HPLC法测定玉米浆中游离氨基酸的含量

建立测定玉米浆中游离氨基酸的反相高效液相色谱法.Diamonsil C18(2)反相柱(5μm,250mm×4.6mm);梯度洗脱,流动相A相:0.05mol/L醋酸钠缓冲溶液(pH6.50),B相:乙腈-水(v/v=1:1),流速1.0mL/min,检测波长360nm.在该条件下所得各氨基酸的线性回归方程相关系数均在0.999以上.测定17种氨基酸的加样回收率94%～105%,相对标准偏差小于2.0%.     

反相高效液相色谱法测定烟叶中的游离氨基酸

先用乙醇提取烟叶中的游离氨基酸 ,提取液经阳离子交换树脂纯化后 ,再用邻苯二甲醛(OPA)、氯甲酸芴甲酯 (FMCF)联合柱前衍生化和反相高效液相色谱法测定了烟叶中 17种带伯氨基和 /或仲氨基的游离氨基酸。方法的重复性为 :天冬氨酸 (Asp)、谷氨酸 (Glu)和组氨酸 (His)的相对标准偏差 (RSD)分别为 8.0 %、8.6 %和 9.0 % ,其它氨基酸的RSD均在 3%～ 7%范围内 ;回收率 ,除苏氨酸 (Thr)的为 6 8.0 %较低外 ,其它氨基酸的在 81.0 %～ 110 .5 %范围内 ,平均为 93.9%。用该方法测定了不同等级烟叶中的游离氨基酸。     

河北省特种桑叶中游离氨基酸的含量测定

测定河北省特种桑叶中游离氨基酸的含量。超声辅助提取桑叶中的游离氨基酸,以异硫氰酸苯酯为柱前衍生化试剂,采用反相高效液相色谱法梯度洗脱测定。液相条件为Kromasil C18色谱柱(4.6 mm×250 mm,5μm),柱温40℃,流速1 m L/min,检测波长254 nm。16种氨基酸在0.03125~1μmol/m L浓度范围内呈现良好的线性关系,r均大于0.9961,平均回收率为92.2%~101.4%(n=6),RSD5.0%。此方法准确可靠,可用于桑叶及其他药食两用植物中游离氨基酸的含量测定。     

家用豆浆机制作胚芽豆浆

以发芽大豆为原料,利用豆浆机工装平台,优化胚芽豆浆的制浆工艺。通过对粉碎温度、煮浆时间的单因素试验,发现较佳的粉碎温度为70℃、煮浆时间为4min。采用优化后的胚芽豆浆程序制得的胚芽豆浆含γ-氨基丁酸1.36mg/100g,游离氨基酸0.455g/100g,游离氨基酸中必需氨基酸0.219g/100g,分别是原程序干豆豆浆的3.68,1.34,8.87倍。尽管胚芽豆浆中胰蛋白抑制剂活力为干豆豆浆的1.27倍,但总体营养价值仍得到显著提升。     

反相高效液相色谱法测定白屈菜种子中挥发油 成分分析及氨基酸含量

目的研究白屈菜种子中挥发油的化学成分并建立一种反相高效液相色谱法对白屈菜种子中游离氨基酸和水解氨基酸含量进行测定。方法采用气质联用的方法对白屈菜种子中的挥发油成分进行分析,采用反相高效液相色谱法,以异硫氰酸苯酯为衍生试剂进行柱前衍生,采用梯度洗脱的方法,检测白屈菜种子中游离氨基酸和水解氨基酸含量。结果挥发油中共鉴定出化学成分27个,其中亚油酸的含量最高可达到65%左右。氨基酸的检测浓度线性范围为0.0020~0.2700 mmol/L,r均≥0.9991。21种游离氨基酸的平均加样回收率在87.88%~100.10%之间,RSD在0.62%~2.58%之间(n=6);水解氨基酸的平均加样回收率在91.79%~100.03%之间,RSD在0.48%~1.97%之间(n=6)。结论白屈菜种子种中挥发油的主要成分为不饱和脂肪酸,本文建立的氨基酸测定方法经方法学验证适合白屈菜种子中游离氨基酸和水解氨基酸的含量测定。     

