Semi-preparative isolation of phosphopeptides derived from bovine casein and dephosphorylation of casein phosphopeptides

Semi-preparative isolation of casein phosphopeptides (CPP) from a tryptic hydrolysate of bovine casein was performed applying a three-step procedure consisting of solid phase extraction, reversed phase HPLC and ion exchange chromatography. Dephosphorylation of CPP was achieved using immobilized alkaline phosphatase. The purified phosphopeptides and their dephosphorylated forms obtained by these methods are suitable for comparative studies on biological activities, especially mineral binding and immunmodulation.     

The ultrasonic properties of skim milk related to the release of calcium from casein micelles during acidification

Milk samples were acidified with different amounts of glucono-δ-lactone (GDL) and samples of permeates were collected rapidly by ultrafiltration at intervals during acidification. Calcium contents of these sera were measured to define the extent and rate of dissociation of micellar calcium phosphate. In parallel samples, measurements were made of the ultrasonic velocity and the ultrasonic attenuation of milks and permeates. This allowed the establishment of a complete profile of the changing mineral distribution of milk and changes in ultrasonic properties, as functions of pH. The results showed that changes in both of ultrasonic parameters depended almost completely on changes in composition of milk serum, and that states of casein micelles made little contribution. This makes ultrasound an excellent method for following the release of calcium and the progress of acidification in milks.     

Microdetermination of phosphorus from infant formulas, casein and casein phosphopeptides

A spectrophotometric method, which has been proposed for the determination of phosphorus in biological fluids based on the formation of a phosphomolybdate complex, is adapted and validated for the determination of phosphorus in milk-based infant formulas, casein, casein phosphopeptides (CPPs) and the soluble fractions resulting from their gastrointestinal digestion, as well as in the fractions resulting from the ion-exchange high-performance liquid chromatography (IE-HPLC) of CE90CPP and in the soluble fraction of infant formula. The detection and quantification limits (1.1 and 3.6 mg P/100 g sample, respectively) are low enough for the purpose described. The linearity (from 0.1 to 8 g of phosphorus in the assay) is adequate. The precision of the method, expressed as relative standard deviation, is lower than 1%, and the accuracy checked by the analysis of SRM 1846: milk-based powdered infant formula is good. The quality of the method, together with the low cost and ease of use, makes it suitable for routine analysis.     

复配粉理化性质与米线质构性质关系的研究

将粳米粉与绿豆淀粉按照一定比例进行混合,得到粳米粉和绿豆淀粉的复配粉体系,并测定了复配粉体系的溶胀性质、糊化性质、凝胶质构性质和拉伸性质,研究了复配米粉体系的拉伸性质与米线质构性质的关系。结果表明:随着绿豆淀粉添加量比例的增加,复配米粉体系的总直链淀粉含量、可溶性直链淀粉含量和不溶性直链淀粉含量明显增加,峰值黏度、谷值黏度、末值黏度、硬度也显著性增加,咀嚼性、拉伸强度和表观弹性模量显著增加,85℃下的溶解度和膨润力显著上升;糊化温度显著降低;衰减值和回生值分别比粳米粉高了33.73 RVU和50.60 RVU;与单一体系相比,由复配粉体系制成的米线呈现较好的硬度、弹性、韧性、蒸煮性和物理性质。当绿豆淀粉∶粳米粉为1∶1时,其制得的米粉的质构性质最好。     

Effect of casein phosphopeptides on bioavailability of the alimentary minerals

Caseinophosphopeptides (CPPs) are phosphorylated casein-derived peptides which possess the ability to bind and solubilise minerals, such as Ca2+. The high bioavailability of Ca2+ fram milk and dairy products has been attributed to the production of CPPs which are produced following digestion of casein by the action of gastrointestinal proteinases. CPPs, which appear to be resistant to extensive proteolytic degradation, accumulate in the distal small intestine where they are purported to play a role in enhancing the passive absorption of Ca2+ and other trace elements. A recent human feeding tral reported improved Ca2+ and Zn2+ absorption following CPPs incorporation into food. This review summarises the production, characterization and potential applications of CPPs.     

