添加不同脂质对豆腐凝胶品质的影响

添加不同种类和含量的脂质于大豆分离蛋白浆液中,并对其制作的豆腐的品质进行分析。试验结果发现：添加了脂质的豆腐口感较为滑润,网络结构较为紧密。脂质对蛋白凝胶的作用主要在于改善口感,提高咀嚼性,增加制品凝胶破断应力、弹性及保水性。而不同种类的脂质对凝胶品质的具体影响又有很大差别。     

无机盐对短链菊粉凝胶性能影响的研究

目的研究无机盐对短链菊粉凝胶指数和保水性的影响,为其实际应用提供理论指导。方法添加不同量的NaCl和CaCl2,测定短链菊粉水溶液凝胶体系的凝胶指数和保水性的变化规律。结果当无机盐添加量一定时,短链菊粉含量越高越有利于凝胶的形成;当菊粉添加量一定时,随无机盐添加量的增加,菊粉的凝胶指数和保水性都呈先增大后减小的趋势,NaCl和CaCl2的添加量分别在4%和5%时达最大值,此时凝胶指数分别为86.68%和94.58%,保水性分别为200.14%和274.86%;在无机盐的添加量相同时,CaCl2对菊粉凝胶性能的影响比NaCl更显著;当菊粉添加量为35%时差异最显著,添加1%CaCl2的凝胶指数和保水性分别比1%NaCl高11.24%和42.85%。结论无机盐能促进短链菊粉凝胶的形成,增加菊粉凝胶的凝胶指数和保水性,CaCl2比NaCl的这种作用更明显。     

δ-葡萄糖酸内酯添加量对豆腐凝胶特性的影响

以内酯豆腐为研究对象,在豆浆中添加不同比例(0.2%、0.3%、0.4%)的δ-葡萄糖酸内酯(GDL),通过质构仪、SDS-PAGE、红外光谱、激光扫描共聚焦显微镜等仪器,对其组织结构、含水量和保水性、凝胶作用力组成、蛋白质亚基组成、二级结构和微观结构进行测定,分析GDL添加量对豆腐凝胶特性的影响。结果表明,随着GDL添加量的增加,其硬度、弹性和咀嚼性显著提高(P<0.05),当GDL添加量为0.4%时,保水性最好,达到了83.38%,豆腐中疏水作用逐渐增强,可溶性蛋白的亚基条带逐渐减少,蛋白质向凝胶转化的趋势增大,豆腐蛋白质中β-折叠含量由31.93%增加到38.43%,无规则卷曲含量由13.93%下降到13.78%。     

不同卤水添加量对豆腐凝胶特性的影响

以大豆为主要原料,在豆浆中添加不同比例卤水(2.0%, 3.5%和5.0%),通过质构仪、SDS-PAGE、傅里叶红外光谱及激光共聚焦等手段对卤水豆腐的质构、得率、蛋白含量、凝胶作用力、二级结构及微观结构等指标进行测定分析。结果表明:随着卤水添加量的增加,豆腐凝胶硬度呈上升趋势;卤水添加量2%时,豆腐含水量、保水性和得率均达到最高,分别为77.96%, 46.85%和166.74%。豆腐的总蛋白含量随着卤水添加量的增加而增加。疏水作用和二硫键是卤水豆腐形成的主要作用力,二者含量达到80%。随着卤水含量的增加, β折叠含量从12.27%增加到13.61%;β转角含量从14.23%下降到13.2%,再升高至13.99%; α螺旋含量从53.1%下降至44.82%;无规则卷曲含量从20.41%上升到27.59%。     

油脂含量对SPI豆腐得率和品质的影响

添加一定量的油脂于大豆分离蛋白(SPI)浆液中,并对其制做的豆腐的微观结构、得率及其品质进行分析.结果发现:添加了油脂的豆腐的网络结构较为紧密,豆腐凝聚的比较集中,因此,促使豆腐得率和质构参数的变化,随着油脂含量的增加,豆腐的得率先是增加后又降低,豆腐的硬度、弹性、黏性和咀嚼性都有一定的变化.油脂含量在一定范围内能够提高豆腐保水性(WHC),另外,豆腐蛋白利用率和豆腐的得率成正相关,豆腐凝胶强度和得率成负相关.最终结果表明添加适量的油脂对于SPI豆腐的得率和品质都有有利的影响.     