6种葡萄籽中水解氨基酸和游离氨基酸含量测定及比较

以异硫氰酸苯酯为柱前衍生试剂,采用Thermo Acclaim~(TM) 120 C_(18)色谱柱(250mm×4.6mm,5μm),流动相A为pH 6.5的乙酸钠缓冲溶液,流动相B为甲醇—乙腈—水(体积比20:60:20),在流速1.0mL/min,梯度洗脱,柱温30℃,检测波长254nm的条件下,建立了高效液相色谱法测定葡萄籽中水解氨基酸和游离氨基酸的含量。结果表明,在试验浓度范围内,17种氨基酸的R~2均0.999 0;水解氨基酸的加样回收率为92.0%～104.6%,RSD为0.83%～4.07%;游离氨基酸的加样回收率为95.2%～102.4%,RSD为1.06%～3.98%。同时,6种葡萄籽中水解氨基酸的含量为130.46～163.24 mg/g,游离氨基酸的含量为2.04～5.13mg/g;用于酿造白葡萄酒的雷司令、赛美容和贵人香3种葡萄籽中游离氨基酸含量较高,用于酿造红葡萄酒的黑皮诺、蛇龙珠和赤霞珠3种葡萄籽中水解氨基酸含量较高。该方法稳定可靠,可用于葡萄籽中水解氨基酸和游离氨基酸的含量测定。     

烘焙期间加料与未加料白肋烟游离氨基酸的变化

采用OPA、FMOC联合在线衍生反相高效液相色谱法测定了烘焙过程中加料和未加料的白肋烟游离氨基酸的变化。结果表明:①烘焙过程中未加料白肋烟的游离氨基酸总量呈先增后减的趋势,烘焙18min后游离氨基酸总量降低19%,其中降幅20%以上的有Asn、Asp、Arg;②加料白肋烟的游离氨基酸总量呈逐渐减少的趋势,烘焙18min后其游离氨基酸总量降低37%,其中降低50%以上的有Glu、Phe,降低40%以上的有Asn、Val;降低30%以上的有Asp、Ser、Arg、Lys、Pro;③未加料和加料的白肋烟中游离氨基酸的变化均主要发生在140℃。     

柱前衍生反相高效液相色谱法测定狭叶红景天中氨基酸含量

目的建立柱前衍生反相高效液相色谱法(reversed-phase high-performance liquid chromatography,RP-HPLC)测定狭叶红景天中游离及水解氨基酸种类及含量。方法以异硫氰酸苯酯为柱前衍生化试剂;色谱柱采用Ultimate Amino Acid氨基酸柱(4.6 mm×250 mm,5μm);流动相A为80%(V:V)的乙腈-水溶液,流动相B为7%(V:V)的乙腈-CH_3COONa溶液(pH=6.5);检测波长为254 nm。结果 21种氨基酸在0.0019~2.700mmol/L内呈良好的线性关系(r~20.9990)。游离氨基酸平均回收率在97.80%~116.82%之间,RSD在1.93%~2.47%之间(n=6);水解氨基酸平均回收率在99.26%~111.23%之间,RSD在1.70%~2.23%之间(n=6)。结论柱前衍生RP-HPLC法灵敏、准确,具有良好的重复性和稳定性,适合对狭叶红景天中氨基酸含量的测定。     

