Amaranth protein films from thermally treated proteins

The usefulness of amaranth protein isolates, native and thermally treated, in edible films preparation was studied. Protein films were prepared by casting using glycerol as plasticizer. Films from amaranth native protein isolates showed low water vapor permeability (WVP) but poor mechanical properties. In order to improve this functionality, proteins were treated at 70 and 90 °C which corresponds to the denaturation temperature of the protein fractions present in the isolates. The unfolded conformation of these thermally treated proteins, when partially or totally denatured, favors the interactions between polypeptide chains during the film formation. These interactions lead to a greater cross-linking degree, which was reflected in the lower amount of water-soluble free peptides that were linked to the matrix. In these thermally treated protein films, a greatest contribution of disulfide and hydrogen bonds to the films stabilization was observed. These changes in the films structural properties would confer them a greater tensile strength and lower water solubility but higher thickness and WVP.     

Rheological Behavior of Hot-Air-Puffed Amaranth Seeds

Force-deformation and force-relaxation experiments were performed on amaranth seeds puffed at 290, 330 and 370°C. Less force and energy was required to cause a given deformation in seeds processed at 290°C than in those puffed at 330 and 370°C. It was also observed that the forces and energies required to produce a given deformation did not differ significantly (p ≤ 0.05) for seeds puffed at 330 and 370°C. The three-element generalized Maxwell model and Peleg model were applied for modeling force relaxation of puffed amaranth seeds. It was found that the generalized Maxwell model predicted the experimental data better than the Peleg model. The elastic parameters and asymptotic residual force of the generalized Maxwell model were significantly affected by puffing temperature, showing an increase with its rise. Relaxation times were not significantly affected by the puffing temperature. It was concluded that a higher puffing temperature resulted in a more rigid material and less viscous behavior.     

籽粒莧婴儿食品的研究

将籽粒苋、大豆和大米混合,通过挤压的方法,制成籽粒苋婴儿食品。挤压的最佳操作条件为:挤压温度160℃,螺杆转速80r/min,原料水分14%。通过强制陈化试验,得出了籽粒苋婴儿食品配方。动物试验表明该产品不但使用方便,而且营养丰富,是一种较为理想的籽粒苋婴儿食品。     

Cholesterol-lowering effect of whole lupin (Lupinus albus) seed and its protein isolate

This study describes the hypocholesterolaemic effect of whole lupin and its protein in hamsters. The diets were: casein (control group HC), lupin protein isolate (group HPI) and whole lupin seed (group HWS). Diets from HPI and HWS promoted a significant reduction of total cholesterol and non-HDL cholesterol in the hamsters’ plasma as compared with HC. The true digestibility of HPI and HC groups were similar and differed significantly from the HWS one, which in turn showed a significant difference in total sterol excretion as compared to the former groups. Histological analysis of the liver revealed that animals fed on HPI and HWS diets presented a low level of steatosis (level 1) as compared to the ones fed on HC diet (level 4). Our findings demonstrate that protein isolate from Lupinus albus from Brazil has a metabolic effect on endogenous cholesterol metabolism and a protector effect on development of hepatic steatosis.     

籽粒苋蛋白质的提取研究

研究了不同的介质pH、提取时间、提取温度和加水比例对籽粒苋蛋白质的可溶出率的影响，分析了3种pH下提取的蛋白质氨基酸组成。结果表明：pH值极大地影响籽苋蛋白质的溶出率，pH2—4．6时，随pH上升，溶出率下降，pH4．6—12时，随pH上升，可溶出率增大；pH值4．6时为最低点，此时可能为籽粒苋蛋白质的等电点；水与粒苋之比为20时，蛋白质的可溶出率较其它比例为高；其它因素对籽粒苋蛋白质的溶出率影响不大。     

籽粒苋蛋白质功能特性的理论研究(II)—籽粒苋蛋白质发泡性的理论研究

采用碱性提取和等电点法分离出籽粒苋蛋白质 ,测定了不同浓度、pH值、离子强度、蔗糖浓度条件下的蛋白质发泡力和泡沫稳定性 ,探讨了籽粒苋蛋白质在不同条件下发泡性的变化规律 ,为籽粒苋蛋白质在食品加工中的应用提供了一定的理论依据。     

Granular Structure and Physicochemical Properties of Starches from Amaranth Grain

