豆粕中残余脂质的提取与分析

豆粕中含有部分正己烷未能去除的残余脂质,采用体积比为2∶1的氯仿-甲醇溶液及水饱和正丁醇从豆粕中提取残余脂质,并对残余脂质成分进行了分析.传统的氯仿-甲醇溶液法可以将豆粕中大部分脂质提取出来,而与蛋白结合能力较强的极性脂需要进一步通过强极性的水饱和正丁醇提取.研究结果显示,豆粕中总脂质含量为2.10％,其中中性脂占25.24％,极性脂占74.76％,中性脂主要包括甘油三酯、FFA、甘油二酯;极性脂主要包括磷脂酰胆碱(PC)、磷脂酰肌醇(PI)、磷脂酰乙醇胺(PE)、磷脂酸(PA).     

脱脂豆粕变性程度对于产物分离蛋白结构性质及贮藏稳定性影响

为研究不同变性程度的原料所制备的大豆分离蛋白(SPI)贮藏稳定性及其与蛋白结构的关系,实验分别以三批不同变性程度(72.6%,29.4%和1.8%)的低温脱脂豆粕制备SPI,以大豆为原料提取的SPI为对照,考察其在贮藏(37℃)10周过程中溶解度变化及其与初始蛋白的聚集和解离程度的对应关系。结果表明:原始SPI(对照)显示出最高初始溶解度(93%),经10周贮藏后其溶解度下降幅度最小。原料变性程度越高,对应SPI初始溶解度越低;而初始溶解度越高,其在贮藏过程中下降越快,10周后三者溶解度几乎降至同一水平。同时,高变性程度原料制备的SPI聚集或解离程度也越高,不利于SPI短期贮藏中(≤6周)的溶解度;原料变性程度和蛋白初始溶解度均相当时,聚集或解离程度高的SPI在贮藏后期(6周)溶解度损失更快。此外,引起蛋白聚集的主要共价键是二硫键,但除此之外也在变性程度原料的SPI中也发现其他共价键。     

低强度亚临界水提取水溶性芝麻蛋白与多肽

以高温芝麻粕为原料，通过碱溶酸沉法提取芝麻蛋白，再利用低强度亚临界水提取芝麻蛋白中水溶性蛋白及多肽。通过单因素试验研究温度、pH、反应时间、液料比对水溶性蛋白及多肽得率的影响，再通过正交试验分别优化水溶性蛋白及多肽的提取工艺参数。结果表明：低强度亚临界水可显著提高水溶性蛋白及多肽的得率；低强度亚临界水提取水溶性蛋白的最优工艺参数为温度125 ℃、pH 1.5、反应时间30 min、液料比30∶ 1，在此条件下水溶性蛋白得率为85.015%；亚临界水提取多肽的最优工艺参数为温度125 ℃、pH 1.5、反应时间60 min、液料比50∶ 1，在此条件下多肽得率为40.537%。亚临界水提取率高，操作简便，为水溶性芝麻蛋白与多肽的提取提供参考依据。     

罗非鱼-豆粕共沉淀蛋白的提取工艺及蛋白组成分析

以罗非鱼肉和脱脂豆粕为原料,采用p H调节法制备罗非鱼-大豆共沉淀蛋白(Co-p),探讨溶解p H、不同质量比混合的原料、溶解时间对可溶性蛋白得率的影响及沉淀p H对蛋白沉淀得率的影响。结果表明,p H调节法回收罗非鱼-豆粕共沉淀蛋白的最佳酸溶p H2.0、3.0,碱溶p H11.0、12.0,原料比1∶1,溶解时间30 min;SDS-PAGE分析显示,可溶性共沉淀蛋白条带深/浅(极端p H2.0蛋白降解),表明可溶性蛋白含量高/低,从分子量分布范围可知,共沉淀蛋白主要由肌球蛋白重链、7 S抗原蛋白的三个亚基、肌动蛋白、肌球蛋白轻链、11 S抗原蛋白的两个亚基和小分子水溶性蛋白组成,表示可溶性共沉淀蛋白组成齐全;酸/碱可溶性共沉淀蛋白最佳沉淀p H为4.5,在此条件下,溶解、沉淀过程的蛋白得率分别为88.05%~94.70%。经冷冻干燥得到共沉淀蛋白粉即Co-p(1∶1),其蛋白含量高于85%,脂肪含量在0.84%左右,灰分含量低于4.17%;可用p H调节法回收罗非鱼-豆粕共沉淀蛋白。     

