不同大米蛋白降低胆固醇及抗疲劳作用的功能性研究

以小鼠为实验对象,通过分别喂养低温处理方法和高温处理方法获取的大米蛋白,考察了不同处理方式的大米蛋白的降低胆固醇以及减缓疲劳的功效,并进行了对比。实验结果表明,大米蛋白降低胆固醇效果明显,降低幅度分别为26.87%(低温)和19.60%(高温)。低温处理的大米蛋白对减缓疲劳也有显著效果,小鼠负重游泳后,服用低温处理的大米蛋白一组的血清中乳酸脱氢酶活力升高15.16%,血尿素氮降低10.7%,而服用高温处理的大米蛋白一组则效果不佳。同时,研究表明大米蛋白的服用未对小鼠肝脏造成不利影响。      

Characterisation of the leaf meals,protein concentrates and residues from some tropical leguminous plants

Leaf meals (LMs) from freshly harvested leaves of butterfly pea (Centrosema pubescens), devil bean (Mucuna pruriens), flamboyant flower (Delonix regia), Bauhinia tomentosa, coast wattle (Acacia auriculiformis), quick stick (Glyricidia sepium) and ipil‐ipil (Leucaena leucocephala) were analysed for their nutrient and anti‐nutritional content. Then, leaf protein concentrates (LPCs) were produced from the leaves by fractionation and characterised along with the fibrous residues. On average, the LM contained 181 g kg^?1 dry matter (DM) CP (range: 100–280 g kg^?1 DM), 139 g kg^?1 DM crude fibre (range: 77–230 g kg^?1 DM) and 133 g kg^?1 DM ether extract (range: 86–165 g kg^?1 DM) while the gross energy averaged 17.0 MJ kg^?1. On average, leaf protein fractionation enhanced the CP, ether extract and the gross energy in the LPC by 39.5%, 33.5% and 22.0%, respectively, while the crude fibre of the LMs was reduced by 41%, on average, in the LPCs. Fractionation reduced the mineral content of the leaves generally. The mean phytin content varied from 0.36 g kg^?1 in LPCs to 0.86 g kg^?1 in leaf meal, while the mean phytin‐P content varied from 0.10 g kg^?1 in LPCs to 0.24 g kg^?1 in leaf meal. The total phenol levels in the LMs were reduced by 33.7% in the LPCs, on average. These results suggest that, while the LPCs from these plants could be used as protein supplements in non‐ruminant feeds in regions where there is an acute shortage of plant protein, the LMs or LPC fibrous residues could be fed to ruminant animals. Copyright © 2006 Society of Chemical Industry     

苜蓿叶蛋白资源的开发和利用

重点介绍了苜蓿叶蛋白的营养特点和国内外研究现状。苜蓿叶蛋白因苜蓿草产量高、适应性强、蛋白含量高、氨基酸平衡而倍受人们的重视并在欧洲得到开发和应用。     

Chemical composition and nutritive value of leaf protein concentrate from leucaena leucocephala

Leaf protein concentrate (LPC) was prepared from Leucaena leucocephala leaf meal (LLM). The recovery of LPC was 7.6 % and analysis showed that the LPC contained 65.91 % crude protein compared with 29.15 % of the LLM, ash content was 17.56% while levels of essential amino acids-lysine, histidine, arginine, isoleucine and leucine—were 5.57, 2.34, 5.88, 5.42 and 10.8% on a dry matter basis, respectively. The LPC had higher in-vivo digestibility than the LLM with values being 63.20 and 48.82%, respectively. The LPC diet supported growth in rats but gave lower nutritive indices than the control diet of soya bean and Guinea corn.     

Separation and determination of isoflavones in the protein concentrate from red clover leaves

Oestrogenic isoflavones were extracted from the protein concentrate of red clover leaves, isolated on columns of Sephadex G-25 using 0.1 M-ammonia and determined spectrophotometrically in the eluted fractions. Most of the chlorophyll and its breakdown products were precipitated from the original aqueous ethanolic extract before the lipids and then the isoflavones were finally extracted.     