The granular structure and physicochemical properties of starches isolated from grain amaranth cultivar K112 (Amaranthus cruentus L.) were studied in this study. Detailed physical and chemical analyses were performed by determining the granular morphology, crystallinity, particle size, thermal characteristics, blue value, enzyme susceptibility, and pasting properties. Results showed polygon-shaped A. cruentus L. K112 starch granules. The average diameter was 1.38 μm, in which half of the diameter was <2.91 μm. An A-type X-ray diffraction pattern was revealed with intense peaks of 15.2°, 17.5°, and 23.2°. The peak viscosity was 181 BU and the breakdown value was 2 BU. Amaranth starch obtained the highest pasting temperature (70.7°C) and enzymatic digestibility (absorbance value = 0.41 ± 0.013) compared with corn, cassava, and sweet potato starches.     

Amaranth seed protein hydrolysates have in vivo and in vitro antihypertensive activity

The objective of this work was to study the hydrolytic release of encrypted peptides with antihypertensive activity from storage proteins of Amaranthus mantegazzianus, as determined by in vitro assays, for the first time by in vivo studies in animal models, and by ex vivo assays. Hydrolysates with hydrolysis degree (DH) of 45% and 65% (IC50 0.12 mg/ml, equivalent to 300–600 μM) exhibited an angiotensin-I converting enzyme 1 (ACE) inhibitory activity equal or higher than the potential inhibitory of the average antihypertensive peptides registered in the BIOPEP database and of semi-purified Amaranthus hypochondriacus albumin and globulin protein fractions. Intragastric administration of hydrolysates with DH of 45% was effective in lowering blood pressure of male spontaneously hypertensive rats (SHR). Experiments performed in papillary muscles isolated from hearts and with isolated aortic smooth muscle of SHR suggest that the hypotensive effect could be attributed to a lowering of the peripheral resistance. We assume that the amaranth hydrolysates would be acting at the level of the local or autocrine renin–angiotensin system (RAS).     

从苋菜中提取氢过氧化物裂解酶工艺

在高等植物中,氢过氧化物裂解酶(hydroperoxide lyase,HPL)可将脂肪氧合酶氧化多不饱和脂肪酸产生的氢过氧化物催化裂解,生成的己醛、己烯醛等芳香性物质具有果蔬的新鲜气味,是食品行业和日化工业中的重要芳香风味添加剂。实验以苋菜为研究对象,在单因素[pH、半胱氨酸浓度、匀浆转速、聚乙烯吡咯烷酮(PVP)浓度]实验基础上,运用4因素3水平的正交实验,对HPL的提取工艺进行了优化,即在12 000 r/min,以pH 8.0的含有1 mmol/L半胱氨酸和0.3%质量浓度的PVP为缓冲液提取HPL,得到的HPL具有很高的酶活。并探索了抽真空对HPL提取的影响,在抽真空完全除去氧的情况下提取HPL,酶活得到显著提高。     

Comparison between isoelectric precipitation and ultrafiltration processes to obtain Amaranth mantegazzianus protein concentrates at pilot plant scale

The aim of this study was to compare protein yield, protein concentration and physicochemical characteristics of Amaranth mantegazzianus protein concentrates (APC) obtained at pilot-scale by a conventional process (CP) (alkaline extraction and isoelectric precipitation) and two alternative processes (AP): (1) acid pre-treatment process combined with isoelectric precipitation and (2) acid pre-treatment process combined with ultrafiltration. Although AP resulted in higher protein concentration, protein yield was lower than in CP. SDS–PAGE and size-exclusion chromatography showed high molecular weight fractions only for isoelectric precipitation concentrates (obtained by CP and AP). The amino acids concentration, especially phenylalanine, isoleucine and methionine, increased in all protein concentrates respect to the amaranth flour. Particularly, the product obtained by ultrafiltration was rich in phenylalanine and lysine, and presented no limiting amino acid with respect to the recommendation of the Food and Agriculture Organization of the United Nations (FAO).     

Amaranth,quinoa and oat doughs: Mechanical and rheological behaviour,polymeric protein size distribution and extractability

The rheological characteristics, static and dynamic mechanical properties of amaranth, quinoa and oat doughs and the relative size distribution of their polymeric proteins were evaluated. For the sake of comparison, semolina dough rheological and mechanical properties and the relative size distribution of proteins were also determined.     