油脂含量对SPI豆腐得率和品质的影响

添加一定量的油脂于大豆分离蛋白（SPI）浆液中，并对其制做的豆腐的微观结构、得率及其品质进行分析。结果发现：添加了油脂的豆腐的网络结构较为紧密，豆腐凝聚的比较集中，因此，促使豆腐得率和质构参数的变化，随着油脂含量的增加。豆腐的得率先是增加后又降低，豆腐的硬度、弹性、黏性和咀嚼性都有一定的变化。油脂含量在一定范围内能够提高豆腐保水性（WHC），另外，豆腐蛋白利用率和豆腐的得率成正相关，豆腐凝胶强度和得率成负相关。最终结果表明添加适量的油脂对于SPI豆腐的得率和品质都有有利的影响。     

豆渣添加量对豆腐凝胶特性和保水性的影响

采用超微处理的豆渣添加到豆浆中制作豆腐。凝固剂为葡萄糖酸内酯（内酯）和硫酸钙。研究结果表明,适量的豆渣可以提高硫酸钙豆腐的凝胶强度和粘附性,但对内酯豆腐来讲,降低了凝胶强度和粘附性。内酯豆腐和硫酸钙豆腐凝胶的硬度都表现出下降的趋势,而弹性和保水性在一定程度上得到增加。结果有益于提高豆腐营养价值,改善豆腐的品质。     

豆腐凝胶强度和保水性能的研究

研究了制作条件对ＧＤＬ豆腐凝胶强度和保水性的影响。研究表明,生豆乳９５℃加热５ｍ ｉｎ左右为宜;豆腐凝胶的保水性不受ＧＤＬ 浓度的影响;随着ＧＤＬ浓度增加,豆腐凝胶强度提高,但当ＧＤＬ浓度超过０．０８Ｍ 时,豆腐凝胶强度缓慢下降。豆乳浓度增加时,豆腐凝胶强度和保水性都增强,但豆乳浓度过高时,对提高豆腐凝胶强度反而不利。提高凝固温度、增加凝固时间都可显著提高豆腐凝胶的强度。本文还讨论了豆腐凝胶的形成机理,认为高浓度豆乳中大豆蛋白变性后热胶凝不利于豆腐凝胶网络的形成。     

葡萄糖酸内酯对猪肉肌原纤维蛋白功能性的影响

在猪肉肌原纤维蛋白中添加不同质量分数(0.5%、1.0%、1.5%、2.0%)的葡萄糖酸内酯(GDL),研究其对肌原纤维蛋白乳化能力和凝胶性的影响。结果显示,添加GDL 能显著提高肌原纤维蛋白的乳化性和乳化稳定性(P ＜ 0.05),但是不同添加量之间差异不显著;凝胶白度随GDL 添加量的增加呈下降趋势;0.5% 以下添加量对凝胶保水性没有显著影响,0.5% 以上的添加量会大幅提高保水性;除凝胶黏附性随GDL 质量分数增加而下降外,凝胶硬度、胶黏性和回弹性都在GDL 添加量0～1.0% 之间有不同程度的下降,然后随着GDL 质量分数增大而升高。综合来看,1.5% 的GDL 添加量对猪肉肌原纤维蛋白的功能性有较好的改善作用。     

大豆油对大豆分离蛋白凝胶特性的影响

通过添加不同比例的大豆油于大豆分离蛋白中,在不同凝胶条件下制备大豆油-大豆分离蛋白复合凝胶。以凝胶强度、弹性、胶凝性、内聚性这4个主要的质构参数,以及二硫键含量、色度和保水性为指标,对不同组分的复合凝胶的凝胶性进行相关研究,用以阐明不同含量的大豆油对大豆分离蛋白凝胶生成机制的影响。结果表明:随着大豆油的添加,原有的蛋白质-蛋白质三维凝胶网络结构被破坏,形成蛋白质-脂肪复合凝胶体系,导致凝胶硬度、内聚性、胶凝性降低,弹性先增加后降低;二硫键含量呈下降趋势;色度的变化较大;保水性逐渐降低。     

Filtration of milk fat globule membrane fragments from acid buttermilk cheese whey

