胰蛋白酶水解玉米胚芽蛋白的研究

研究了胰蛋白酶对玉米胚芽蛋白的水解作用,分析了酶浓度、pH、反应温度、底物浓度等因素对水解度的影响。结果表明:最佳水解条件为酶与底物比2%、温度40℃、pH8.0、底物浓度8%。在此条件下水解4 h,水解度可达10.4%。高效凝胶过滤色谱(HPSEC)分析酶解产物分子量分布发现,酶解产物的分子量主要集中在200~4 000 Da。     

木瓜蛋白酶水解绿豆蛋白制备可溶性肽的研究

通过研究木瓜蛋白酶对绿豆蛋白的水解作用,分析了酶浓度、底物浓度、温度、pH、水解时间等因素对水解度的影响,从而确定木瓜蛋白酶水解绿豆蛋白制备绿豆多肽的最佳水解条件,并利用葡聚糖凝胶(SephadexG-15)柱层析测定绿豆多肽分子量。实验结果表明,当水解度为30%时,绿豆多肽分子量绝大多数在1000Da以下。     

复合酶水解蚕蛹蛋白制备功能性寡肽的工艺研究

为了制备分子量低、肽含量高的蚕蛹功能性寡肽,本文采用单素实验与响应面分析法,对不同蛋白酶及其不同组合、温度、pH值、底物浓度、酶的添加量等因素对蚕蛹分离蛋白水解工艺的影响进行了研究.研究结果表明,多酶复合水解可显著提高蚕蛹蛋白的水解度和寡肽得率,其中胰酶、风味蛋白酶与中性蛋白酶是最佳多酶组合,其最佳水解条件为底物浓度7.33％、酶添加量[E]/[S]3.62％、pH7.38、水解温度54.6℃、水解时间6h.在此条件下,蚕蛹蛋白的水解度高达29.2％,寡肽得率高达为81.14％.酶解后产品数均分子量为665.5 Da,重均分子量为726.9 Da,肽含量高达74.6％,而游离氨基酸含量仅为7.33％,表明复合酶解虽然提高了蚕蛹蛋白的水解度,但主要产物仍然是低分子寡肽,并没有大量生成游离氨基酸.     

双酶法制备大豆肽工艺优化研究

以大豆分离蛋白为原料,通过单因素试验研究蛋白液的浓度、水解的温度、水解时间、酶的加入量及pH等因素对大豆分离蛋白水解度的影响,确定适宜的范围值和因素组合。结果表明,大豆分离蛋白在蛋白液浓度8%,加酶底物比为2%,在55℃水解4 h,水解初始pH为9.0~10.0时水解率最高。水解后pH稳定在7左右。通过苦味值测定,结果表明,风味酶在50℃条件下,水解1 h,苦味值最低。液相色谱检测水解后肽的分子量主要分布在300 Da~1 000 Da范围。小于1 000 Da以下的肽占总量的80.3%,2 000 Da以下的肽含量占91.5%。     

Protex-6L碱性蛋白酶酶解绿豆分离蛋白的工艺研究

选用Protex-6L蛋白酶对绿豆分离蛋白进行酶法水解生成肽和氨基酸。以水解度为考察指标,对其酶解工艺进行优化。基于单因素实验,考察了酶解参数:pH、酶解温度、底物浓度、加酶量、酶解时间等对酶解的影响,利用designexpert软件设计响应面对酶解条件进行优化分析,并在最优条件下通过SephadexG-75分析水解产物的分子量分布。结果表明:pH8.85、酶解温度57.34℃、底物质量分数7.00%、加酶量6884.36U/g、酶解时间4.19h,此条件下的绿豆分离蛋白的水解度(DH)为36.60%。水解得到的小肽分子量大部分都小于4000u。     

右旋糖酐酸解与酶解产物比较

目前工业生产药用右旋糖酐常用酸解法,能耗高,污染大,而酶解法反应条件温和,反应速度快,可以在右旋糖酐发酵的同时进行,可大大降低能耗,减轻污染.本文通过对右旋糖酐酸水解和酶水解产物的成分和分子量分布的研究,为酶解法生产药用右旋糖酐新工艺打好基础.实验结果表明:酸水解的终产物基本上为葡萄糖,而酶水解终产物为异麦芽寡糖;水解到重均分子量为20000 Da以上时,2种水解方法对右旋糖酐含量和分布系数影响不大;水解到重均分子量小于20000 Da之后,酶解产物右旋糖酐含量下降.     