不同水解度酪蛋白磷酸肽的理化性质和持钙能力比较

目的 研究不同水解度(degree of hydrolysis, DH)酪蛋白磷酸肽(casein phosphopeptide, CPP)的理化性质和持钙能力。方法 实验室自制得到水解度分别为4.32%～26.76%的CPP样品,分别测定CPP含量[高效液相色谱法(high performance liquid chromatography, HPLC)和钡-乙醇沉淀法]、等电点不溶物含量、相对分子质量分布和持钙能力。结果 随着水解度的上升,通过HPLC测定的CPP标志峰的峰面积随之增加,等电点不溶物含量随之减少,而通过钡-乙醇沉淀法得到的CPP含量无明显变化,可将等电点不溶物含量作为评价产品质量的指标;目前的相对分子质量分布检测方法对不同水解度的CPP样品检测误差较大,需使用酸溶蛋白含量作为校正系数进行校正后方可使用;当CPP的质量浓度为0.6～0.8mg/mL时,水解度为9.22%和15.06%的CPP的持钙能力效果优于其他水解度的CPP。结论 水解度对酪蛋白磷酸肽的理化性质和持钙能力有明显的影响,在实际应用时应选用合适的水解度和检测方法。     

Physicochemical and functional properties of whole legume flour

The physicochemical, functional and pasting properties of whole flours from pinto bean, lima bean, red kidney bean, black bean, navy bean, small red bean, black eye bean, mung bean, lentil and chickpea were investigated. Significant differences in physicochemical characteristics and functional properties were observed (P < 0.05). Bulk densities, water absorption indices, water solubility indices, oil absorption capacities, emulsion activities, and emulsion stabilities ranged from 0.543 g/mL to 0.816 g/mL, 4.09 g/g to 6.13 g/g, 19.44 g/100 g to 29.14 g/100 g, 0.93 g/g to 1.38 g/g, 61.14%–92.20%, and 84.15%–96.90%, respectively. Phaseolus legume flour exhibited higher water absorption capacity, oil absorption capacity, emulsion activity, and emulsion stability compared with other kinds of legume flour. Pasting properties were significantly different (P < 0.05). Pasting temperatures and the peak, final, and setback viscosities of the flours ranged from 73.2 °C to 83.0 °C, 96.2 RVU to 216.8 RVU, 118.5 RVU to 243.8 RVU, and 28.3 RVU to 103.2 RVU, respectively.     

Cytochemical assessment of phosphopeptides derived from casein as potential ingredients for functional food

Phosphopeptides derived from casein hydrolysis are suggested to have beneficial effects beyond their mere nutritive value by enhancing availability of dietary minerals, especially calcium, iron and zinc. Apart from a possible positive action the potential may exist for adverse effects that could impose restrictions to their widespread application in functional foods for human nutrition. In the present work, various case-inophosphopeptide (CPP) preparations were assessed using different human cell culture model systems in order to estimate their cytotoxic potential and their influence on epithelial properties and differentiation of human intestinal cells (Caco-2). The general cytotoxic potential of CPPs was tested using the AlphaTox NR assay. Structural and functional differentiation of intestinal Caco-2 cells was determined by measuring transepithelial electrical resistance and activity of brush border associated alkaline phosphatase over an extended cultivation period. No loss in cell viability with respect to membrane integrity could be detected, as uptake and retention of neutral red dye (AlphaTox assay) into HeLa cells was not affected by the presence of CPPs. Cytochemical assays conducted on epithelial cells (Caco-2) showed no disturbance of normal cell development and differentiation with respect to structural as well as functional differentiation markers. As all CPPs tested did not provoke any adverse effects in terms of cytotoxicity and showed no impairment of cell differentiation and monolayer integrity of human intestinal cells, it may be supposed that CPPs do not provoke a cytotoxic response in vivo in the cells assayed in the present study.     

响应曲面法优化酪蛋白磷酸肽的制备

采用Plackett-Burman设计法和响应面分析法相结合,以CPP（酪蛋白磷酸肽）得率作为指标,进行碱性蛋白酶水解酪蛋白的条件优化。结果表明,底物浓度、温度和pH是影响CPP得率的主要因素。最佳水解条件为温度55℃、底物浓度16%、pH10.8、酶底比1.5%,水解时间4.5h,在此条件下,CPP得率可达33.2mg/mL。      

全谷物脱脂酸牛奶的理化性质及流变学特性研究

为了获得富含益生菌和益生元的健康酸牛奶产品,该文应用益生菌发酵剂XPL-1和068发酵添加了全谷物粉的脱脂牛奶,并研究其理化性质和流变学特性,同时分析保质期内酸牛奶中乳酸菌数的变化情况。结果表明,全谷物粉的添加可提高脱脂酸牛奶的持水力以及产品的柔软性、光滑细腻程度和流动性,总体可接受性明显提升;此外,在保质期内全谷物酸牛奶样品中的活菌数均稳定在108 CFU/g以上。研究结果为全谷物脱脂酸牛奶的开发应用奠定了理论基础。     

