural carbohydrates (intermediate NDF/ADF fraction) was not related to C mineralisation between days 1 and 9. In contrast, a model including starch and protein in addition to the non-cellulose structural carbohydrates, with the hemicelluloses replaced by arabinose and xylose, showed a strong relationship with evolved CO₂ (R ² = 0.87). Carbon mineralisation between days 9 and 34 was better explained by xylan, cellulose and lignin (R ² = 0.72) than by lignocellulose in the ADF fraction. Our results indicated that proximate analyses were not sufficient to explain differences in decomposition. To predict C mineralisation from the range of plant materials studied, we propose a minimum set of analyses comprising total N, free sugars, starch, arabinose, xylan, cellulose and lignin.     

阿拉伯糖与赖氨酸或甘氨酸的模式Maillard反应产物抗氧化性研究

[目的]研究不同模式下Maillard反应及其产物（MRPs）的抗氧化活性。[方法]以阿拉伯糖与赖氨酸或甘氨酸为原料,合成一系列不同反应条件下的MRPs,测定其抗氧化活性。[结果]阿拉伯糖-赖氨酸体系的最佳条件为：pH值=10,反应物摩尔比1∶2,加热7 h;阿拉伯糖-甘氨酸体系最佳条件为：pH值=10,摩尔比1∶1,反应6 h。[结论]在一定的浓度下,上述条件制备的MRPs的抗氧化能力可优于常用食品抗氧化剂TBHQ,为开发天然抗氧化剂提供了新的途径。     

Phenolic compounds,antioxidant capacity and gelling properties of glucoarabinoxylans from three types of sorghum brans

Arabinose to xylose ratio (A/X), phenolics, antioxidant capacity and gelling properties were evaluated in glucoarabinoxylans (GAX) extracted from white (W-GAX), red (R-GAX) and high tannin (T-GAX) sorghum brans (SB). The characterization of arabinoxylans from corn fiber (CFAX) was used as benchmark. Sorghum GAX had higher branched structure (A/X 1.08–1.41) than CFAX (0.59). Nine 3-deoxyanthocyanins (3-DAs) were identified in SB and two glycosylated forms remained associated to the R-GAX and T-GAX extracts. T-GAX was the only that contained tannins (0.41 mg catechin equivalents (CE)/g dry basis (db)) and exerted the highest antioxidant capacity (81.75 mM Trolox equivalents (TE)/g db) followed by R-GAX (48.49 mM TE/g db), which contained the highest amount of 3-DAs (0.11 mg Luteolinidin equivalents (Lut eq)/g db), and W-GAX (35.45 mM TE/g db) that was not significantly different from the CFAX (25.83 mM TE/g db). Among sorghums, only the W-GAX gelled but it formed a weaker gel compared to CFAX likely due to its lower hydroxycinnamic acids (HCA) concentration. The presence of 3-DAs in the structure of R-GAX and T-GAX affected negatively their solubility and gelling properties. The different SB showed potential as sources of GAX with antioxidant capacity.