热应激时奶牛血液中游离氨基酸流向与乳蛋白下降的关系研究

目的:探讨热应激时奶牛血液中氨基酸与乳蛋白的相互关系。方法:选取6头相同泌乳期奶牛,正常饲喂和饮水,实验期35 d(6月29日—8月5日)。每日10:00和18:00记录气温,统计产奶量,每周取全天奶样,Foss乳成分分析仪检测乳蛋白含量。于实验开始第1周和最后1周采集颈静脉血液,反相高效液相色谱法检测血液中游离氨基酸含量。结果:随着气温的升高(由26℃升高至最高38℃),实验奶牛日均产奶量由15.2 kg/d下降至10 kg/d,乳蛋白产量由0.47 kg/d下降至0.31 kg/d。血液中Glu、Asp、Gly和Val等主要的生糖氨基酸(参与糖异生作用)以及Leu、Ile等生酮氨基酸均升高或显著升高(0.01P0.05);总支链氨基酸(Val、Ile、Leu,主要参加免疫反应)含量显著增加(P0.05),在必需氨基酸中所占的比例由54.75%增至67.89%。结论:在夏季高温高湿条件下,奶牛可发生热应激,产奶量和乳蛋白含量均降低,但血液中游离氨基酸,特别是支链氨基酸含量显著升高。提示热应激时奶牛血液中高水平的游离氨基酸并未完全用于乳蛋白的合成,还发挥了除此之外的其他作用,而后者的作用优先于参与乳蛋白的合成,即可能优先作为功能性氨基酸参与了机体的其他活动。     

基于游离氨基酸水平对葡萄酒产地和品种的判别分析

以47款来源于3个产地和5个品种的中国葡萄酒原酒为实验样本,通过反相高效液相色谱法技术对其中的17种主要的游离氨基酸进行了定性定量分析。中国葡萄酒原酒中游离氨基酸含量范围为447.13~1 359.06 mg/L。在游离氨基酸中,脯氨酸、精氨酸、谷氨酸均为含量最为丰富的氨基酸。基于游离氨基酸和含量水平对葡萄酒产地和品种进行判别分析,正确分类结果分别为85.1%和100.0%,实现了对中国葡萄酒产地和品种的良好识别。     

碱提酸沉法提取茶叶蛋白质的研究

以绿茶为原料,采用碱提酸沉的方法提取茶叶蛋白质,以料液比、碱液浓度、温度、时间为考查因素,研究茶叶蛋白质的最佳提取工艺条件,并对提得的茶叶蛋白质进行了氨基酸分析.结果表明:碱提酸沉法提取茶叶蛋白质的最佳工艺条件为料液比1∶25(m/V),碱液浓度03 mol/L,提取温度50℃,提取时间1 h,连续提取两次,茶叶蛋白质...     

Trans18:1 and 18:2 isomers in blood plasma and milk fat of grazing cows fed a grain supplement containing solvent-extracted or mechanically extracted soybean meal

Thirty Holstein cows grazing mixed clover-grass pastures for 12 wk from May through July were fed a grain supplement containing solvent-extracted soybean meal (SES), or mechanically extracted soybean meal (MES) to determine whether differences in supplemental 18:2n6 fatty acid intake altered secretion of unsaturated fatty acids. Groups of 10 cows each were fed in two equal feedings a supplement (7.3 kg/d) containing ground corn plus either 1.8 kg of SES, 2.2 kg of MES, or 2.2 kg of MES plus 30 g of methionine hydroxy analog (Alimet; MESM). Fatty acid content (% of DM) of grass and clover in pastures averaged 1.9 and 1.5%, respectively. Concentration of 18:3n3 was higher in grass compared with clover (532 vs. 454 mg/g of total fatty acids). Yield of milk (32 kg/d average) and milk components did not differ by supplements. Total blood plasma fatty acids (mg/ml) during wk 4 were higher due to MESM (1.0) compared with MES (0.6) or SES (0.6). Cows fed MESM or MES had greater concentrations of 18:2n6, trans11-18:1, and cis9,trans11-18:2 in plasma compared with cows fed SES. The additional trans11-18:1 was found exclusively in plasma triglycerides, whereas the additional cis9,trans11-18:2 was found in plasma phospholipids and free fatty acids. Daily yields of 18:2n6, trans11-18:1 and cis9,trans11-18:2 in milk fat were greater for cows fed MES or MESM compared with SES. Results indicate yields of trans11-18:1, cis9, trans11-18:2, 18:2n6, and 18:3n3 in milk fat of pasture-fed cows were enhanced by feeding a grain supplement containing mechanically extracted, rather than solvent-extracted, soybean meal.     

