考马斯亮蓝法测定野木瓜多糖中蛋白质的含量

采用考马斯亮蓝染色法对野木瓜多糖中蛋白质含量进行测定,在波长595 nm处测定吸光度,实验表明标准蛋白质在1.67μg/mL～16.67μg/mL之间呈现良好的线性关系,该法简便迅速,灵敏度高、重现性好,是测定野木瓜多糖中蛋白质含量的有效方法,并通过此法测得野木瓜多糖中蛋白质平均含量为12.17%.     

钛铁合金中钛含量测定方法的改进--过氧化氢光度法测定钛量

文章主要对过氧化氢光度法测定钛铁合金中钛量的方法进行了讨论。结果表明此法具有简单、快速、适用范围广等优点，而且准确度高，重现性好。     

紫外吸收光谱法测定猪肉中蛋白质的含量

用紫外吸收光谱测定法测定了猪肉中蛋白质的含量，与凯氏定氨法对照，二者无显著性差异，前者准确度较高，重现性好，简单方便。     

应用自动电位滴定技术改进凯氏定氮法

本文介绍应用自动电位滴定法改良凯氏定氮法中的滴定步骤，进行食品中蛋白质的测定，操作简便，重现性好，标准误差为０．１６％，回收率为１１１％，适用于众多样品连续测定。     

氧化亚铜还原杂多酸-磷钼酸钼蓝比色法测定食品还原糖的探讨

用氧化亚铜还原杂多酸—磷钼酸钼蓝比色法测定食品中的还原糖,设备简单操作快速,回收试验及重现性测定结果满意,其色泽稳定1小时不变。证明此法的引用是成功的。     

新型婴儿配方乳粉蛋白质消化性研究

采用动物消化性试验的方法对新型婴儿配方粉中的蛋白质质量进行评价,通过测定小鼠消化4 h内肠液内可溶性氨基氮水平来反应蛋白质的可消化性,并对处在肠消化高峰时的1 h小鼠肠液进行游离氨基酸分析。结果发现氨基酸母乳化新型婴儿配方乳粉的动物消化性良好,易于被小鼠消化吸收,新型婴儿配方粉3在消化时间为1 h时小鼠肠液内游离氨基酸含量与市售婴儿配方粉基本持平,说明新型婴儿配方粉提供的蛋白质消化吸收性较好,能作为婴儿优质蛋白质来源。     

氨气敏电极测氨基酸口服液中的总氮含量

采用ＰＳＸ－５数字型离子酸度计，５０１型氨气敏电极，在ｐｈ〉１２的条件下直接测定平衡电位值。由于电极电位的重现性较差，影响了分析的准确度，本实验采用了两点标准与样品同步进行测试的方案，与回归曲线相配合，可快速、简便、精确地测定氨基酸口服液中总氮含量，此法的准确度和精密度都较为理想。     

分光光度法测定粮食中蛋白质含量

报告了采用分光光度法，以过氧化氢─硫酸快速消解测定粮食中蛋白质含量，同传统的凯氏定氮法相比，具有操作简便，快速省时，设备简单的特点。经ｔ值检验，Ｐ＞０．０５，准确度高，重复测定ＣＶ％＝１．３６，重现性好，有一定的实用价值，便于推广。     

分光光度法测定粮食中蛋白质含量

报告了采用分光光度法，以过氧化氢－硫酸快速消解测定粮食中蛋白质含量，同传统的凯氏定氮法相比，具有操作简便，快速省时，设备简单的特点。经ｔ值检验，Ｐ＞０．０５，度高，重复测定ＣＶ％＝１．３６，重现性好，有一定的实用价值，便于推广。     

苯酚-硫酸法测定野木瓜中多糖含量的研究

采用苯酚-硫酸法对野木瓜中的多糖含量进行测定,在波长490nm处测定吸光度,实验表明标准葡萄糖在8～64μg之间呈良好的线性关系,该法简便易行,准确性高,重现性好。本文探讨了测定过程的影响因素,并通过此法测得野木瓜中多糖含量为12．02%。     

国内外婴幼儿食品中蛋白质质量评价方法的对比研究

婴幼儿食品中蛋白质的质量直接影响着婴幼儿的健康成长.本文论述了目前国内外婴幼儿食品中蛋白质质量的评价方法,主要对数值评价、消化率评价、生物学评价和氨基酸评价4类方法进行对比分析,结果表明:用蛋白质消化率校正的氨基酸记分法(PDCAAS)是各种方法中相对较完善的方法.本研究结果对促进我国婴幼儿食品品质的鉴定、新的食品资源的研究和开发以及婴幼儿合理膳食指导具有重要的意义.     