Amaranth functional cookies exert potential antithrombotic and antihypertensive activities

In this study, amaranth flour was used as an ingredient to prepare gluten-free cookies. The production process and attributes of amaranth cookies were characterised, and the potential use of amaranth flour as a functional ingredient was analysed. Cookies exhibited a non-uniform reddish brown colour and a cookie factor ratio of 4.5 ± 0.6. Storage studies indicated that after 3 weeks at room temperature cookies presented slight variations in the texture. Simulated gastrointestinal digestion of this product was able to release peptides capable of exerting potential antithrombotic and antihypertensive activities, IC₅₀ values of 0.22 ± 0.04 and 0.23 ± 0.03 mg mL⁻¹ protein, respectively. This work demonstrates for the first time that food made with amaranth flour exerts potential antithrombotic and antihypertensive activity. In conclusion, these amaranth cookies could be an alternative way of incorporating potentially health beneficial products for people who choose a conscious diet, including coeliac or vegan consumers.     

Amaranth starch-rich fraction properties modified by extrusion and fluidized bed heating

Today amaranth is a promising food source yet its technological properties are not well known. The modification of some properties of an amaranth starch-rich fraction by a controlled heating is studied. This fraction was obtained by the differential milling of Amaranthus cruentus grains.Tests were performed by both fluidized bed and extrusion heating, according to a factorial experimental design of two variables: temperature and moisture, at three levels 150-170-200 °C and 120-160-200 g/kg wb, respectively. Effects were evaluated by the ANOVA method. As responses, solubility and water absorption, amylographic and dynamic rheological properties, crystallinity, granular integrity and resistant starch content were evaluated. Flours obtained from samples heated by fluidized bed gave aqueous dispersions with high consistencies when cooked, and they had low solubility in water and preserved part of the starch crystalline structure. Flours obtained from extrusion-heated samples gave very high solubility in water but had lower consistency of the aqueous dispersions when cooked, and they showed a complete loss of the crystalline and granular structure.By applying each of the two heating processes, it was possible to modify, according to selected targets, the amaranth starch-rich fraction, what would allow to obtain pre-cooked amaranth flours with a wide range of hydration and rheological properties.     

Isolation and structural properties of the major protein fraction in Australian wattle seed (Acacia victoriae Bentham)

The major protein fraction of wattle (Acacia victoriae Bentham) seed was isolated by anion-exchange and gel permeation chromatography. The protein was then characterised by its amino acid composition, gel electrophoresis, fluorimetry and circular dichroism (CD) in order to elucidate its nature and structural properties. The major amino acids were found to be glutamate (14.4%), aspartate (11.1%) and lysine (9.13%) while the contents of sulphur-containing amino acids (cysteine and methionine) and tryptophan were very low. The native protein, with an isoelectric point of 6.85, was comprised of two subunits of molecular masses 62 and 125 kDa, the bigger unit being joined by at least one disulphide bond. Far-UV-CD spectra showed that the protein consisted mainly of equal amounts of β-sheets and random structures (39% each), about 19% β-turns and relatively little α-helix (3.6%). These structures were also found to be very stable to changes in pH (3–9), temperature and ionic strength. Based on the fluorescence emission and near-UV-CD data, however, the tertiary structure was more sensitive to pH, temperature and ionic strength.     

Properties of Korean Amaranth Starch Compared to Waxy Millet and Waxy Sorghum Starches

Characteristics of waxy type starches isolated from amaranth, waxy millet and waxy sorghum harvested in Korea were evaluated. Shapes of all starch granules were polygonal or slightly round and the surfaces of waxy millet and waxy sorghum starch granules showed visible pores. Amylose contents of the three starches were between 3.2–6.0% and amaranth starch showed the highest water binding capacity (WBC) (130.7%). The swelling power and solubility of amaranth starch studied at 65.0–95.0°C increased about 13.7‐ and 14.0‐fold, respectively, with increase in temperature. Swelling power of waxy sorghum starch was the highest (72.6 at 95°C) among the starches studied, while amaranth starch had a constant swelling power and its rate of solubility increasely only slowly at temperatures higher than 75°C. From RVA data, initial pasting temperatures of amaranth, waxy sorghum and waxy millet starches were 75.7, 73.3 and 75.2°C, respectively. Peak viscosity, breakdown, and setback from trough of amaranth starch were 68.3, 16.7 and 7.5 RVU, respectively, which were the lowest values among the starches investigated. Using DSC, onset temperature of gelatinization of amaranth starch was 1.5–4.0°C higher than those of waxy sorghum and millet starches, corresponding to the RVA result. The enthalpies of gelatinization of the starches studied in our laboratory were in the range of 8.5–12.7 J/g with decreasing order of waxy sorghum > amaranth > waxy millet starch.     