The proteins and polar lipids present in milk fat globule membrane (MFGM) fragments are gaining attention for their technological and nutritional properties. These MFGM fragments are preferentially enriched in side streams of the dairy industry, like butter serum, buttermilk, and whey. The objective of this study was to recover MFGM fragments from whey by tangential filtration techniques. Acid buttermilk cheese whey was chosen as a source for purification by tangential membrane filtration because it is relatively rich in MFGM-fragments and because casein micelles are absent. Polyethersulfone and cellulose acetate membranes of different pore sizes were evaluated on polar lipid and MFGM-protein retention upon filtration at 40°C. All fractions were analyzed for dry matter, ash, lipids, proteins, reducing sugars, polar lipid content by HPLC, and for the presence of MFGM proteins by sodium dodecyl sulfate-PAGE. A fouling coefficient was calculated. It was found that a thermocalcic aggregation whey pretreatment was very effective in the clarification of the whey, but resulted in low permeate fluxes and high retention of ash and whey proteins. By means of an experimental design, the influence of pH and temperature on the fouling and the retention of polar lipids (and thus MFGM fragments), proteins, and total lipids upon microfiltration with 0.15 μM cellulose acetate membrane was investigated. All models were highly significant, and no outliers were observed. By increasing the pH from 4.6 to 7.5, polar lipid retention at 50°C increased from 64 to 98%, whereas fouling of the filtration membrane was minimized. A 3-step diafiltration of acid whey under these conditions resulted in a polar lipid concentration of 6.79 g/100 g of dry matter. As such, this study shows that tangential filtration techniques are suited for the purification of MFGM fragments.     

Effect of components extracted from okara on the physicochemical properties of soymilk and tofu texture

ABSTRACT:  The physicochemical properties of soymilk and the texture of tofu were compared with regard to 2 kinds of soymilk, one of which was prepared by squeezing homogenates before heating and the other was prepared by squeezing after heating raw soymilk with okara, residue of soymilk production. Relative particulate protein content and viscosity were higher and pH was lower in the soymilk prepared by the latter method, in which liberated lipid bodies were decreased and more lipids were precipitated with protein after centrifugation, suggesting a change in the interaction between proteins and lipids. A difference in the distribution of proteins and lipids was also implied by analysis with a laser particle size analyzer. The breaking stress of tofu made with 0.30% glucono-delta-lactone increased in accordance with an increase in particulate protein. The calcium and magnesium contents increased in soymilk prepared by squeezing after heating with okara. Viscosity was slightly increased and pH decreased by adding calcium to the soymilk, but the particulate protein content and breaking stress of tofu did not increase significantly. To examine the effect of macromolecules, okara was extracted by boiling and dialyzed. Viscosity and particulate protein content in soymilk increased as the dialyzed extracts of the okara were added. The breaking stress of tofu was increased by adding the dialyzed extracts but excessive amounts of the extracts resulted in softer tofu. Spectra of Fourier-transform infrared spectroscopy and electrophoresis-separated patterns of proteins indicated that the dialyzed extracts contained mainly polysaccharides and the Basic 7S globulin protein.     

Quality improvement of kenaf-based tofu: effects of kenaf seed substitution,and coagulant types and concentrations on the physicochemical quality,texture profile and microstructure of the tofu

Tofu was made by substituting kenaf seed (K) with soybean (S) at 100 (positive control), 50%, 40%, 30%, 20%, 10% and 0% (negative control). The results indicated that kenaf seed substitution at all ratios significantly increased the soluble solids and protein content of the milky extracts. The yield, moisture and protein content of the tofu were significantly increased with the increase in kenaf seed substitution, while the lipid content was significantly decreased. The tofu made with kenaf seed substitution of 50%, 40% and 30% had the same protein content (43.76–45.36 g/100 g) with the positive control (45.36 g/100 g), but a significantly higher lipid content (32.00–35.75 g/100 g) than that of the positive control (27.50 g/100 g). The microstructure of the tofu revealed that only the positive control had a honey-comb structure, whilst the tofu made from kenaf seed-soybean blends had a pseudo-honey like structure. Up to 30% of soybean can be added into the kenaf-based tofu, without any negative effect on the textural and colour properties and, protein content, but significantly improved the essential amino acids content of the kenaf-based tofu. Therefore, the blend of 70K:30S ratio using 0.5 g% glucono delta-lactone as a coagulant is recommended to produce kenaf seed-soybean tofu.     

