Influence of hydrolysed lecithin addition on protein adsorption and heat stability of a sterilised coffee cream simulant

Within an overall goal to enhance the stability of coffee cream, the influence of hydrolysed soybean lecithin addition was investigated. To avoid the seasonal variations in milk composition a model system was used containing 5% (w/w) soybean oil and 12% (w/w) skimmed milk powder with and without lecithin addition before a two-step high-pressure homogenisation. Addition of 20% (w/v) caesium chloride enabled a nearly complete recovery of the fat in the cream layer upon centrifugation of casein-stabilised emulsions. From the fat and protein content of this cream layer, it was concluded that lecithin addition did not significantly affect the protein content of the cream layer after emulsion preparation, but significantly reduced the additional milk protein adsorption at the oil/water interface upon sterilisation. The experimental data suggest that the enhanced heat stability of the lecithin-supplemented coffee cream simulant may be explained by the fact that hydrolysed lecithin largely reduces attractive protein–protein interactions during sterilisation.     

仿母乳奶油粉的营养功能特性和婴儿配方奶粉干法生产

按母乳脂肪酸组成将玉米油、豆油、茶油、棕榈油进行调配，使亚油酸等不饱和脂肪酸接近母乳脂肪；添加婴儿成长发育需要的DHA(二十二碳六烯酸)、AA酸(花生四烯酸)后利用微胶囊技术，采用乳糖(或D90脱盐乳清粉)或糊精、酪蛋白等壁材，经过乳化、均质、喷雾造粒干燥生产婴儿配方奶粉专用仿母乳奶油粉。结果表明，仿母乳奶油粉与牛奶粉和其他营养组分均匀混合(干法)生产婴儿配方奶粉，营养成分及性能与母乳接近，弥补了牛奶粉营养成分的某些不足。仿母乳奶油粉油脂富含亚油酸，赋予了产品更好的流动、乳化和溶解性。     

Effects of buttermilk powders on emulsification properties and acid tolerance of cream

Emulsifying properties and acid tolerance are 2 of the most important characteristics of cream. The effects of the buttermilk component, especially its phospholipids, on the emulsifying properties and acid tolerance of cream were investigated in this study. Two buttermilks with differing phospholipid contents and skimmed milk were used to evaluate the effects of phospholipids on the aforementioned parameters. The mean diameter of fat globules and the cream viscosity were used as indicators of emulsifying properties. Acid tolerance was evaluated by studying the effect of citric acid on the maximum viscosity of cream. This was tested by adding 400 μL of 10% (w/w) citric acid solution to cream every minute and simultaneously measuring pH and viscosity. In 45% and 40% fat cream systems, buttermilk, and especially that with higher phospholipid content, improved the emulsifying properties and acid tolerance of the cream. The components of buttermilk could alter the properties of the surface of fat globules, thereby altering the emulsification properties of the cream. However, neither of the tested buttermilks affected the emulsifying properties and acid tolerance of lower-fat (35% and 30%) cream systems. Emulsifying components exist in proportionately larger amounts in lower-fat creams, which could render the emulsifying properties resistant to change. The number of fat globules may also influence acid-induced changes in viscosity. The addition of phospholipids or lysophospholipids did not improve the acid tolerance of creams, a finding that may be attributable to the formation of complexes of phospholipids and protein. PRACTICAL APPLICATION: The findings presented herein demonstrate the ability to improve the acid tolerance of cream using materials derived from milk. Implementing these findings appropriately may result in a high-quality cooking cream.     

大豆多酚氧化酶、过氧化物酶的酶学特性研究

对大豆氧化还原酶系中的多酚氧化酶和过氧化物酶的酶学特性进行了较深入系统地研究,其中包括酶活力、酶热稳定性、pH值的影响,以及大豆卵磷脂、二巯基丙醇对酶活力的抑制作用.结果表明多酚氧化酶在120℃时,酶活力值已达到不可逆失活状态,pH6～7时酶活力最大,当二巯基丙醇的浓度为1.5mmol/L时其酶活力降至6%以下.过氧化物酶具有较高的耐热性,酶活力最适的pH值为5.5左右,大豆卵磷脂浓度达到80mg/L时其酶活力可降至20%左右.     