萃取方式对小麦胚芽油品质的影响研究

以稳定化小麦胚芽为原料,分别采用亚临界丁烷、超临界CO2和有机溶剂萃取小麦胚芽油,通过对比分析小麦胚芽油得率、水分含量、酸值、过氧化值、茴香胺值、脂肪酸组成、VE以及氧化稳定性指数(OSI),研究萃取方式对小麦胚芽油品质的影响。结果表明:在3种萃取方式中,超临界CO2萃取的小麦胚芽油水分含量最高,为4.32%;亚临界丁烷萃取的小麦胚芽油的得率(9.24%)、OSI(2.55 h)、VE含量(3 749.79 mg/kg)最高,而有机溶剂萃取的小麦胚芽油的酸值、过氧化值和茴香胺值最高;萃取方式对小麦胚芽油的脂肪酸组成无显著性差异。由此可见,小麦胚芽油的品质受萃取方式的影响,亚临界丁烷萃取的小麦胚芽油品质较高。     

小麦胚芽多糖的亚临界水萃取的工艺研究

以小麦胚芽为原料,研究亚临界水萃取小麦胚芽多糖的工艺流程及条件,探讨水料比、pH、萃取时间和萃取温度对小麦胚芽多糖提取得率的影响。结果表明,通过单因素试验和响应面试验优化得到的最佳提取条件为:pH 6,水料比20︰1(mL/g),提取温度150℃,浸提时间10 min。在这个条件下小麦胚芽多糖的提取得率为7.26%。而传统热水浸提法多糖得率为3.29%,与传统热水浸提法相比,亚临界水浸提法具有明显的优势。红外光谱分析表明亚临界水萃取对小麦胚芽多糖的结构无影响,亚临界水萃取可用于小麦胚芽多糖的提取。     

亚临界流体萃取缬草精油工艺优化及其成分分析

为了开发一种萃取条件温和、得率高的缬草精油提取工艺,以缬草根为原料,采用亚临界流体萃取缬草精油。以缬草精油得率为考察指标,通过单因素试验探讨了萃取溶剂、液料比、萃取时间、萃取温度、萃取压力、萃取次数的影响,进而采用均匀设计法优化亚临界流体萃取缬草精油的工艺条件,并运用GC-MS分析缬草精油的组成成分。结果表明：亚临界流体萃取缬草精油的最佳工艺条件为以丁烷为萃取溶剂、萃取压力0.47 MPa、萃取温度47℃、液料比11∶1、萃取时间25 min、萃取次数4次,在此条件下缬草精油得率达到(3.383±0.004)%;亚临界丁烷萃取的缬草精油中共鉴定出57种成分,主要成分为乙酸龙脑酯,相对含量为29.63%,关键药理成分缬草醛和缬草素相对含量分别为2.28%和0.25%。综上,亚临界丁烷萃取缬草精油得率高,缬草精油中含有一定量的缬草醛和缬草素,具有潜在的产业化应用价值。     

亚临界水法提取茶多糖及抗氧化活性研究

为了开发先进的茶多糖提取方法,采用响应面实验优化了亚临界水法提取茶多糖的工艺,并对提取的茶多糖的化学组分、单糖组成进行了简单分析,对其抗氧化活性及DNA损伤的保护活性进行了评价。结果表明,亚临界水法提取茶多糖的最佳工艺条件为液料比为30:1 mL/g、亚临界温度150℃、亚临界时间12min,在此条件下粗茶多糖得率为(5.86±0.23)%,约为传统的热水浸提法得率[(2.917±0.21)%]的2倍,该结果表明亚临界水法提取茶多糖是一种高效的提取技术。所提取的茶多糖中糖含量为57.82%、蛋白含量为10.14%、糖醛酸含量为8.31%。茶多糖主要由阿拉伯糖、葡萄糖、半乳糖、半乳糖醛酸组成,各单糖之间摩尔质量比为0.20:4.88:0.32:0.13。此外,亚临界水法提取的茶多糖能保持与传统热水浸提法相当的清除羟基和ABTS自由基的能力,很好地保持了茶多糖良好地生物活性。DNA损伤的保护试验表明,茶多糖对DNA损伤具有良好的保护性能。因此,亚临界水法提取茶多糖具有广阔的应用前景。     