氨基酸分析仪检测牛乳中掺入的大豆蛋白

利用氨基酸分析仪对牛乳和大豆分离蛋白中的17 种氨基酸进行分离测定,氨基酸浓度在0.025～0.350 μmol/mL时,其峰面积和氨基酸浓度的线性相关系数均不小于0.988,重复性较好,牛乳加标回收率范围在94.2%～103.1%,相对标准偏差在0.89%～3.31%。通过对比分析牛乳和大豆的氨基酸图谱找到含量差异较大的6 种氨基酸,并根据模拟掺假实验样品的氨基酸分析6 种氨基酸含量和掺假量的线性关系,相关系数R2达0.889,建立牛乳中大豆蛋白掺假的定性定量检测方法。     

野生山毛豆蛋白制备及体外消化模拟研究

通过碱提酸沉法制备野生山毛豆蛋白,并模拟人体消化环境,采用胃蛋白酶、胰蛋白酶两步消化法分析山毛豆蛋白的消化行为。结果表明：山毛豆中蛋白质含量约为(47.12 ± 0.35)%,大豆中蛋白质含量约为(44.17 ±0.48)%,山毛豆含有18 种氨基酸,其中包括人体必需的8 种氨基酸,从非必需氨酸酸来看,山毛豆蛋白与大豆蛋白有相似的氨基酸组分,氨基酸平衡状况较好,接近参考蛋白模式;山毛豆的体外消化率为(84.86 ± 0.75)%,大豆的体外消化率为(91.71 ± 0.88)%,山毛豆酶解液中的总氨基酸含量比大豆的略低,但山毛豆酶解液中甘氨酸和色氨酸含量比大豆酶解液高很多,游离氨基酸(FAA)含量比大豆的略高。     

Feeding polyunsaturated vegetable oils to lactating cows

Holstein cows fed concentrate:hay diets also were fed for 14 days supplements of soybean oil plus casein, soybean oil protected from ruminal hydrogenation by encapsulation in a casein-formaldehyde matrix, cottonseed oil plus casein, or cottonseed oil protected with casein formaldehyde. The supplements were fed at rates to give a linoleic acid (18:2) intake of 225 g/day. Yields of milk and milk protein were not affected by treatment. Milk 18:2 was not increased by the unprotected soybean oil or cottonseed oil but was increased by protected soybean and cottonseed oil from a control of 2.3 to 5.7% of total milk fat. Milk 18:0 and 18:1 also increased. Compensatory declines were observed in milk 16:0 and 14:0 acids. In fecal fatty acids during the treatment periods, percentage of 18:2 of the total fat decreased and 18:0 markedly increased. These results indicate hydrogenation of the dietary oils in the alimentary tract or a differential absorption. Fecal 16:0 and 14:0 decreased.     

Extruded blend of soybean meal and sunflower seeds for dairy cattle in early lactation

An extruded blend of 44% crude protein soybean meal (50%), whole sunflower seeds (45%), and premix (5%) was evaluated as a protein and energy source for dairy cows in early lactation. Thirty Holstein cows (24 multiparous and 6 primiparous) were assigned to either a corn-oats-soybean meal concentrate or a concentrate where soy-sunflower blend replaced all soybean meal and portions of corn and oats. Dry matter of total mixed diets was 36% corn silage, 21% alfalfa haylage, and 43% concentrate. Yields of milk (33.6 and 33.8 kg/d) and 4% fat-corrected milk (30.9 and 30.5 kg/d) were similar, and percentages of total solids (11.92 and 11.38), fat (3.55 and 3.30), and protein (2.91 and 2.74) were lower in milk from cows fed soy-sunflower blend. Milk from cows fed soy-sunflower blend contained fewer short- and medium-chain fatty acids, more 18-carbon fatty acids, and was more unsaturated than from cows fed soybean meal. Intakes of dry matter and changes in body weight were not different among diets. Ruminal fluid pH and molar ratio of acetate to propionate were higher, and concentrations of total volatile fatty acids and ammonia were lower in cows fed soy-sunflower blend. Concentrations of essential amino acids in arterial serum, calculated mammary uptakes, and transfer efficiencies indicated more desirable amino acid balance in cows fed soy-sunflower blend. Methionine appeared to be most limiting with both diets.     