木瓜蛋白酶水解豌豆蛋白的工艺研究

研究木瓜蛋白酶对豌豆蛋白的水解作用,分析了酶量、底物浓度、温度、pH、水解时间因素对水解度的影响,确定木瓜蛋白酶水解豌豆蛋白制备豌豆多肽的最佳水解条件为:酶浓度8%(E/S质量比),底物浓度7%(固液比).反应温度65℃,反应时间3.5 h,pH6.5,并利用高效液相色谱法测定豌豆多肽分子量.试验结果表明,当水解度为30%时,豌豆多肽混合物分子量80%集中在500u左右.     

复合酶法制备小麦低聚肽的工艺研究

以小麦蛋白为原料,采用酶解法水解小麦蛋白制备小麦低聚肽。筛选出水解度最佳的单酶以及复合酶。通过单因素试验以及正交试验优化小麦蛋白的水解工艺的条件可以得出:胰蛋白酶与碱性蛋白酶复合水解时,小麦蛋白的水解度最高,水解度可达到37.72%。最佳条件为:先采用胰蛋白酶进行水解,水解温度40℃、p H为10、酶添加量7%、水解时间4 h;再利用碱性蛋白酶水解小麦蛋白,水解温度65℃、p H为8、酶添加量7%、水解时间3 h。采用高效液相色谱测出水解产物分子量大部分集中在1374~445 Da,且由峰面积计算含量为52.03%。     

酶法制备不同水解度高温豆粕水解产物的理化特性研究

采用Alcalase酶和木瓜蛋白酶分别对高温大豆粕进行酶解,通过控制酶解反应得到水解度为5%、10%和15%的6种水解产物,研究两种酶对不同水解度的水解产物理化特性的影响。结果表明,Alcalase酶和木瓜蛋白酶均可产生6种不同分子量范围的水解产物,但各部分比例具有显著差异(P0.5),其平均分子量随水解度的增加逐渐减少,Alcalase酶的水解产物中小于2562 Da小分子量肽所占比例更高。豆粕蛋白的疏水基团在酶解反应中发生暴露与断裂的数量差,导致其表面疏水性随水解度增加呈现先下降再上升的变化,即水解度为10%的表面疏水性最低。zeta电势的绝对值随水解度不断上升,分子间的斥力增大,相同水解度下两种酶对zeta电势的影响并不显著。此外,在pH值为3、5、7和9时,水解产物的溶解性随着水解度的增加而逐渐增高,乳化活性和乳化稳定性则逐渐降低。     

双酶水解乳清蛋白ACE抑制肽的制备工艺优化

以乳清蛋白为原料,采用胃蛋白酶和胰蛋白酶双酶先后水解乳清蛋白,通过单因素试验和正交试验优化胃蛋白酶和胰蛋白酶水解乳清蛋白制备血管紧张素转换酶(ACE)抑制肽的工艺,将水解物以3 kDa超滤膜过滤,研究表明,胃蛋白酶水解乳清蛋白最佳酶解工艺条件为水解温度37℃、底物质量浓度6 g/100 mL、酶与底物比3 728 U/g,此时乳清蛋白ACE抑制率为86%;胰蛋白酶水解乳清蛋白最佳酶解条件为温度55℃、底物质量浓度6 g/100 mL、酶与底物比3 480 U/g,此时ACE抑制率为72%。利用超滤离心管获得分子量小于3 kDa的乳清蛋白ACE抑制率96%。     

Characteristic and antioxidant activity of retorted gelatin hydrolysates from cobia (Rachycentron canadum) skin

Alkali-pretreated cobia (Rachycentron canadum) skin was extracted in a retort (121 °C) for 30 min to obtain a retorted skin gelatin hydrolysate (RSGH). The molecular mass distributions and antioxidant activities of cobia RSGH and enzyme-treated RSGHs (ET-RSGHs) derived from bromelain, papain, pancreatin, and trypsin digestion were then characterized. The molecular mass distribution of the RSGH ranged mainly between 20,000 and 700 Da and those of ET-RSGHs ranged between 6500 and 700 Da. The DPPH (α,α-diphenyl-β-picrylhydrazyl) radical scavenging effects (%) of 10 mg/ml of RSGH and 10 mg/ml of the four ET-RSGHs were 55% and 51–61%, respectively. The lipid peroxidation inhibition (%) of RSGH and ET-RSGHs (10 mg/ml) were 58% and 60–71% on the fifth day in a linoleic acid model system, respectively. The 3Kd-ET-RSGHs, obtained by using a series of centrifugal ultrafiltration filters (molecular weight cut-offs of 10, 5, and 3 kDa done sequentially with decreasing pore size), exhibited dramatically improved antioxidant activity, with most of the molecular mass ranging below 700 Da. Compared to 10 mg/ml of the RSGH, 10 mg/ml of 3Kd-ET-RSGHs exhibited 45–65% more scavenging of DPPH radical and 24–38% more inhibition of lipid peroxidation. The peptides with molecular masses below 700 Da in the ET-RSGHs or 3Kd-ET-RSGHs significantly affect the antioxidant properties. These peptides are composed of a small number of amino acids or free amino acids and have the potential to be added as antioxidants in foods.     