Optimisation of experimental conditions for binding of divalent iron to bioactive casein phosphopeptides

Casein phosphopeptides (CPPs) are mineral‐binding bioactive peptides derived from enzymatic digestion of casein. They have been shown to increase iron bioavailability due to increasing iron solubility at the alkaline pH of the intestine. Thus, they are potentially applicable as an advantageous preparation for iron fortification of food. This study aimed to characterise a commercially available CPP and determines optimum experimental conditions for binding it with ferrous iron. The effect of three variables – pH (5–7.5), mass ratio of iron to CPP (MR) (0.04–0.16) and holding time (40–80 min) – on the CPP's iron content was investigated using the central composite design (CCD) in response surface methodology (RSM), and a quadratic model was developed. The optimisation in this survey was based on the maximum response. Among all the regression's terms, the main and quadratic effects of pH represented the most significant influences on the iron content (P‐value <0.05). The obtained optimum conditions were as follows: pH 6.5, MR 0.14 and holding time 72 min, resulting in binding 68.66 mg iron per gram of the CPP. The quantity of iron bound to the CPP depended considerably on the experimental conditions and proved the importance of optimisation.     

牦牛与奶牛酪蛋白制备CPPs的酶工艺优化及其离子交换纯化研究

优化了以牦牛酪蛋白与奶牛酪蛋白为原料酶法制备酪蛋白磷酸肽（CPPs）的工艺条件，并评估了离子交换对CPPs粗制品的纯化效果。结果表明，牦牛酪蛋白与奶牛酪蛋白的产率最优化条件以及氮磷比r（N／P）最优化的酶解工艺条件均基本一致，产率最大的胰蛋白酶酶解工艺条件为：底物浓度13．1％，酶解反应时间104min，酶底物浓度比0．9％；r（N／P）最优（小）的酶解工艺条件为：底物浓度7．6％，酶解反应时间155min，酶底物浓度比1．2％。牦牛及奶牛CPPs粗制品经过阴离子交换树脂纯化后，所获得的精制CPPs其，（N／P）均明显降低，对于CPPs的产率最优样品其，（N／P）由原来的12．2～12．4降低到6．3～6．9；对于r（N／P）最优样品，其r（N／P）由原来的9．90～0．95进一步降低至5．6～5．8。研究表明：无论以产率或制品质量为优化指标，牦牛与奶牛酪蛋白的酶解工艺优化条件基本一致。而且利用阴离子交换树脂处理可以有效地降低CPPs粗制品的r（N／P）、提高制品的质量。     

Physicochemical properties of whole soybean curd prepared by microbial transglutaminase

Whole soybean curd (WSC) was manufactured using micronized full-fat soybean (MFS) powder and microbial transglutaminase (TGase). The WSC prepared with 15% MFS had typical soybean curd texture with a hardness of 513 dyne/cm². It was confirmed that 7S and 11S protein fractions as major soy proteins disappeared in SDS-PAGE. Also, WSC prepared with 15% MFS and 10% TGase had excellent textural properties with a hardness of 645 dyne/cm² and springiness of 0.98. Addition of 0.5% gelatin in WSC prepared with 15% MFS and 5% TGase resulted in higher hardness (708 dyne/cm²) and springiness (0.98), as well as the highest values of G′ and G″. The surface properties of WSC were observed using a SEM, indicating the interrelationship of higher hardness and compact protein network filled with small cells. It was concluded that WSC prepared after heat treatment of 15% MFS at 95°C for 5 min, followed by an enzyme reaction with 10% TGase for 1 h, had more enhanced hardness and springiness than commercial WSC. Despite the addition of 5% TGase, WSC with improved textural properties can be manufactured by the fortification of 0.5% gelatin.     

