Effect of lipoxygenase activity and red seed coat on rice bran deterioration

BACKGROUND: Many studies have suggested that the main reason for rice bran deterioration is the effect of lipase, but there have been fewer reports about the effect of lipoxygenase (LOX) activity and red seed coat on rice bran deterioration. In this study, several rice bran materials with white or red coat and different LOX isozyme activities and near isogenic lines about the colour of coat and LOX isozymes were subjected to accelerated aging experiments, during which their fatty acid values were monitored. RESULTS: Rice bran materials with different LOX isozyme activities and colour of coat showed different changes in fatty acid value during aging. Red coat with high LOX‐1,2 and low LOX‐3 activity caused the fatty acid value to increase at a lower rate than white coat with low LOX‐1,2 and high LOX‐3 activity, while the latter caused the fatty acid value to increase at a lower rate than white coat with low LOX‐1,2,3 activity. The results for the near isogenic line further confirmed the role of LOX isozyme activity and the colour of coat in rice bran deterioration. CONCLUSION: It can be inferred that high LOX isozyme activity is beneficial to delay rice bran deterioration; for example, high LOX‐1,2 activity is essential for red rice bran storage, while high LOX‐3 activity is essential for white rice bran storage. The results of this investigation may be helpful in further studies of the mechanism of rice bran deterioration. Copyright © 2009 Society of Chemical Industry     

Effect of drying and proline addition on aroma volatile compounds of acid‐hydrolysed rice bran protein concentrate

Rice bran protein concentrate (RBPc) was hydrolysed by 0.5 N aqueous HCl at 95 °C for 12 h. The liquid hydrolysate obtained was prepared as hydrolysate powder by spray drying. Aroma volatile compounds in liquid hydrolysate and its hydrolysate powder were tentatively identified by GC‐MS. Furfural and vanillin were found in both hydrolysates with high concentration, and vanillin showed the highest odour activity value. Hexanal was present in only liquid hydrolysate. Concentrations of carboxylic acids and heterocyclic compounds, especially 2‐methoxy‐6‐methylpyrazine, increased after drying. Amino acid composition of the hydrolysate powder showed high aspartic acid and glutamic acid. Aroma volatile compounds of hydrolysate powder prepared by the addition of proline at pH 6.0 (Pro6.0‐H) and pH 7.5 (Pro7.5‐H) before drying were investigated. Furaneol was found only in Pro6.0‐H, but it was not detected in Pro7.5‐H and hydrolysate powder without proline addition. Pro7.5‐H had higher furfural and vanillin concentrations than Pro6.0‐H.     

Chymotryptic hydrolysates of α-kafirin,the storage protein of sorghum (Sorghum bicolor) exhibited angiotensin converting enzyme inhibitory activity

Kafirin is the main storage protein (prolamin) in sorghum grains. α-Kafirin, the alcohol soluble fraction, was isolated from sorghum flour. Treatment of α-kafirin with chymotrypsin yielded a hydrolysate which on fractionation, using Sephadex G-25 column, yielded four fractions with significant angiotensin converting enzyme (ACE) inhibitory activity in vitro. The IC₅₀ values of these fractions ranged from 1.3 to 24.3 μg/ml. Two of the fractions were found to be competitively inhibiting the enzyme, while two other fractions were non-competitive inhibitors. These results demonstrate that chymotryptic hydrolysates of sorghum prolamin could serve as a good source of peptides with angiotensin I converting enzyme inhibitory activity.     

米糠蛋白ACE抑制肽在大鼠体内降压效果的研究

采用灌胃和静脉注射的方法,观察了米糠蛋白ACE抑制肽对应激性高血压(SHR)大鼠的降压效果,并与卡托普利的降压效果进行了比较。分别以50、100、150 mg/kg·bw剂量的米糠蛋白ACE抑制肽一次性给药后,每2 h测量大鼠血压,连续测量8 h;实验持续4周,每天灌胃一次,每周测量血压及体重一次。SHR大鼠给予米糠蛋白ACE抑制肽后,血压均显著下降(p<0.05),并均在灌胃后2 h达到最低值,血压下降最大幅度为(31±6.8)mm Hg;而正常大鼠灌胃米糠蛋白ACE抑制肽后血压无显著变化,灌胃卡托普利则会明显降低其血压;长期灌胃米糠蛋白ACE抑制肽可使SHR大鼠血压下降明显(p<0.05),且降压效果稳定。      