Blood amino acids and milk composition from cows fed soybean meal, fish meal, or both

Twelve multiparous Holstein cows at 48 +/- 8 d in milk were used in a 4 x 4 Latin square with 21-d periods to determine the effect on feed intake, milk yield, milk composition, and blood amino acids when soybean meal was replaced with fish meal. Fish meal substituted for soybean meal on an isonitrogenous basis at 0, 25, 50, and 100% of supplemental protein. Total mixed diets were (dry matter basis) 25% corn silage, 25% alfalfa hay, and 50% concentrate mix. Intake of dry matter (27.9, 27.8, 26.1, and 25.8 kg/d for diets 1 to 4, respectively) was similar for all diets. Milk yield (37.5, 37.8, 37.2, and 37.7 kg/d) was not affected by diets. Milk protein percentages (3.23, 3.24, 3.31, and 3.35) increased with 100% fish meal supplementation and tended to be higher, with 50% fish meal supplementation compared with 100% soybean meal diet. Milk fat percentages (3.18, 2.99, 3.04, and 2.87) and yields were lower with the 100% fish meal than with the 100% soybean meal diet. Molar proportions of ruminal volatile fatty acids and ammonia were not greatly affected by diet. Fish meal supplementation slightly improved Met status, as shown when blood amino acid data were evaluated. Both extraction efficiency and transfer efficiency of amino acids from the blood by the mammary gland indicated that Met, Lys, and Phe were the most limiting amino acids in all diets. Replacing as much as 50 or 100% of dietary soybean meal with fish meal may improve the amino acid balance and increase the protein content in milk; however, feeding 100% fish meal will likely decrease milk fat percentages.     

Effect of fat and lactose supplementation on digestion in dairy cows. 2. Long-chain fatty acids

Dairy cows fitted with rumen and proximal duodenal cannulae were given diets of 60% hay, 7% soybean and rapeseed meal, and either 33% concentrate (control diet) or 33% milk (lipid-supplemented diet: "milk" diet). Amounts of total long-chain fatty acids consumed, entering the duodenum and excreted in the feces were examined. Long-chain fatty acid intake was 192 and 764 g/d with the control and milk diets, respectively. The duodenal flow of long-chain fatty acids was greater (17.3%) than the amount consumed when the control diet was fed; with the milk diet, there was a net loss (-22.2%), mainly due to a decrease in total C16 and C18 acids. The extent of C18:2 hydrogenation in the rumen was reduced by the high fat ration, but for C18:3, hydrogenation was very high and unchanged. Apparent intestinal digestibility of fatty acids was high, especially on the milk diet (86.1%), although the amount of fatty acids absorbed (60.6 g/kg dry matter intake/d) was three times greater than with the control.     

黄豆渣酱的品质分析及其抗氧化活性

为实现豆渣的高值化利用,以豆渣为主要原料,采用米曲霉（Aspergillus oryzae）AS3.951制曲后发酵制备黄豆渣酱。采用气相色谱-质谱（GC-MS）、氨基酸自动分析仪、超高液相色谱串联质谱（UPLC-MS/MS）对其品质进行分析,并对其抗氧能力进行测定。结果表明,黄豆渣酱的感官、理化及微生物指标均符合相关国标要求。黄豆渣酱中共检出60种挥发性风味成分,包括4种醇类、12种酸类、11种酯类、11种醛类、6种酮类、3种酚类和13种其他类;黄豆渣酱中共检出18种游离氨基酸（包含7种必需氨基酸）,总含量为1.403 g/100 g;黄豆渣酱中检出9种异黄酮及7种酚类物质,清除ABTS、DPPH自由基的半抑制浓度（IC50）值分别为36.52 μmol维生素C当量（VCE）/g、10.824 μmol VCE/g,表明黄豆渣酱具有较好的抗氧化能力。