In-vitro multienzyme digestibility of protein of some plant source flours blended with bovine plasma protein concentrate

The in-vitro multienzyme protein digestibilities of the flours of maize, cassava, pigeon pea (Cajanus cajan), African yambean (Sphenostylis stenocarpa) and bambara groundnut (Vigna subterranea), blended with bovine plasma protein concentrate were investigated. The multienzyme system consists of trypsin, chymotrypsin and peptidase. It was found that the addition of bovine plasma protein concentrate improved the protein digestibility of the flours compared with flours without the additive. The digestibilities were increased by between 3% in bambara groundnut blended flour to about 10% in cassava blended flour. When the flours were wet-heat treated, the digestibilities further increased in all samples with increments between 7·5 % in bambara groundnut and 16·6% in cassava flour. Bovine plasma protein concentrate may be a good source of protein for the fortification of protein-deficient foods, particularly maize and cassava flours.     

不同大米蛋白降低胆固醇及抗疲劳作用的功能性研究

以小鼠为实验对象,通过分别喂养低温处理方法和高温处理方法获取的大米蛋白,考察了不同处理方式的大米蛋白的降低胆固醇以及减缓疲劳的功效,并进行了对比.实验结果表明,大米蛋白降低胆固醇效果明显,降低幅度分别为26.87％(低温)和19.60％(高温).低温处理的大米蛋白对减缓疲劳也有显著效果,小鼠负重游泳后,服用低温处理的大米蛋白一组的血清中乳酸脱氢酶活力升高15.16％,血尿素氮降低10.7％,而服用高温处理的大米蛋白一组则效果不佳.同时,研究表明大米蛋白的服用未对小鼠肝脏造成不利影响.     

Effect of various dietary fats and proteins on serum cholesterol level in rats

A 60 day experiment on growing rats was performed to evaluate the effect of two protein sources (casein and soybean protein isolate) and four fats (olive oil, OO; evening primrose oil, EO; linseed oil, LO; and butter, B) on plasma lipoprotein fractions: total cholesterol (TC), high‐density lipoprotein cholesterol (HDL‐C), low‐density lipoprotein cholesterol (LDL‐C) and triacylglycerol (TAG) levels. The different protein and fat sources had no influence on body weight gain of rats. Fats had no significant effect on TC and LDL‐C. Significant differences were found only in HDL‐C. OO gave the lowest (43.3 mg dl^?1) and EO the highest (54.4 mg dl^?1) value. Proteins had a significant influence on all lipids analysed. Soybean protein caused higher TC (78.5 vs 67.9 mg dl^?1), HDL‐C and TAG levels but significantly lowered LDL‐C in the plasma of rats. These results suggest that protein has a stronger effect on cholesterol level than fat. © 2002 Society of Chemical Industry     

Fish protein decreases serum cholesterol in rats by inhibition of cholesterol and bile acid absorption

Fish protein has been shown to decrease serum cholesterol content by inhibiting absorption of cholesterol and bile acid in laboratory animals, though the mechanism underlying this effect is not yet fully understood. The purpose of this study was to elucidate the mechanism underlying the inhibition of cholesterol and bile acid absorption following fish protein intake. Male Wistar rats were divided into 2 dietary groups of 7 rats each, 1 group receiving a diet consisting of 20% casein and the other receiving a diet consisting of 10% casein and 10% fish protein. Both experimental diets also contained 0.5% cholesterol and 0.1% sodium cholate. After the rats had been on their respective diets for 4 wk, their serum and liver cholesterol contents and fecal cholesterol, bile acid, and nitrogen excretion contents were measured. Fish protein consumption decreased serum and liver cholesterol content and increased fecal cholesterol and bile acid excretion and simultaneously increased fecal nitrogen excretion. In addition, fish protein hydrolyzate prepared by in vitro digestion had lower micellar solubility of cholesterol and higher binding capacity for bile acids compared with casein hydrolyzate. These results suggest that the hypocholesterolemic effect of fish protein is mediated by increased fecal cholesterol and bile acid excretion, which is due to the digestion products of fish protein having reduced micellar solubility of cholesterol and increased bile acid binding capacity.     