超声-微波协同提取富硒米糠蛋白的工艺优化及其抗氧化活性评价

为解决富硒米糠蛋白提取率低、提取时间长及提取后功能特性下降等问题,以脱脂富硒米糠粉为原料,通过单因素试验和正交试验对超声-微波协同提取富硒米糠蛋白的工艺进行优化,通过与超声辅助法、微波辅助法和碱提法比较,探究该提取方法对富硒米糠蛋白的提取效果、抗氧化活性以及提取后米糠颗粒表面形貌变化的影响。结果表明,超声-微波协同提取富硒米糠蛋白的最佳工艺条件为超声功率600 W、微波功率500 W、提取时间20 min、料液比1∶40,在此条件下富硒米糠蛋白的提取率为86.94%,与超声辅助法、微波辅助法、碱提法相比富硒米糠蛋白提取率分别提高了40.96%、48.00%、53.50%,并且提取的富硒米糠蛋白抗氧化能力和硒含量更高。扫描电镜结果显示,超声-微波协同提取后米糠颗粒表面疏松卷曲,完整皮层结构消失,说明超声-微波协同能通过强烈破坏米糠颗粒结构增加富硒米糠蛋白的提取率,并提高其抗氧化活性。综上,超声-微波协同提取技术能够促进富硒米糠蛋白的提取并提高其抗氧化活性。     

Effect of fermentation by Bacillus subtilis on antioxidant and cytotoxic activities of black rice bran

Black rice bran was fermented with Bacillus subtilis KU3 isolated from Korean traditional food, Kimchi. Antioxidant and cytotoxic activities of the fermented black rice bran were investigated. Total phenolic and anthocyanin contents decreased from 171.54 mg GAE g^?1 and 2.31 mg g^?1 to 139.13 mg GAE g^?1 and 2.12 mg g^?1, respectively, after fermentation. Antioxidant activities determined by 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging, β‐carotene bleaching and ferric thiocyanate assay were correlated with total phenolic and anthocyanin contents. Non‐fermented black rice bran extract (NFBE) showed greater antioxidant activities than fermented black rice bran extract (FBE). Cytotoxic activities measured by MTT assay showed that both NFBE and FBE had over 50% activities. The cytotoxic activities of FBE against MCF‐7 and HeLa cells were 71.65% and 68.07%, respectively, at 8.0 mg mL^?1, but those of NFBE were lower than 50%. These results suggested that the cytotoxic activity of black rice bran improved through fermentation, while antioxidant activity reduced.     

米糠蛋白乳化性能及其改性方法研究进展

天然米糠蛋白的乳化性较差,限制了其在食品工业中的应用,需采用合适的方法对其进行改性。文章以米糠为研究对象,总结了米糠蛋白的组成、乳化性能以及改性方面的最新研究进展,提出通过改进米糠蛋白的改性工艺,或利用融合不同高新技术来改善米糠蛋白的乳化性能,并以此扩展米糠蛋白的开发利用思路,加速米糠蛋白在食品及化妆品中的应用进程。     

米糠蛋白酶法改性前后的功能特性变化研究

以蛋白质为配料的产品中,蛋白质功能性质往往比营养价值更重要,直接影响到米糠蛋白的应用前景。实验研究了经碱性蛋白酶改性后的米糠蛋白功能特性,并与其改性前进行了比较。测定了改性前后米糠蛋白的溶解性、乳化性及乳化稳定性、起泡性及泡沫稳定性,并确定浓度、温度等因素对上述指标的影响。实验结果表明,改性后米糠蛋白的溶解性、起泡性及乳化性与改性前相比均有较大改善,分别提高了140.46%、117.38%、100.50%。米糠蛋白溶解性在pH4.0～6.0较低,在碱性条件下较高,随温度升高而增大;米糠蛋白乳化性、起泡性在碱性条件下较高,随温度的升高其起泡能力和乳化能力均增强。      

超声波处理时间对米糠蛋白理化和功能特性的影响

研究超声处理时间对米糠蛋白(RBP)理化功能特性的影响。分别探讨了不同超声时间对米糠蛋白溶解性、乳化性、起泡性、表面疏水性、游离巯基及亚基组成的影响。结果表明,经过超声处理后的RBP的溶解性由25.52%增加到79.23%~83.88%;超声45 min时,乳化性和起泡性比对照组分别提高了82.28%和36.12%;超声30 min时,表面疏水性达到最大;随着超声时间的延长,游离巯基的含量呈先增加后减小趋势;还原与非还原SDS-PAGE结果显示,不同超声时间对RBP的亚基组成无影响。说明适当的超声处理能够在不影响蛋白一级结构的情况下改善RBP的理化功能特性。     

超声辅助木瓜蛋白酶改性对米糠蛋白溶解性和乳化性的影响

采用超声辅助木瓜蛋白酶改性技术提高米糠蛋白溶解性和乳化性。首先米糠蛋白在超声功率密度5 W/m L、超声时间30 min、蛋白质量浓度4 g/100 m L条件下进行预处理,然后通过单因素实验优化了酶反应条件。结果表明:最佳酶反应条件为酶添加量2. 5 g/100 m L、酶反应时间3 h、pH 7、酶反应温度50℃;改性后米糠蛋白溶解性和乳化活性增强,乳化稳定性降低;改性后米糠蛋白二硫键、α-螺旋和β-转角含量减小,表面疏水性、β-折叠和无规则卷曲含量升高,表明超声辅助木瓜蛋白酶改性破坏了蛋白质空间结构,进而改善了米糠蛋白溶解性和乳化性。     