热处理对大豆蛋白分级分离的影响

对大豆粕进行不同热处理(湿热、干热和压热),研究热处理对大豆蛋白分级分离的影响。研究表明未热处理低温豆粕11S与7S分级不完全,高温豆粕蛋白质得率虽不及低温豆粕的1/2,但高温豆粕中11S与7S级分更易于分离。湿热处理对7S级分纯度影响较大,特别是90℃时7S级分纯度仅为(23.5±0.71)%、得率仅为未加热低温豆粕的1/14。干热处理(特别是70℃时)所得11S和7S级分纯度较高且蛋白质得率损失少。压热处理蛋白质得率大大降低。各级分的脂含量分析表明:高温豆粕IM和7S级分脂含量明显高于未加热低温豆粕。未加热低温豆粕的脂类主要集中于11S和IM级分,湿热处理使脂类向7S级分富集,70℃干热处理IM级分的脂含量最高。结果表明:70℃干热处理2 h的低温豆粕对大豆蛋白的分级分离效果较好。     

不同提取方法对酸枣仁油成分与品质的影响

以酸枣仁为主要原料,分别采用亚临界丁烷萃取法、索氏抽提法和超声辅助提取法提取酸枣仁油,研究不同方法下酸枣仁油的得率、脂肪酸组成及主要理化指标;采用Schaal烘箱法对不同方法提取的酸枣仁油的氧化性质进行了对比研究。结果表明:亚临界丁烷萃取法、索氏抽提法和超声辅助提取法提取酸枣仁油的得率分别为26.73%、28.02%、24.45%。气相色谱-质谱分析三种方法提取的酸枣仁油中主要脂肪酸种类基本相同,以油酸、亚油酸为主,其中不饱和脂肪酸含量为亚临界丁烷萃取法(74.12%)>超声提取法(71.46%)>索氏抽提法(69.78%)。亚临界丁烷萃取法获得酸枣仁油中总不饱和脂肪酸含量和品质明显高于其他两种方法。高效液相色谱法对酸枣仁油进行V_E含量测定,依次为亚临界丁烷萃取法(202.71 mg/kg油)>索氏抽提法(139.01 mg/kg油)>超声提取法(87.04 mg/kg油)。由三种方法提取的酸枣仁油的自氧化实验可知,过氧化值变化由大到小为亚临界丁烷萃取法、超声提取法、索氏抽提法。总之,3种方法各有特点,相对于其他两种方法,亚临界丁烷萃取法所提油得率更多,品质更高,安全性好,更适宜酸枣仁油的提取。     

不同预处理对低温脱脂豆粕中大豆β－伴球蛋白功能性质的影响

采用新鲜低温脱脂豆粕、干热处理脱脂豆粕和溶剂浸提脱脂豆粕为原料制备大豆β-伴球蛋白,研究预处理对低温脱脂豆粕残余脂质含量和脂肪氧合酶酶活以及制备大豆β-伴球蛋白功能性质的影响。干热处理对低温脱脂豆粕中残余脂质含量无显著影响,但可使得脂肪氧合酶酶活下降7．69％;溶剂浸提使得低温脱脂豆粕中残余脂质含量和脂肪氧合酶酶活分别下降98．08％和96．12％,表明溶剂浸提可显著抑制低温脱脂豆粕中脂质过氧化反应的发生。干热处理低温脱脂豆粕使得制备大豆β-伴球蛋白溶解性、持帕性、持油性、乳化性、起泡性以及凝胶性质变差,溶剂浸提低温脱脂豆粕可改善制备大豆β-伴球蛋白溶解性、持抽性、持油性、乳化性、起泡性和凝胶性质。这一研究结果为改善大豆蛋白功能性质提供前期研究基础。     

Effect of lipoxygenase activity in defatted soybean flour on the gelling properties of soybean protein isolate