Characteristics of lipids in buckwheat grain and isolated starch and their changes after hydrothermal processing

Studies were carried out on bond and free lipids of buckwheat grain and isolated starch. As regards free and bond lipids, fraction composition (percentages of neutral and polar fraction) and fatty acids were determined. It was found that the content of free lipids in buckwheat grain was twice higher than of bond lipids. On the other hand, in case of starch percentage of free lipids was twice lower than of bond lipids. As regards free and bond lipids of buckwheat grain and starch, main fraction was represented by the neutral one. Percentages of glycolipids and phospholipids amounted to only from 5 to 7%. Fatty acids were predominated by unsaturated acids C_18:2 and C_18:1. Fire and steam hydrothermal processing resulted in several quantitative changes, the most important ones being an increase of free lipid content in the grain and of bond lipid content in the starch, changes in the percentage of glycolipids and phospholipids, an increase of saturation of free lipid fatty acids in the grain, and of saturation of bond lipid fatty acids in the starch.     

Effects of exogenous porcine somatotropin (pST) administration on pork meat quality

Two experiments were conducted on Large White pigs in order to assess the effect of porcine somatotropin (pST) administration upon meat quality criteria. No clear trend was observed concerning pH1 or pH2 measurements in Longissimus dorsi (LD), Adductor femoris (AF) and Semi spinalis (SS) muscles or drip loss in LD. Cooking loss in LD was not affected by pST treatment. Intramuscular lipid content was decreased by pST in LD and AF. Only non-polar lipids were affected by pST, whereas polar lipid content was similar in control and pST treated pigs. Percentage polyunsaturated fatty acids was significantly increased by pST in backfat and LD lipids, whereas no clear trend was observed concerning fatty acid composition of AF lipids.     

Characterization of the Lipid Fraction in Lamb Meat: Comparison of Different Lipid Extraction Methods

The aim of this study was to evaluate the performance of four different extraction methods commonly used to quantify the intramuscular lipid content in meat: the Association of Analytical Chemists (AOAC) method (reference method) and methods based on the use of a solvent mixture with different polarities, such as chloroform–methanol described by Folch et al. (J Biol Chem 226:497, 1957) and Christie (1989) or hexane–isopropanol described by Hara and Radin (Anal Biochem 90:420, 1978). The following parameters were taken into account: lipid content; relative proportions of neutral and polar lipids; fatty acid composition of total, neutral, and polar lipid fractions; and phospholipid composition. The use of a combination of solvents with different polarities (Hara–Radin, Folch, and modified Folch methods) was more effective in extracting intramuscular lipids than the use of a single solvent (AOAC, reference method). The Hara–Radin method provided a cleaner lipid extract with a significantly higher content of total fatty acids than that obtained with the Folch and modified Folch methods. The lower polarity of the hexane–isopropanol mixture allowed us to obtain an extract richer in neutral lipids (triglycerides and diglycerides) and thus in saturated and monounsaturated fatty acids. The percentage distribution of individual fatty acids in the neutral lipid fraction was generally not affected by the extraction method adopted, while lipid obtained with both the Hara–Radin and Folch methods had a polar fraction with a higher percentage of polyunsaturated fatty acids. The use of the Hara–Radin method provided a polar fraction with less nonlipid material and lower phospholipid degradation.     

基于豆清发酵液点浆的 二次浆渣共熟生产豆腐的工艺优化

采用豆清发酵液为豆腐点浆的凝固剂,通过单因素实验研究水豆质量比、煮浆温度、豆清发酵液的添加量和煮浆时间对豆腐品质影响。以豆腐得率和蛋白质含量为指标,通过Box-Behnken实验结合响应面法建立二阶多项非线性回归方程和数据模型优化豆腐工艺,结果表明,最佳加工工艺条件为水豆质量比是6:1 kg/kg,煮浆温度是105.7 ℃,煮浆时间是5.8 min,豆清发酵液添加量26.3%。在最佳工艺条件下得到的豆清发酵液豆腐的得率和蛋白质含量分别最高达255%、11.12%,此时豆腐的水分含量及保水性达到最佳,优于市售同类产品,对于豆清发酵液豆腐的制作提供了借鉴价值。     

Total milk fat extraction and quantification of polar and neutral lipids of cow,goat, and ewe milk by using a pressurized liquid system and chromatographic techniques