磺化大豆磷脂的结构和性能研究(Ⅰ)--磺化大豆磷脂的结构解析和理化性能

通过对磺化大豆磷脂SPS这种新型阴离子表面活性剂的化学和仪器分析 ,探明SPS中活性基团的种类、数量、部位及不同SO3 结合量对其表面张力、渗透力、乳化力等理化性能的影响 ,确定了SPS的结构与理化性能的关系。     

Interactions between whey protein or polymerized whey protein and soybean lecithin in model system

Soybean lecithin is often used as a surfactant in food formulation. The aim of this study was to investigate the interactions between soybean lecithin (SL, 0–3%, wt/vol) and whey protein (WP, 10%, wt/vol) or polymerized whey protein (PWP, 10%, wt/vol) induced by heating WP solutions at 85°C for 0 to 20 min at pH 7.0. The samples were evaluated for zeta potential, particle size, morphology, rheological properties, thermal properties, secondary structure, and surface hydrophobicity. Zeta potential of WP increased linearly as SL level increased from 0 to 3%, whereas that of PWP changed with plateau at SL level of 1%, which may be due to the aggregation of SL. The addition of SL increased the particle size and apparent viscosity of both WP and PWP. All the samples exhibited different morphology depending on SL level and heating time according to transmission electron microscopy images. Whey protein showed obviously decreased gelation time and increased storage modulus in the presence of SL. Differential scanning calorimetry curves confirmed the effects of SL on the thermal properties of both WP and PWP. Circular dichroism spectra indicated that SL had effects on the secondary structure of both WP and PWP. The changes in surface hydrophobicity indicated the hydrophobic interactions between WP/PWP and SL. Data indicate that the physicochemical and functional properties of WP and PWP can be altered by adding soybean lecithin.     

Effects of homogenisation conditions on the physical properties of high-fat ice cream

The effect of homogenisation pressure on the physical properties of high-fat ice cream was investigated. Nonhomogenised ice cream was hard, with low resistance to meltdown, and ice crystals grew rapidly therein. Fat globule networks were not formed in the nonhomogenised ice cream. The ice cream homogenised at 5 MPa or more was harder and showed a higher resistance to meltdown. Ice crystals in the ice cream homogenised at 5 MPa or more grew slowly. The physical properties of each ice cream varied with homogenisations from 5 to 25 MPa and could be controlled by homogenisation pressure.     

大豆浓缩磷脂设备与工艺探讨

通过研究在工业条件下,如何利用水化豆油的油脚加工浓缩大豆磷脂,详细介绍了大豆磷脂的生产工艺过程,并对生产过程中的工艺条件控制进行了逐一的分析论述,同时对关键生产设备和操作安全注意事项进行了重点描述。     

大豆分离蛋白与大豆磷脂比例对超声乳化亚麻籽油乳液特性的影响

适宜的乳化剂组成对于乳液的特性及稳定性有重要的影响。为超声乳化制备稳定的亚麻籽油乳液,以大豆分离蛋白（SPI）和大豆磷脂（SLT）为乳化剂,亚麻籽油为油相制备O/W乳液,研究SPI与SLT比例对亚麻籽油乳液特性的影响,从乳液的微观结构、水合平均粒径、多分散指数、ζ-电位、分层稳定性、表观黏度及低场核磁共振弛豫特性等方面进行了比较。结果表明,随着SPI与SLT比例从3∶ 1减小至1∶ 3,乳液的水合平均粒径增大,多分散指数先减小后增大,ζ-电位绝对值、乳层析指数及表观黏度总体增大,且T2弛豫图谱右移,体系中氢质子所受的束缚力减小。当SPI与SLT比例为1∶ 1时,乳液的多分散指数最低（0.07±0.07）且粒径呈单峰分布,ζ-电位绝对值较高,乳层析指数较低,同时体系中氢质子所受的束缚力较大,表观黏度较大,说明所形成的亚麻籽油乳液体系更为均匀、稳定。     

Effects of fermentation by Bifidobacterium bifidum on the rheology and physical properties of ice cream mixes made with cow and vegetable milks

Fermented and nonfermented probiotic ice creams were made by incubating Bifidobacterium bifidum (Bb‐12) culture in ice cream mixes with cow, soya, coconut and composite milks (combinations of coconut or cow milks with soya milk). The changes in ice cream‐eating qualities and physical properties (melting rate, apparent viscosity, hysteresis, fat globule size, zeta potential, microscopic structure and freezing behaviour) were evaluated. In general, fermentation decreased the melting rate and total acceptability of ice creams but increased the apparent viscosity, hysteresis, particle size and freezable water. For fermented ice creams containing composite milk, those containing cow milk showed a higher percentage change than those containing coconut milk in respect of hysteresis, particle size and freezable water; however, the apparent viscosity was not affected.     