发芽糙米中粗多糖的纯化及分子量测定

本文对发芽糙米粗多糖进行纯化,通过比较活性炭吸附法、过氧化氢氧化法、大孔树脂吸附法三种方法的脱色效果,以及Sevage法、三氯乙酸法、酶与Sevage结合方法三种方法的脱蛋白效果,筛选出发芽糙米粗多糖脱色、脱蛋白的最佳方法。分别比较了DEAE-Sepharose CL-6B、DEAE Fast Flow、DEAE Sepharose 52三种柱层析填料对糙米粗多糖的层析纯化效果,筛选出最优填料。并对纯化后的发芽糙米多糖各组分进行分子量的测定。结果表明:大孔树脂AB-8对发芽糙米粗多糖脱色效果最佳,脱色率为86.57%,多糖损失率为28.96%。酶-Sevage法脱蛋白效果较好,且多糖损失率低,脱蛋白率为74.36%,多糖损失率为14.09%。对发芽糙米多糖进行柱层析的最佳填料为DEAE-Sepharose CL-6B。根据线性回归方程计算其平均分子量,水洗多糖组分的平均分子量为1.47×105 Da,盐洗多糖组分的平均分子量分别为9.62×105、5.59×106、3.15×105 Da。结论:确定了针对发芽糙米粗多糖的去除蛋白质和脱色的方法,并筛选出最佳的柱层析填料,分离出四个组分发芽糙米多糖,为发芽糙米粗多糖的提取、纯化、分离逐渐转变为工业化生产提供了理论基础。     

体外胃肠道消化及跨膜转运对干腌火腿肽抗炎活性的影响

以宣威火腿为原料提取火腿中生物活性肽,通过体外模拟胃肠道消化和Caco-2细胞单层膜转运实验,进一步分析火腿肽的序列及抗炎功能变化。结果表明：经模拟胃肠道消化后,宣威火腿肽的总体数量增加,其中1 000 Da以下多肽的数量占比从40.18%增加到57.40%;模拟消化后火腿肽抑制RAW264.7巨噬细胞炎症因子分泌的作用增强,经Caco-2细胞跨膜转运后共检测到24 条多肽序列,其中包括12 条四肽和5 条三肽,分子质量小于500 Da的小肽占62.50%;合成小肽PAG、LVG、LGV、PVL具有缓解巨噬细胞分泌NO、肿瘤坏死因子-α的功能。因此,模拟胃肠道消化可以改变火腿肽的组成,进而提升其抗炎活性;跨膜转运后的小肽具有缓解巨噬细胞炎症因子分泌的功能。     

面筋蛋白咸味肽的分离纯化及结构鉴定

为了明确面筋蛋白酶解液中的咸味肽序列，对面筋蛋白咸味酶解物进行了分离纯化和结构鉴定。对酶解物脱盐处理后进行分离纯化。经过分级超滤，选择咸味最高、分子质量1 000 Da以下的组分进行葡聚糖凝胶Sephadex G-15过滤层析，结合感官评定结果筛选出咸味最强的组分，并利用液相色谱-串联质谱鉴定其氨基酸序列。最终得到面筋蛋白中咸味肽氨基酸序列为PFGQQ、PFSPQ、QPFP、PDFP、FDDP，分子质量分别为576.28、575.28、488.25、475.22、493.21 Da。本研究为面筋蛋白咸味肽的开发提供了一定理论依据。     

Migration from can coatings: Part 3. Synthesis, identification and quantification of migrating epoxy-based substances below 1000 Da