Effects of alfalfa protein concentrate on spatial learning and memory in weaned rats

Alfalfa has been used as animal feedstuff and nowadays as a human dietary supplement in undernourished populations. Therefore, we considered whether a 65 °C prepared unfractionated alfalfa protein concentrate (UAPC) could be capable of supporting the normal body growth of weaned rats as well as their spatial learning, memory and astroglial organization. Rats were fed isocaloric (1.8 kJ g^?1) and isoproteic (100 g kg^?1) diets for 28 days containing UAPC or casein as their protein source. Thereafter, animals were submitted to a Morris water maze test (MWM) followed by an evaluation of memory retention. At the end of the spatial learning tests, the cerebral cortex, hippocampus and hypothalamus astrocyte population was morphologically and immunohistochemically analyzed. UAPC had two limiting essential amino acids that seem to have retarded rates of growth and caused temporary learning and memory alterations. The UAPC diet induced a transitory memory loss as well as a recoverable memory retention delay after returning to a commercial ration. The astrocyte cell number was decreased in the parietal cortex and arcuate nucleus but not in the hippocampus; however, the latter showed a minor reduction in their cell density. UAPC did not adequately support the development of weaned rats, and decreased the number of astrocytes in the cerebral cortex and hypothalamus. Copyright © 2005 Society of Chemical Industry     

Improvement of the nutritive value of cereals by leaf protein supplementation

The gross composition and amino acid content of the proteins of barley, corn, rye and wheat grains were determined. Leaf protein concentrates (LPC) were produced from the green matter of clover, lucerne, barley and ryegrass using standard methods and analysed as for the cereal grains. Each cereal was mixed with each concentrate at a protein ratio of 2:1, respectively. The chemical score (CS) and essential amino acid index (EAAI) of the cereals, the protein concentrates and their mixtures were calculated. The biological value (BV) and true digestibility (TD) of all proteins were determined on rats using the Thomas-Mitchell balance method. LPC proteins contained more lysine (4.6–6.0%) but less cystine than cereal proteins (2.8–3.8 and 2.3–2.7 g per 16 g N, respectively). The CS and BV of LPC proteins were low (30–40 and 44–58, respectively) because of the low cystine content. Mixing cereals with LPC improved the CS, EAAI and BV of their proteins. The BV of the protein mixtures was in almost every case higher than that of either protein alone, but the digestibility of the cereal proteins was reduced as a result of admixture with LPC, especially with clover LPC.     

烟叶叶蛋白的提取研究

对烟叶LPC(叶蛋白)主要提取工艺进行分析比较。通过不同pH值、不同的加热时间、不同的加盐比例对烟叶叶蛋白得率的影响试验,对叶蛋白提取工艺进行研究。研究结果表明:烟叶LPC凝集物随着加热时间的延长而增加,最佳加热时间为9～11m in;烟叶LPC凝集物随着pH值的增加呈先增大后减小的趋势,最佳提取pH为3～3.5;烟叶LPC凝集物随着(NH4)2SO4饱和度的增加也呈增加的趋势,最佳饱和度为65%～75%。响应面分析可知pH和加热时间t之间没有交互作用;pH对烟叶LPC的影响更显著。     

从马齿苋中提取叶蛋白工艺的研究

采用酸法及加热法，分析了从马齿苋中提取叶蛋白的工艺条件。结果表明：从马齿苋中提取叶蛋白工艺的最佳条件：加热时间为9min，加热温度为75℃，盐酸调pH值为3，液料比为4；该工艺提取叶蛋白的提取率为0.95％，叶蛋白的沉淀率为20.02％。     