新鲜奶油中黄嘌呤氧化酶的纯化及其酶学性质

采用正丁醇处理、硫酸铵沉淀、凝胶过滤层析和阴离子交换层析等分离技术,从新鲜的稀奶油中纯化得到SDS-PAGE电泳纯的黄嘌呤氧化酶,其最终回收率为19.9%,纯化倍数为82.42,酶比活为8.65U/mg。该黄嘌呤氧化酶的相对分子质量约为280kDa,最适作用温度为40℃,在35℃以下比较稳定;最适pH值是8.5,在pH6.5～8.5时较稳定;Zn2+、Fe2+和K+对黄嘌呤氧化酶活性有促进作用,Ag+、Mn2+、Ca2+和SDS对黄嘌呤氧化酶活性有抑制作用。     

Recovered Camellia oleifera lecithin by acid and enzymatic oil-degumming: chemical composition and emulsifying properties

In this study, the chemical composition and emulsifying properties of camellia lecithin recovered from crude camellia oil by both acid and enzymatic degumming were investigated. Camellia lecithin recovered from acid degumming (CLAD) mainly comprised phospholipids (PS, PI, PE and PA), whereas camellia lecithin recovered from enzymatic degumming (CLED) contained more lysophospholipids (LPI, LPE, LPA). The saturated fatty acids made up a large portion of total fatty acids in CLED compared to CLAD. CLED-stabilised emulsions tended to be more stable than CLAD-stabilised emulsions. Meanwhile, emulsions stabilised by CLED exhibited smaller particle size in agreement with their microstructures. Moreover, both CLED and CLAD-stabilised emulsions were sensitive to pH and ionic strength changes and provided smaller particle size and higher stability at pH = 7 and 1 mm NaCl concentration. These findings provide valuable information for potential applications of camellia lecithin with characteristic phospholipid composition as alternative o/w emulsifiers in food industry.     

大豆油酶法脱胶与吸附脱酸工艺的优化研究

本研究以大豆毛油为原料,采用酶法脱胶和物理脱酸法对其进行精炼处理。通过单因素实验和正交实验进行工艺优化,以获得合适的大豆油精炼条件。结果表明：采用磷脂酶C酶法脱胶的最佳工艺条件为pH 5.4,酶添加量10.0 μL/kg,酶解温度45.0 ℃。在此条件下,大豆毛油磷含量可降低至7.3 mg/kg;最佳的脱酸工艺条件为保温时间40.0 min、加水温度90.0 ℃、加水量3.5%、絮凝剂量0.7%,此条件下大豆油酸值为0.08 mg/g,磷含量为5.5 mg/kg。大豆毛油经酶法脱胶和物理脱酸处理后的磷含量和酸价显著降低,品质提高。实验结果为大豆油的非化学精炼提供了依据。     

大豆卵磷脂对超级棕榈液油氧化稳定性的影响

分析了不同比例大豆卵磷脂加入到超级棕榈液油中油脂过氧化值的变化情况,以期研究大豆卵磷脂在超级棕榈液油中的抗氧化性能。采用Schaal烘箱加速氧化法研究了大豆卵磷脂对超级棕榈液油过氧化值的影响;根据Arrhenius经验公式,推测其保质期;并利用Rancimat法测试氧化诱导期。研究表明:大豆卵磷脂对超级棕榈液油的抗氧化能力有剂量效应关系,随着大豆卵磷脂浓度的增加,体系反应活化能增加,氧化反应速率降低,与空白油样相比,添加1.00%大豆卵磷脂,其体系的反应活化能增加5.84 k J/mol。根据推测的公式计算出20℃下,体系初始过氧化值为1 meq/kg时的保质期,添加1.00%大豆卵磷脂,超级棕榈液油的保质期可以增加7个月。根据诱导期计算抗氧化系数,其值介于1~2之间,说明大豆卵磷脂具有较好的抗氧化能力,是一种优良的天然抗氧化剂。      

Effect of substituting whey cream for sweet cream on the textural and rheological properties of cream cheese