Although milk polar lipids such as phospholipids and sphingolipids located in the milk fat globule membrane constitute 0.1 to 1% of the total milk fat, those lipid fractions are gaining increasing interest because of their potential beneficial effects on human health and technological properties. In this context, the accurate quantification of the milk polar lipids is crucial for comparison of different milk species, products, or dairy treatments. Although the official International Organization for Standardization-International Dairy Federation method for milk lipid extraction gives satisfactory results for neutral lipids, it has important disadvantages in terms of polar lipid losses. Other methods using mixtures of solvents such as chloroform:methanol are highly efficient for extracting polar lipids but are also associated with low sample throughput, long time, and large solvent consumption. As an alternative, we have optimized the milk fat extraction yield by using a pressurized liquid extraction (PLE) method at different temperatures and times in comparison with those traditional lipid extraction procedures using 2:1 chloroform:methanol as a mixture of solvents. Comparison of classical extraction methods with the developed PLE procedure were carried out using raw whole milk from different species (cows, ewes, and goats) and considering fat yield, fatty acid methyl ester composition, triacylglyceride species, cholesterol content, and lipid class compositions, with special attention to polar lipids such as phospholipids and sphingolipids. The developed PLE procedure was validated for milk fat extraction and the results show that this method performs a complete or close to complete extraction of all lipid classes and in less time than the official and Folch methods. In conclusion, the PLE method optimized in this study could be an alternative to carry out milk fat extraction as a routine method.     

点浆条件对酸浆豆腐品质的影响

为探究点浆时豆乳温度、点浆后蹲脑温度和蹲脑时间对酸浆豆腐品质的影响,提高酸浆豆腐品质,本研究利用质构分析、SDS-PAGE和低场核磁等技术分析了豆腐品质、豆乳中蛋白凝固过程、大豆蛋白各亚基含量和水分分布的变化规律。结果表明,点浆时豆乳温度对豆乳沉淀中蛋白和大豆蛋白各亚基含量无显著影响,但对豆腐品质和水分分布有较大影响。当点浆时豆乳温度为75℃时,豆腐的硬度最小,而其弹性、得率、含水量、保水性、感官得分和T₂₁弛豫时间最大。蹲脑温度和蹲脑时间对豆腐品质、豆乳沉淀中蛋白含量和大豆蛋白各亚基含量影响显著,当蹲脑温度75℃和蹲脑时间20 min时,豆腐硬度最小为15.80 N,而弹性、得率、含水量、保水性和T₂₁弛豫时间最佳,分别为5.15 mm、241.3%、76.36%、65.68%、43.29 ms,且豆腐品质豆乳沉淀中蛋白含量最佳。当点浆时豆乳温度为75℃、蹲脑温度为75℃和蹲脑时间20 min时,豆腐品质和感官得分最优。     

Polar lipid fraction from oat (Avena sativa): characterization and use as an o/w emulsifier

Oat seeds have an oil content of up to 13?%, of which up to 34?% can be polar lipids (glycolipids and phospholipids). Because of their amphiphilic structure, these polar lipids are potential emulsifiers. In this study, polar lipid fraction from oat produced by a supercritical fluid extraction process was fractionated into different polar lipid classes by HPLC and the lipid classes in subfractions were identified by comparing retention times with reference compounds and performing co-injections. The oat polar lipid fraction contained monogalactosyldiacylglycerol, digalactosyldiacylglycerol, steryl glycoside, and phosphatidyl choline, and also possibly phosphatidyl inositol. The polar lipid fraction was also used as an emulsifier to produce oil-in-water emulsions with different amounts of emulsifier and oil, and the stability and other properties of emulsions were studied. Emulsions were formed quite easily, but they were prone to rapid creaming even after a couple of days of storage at ambient conditions. Droplet size and droplet size distribution of the emulsions seemed to be slightly smaller with smaller amount of oil and larger amount of emulsifier. Generally, the droplet size of the emulsions was in the range of 0.2?C4???m, and with the largest amount of oil (5?%, w/v) up to 10???m. The upper phase of creamed emulsions contained slightly larger droplets, up to 30???m, while the lower phase retained smaller droplets. Microscopic investigation revealed that the increase in droplet size of the upper phase was mainly due to aggregation, which implies that these emulsions may be stable against coalescence to some extent.