大米蛋白调控胆固醇代谢的研究进展

由于胆固醇代谢紊乱已成为威胁人类健康的第一杀手,胆固醇与许多疾病如冠心病及动脉粥样硬化等疾病密切相关,所以开发一种降低胆固醇的保健食品已经成为世界范围研究的热点。大米蛋白具有高营养价值,是一种优质的植物蛋白。介绍了大米蛋白的营养价值和大米蛋白的结构组成,并对国内外大米蛋白的降低胆固醇水平及调控胆固醇代谢机制进行了综述。研究表明,大米蛋白能够降低血液和肝脏的胆固醇水平,促进粪便和类固醇的排泄,降低LDL的水平。     

Inhibitory effect of Piper betel leaf extracts on copper-mediated LDL oxidation and oxLDL-induced lipid accumulation via inducing reverse cholesterol transport in macrophages

Piper betel leaf (PBL) has the biological capabilities of detoxification and can work as an anti-inflammatory agent and an anti-oxidant. In this study, we evaluated the anti-oxidative activity of the extract of Piper betel leaves (PBLs) on the basis of Cu²⁺-mediated oxidation, and its ability to prevent foam cell formation in a model for oxidised low density lipoprotein (oxLDL)-induced lipid accumulation in macrophages. Our data demonstrated that PBLs were able to inhibit LDL oxidation in vitro and are able to reduce the lipid accumulation in macrophages. We showed the underlying mechanisms to be the following: PBLs up-regulated the protein levels of the class A and class B scavenger receptors, the membrane lipid transporter ABCA1, and its upstream regulator Liver X receptor (LXR) in the macrophages exposed to oxLDL. The results suggested that PBLs activated the reverse cholesterol transport mechanism to enhance the metabolism of the oxLDL that could prevent both lipid accumulation and foam cell formation and further minimise the possible damage of vessels caused by the oxLDL.     

花椰菜废弃茎叶中叶蛋白提取工艺的研究

为了充分利用花椰菜废弃物,以花椰菜废弃茎叶为原料,分别采用直接加热法、酸沉淀法、碱沉淀法、酸热沉淀法、碱热沉淀法、酸絮凝剂法提取叶蛋白,得到花椰菜废弃茎叶叶蛋白提取最佳方法为酸絮凝剂法。在此基础上设计了料水比、pH、壳聚糖添加量三个因素进行酸絮凝剂法实验,并在单因素的基础上进一步设计正交实验。正交实验结果表明,酸絮凝剂法的最佳工艺条件为:料水比1∶4(g/mL),pH4.0,壳聚糖添加量0.4g/L。在此工艺条件下叶蛋白得率为14.79%,提取率为39.01%。该研究确定了花椰菜废弃茎叶叶蛋白提取的最佳工艺,为花椰菜废弃物的开发和利用提供了科学依据。      

Heat-moisture treatment of high-amylose corn starch increases dietary fiber content and lowers plasma cholesterol in ovariectomized rats

ABSTRACT:  The effect of dietary high-amylose corn starch (HACS) of varying dietary fiber (DF) content on plasma cholesterol was examined in ovariectomized (OVX) rats. Gelatinized normal corn starch (G-CS) was used as a reference. OVX rats were fed a fiber-free purified diet containing G-CS, HACS, gelatinized high-amylose corn starch (G-HACS), or heat-moisture treated HACS (HM-HACS) at 400 g starch/kg diet for 21 d. The DF content of G-CS, HACS, G-HACS, and HM-HACS measured by the AOAC method was 0.1, 19.3, 2.4, and 64.5 g/100 g, respectively. The dry weight of cecal contents, cecal wall weight, the amount of short chain fatty acids in cecal contents, the amount of bile acids in small intestinal contents, and fecal excretion of neutral sterols increased logarithmically with increasing DF, while total plasma cholesterol concentration decreased. On the other hand, hepatic CYP7A1 activity, fecal dry weight, and fecal excretion of bile acids increased linearly with increasing DF, while body weight gain decreased. The hypocholesterolemic effect of HACS in OVX-rats appeared to be more effective by heat-moisture treatment.     