大米蛋白肽的制备与ACE抑制活性分析

通过优化大米蛋白的单酶酶解与双酶酶解工艺,确定了采用碱性蛋白酶加蛋白酶B复合酶解制备大米蛋白肽的工艺.蛋白回收率高达43.9％,制备的大米蛋白肽感官评价高、苦味低、分子质量小.对比市售的大豆蛋白肽、鱼胶原蛋白肽,3种蛋白肽的水分含量、蛋白质含量、脂肪含量基本接近.大米蛋白肽与大豆蛋白肽中分子质量<2000 Da的总比例...     

利用米糠蛋白制备类阿片拮抗肽和降血压肽的研究

采用离体豚鼠回肠(GPI)检定法测定不同米糠蛋白胰蛋白酶水解物的类阿片拮抗活性,结果发现跟新鲜米糠一样,低温脱脂米糠蛋白的酶解物具有较高的类阿片拮抗活性,高温脱脂米糠蛋白的酶解物无类阿片拮抗活性。采用低温脱脂米糠蛋白为原料,研究其制备类阿片拮抗肽后的残留蛋白酶解物的ACE抑制活性,结果发现在6种酶解物中,水解度(DH)为15.4%的碱性蛋白酶水解物的ACE抑制活性最高。     

热处理对过氧自由基氧化米糠蛋白体外胰蛋白酶消化性质及消化产物抗氧化性的影响

选用不同浓度的2,2’-盐酸脒基丙烷(2,2’-azobis (2-amidinopropane) dihydrochloride,AAPH)在有氧条件下热降解生成的过氧自由基氧化米糠蛋白,再通过95℃水浴处理氧化米糠蛋白,研究热处理对过氧自由基氧化米糠蛋白体外胰蛋白酶消化性质及消化产物抗氧化性的影响。结果表明:随着AAPH浓度的增加,过氧自由基氧化米糠蛋白体外胰蛋白酶消化率、初始消化速率、消化产物分子质量分布在500～1 500 u的肽含量、消化产物清除ABTS~+·、·OH、O~-_2·能力和还原能力均先上升后下降,消化产物清除DPPH·能力和金属螯合能力先不变后下降;而热处理后,氧化米糠蛋白体外胰蛋白酶消化产物金属螯合能力先上升后下降,ABTS~+·清除能力和还原能力先不变后下降。同未热处理相比,热处理显著提高了相同氧化程度下米糠蛋白体外胰蛋白酶消化率、初始消化速率以及消化产物抗氧化性。表明过氧自由基氧化会改变米糠蛋白体外胰蛋白酶的消化性质,而热处理可以改善相同氧化程度下米糠蛋白体外胰蛋白酶的消化率和消化产物的抗氧化性。     

Angiotensin I‐converting enzyme inhibitory activity of protein hydrolysates prepared from three freshwater carps (Catla catla,Labeo rohita and Cirrhinus mrigala) using Flavorzyme

Fish protein hydrolysates from three freshwater carps, Catla catla, Labeo rohita and Cirrhinus mrigala with different degree of hydrolysis (DH) (5%, 10%, 15% and 20%), were prepared using Flavorzyme enzyme and designated as HCF, HRF and HMF, respectively. The angiotensin I‐converting enzyme (ACE) inhibitory activity of hydrolysates was found to vary from 43 ± 2% to 71 ± 3%. Based on ACE inhibitory activity, HRF with DH‐15% was taken up for further study. The mode of ACE activity inhibition by HRF‐DH 15% was mixed type as revealed by Lineweaver–Burk plot. Sequential digestion of HRF‐DH 15% using pepsin and pancreatin decreased the ACE inhibitory activity from 76% to 63%. Partial purification of HRF‐DH 15% by size exclusion chromatography gave three different fractions designated as F‐1, F‐2 and F‐3 with the molecular mass in the range of 6456–407 Da. Fraction 2 had significantly higher ACE inhibitory activity than the other fractions.     