In the manufacture of cream cheese, sweet cream and milk are blended to prepare the cream cheese mix, although other ingredients such as condensed skim milk and skim milk powder may also be included. Whey cream (WC) is an underutilized fat source, which has smaller fat droplets and slightly different chemical composition than sweet cream. This study investigated the rheological and textural properties of cream cheeses manufactured by substituting sweet cream with various levels of WC. Three different cream cheese mixes were prepared: control mix (CC; 0% WC), cream cheese mixes containing 25% WC (25WC; i.e., 75% sweet cream), and cream cheese mixes with 75% WC (75WC; i.e., 25% sweet cream). The CC, 25WC, and 75WC mixes were then used to manufacture cream cheeses. We also studied the effect of WC on the initial step in cream cheese manufacture (i.e., the acid gelation process monitored using dynamic small amplitude rheology). Acid gels were also prepared with added denatured whey proteins or membrane proteins/phospholipids (PL) to evaluate how these components affected gel properties. The rheological, textural, and sensory properties of cream cheeses were also measured. The WC samples had significantly higher levels of PL and insoluble protein compared with sweet cream. An increase in the level of WC reduced the rate of acid gel development, similar to the effect of whey phospholipid concentrate added to mixes. In cream cheese, an increase in the level of added WC resulted in significantly lower storage modulus values at temperatures <20°C. Texture results, obtained from instrumental and sensory analyses, showed that high level of WC resulted in significantly lower firmness or hardness values and higher stickiness compared with cream cheeses made with 25WC or CC cream cheeses. The softer, less elastic gels or cheeses resulting from the use of high levels of WC are likely due to the presence of components such as PL and proteins from the native milk fat globule membrane. The use of low levels of WC in cream cheese did not alter the texture, whereas high levels of WC could be used if manufacturers want to produce more spreadable products.     

大豆卵磷脂的分离纯化研究进展

本文介绍了大豆卵磷脂的结构、性质，功能，综述了国内外对大豆卵磷脂的提纯方法，分别对规模生产大豆卵磷脂纯化方法的研究和高纯大豆卵磷脂纯化方法的研究作了展望。     

Effects of dietary deoiled soy lecithin supplementation on milk production and fatty acid digestibility in Holstein dairy cows

Deoiled soy lecithin is a feed additive enriched in phospholipids. Our study evaluated the effects of dietary deoiled soy lecithin supplementation on (1) milk production and composition, (2) plasma and milk fatty acid (FA) content and yield, and (3) apparent FA digestibility and absorption in lactating dairy cows fed fractionated palm fat. In a split-plot Latin square design, 16 Holstein cows (160 ± 7 days in milk; 3.6 ± 1.2 parity) were randomly allocated to a main plot receiving a corn silage and alfalfa haylage-based diet with palm fat containing either moderate (MPA) or high palmitic acid (HPA) content at 1.75% of ration dry matter (72 or 99% palmitic acid, respectively; n = 8/palm fat diet). On each palm fat diet, deoiled soy lecithin was top-dressed at 0, 0.12, 0.24, or 0.36% of ration dry matter in a replicated 4 × 4 Latin square design. Following a 14-d covariate period, lecithin supplementation spanned 14 d, with milk and blood collected during the final 3 d. Milk composition and pooled plasma markers were measured. The statistical model included the fixed effects of palm fat type, lecithin dose, period, and the interaction between palm fat type and lecithin dose. The random effect of cow nested within palm fat group was also included. Lecithin linearly decreased dry matter intake. In cows fed HPA, lecithin feeding reduced milk fat content and tended to decrease milk fat yield. Although no changes in milk yield were observed, a quadratic reduction in 3.5% fat-corrected milk was observed with increasing lecithin dose. Lecithin linearly increased energy-corrected milk efficiency in cows fed MPA. Lecithin supplementation also decreased milk urea nitrogen, relative to unsupplemented cows. The proportion of 16-carbon FA in milk fat decreased linearly with lecithin dose, whereas 18-carbon FA increased linearly. Lecithin reduced de novo FA (<16-carbon) content and tended to increase preformed FA (>16-carbon) content in a linear manner. Compared with MPA, HPA diets reduced apparent total and 16-carbon FA digestibility and absorption. Deoiled soy lecithin feeding did not modify FA digestibility or absorption. Our observations suggest that soy lecithin feeding modifies rumen digestion to reduce dry matter intake and change milk composition.