Physicochemical properties related to long-term phosphorus retention by drinking-water treatment residuals

Drinking-water treatment residuals (WTRs) are nonhazardous materials that can be obtained free-of-charge from drinking-water treatment plants to reduce soluble phosphorus (P) concentrations in poorly P sorbing soils. Phosphorus sorption capacities of WTRs can vary 1-2 orders of magnitude, on the basis of short-term equilibration times (up to 7 d), but studies dealing with long-term (weeks to months) P retention by WTRs are lacking. Properties that most affect long-term P sorption capacities are pertinent to the efficacy of WTRs as amendments to stabilize P in soils. This research addressed the long-term (up to 80 d) P sorption/desorption characteristics and kinetics for seven WTRs, including the influence of specific surface area (SSA), porosity, and total C content on the overall magnitude of P sorption by seven WTRs. The data confirm a strong but variable affinity for P by WTRs. Aluminum-based WTRs tended to have higher P sorption capacity than Fe-based WTRs. Phosphorus sorption with time was biphasic in nature for most samples and best fit to a second-order rate model. The P sorption rate dependency was strongly correlated with a hysteretic P desorption, consistent with kinetic limitations on P desorption from micropores. Oxalate-extractable Al + Fe concentrations of the WTRs did not effectively explain long-term (80 d) P sorption capacities of the WTRs. Micropore (CO2-based) SSAs were greater than BET-N2 SSAs for most WTRs, except those with the lowest (<80 g kg(-1)) total C content. There was a significant negative linear correlation between the total C content and the CO2/N2 SSA ratio. The data suggest that C in WTRs increases microporosity, but reduces P sorption per unit pore volume or surface area. Hence, variability in C content confounds direct relations among SSA, porosity, and P sorption. Total C, N2-based SSA, and CO2-based SSAs explained 82% of the variability in the long-term P sorption capacities of the WTRs. Prediction of long-term P sorption capacities for different WTRs may be achieved by taking into account the three proposed variables.     

Influence of bovine and caprine casein phosphopeptides differing in alphas1-casein content in determining the absorption of calcium from bovine and caprine calcium-fortified milks in rats

Bovine and caprine milks have a similar overall gross composition, but vary considerably in the ratios of their casein components. These differences cause significant changes in the ability of caseins to bind and stabilize calcium (Ca). It might be expected that these in vitro variations, which are thought to be due to differences in casein phosphopeptides (CPP) content, could lead to in vivo differences in the digestion and absorption of Ca. To test this hypothesis three milks with different casein ratios [bovine (B), caprine high in alphas1-casein (CH) and caprine low in alphas1-casein (CL)] were compared with regard to Ca absorption and deposition in growing male rats. For comparison, each milk was Ca-fortified (BCa-milk, CHCa-milk, and CLCa-milk) and CPP, prepared by enzymatic hydrolysis from the respective caseins (extrinsic CPP), were added to both native and Ca-milks. The effects of added CPP (extrinsic) could then be compared with intrinsic CPP released from the gastrointestinal digestion of caseins. Total gastric Ca was sampled at 15, 30 and 60 min after ingestion. No differences were found among the native milks with or without CPP, but the Ca from all Ca-milks (regardless of casein type) appeared to clear the stomach more rapidly and this was enhanced by the extrinsic CPP. The total intestinal Ca was not different among the native milks+/-CPP, however, it rose more rapidly with Ca fortification, and was higher at 30 min for all CPP-Ca-milks. At 60 min the total intestinal Ca level fell for the CPP-Ca-milks while all others continued to rise. These observations suggest that the CPP in Ca-milks enhance gastric clearance and uptake from the intestine. Ca availability from BCa-milk, CHCa-milk, and CLCa-milk with and without CPP was estimated by both plasma and femur uptake of 45Ca. Ca availability was enhanced at 5 h in the plasma in each case by added CPP. In all cases CPP stimulated Ca availability in the femur, but the CL-CPP was higher (P<0.05) than that of either CH-CPP or B-CPP (extrinsic CPP). Based on the results of this study we can conclude that the addition of CPP will have beneficial effect on the absorption of Ca in growing rats from CaCO3 added to bovine and caprine milks.     