Soybean lipoxygenase was inactivated to different degrees by dry heating of defatted soybean flour for 0, 5, 10, 15, 20 and 25 min and soy protein isolates were prepared thereof by isoelectric precipitation of the water extract of the defatted soybean flour. The fluorescence emission intensity at 420 nm of the chloroform–methanol extract of soy protein isolates, which was indicator of the existence of peroxidized lipid, varied in parallel with the lipoxygenase residual activity in defatted soybean flours. The dispersion of soy protein isolate showed an increasing turbidity with the increase of lipoxygenase residual activity in the starting defatted soybean flour, suggesting an elevated tendency to form insoluble aggregates during the preparation of soy protein isolate. Small deformation rheological test revealed that the gelling times were shorter for those soy protein isolates derived from low lipoxygenase activity defatted soybean flours than that of high lipoxygenase activity. Frequency sweep showed that G′ of soy protein isolate derived from low lipoxygenase defatted soybean flour was independent of oscillation frequency in contrast to that of derived from non dry-heated defatted soybean flour, the latter showed a marked frequency dependence. Large deformation test revealed that the gel hardness increased about 10 times after dry heating of defatted soybean flour for 20 min. As the increase of the lipoxygenase residual activity, the gel permeability increased markedly, suggesting that soy protein isolate from high lipoxygenase defatted soybean flour produced coarser textured gel, which corresponded well with the results of scanning electron microscopy.     

Effects of endogenous flour lipids on the quality of short‐dough biscuits

Fractionation and reconstitution techniques were used to study the contribution of endogenous flour lipids to the quality of short‐dough (shortcake type) biscuits. Biscuit flour was defatted with chloroform and baked with bakery fat, but without endogenous lipid. Short‐dough biscuits baked from defatted flour had smaller diameters, and were flatter, denser and harder than control biscuits. Defatted flour shortcake doughs exhibited different rheological behaviour from the control samples, showing higher storage and loss moduli (G′ and G″ values), ie higher viscoelasticity. Functionality was restored when total non‐starch flour lipids were added back to defatted flour. The polar lipid fraction had a positive effect in restoring flour quality whereas the non‐polar lipid fraction had no effect. Both fractions were needed for complete restoration of both biscuit quality and dough rheological characteristics. A study of the microstructure of defatted biscuits revealed that their gluten protein was more hydrated and developed than the gluten of the control biscuits. This conclusion was supported by the higher water absorption of the defatted gluten. Copyright © 2004 Society of Chemical Industry     

Effect of denaturation during extraction on the conformational and functional properties of peanut protein isolate

Peanut protein isolate (PPI) was extracted by alkali dissolution and acid precipitation from defatted peanut flour. The effects of extraction conditions on the denaturation and functional properties of PPI were investigated. In comparison with native peanut protein (NPP) which was extracted by ammonium sulfate, the PPI extracted by alkali dissolution and acid precipitation had a higher extent of denaturation. Arachin was affected more easily by the extraction process than conarachin and led to a noticeable decrease of thermal stability of PPI. PPI contained much lower sulfhydryl and disulfide bond contents than NPP. The analyses of intrinsic fluorescence spectra indicated a more compacted tertiary conformation of NPP than PPI. Extraction process influenced the functional properties of PPI, such as protein solubility, emulsifying activity index and foaming capacity. The relatively poor functional properties of PPI might be associated with protein denaturation/unfolding and subsequent protein aggregation.

Industrial relevance

Peanut is an important oilseed crop and a well-accepted food. After oil production through thermal treatment, the defatted peanut flour is the main byproduct, which possesses a large amount of proteins. However, due to the low extraction yield and poor functional properties of these proteins, they are not well utilised in industry till now. In this work, peanut proteins were extracted by two techniques. The results indicated that extraction technique could significantly modify the functional properties of peanut proteins. Therefore, this work is helpful for industrial utilisation of peanut proteins.     