True ileal amino acid digestibility of goat and cow milk infant formulas

Goat milk is used as an alternative to cow milk for the production of infant formulas. However, little is known about the protein quality and, specifically, about the digestible AA pattern of goat milk formulas compared with their cow milk counterparts. In this study, the true ileal AA digestibility of a goat milk infant formula was compared with a premium cow milk infant formula. The 3-wk-old piglet was used as a model for the 3-mo-old infant. Both milk formulas were prepared as described by the manufacturer, with titanium dioxide added as an indigestible marker. The formulas were fed to the piglets over a 2-wk trial period. Digesta from the terminal ileum were collected post euthanasia and analyzed for AA content, along with samples of the formulas. True AA digestibility was determined after correcting for endogenous AA loss at the terminal ileum of pigs fed an enzyme-hydrolyzed casein-based diet, followed by ultrafiltration (5,000 Da) of the digesta. Total urine and feces collection was also undertaken to determine the nitrogen retention from the diets. The true ileal AA digestibility was similar between the goat and cow milk infant formulas for all AA except Gly and Trp. There was no significant difference in the nitrogen retention of piglets fed the two different formulas. The goat milk infant formula and the premium cow milk infant formula were similar in terms of protein quality.     

Enzyme Diafiltration Technique for In Vitro Determination of Protein Digestibility and Availability of Amino Acids of Legumes

In vitro protein digestibility determined by peptic hydrolysis in a diafiltration reactor gave values comparable to the published in vivo digestibility data in 16 samples from both animal and plant sources. The in vitro technique is easier to perform and the reproducibility is greater than that reported for in vivo rat assays. A high performance liquid chromatographic method was modified to determine the amino acids in the pepsin hydrolysates. The amino acid content of nine samples were compared to the FAO-WHO (1973) reference protein standard and the geometric mean of the essential amino acid content were compared with values for Protein Efficiency Ratio (PER), Net Protein Utilization (NPU), and Biological Value (BV). The geometric mean was most closely related to the NPU value with a correlation coefficient of 0.96.     

Protein Concentrate from Chickpea: Nutritive Value of a Protein Concentrate from Chickpea (Cicer arietinum) Obtained by Ultrafiltration and Its Potential Use in an Infant Formula

A protein concentrate from chickpea (Cicer arietinum) obtained by ultrafiltration for special infant formulas was evaluated for nutritive value with and without methionine supplementation. An infant formula prepared with the concentrate was also evaluated. The Adjusted Protein Efficiency Ratio (A-PER) (official method) values, were 1.86 and 2.14 for the concentrate and concentrate plus methionine, respectively (p < 0.05). Relative Net Protein Ratio (R-NPR) values were 77.4% for the concentrate, and 81.3% of ANRC-casein for the supplemented concentrate. Apparent protein digestibility values were significantly higher concentrates with respect to raw chickpea (p < 0.05). An infant formula based on the concentrate had a R-NPR value of 83.6% that of ANRC-casein, compared to 81.3% in the concentrate, indicating no apparent change in protein quality during processing. The infant formula met Codex Alimentarius Commission Standards (FAO/WHO).     

Complex experimental assessment of potential allergenicity of various isolates of soy proteins

The complex evaluation was carried out of potential allergenicity of three soya protein specimens - IPS, IPS-1 and IPS-2 manufactured by Ardex R, USA, which were attended for employment as protein component of specialized infant formulae. The content of total protein, amino-nitrogen, peptide fractions of molecular weight below 9000 D, precipitating protein antigens, trypsin inhibitor, was studied in the specimens. The apparent digestibility was measured by a multienzymatic system in vitro. The allergenicity of isolates was compared by means of histamine LD50 resistance test in guinea pigs and also by the reaction of active anaphylactic shock (AAS). The evidences have been obtained that IPS specimen containing the lowest levels of trypsin inhibitor and small peptide levels is characterized by the lowest sensitizing activity in AAS and simultaneously decreases the animals' resistance to histamine in the highest degree. Apparent digestibility of all the three specimens did not differ significantly. A conclusion has been made that the evaluation is necessary of infant hypoallergenic formulae components by a complex of independent experimental data.     