Bisphenol A-derived glycidyl ethers as well as its reaction products with other lacquer components can migrate into the packed food from epoxy-based can coatings. A sensitive and selective method is presented using high-performance liquid chromatography coupled with ultraviolet light, fluorescence and electrospray ionization-mass selective detection for the identification and quantification of all migrants with a bisphenol A backbone and a molecular weight below 1000 Da, an estimated boundary for the absorption in the gastrointestinal tract. The identification of migrants was confirmed by microreactions of technical bisphenol A diglycidyl ether with solvents and phenols, which provided the fragmentation pattern of the mass selective detection and relative retentions of 42 different bisphenol A-related substances. It was shown by calibration of different isolated and synthesized bisphenol A derivatives that the fluorescence response relies on the amount of bisphenol A moiety in the respective molecule. Therefore, all migrating bisphenol A-related substances below 1000 Da were determined as bisphenol A diglycidyl ether equivalents using a calibration (fluorescence detection) of the commercially available bisphenol A diglycidyl ether monomer. The limit of quantification was set at 5 μg bisphenol A diglycidyl ether equivalents kg^-1 (or 0.8 μg dm^-2). This method was validated for epoxy coatings (0.1 μg dm^-2 limit of detection and 24 μg bisphenol A-related substances below 1000 Da dm^-2 standard deviation, corresponding to 4.4% relative standard deviation). The quantification could be extended by combining the fluorescence response and structural information gained from the mass spectra, which provides more accurate results for each migrant. The calculation is based on the calibration of the bisphenol A chromophore content of the molecule. According to this method, the amount of migrating bisphenol A-related substances below 1000 Da in the acetonitrile extract (assuming a worst case) varied from about 0.4 to 0.7 mg dm^-2 in the examined coatings. The determined amounts comply with about 50% of the total migrate below 1000 Da.     

Molecular size evolution of oligomers in organic aerosols collected in urban atmospheres and generated in a smog chamber

Only a minor fraction of the total organic aerosol mass can be resolved on a molecular level. High molecular weight compounds in organic aerosols have recently gained much attention because this class of compound potentially explains a major fraction of the unexplained organic aerosol mass. These compounds have been identified with different mass spectrometric methods, and compounds with molecular masses up to 1000 Da are found in secondary organic aerosols (SOA) generated from aromatic and terpene precursors in smog chamber experiments. Here, we apply matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to SOA particles from two biogenic precursors, alpha-pinene and isoprene. Similar oligomer patterns are found in these two SOA systems, but also in SOA from trimethylbenzene, an anthropogenic SOA precursor. However, different maxima molecular sizes were measured for these three SOA systems. While oligomers in alpha-pinene and isoprene have sizes mostly below 600-700 Da, they grow up to about 1000 Da in trimethylbenzene-SOA. The final molecular size of the oligomers is reached early during the particle aging process, whereas other particle properties related to aging, such as the overall acid concentration or the oligomer concentration, increase continuously over a much longer time scale. This kinetic behavior of the oligomer molecular size growth can be explained by a chain growth kinetic regime. Similar oligomer mass patterns were measured in aqueous extracts of ambient aerosol samples (measured with the same technique). Distinct differences between summer and winter were observed. In summer a few single mass peaks were measured with much higher intensity than in winter, pointing to a possible difference in the formation processes of these compounds in winter and summer.     

Alcalase水解丝素蛋白的特性

研究了Alcalase水解丝素蛋白的特性。结果表明,Alcalase水解丝素蛋白的最佳条件是:丝素蛋白质量浓度50 mg/mL,pH值9.0,温度60℃;丝素肽中主要氨基酸(甘氨酸、丙氨酸、丝氨酸和酪氨酸)的含量之和占其氨基酸总量的85%左右;水解度为17%的丝素蛋白水解产物中主要组分的相对分子质量分别为249 Da和762 Da,含量分别约占72.9%和15.5%,水解度为21%的丝素蛋白水解产物中主要组分的相对分子质量分别为209 Da和668 Da,含量分别约占84.4%和7.2%。     

胡芦巴中性多糖酸水解工艺优化的研究

本文对胡芦巴中性多糖酸水解的工艺条件进行研究。以还原糖得率为指标,采用L9(34)正交设计对酸浓度、反应时间、反应温度的参数进行优选。结果表明,从水解产物低聚糖产量考虑,6mol/L盐酸浓度,100℃反应温度,1h反应时间为最佳工艺条件,此时低聚糖的得率为43.97%,低聚糖的分子量约为500～1000Da;以获得较小分子量的低聚糖为目的,则6mol/L盐酸浓度,90℃反应温度,2h反应时间为最佳实验条件,此时低聚糖的分子量约为300～750Da,得率为13.52%。