微波预处理对脱脂豆粕蛋白水解度的影响

为得到高水解度的脱脂豆粕蛋白酶解液,在相同酶解条件下,研究微波预处理对脱脂豆粕蛋白水解度的影响,并运用响应面法对微波预处理的功率、温度和持续时间进行优化。结果表明：微波预处理的最佳工艺条件为底物质量分数2%、功率414W、温度79.6℃、持续时间111s;而后经碱性蛋白酶Alcalase酶解水解度能达到30.46%,比未经预处理的样品水解度提高了18.45%,这说明微波处理是一种非常有效的酶解预处理手段。     

Soybean okara: Effect of ultrasound on compositional and emulsifying properties

High-intensity ultrasound is widely used to modify the functional properties of macromolecules (proteins, polysaccharides, etc.) and to expand their range of potential applications. This work is aimed at studying the effects of ultrasound treatments on the composition of different soybean okara samples and their potential as an emulsifying agent. Defatted solvent-free soybean flour (DSF) was extracted by adjusting dispersion to pH 9.0. Insoluble residues obtained after centrifugation were dried, and an unsonicated okara sample (UOK) was obtained. Furthermore, the soybean flour dispersion was subjected to treatment in a probe-type ultrasonic homogeniser before or after the alkaline extraction process, thus producing SOK and OKS samples, respectively. The sonication process generated compositional and structural changes in okara soybeans. SOK had higher yield and protein content than UOK and OKS due to the insolubilisation of the glycinin (11S) fraction of soybean storage proteins. Due to these characteristics, the SOK sample showed the best emulsifying activity.     

大豆浓缩蛋白制备新工艺及其对产品性质的影响

以脱脂豆粉为原料,研究一种基于稀酸浸提的新的大豆浓缩蛋白的制备工艺,并测定不同工艺条件下产品的功能及理化性质。结果表明,脱脂豆粉经稀酸水洗20 min,重复水洗3次,再经碱改性(pH 11)处理6 h的制备工艺得到的大豆浓缩蛋白的溶解度和乳化性均优于大豆分离蛋白(SPI),并且蛋白质的分子结构发生了不同程度的解离和聚集,蛋白质分子量和粒径分布指数增大。     

过氧化脂质对分离蛋白凝胶性质的影响

以大豆为原料,通过常温下正己烷浸提去油,得到高脂肪氧合酶活力的豆粕,采用不同干热程度处理得到酶活不同的豆粕,进而以碱溶酸沉法制备分离蛋白。发现不同脂质过氧化程度的豆粕提取出的分离蛋白性质差异比较显著。不同蛋白氯仿-甲醇提取液的荧光测定证实了过氧化脂质的存在。浊度反映了蛋白中不溶性聚集体的含量。凝胶的流变、质构和渗透性测定表明了不同程度蛋白聚集的凝胶性质的变化,而凝胶的扫描电镜图也显示了凝胶微观结构随灭酶程度的变化。     

Comparative study of the emulsifying and foaming properties of defatted coriander (Coriandrum sativum) seed flour and protein concentrate

Emulsifying and foaming properties were determined for coriander protein products (defatted flour and protein concentrate) at pH 4.0, 7.0 and 9.0 and the results compared with those obtained for defatted soybean flour. Mean oil droplet size and interfacial protein concentration was smallest for emulsions (∼17% oil, v/v) stabilized by the coriander protein concentrate, when compared to the coriander and soybean flours. Polypeptide composition of the interfacial protein membrane of the emulsions was different from the polypeptide composition present in the respective coriander flour and protein concentrate. In contrast, soybean flour-stabilized emulsions contained similar polypeptide composition to that of the flour. Soybean flour formed the greatest amount of foams at pH 4.0, 7.0 and 9.0 followed by the coriander flour, which had greater amounts of foam at pH 4.0 and 5.0. The foam stability of both the coriander flour and protein concentrate were significantly (P⩽0.05) less than those of the soybean flour. It was concluded that the reduced level of non-protein components in the coriander protein concentrate favoured increased surface activity at the oil–water interface but not at the air–water interface.     

大豆粉对馒头品质影响的研究

通过向小麦粉中添加全脂豆粉、脱脂豆粉及大豆蛋白,来研究其对小麦粉及馒头品质的影响.结果表明:随着全脂豆粉、脱脂豆粉及大豆蛋白使用量的增加,小麦粉湿面筋含量与沉降值逐渐下降,馒头的比容逐渐减小,品质逐渐变差;但当全脂豆粉与脱脂豆粉添加量在10%以内,大豆蛋白的添加量在5%以内时不会对馒头的品质产生不良影响,还可以弥补馒头中必需氨基酸特别是赖氨酸的不足,提高馒头的营养价值.