黑蒜类黑精高静水压辅助提取工艺及其抗氧化性和稳定性研究

通过正交试验优化了黑蒜类黑精高静水压辅助提取工艺,并对0.5～2.5 mg/mL浓度范围内的类黑精溶液进行了抗氧化活性测定,同时探究了溶液体系(氧化剂H_2O_2、还原剂Na_2SO_3、葡萄糖、蔗糖)、温度区间(20～100℃)、光照条件对类黑精溶液稳定性的影响。结果表明,高静水压辅助提取类黑精的最优提取条件为处理压力300 MPa、保压时间8 min,料液比1∶6。与对照组相比,高静水压辅助处理使类黑精的DPPH、ABTS自由基清除能力及还原能力分别提高了14.36%～105%、3.40%～78.22%和56.67%～123.31%。类黑精在还原剂、糖溶液中稳定,而在氧化剂溶液中不稳定;温度、散光、暗光及白炽灯光照射对类黑精稳定性无显著影响,而日光、紫外光照射使其稳定性降低。上述结果说明高静水压辅助提取可以提高黑蒜类黑精的提取效率,并增强其抗氧化活性。此外,在类黑精使用过程中,应避免日光、紫外光照射以及与氧化剂混合使用。     

食品中类黑精的提取分离研究进展

类黑精是美拉德反应后期形成的一种结构复杂、分子量较大的棕褐色聚合物,因其具有广泛的营养价值和生理功能而日益受到人们的关注。然而由于其结构上的复杂性和不稳定性,目前在提取分离上还存在一定的困难。本文简要介绍了类黑精的3种推测结构与其抗肿瘤、抗氧化、抗菌等的生理功能,并对其现有的提取分离方法,包括水浸提法、沉淀法、大孔树脂吸附法、乙醇溶液提取法、酶提取法等方法进行了总结,最后展望了非热加工技术如超声辅助提取、超临界流体萃取、高静水压萃取、脉冲电场等技术在类黑精提取上的应用前景,旨在为下一步分离纯化类黑精提供比较系统的信息依据。     

Nitrogen balance in a soil‐wheat system under plow‐ and no‐tillage in the argentine humid pampa

Abstract

Changing conventional tillage to conservation tillage systems affects nitrogen (N) cycling in agroecosystems. Our objective was to evaluate the role of soil organic pools, specially plant residues, as sources‐sinks of nitrogen in an humid and warm temperate environment cropped to wheat, under plow‐ and no‐tillage. The experimental site was in the Argentine Pampa on a Typic Hapludoll. A balance‐sheet method was used: Nupt+Nres=Nsow+Nmin, where Nupt=N uptake by the crop at harvest; Nsow=soil mineral N as NH₄ and NO₃ at 0–90 cm depth, one month before sowing, plus N added as fertilizer; Nres=residual soil mineral N as NH₄ and NO₃ at 0–90 cm depth, at harvest; Nmin=N mineralized from humus and plant residues during wheat growing period. Nupt did not differ between tillage systems. Nitrogen supply by the mineral N pool, estimated by the difference Nsow‐Nres, was ca. 150 kg N ha^‐1 in both tillage systems. Plant residues decomposed and released N under both treatments. This organic N pool decreased 77% along the crop cycle. Nmin, calculated using the balance equation was 83 kg N ha^‐1, and did not differ between tillage managements, representing 35% of Nupt. This results highlight the importance of the organic pools as sources of N for wheat in the Humid Pampa. They also brink our attention on the importance for evaluate residue decomposition and humus mineralization in warm‐temperate regions when fertilizer requirements are determined, in order to minimize environmental hazard and economic losses by overfertilization.     

板栗非酶促褐变产物类黑精的研究

研究板栗非酶促褐变产物类黑精提取和测定的方法。采用对板栗果仁先微波灭酶,后砂炒的加工方法,保证板栗发生非酶促褐变;通过乙醇浓度、提取时间、料液比、提取温度等单因素试验及正交试验,对板栗非酶促褐变产物类黑精进行溶剂浸提和含量测定,并确定类黑精的最佳提取工艺参数。结果表明:提取板栗非酶促褐变产物类黑精的最佳工艺参数为乙醇浓度60%,提取时间5h,料液比1∶12.5,提取温度60℃,在该处理方法下板栗中非酶促褐变产物类黑精提取量为1.41mmol/L。