A comparative study on free and bound phenolic acid content and their antioxidant activity in bran of rice (Oryza sativa L.) cultivars of Eastern Himalayan range

In our study, seven most prevailing but unexplored indigenous rice cultivars of northeast India, situated in the Eastern Himalayan Range, were investigated for their phenolic acid profile, total phenolic content (TPC) and antioxidant capacities in free and bound phenolic extracts of their bran. HPLC studies showed the presence of ferulic, p‐coumaric, sinapic, caffeic, chlorogenic and vanillic acids, with ferulic and p‐coumaric acids being the dominant phenolic acids in the bound form. The lower EC₅₀ values of the bound extracts than the free extracts suggested the better radical scavenging activity of the bound extracts. Significant correlations were observed between TPC and phenolic acid content (HPLC‐DAD) of bound extracts, and between Trolox equivalents antioxidant capacity (TEAC) and phenolic acid content (HPLC‐DAD) of both free and bound extracts. The findings suggest that phenolic acids in the rice cultivars investigated were exclusively present in bound form and contribute significantly towards their antioxidant capacity.     

米糠蛋白的静高压联合酶法改性工艺优化及其特性研究

采用静高压联合碱性蛋白酶对米糠蛋白进行改性。考察静压力、保压时间对米糠蛋白溶解性的影响,优化静高压改性条件。以米糠蛋白溶解性、乳化性和乳化稳定性为指标,通过单因素试验和正交试验综合评分法优化了酶法改性工艺。结果表明,米糠蛋白最适改性条件为静压力200 MPa、保压时间15 min、碱性蛋白酶添加量1 500 U/g、pH 8、酶解温度50 ℃和酶解时间80 min,在此条件下米糠蛋白溶解性、乳化性、乳化稳定性、起泡性和泡沫稳定性分别增加了57%、88%、182%、185%、43%。     

Effects of thermal processing on antioxidant activities,amino acid composition and protein molecular weight distributions of jasmine rice bran protein hydrolysate

This research aimed to evaluate the effects of thermal processing on the amino acid composition, molecular weight distribution (MW) and antioxidant activities of Jasmine rice bran protein hydrolysates (JBH). JBH was prepared by enzymatic hydrolysate (alcalase and flavourzyme at a ratio of 9.81:90.19, 2.84% w/w) for 60 min. JBH samples were treated as follows: non-heat (NJBH), pasteurisation (72ºC, 15 min; PJBH) and sterilisation (121ºC, 15 min; SJBH). For SJBH treatment, the browning index and fluorescence intensity increased (P < 0.05). FTIR showed that thermal process changed the intensities and location of some bands. Thermal processing affected MW by decreasing it from high MW (>10 kDa) to medium (3–10 kDa) and low MW (<3 kDa). Val, Met, Ile and Leu contents increased after thermal processing. Compared with NJBH, the IC₅₀ values of ABTS and FRAP of SJBH were not significantly different, while the IC₅₀ of DPPH increased (P ≥ 0.05).     

Characteristics of Aspergillus niger xylanases produced on rice husk and wheat bran in submerged culture and solid‐state fermentation for an applicability proposal

Xylanolytic rich filtrates were obtained by A. niger sp in both submerged and solid‐state culture using rice husk or wheat bran as the only carbon source. Filtrates obtained on rice husk showed the highest activities (~6500 and 5200 U g^?1, respectively). Independent of carbon source, these filtrates were very stable in an acidic pH range (4–7) and mild temperatures, with high half‐life time values (more than 7 h at 50 °C) in the corresponding inactivation kinetic models. Also the effect of different metallic ions and denaturing substances was verified finding that these enzymes are not metaloproteins, and metals as Hg²⁺ and Pb²⁺ caused the greatest loss of xylanolytic activity (not higher than 30%). Xylanases produced by this A. niger strain showed important features that make them potential candidates for applications on human and livestock food industries.     

超声协同大豆分离蛋白对米粉和米面包品质的影响及机制研究

目的 探究超声协同大豆分离蛋白(soybean isolate protein, SPI)对米粉以及米面包品质的影响。方法 以碎米为主要原料，5个梯度（0%、3%、6%、9%、12%，以碎米粉质量计）的大豆分离蛋白(soybean isolate protein, SPI)为辅料，比较超声协同5个梯度SPI对混合粉热机械学特性、糊化特性、流变特性以及米面包比容、损耗率、感官评价的影响。结果 与未进行超声处理的样品相比，超声协同SPI处理的米粉的吸水率从64.90±0.00增加至94.80±0.00，其混合粉的峰值黏度从2704.00±47.76降低至1567.00±116.73，表明超声使淀粉部分支链断裂，生成大量短直链淀粉，导致分子量下降，相互作用减弱；超声处理后的样品G′曲线呈现出先增加后降低的趋势，G''曲线随着SPI含量的增加呈现出逐渐降低的趋势。当SPI添加量为9%时，米面包的比容达到最大值，为0.86±0.08，感官评分从50.05±3.75增加至86.27±2.28分；当SPI添加量达到12%时，米面包的损耗率达到最低。结论 综上所述，采用9% SPI的方法制备米面包，可以有效的改善米面包品质，本研究为米面包在食品领域的应用提供了理论基础。