苋籽ACE抑制肽降血压的体外评价

利用循证医学,依据血管紧张素转换酶(ACE)对血压的调节机理,以呋喃丙烯酰三肽(FAPGG)为血管紧张素Ⅰ模拟物,建立了胰蛋白酶模拟体外消化体系和大鼠肝脏混合功能氧化酶(MFO)模拟肝脏代谢体系,测得了未经处理的苋籽水解肽IC50值为1mg/mL,经过体外模拟消化和孵育处理后的苋籽水解肽IC50值为10mg/mL。      

Influence of heating,protein and glycerol concentrations of film-forming solution on the film properties of Argentine anchovy (Engraulis anchoita) protein isolate

This study was conducted to evaluate the influence of thermal treatment (74, 82, and 90 °C), glycerol (30%, 35%, and 40%, w/w) and protein concentrations (3.0%, 3.5%, and 4.0% w/w) of film-forming solution on the properties of Argentine anchovy (Engraulis anchoita) protein isolate (API) films produced by casting. The API presented 88.8% of proteins, 5.5% moisture, 1.3% lipids, 1.0% ash and 53.3% of polar amino acids. The DSC of protein isolate was observed at maximum temperature of 62.2 °C and ΔH 6.4 J/g. The thickness, water vapor permeability, color difference and opacity of the films were not affected by the experimental variables studied (p > 0.05). The lowest solubility, elongation, and highest tensile strength of the films occurred at low temperature, low protein and glycerol concentrations (p < 0.05). Micrographs obtained by scanning electron microscopy of the films showed homogeneous surfaces at low temperature.     

籽粒苋油的超临界CO2萃取及其色谱分析

应用超临界CO2萃取技术,研究了籽粒苋油的提取工艺.采用三因素三水平正交试验,考察了萃取压力、温度、CO2流量对籽粒苋油萃取率的影响.研究得出最佳萃取条件为:萃取压力35 MPa,萃取温度35℃,CO2流量10 L/h.在最佳萃取条件下,籽粒苋油萃取率达5.96%.利用气相色谱仪分析了籽粒苋油的脂肪酸组成,结果表明,籽粒苋油总不饱和脂肪酸含量高达70%,还含有7.14%的角鲨烯,是一种理想的营养保健食用油.     

Amaranth starch-rich fraction properties modified by high-temperature heating

The effect of high-temperature fluidized-bed heating on some properties of an amaranth high-starch fraction obtained from Amaranthus cruentus grains was evaluated. A two-factor at three levels factorial experimental design (3²) was adopted, one factor being the heating temperature (190, 200 and 210 °C) and the other, the moisture content of the high-starch fraction (12%, 16% and 20% wet basis). The effects on the responses water solubility, swelling power, amylographic and dynamic responses, crystallinity degree and gelatinization enthalpy were established by using response surface methodology. A partial loss of starch crystalline structure was observed but most of their granular integrity was preserved. As temperature and moisture increased, loss of crystalline structure and degree of gelatinization also increased. The obtained amaranth high-starch flours were of a solid character at low temperature, with high consistency when cooked and low water solubility, which make them suitable for industrial applications.     

Functional properties of protein preparations from amaranth seeds in model system

The gross chemical composition and functional properties (solubility, emulsifying and foaming properties) of different amaranth protein preparations were studied in model systems and were compared to those of casein and soy protein isolates. Preparations of alkaline-soluble total protein, albumin, globulin, and glutelin-like alkaline-soluble residual protein were produced from two different types of defatted amaranth meals by extraction and fractionation. Although similarity can be shown between protein patterns of legumes (including soy) and amaranth, the emulsifying and foaming properties of amaranth protein preparations are relatively poor in comparison to the reference proteins, except foaming properties of albumin preparations. Nevertheless, taking in mind that these properties depend on interactions with other food components and textural requirements of individual food products, the amaranth protein preparations may be treated as potential protein sources and food ingredients.