The nutritive value of mixtures of white leaf protein and food proteins

White leaf protein products were obtained from Medicago sativa by precipitation with isopropanol and from Chenopodium quinoa by heat fractionation and ultrafiltration/diafiltration. The isopropanol precipitated protein concentrate from Medicago contained less protein and more ash than the heat fractionated preparation from Chenopodium. The biological value of the protein fraction obtained from Medicago, estimated on rats using the Thomas-Mitchell balance method, was 59. The biological value of the protein preparation from Chenopodium was low (36). The preparations obtained were mixed with soya bean meal, wheat gluten, bone-meat meal, fish meal, skim milk and whey in a protein ratio 1:1. In every case, except fish meal, the biological value of the mixtures was higher than that of each component separately. This improvement of the nutritive value can not be explained from the amino acid composition; possibly the lysine availability was low. White leaf protein can, with advantage, supplement other food proteins.     

Use of milk protein concentrate to standardize milk composition in Italian citric Mozzarella cheese making

To better exploit manufacturing facilities and standardize cheese quality, milk composition could be standardized by fortifying its protein content with a milk protein concentrate (MPC) addition so avoiding partially skimming the milk. With this aim Mozzarella cheese was obtained adding citric acid into milk standardized at 4% protein and a fat to protein ratio of 1.0. Protein fortification was obtained adding MPC produced by ultrafiltration. Milk, whey, curd, cheese and stretching water were weighed and analysed for total solid, fat and protein content, to measure component recovery and yield. Yield increase (from 13.8% to 16.7%) was due to the higher recovery of the milk total solids and proteins in MPC cheese (48.2 and 78.3%, respectively) and to the slightly higher cheese moisture, obtained with a little modification of the cheese technology when adding MPC. Milk fat in cheese was lower than that reported in literature. Hot water stretching of the curd resulted in very low losses (1%) of protein and considerable losses (14%) of fat for both control and MPC cheeses. The likely reasons of this low recovery are discussed and it can be supposed that a further cheese yield increase is possible by changing the curd stretching procedures.     

Influence of skimmed milk concentrate replacement by dry dairy products in a low fat set‐type yoghurt model system. I: Use of whey protein concentrates,milk protein concentrates and skimmed milk powder

Ten commercial samples of dry dairy products used for protein fortification in a low fat yoghurt model system at industrial scale were studied. The products employed were whey protein concentratres, milk protein concentrates, skimmed milk concentrates and skimmed milk powder which originated from different countries. The gross chemical composition of these dried products were determined, including polyacrylamide gel electrophoresis (SDS‐PAGE) and isoelectric focusing of the proteins, and minerals such as Na, Ca, K and Mg. Yoghurts were formulated using a skim milk concentrated as a milk base enriched with different dry dairy products up to a 43 g kg⁻¹ protein content. Replacement percentage of skim milk concentrated by dry dairy products in the mix was between 1.49 and 3.77%. Yoghurts enriched with milk protein concentrates did not show significantly different viscosity (35.12 Pa s) and syneresis index (591.4 g kg⁻¹) than the two control yoghurts obtained only from skimmed milk concentrates (35.6 Pa s and 565.7 g kg⁻¹) and skimmed milk powder (32.77 Pa s and 551.5 g kg⁻¹), respectively. Yoghurt fortified with the whey protein concentrates, however, was less firm (22.59 Pa s) and had less syneresis index (216 g kg⁻¹) than control yoghurts. Therefore, whey protein concentrates may be useful for drinking yoghurt production. © 1999 Society of Chemical Industry