Physicochemical properties of whole milk powder derived from cows fed pasture or total mixed ration diets

This study examined the effect of dietary factors on compositional and functional properties of whole milk powder (WMP) produced from bovine milk. Raw milk samples were obtained from 3 groups of 18 Holstein Friesian spring-calving cows randomly assigned to diets based on perennial ryegrass (GRS), perennial ryegrass/white clover sward (CLV), and total mixed ration (TMR). Raw milks obtained in late lactation were subsequently standardized for fat, heat-treated (90°C for 30 s), evaporated, and homogenized before spray drying. The WMP produced from each diet were analyzed to determine differences in color, particle size distribution, heat coagulation time, yogurt gelation, texture profile, and protein profile due to each diet. Significant differences in heat coagulation time were observed between the CLV and TMR samples, whereas color values were significantly different between GRS and TMR samples. No significant differences in gross composition, protein profile, or whey protein nitrogen index were found between the 3 WMP samples. Average D₉₀ values (the particle size at which 90% of the particles were smaller than the specified size) for fat globules were significantly lower in the TMR sample compared with the GRS and CLV samples. Yogurts produced from GRS- and CLV-derived WMP had significantly higher elastic moduli (G′) than those produced from TMR-derived WMP. Similarly, texture profile analysis revealed significantly higher firmness values in yogurt samples derived from CLV compared with TMR samples. Our data characterize the effect of these diets on the composition and functional properties of fat-standardized WMP, suggesting better yogurt functionality and thermal stability in WMP derived from pasture-based bovine diets.     

紫茉莉籽淀粉的物化特性研究

以紫茉莉籽为原料提取淀粉,研究其物化特性,并与玉米、马铃薯、绿豆等淀粉进行比较,为紫茉莉籽的应用提供一定的依据。采用物理化学方法、以流变仪、质构仪等研究了紫茉莉籽淀粉的直链淀粉含量、糊透明度、溶解率、膨胀势、冻融稳定性、糊化特性、流变特性和质构特性。结果表明:紫茉莉籽淀粉的直链淀粉含量为23.6%,与玉米淀粉相当(23.7%),显著低于马铃薯淀粉(28.5%)和绿豆淀粉(37.1%);紫茉莉籽淀粉糊透明度、溶解率和膨胀势分别为0.6%、2.3%和9.1%,均小于其他三种淀粉,且其冻融稳定性最差。紫茉莉籽淀粉的糊化温度最大,为73.8℃;显著高于马铃薯淀粉和绿豆淀粉;紫茉莉籽淀粉两浓度下(6%和8%)的峰值黏度、保持黏度、最终黏度、降落值和回生值均小于其他三种淀粉,且降落值较小(0.01Pa·s),回生值/峰值黏度较大;紫茉莉籽淀粉流变指数为0.724和0.738,属于假塑性流体,且呈现剪切稀化现象。紫茉莉籽淀粉的凝胶强度略大于马铃薯淀粉;但其硬度、弹性、黏聚性、胶黏性、咀嚼性和回复性均小于其他三种淀粉。结论:紫茉莉籽淀粉颗粒不易吸水膨胀,糊化后透明度小,冻融稳定性差,黏度低,且不易形成凝胶。     

Physicochemical and functional properties of whole and defatted meals from Mexican (Cucurbita pepo) pumpkin seeds

Chemical composition and some functional and thermal properties in whole pumpkin seed meal (WPSM) and defatted pumpkin seed meal (DPSM) were determined. The DPSM exhibited higher water absorption capacity (3 g H₂O per g sample), water solubility capacity (8.75%), oil absorption capacity (2.73 g oil per g sample), emulsifying capacity (61.71%), foaming capacity (51.92%) and gelling capacity (12% w/v) than the WPSM. The DPSM also had better swelling power (3.33% at 60 °C, rising to 4.31% at 90 °C), higher phase transition temperatures (T₀ = 80.04 °C, T_p = 86.50 °C and T_f = 93.20 °C) and a higher phase transition energy (0.93 J g^?1). However, the WPSM had higher bulk density (0.57 g cm^?3) and better foam stability (from 30 to 120 min). Micrographs showed defatting to cause microstructural changes in meal starch granules and proteins. Its high protein content makes the DPSM a potential alternative input in the food industry.     

不同品种白果淀粉的理化性质研究

系统研究测定了不同品种白果淀粉的各种理化性质。结果表明,实验室碱法提取大圆铃、大梅核、佛指品种白果淀粉中直链淀粉含量分别为26.51%、31.82%与29.03%,淀粉碘复合物可见光吸收光谱的最大吸收波长为625nm,吸光度值排列大圆铃>大梅核>佛指。白果淀粉颗粒多呈椭圆的卵形,少数圆形,且偏光十字明显,颗粒粒径在5～20μm。淀粉的膨胀度和溶解度均随着温度升高而增加,三种淀粉的体外模拟消化曲线基本相似,佛指白果淀粉糊的透明度、冻融稳定性、凝沉性优于大梅核与大园铃白果淀粉糊。