Proteins and proteolysis in pre-term and term human milk and possible implications for infant formulae

Understanding the differences between the protein system of human milk and bovine milk is critical in the development of infant formulae. In this study, the proteins of bovine milk and a bovine-based whey-dominant infant formula were compared with those of human milk for infants born prematurely (pre-term) or at full term (term). The protein distribution of infant formula differed significantly from that of either type of human milk. A proteomic comparison between pre-term and term human milk showed a reduction of levels of β-casein and α_s-casein and appearance of additional products, corresponding to low molecular weight hydrolysis products of the caseins, in pre-term milk. Pre-term milk samples also had higher total nitrogen concentration and plasmin activity, consistent with the proteomic data. These results suggest the operation of a physiological mechanism that may adjust enzyme and/or protein expression to modify protein digestibility, and may facilitate design of infant formulae, closer to maternal milk, particularly for premature infants.     

挤压膨化处理对婴幼儿米粉理化和体外消化特性的影响

为探讨婴幼儿米粉基料干法制造过程中挤压膨化处理对米粉特性的影响规律,对不同品种大米经挤压膨化得到米粉的理化和消化特性差异进行比较分析,结果表明:在相同挤压膨化条件下,不同大米之间淀粉组成差异明显,导致膨化度、吸水指数和水溶性指数差异显著(P<0.05);处理后由淀粉体外消化特性得出:早籼米中抗性淀粉含量最高,接近15%;糯米快速消化淀粉含量最低,小于75%。蛋白质消化特性结果显示,糯米制品的胃蛋白酶消化率和蛋白质总消化率均低于其它3种米粉,这可能是因糯米中蛋白质的结构和组成不同所致。研究结果为挤压膨化技术在米粉生产中的应用及对不同品种大米米粉的性能影响提供理论依据。     

高效液相色谱-串联质谱法测定婴幼儿配方奶粉中酪蛋白磷酸肽含量

建立一种同位素稀释-高效液相色谱-串联质谱法定量检测婴幼儿配方奶粉中酪蛋白磷酸肽（casein phosphopeptides,CPPs）含量的方法。经Q Exactive Orbitrap扫描,Uniprot蛋白质数据库初步确定CPPs所含肽段,根据质谱响应以及加标回收率等方法学验证实验进一步筛选确定CPPs的特征肽段。样品经过前处理后,采用ACQUITY UPLC BEH 300 C18色谱柱分离,多反应离子监测模式定量测定其中的CPPs特征肽。根据CPPs原料与CPPs特征肽含量的折算系数,从而确定出样品中CPPs的含量。方法学验证结果表明,所建立的方法在10～150?mg/100?g范围内线性关系良好,相关系数大于0.999。在高、中、低3?水平加标实验中,回收率在96.2%～100.2%之间,日间重复性在5.3%～7.8%之间。方法定量限为1?mg/100?g,可以满足婴幼儿配方奶粉中不同CPPs含量水平的定量要求。     

In-vivo and in-vitro digestibility of starch in autoclaved pea and potato products

The digestibility of starch in homogenized/autoclaved pea plus potato products was studied in vitro and in vivo. The products were a canned infant purée based on peas and potatoes and products prepared in the laboratory by repeated autoclaving and cooling of either homogenized potatoes or homogenized peas. Small-intestinal digestibility was evaluated through balance experiments in rats treated with an antibiotic (Nebacitin) to supress microbial activity in the hind gut. Parallel experiments in normal rats were performed to study the fermentability of undigested starch. The small-intestinal digestibility was 93, 82 and 70% of tolal starch in the potato product, infant purée and pea product, respectively. Consequently, significant amounts of starch left the small intestine undigested, particularly with pea-based products. The major portion of the undigested starch consisted of a fraction which resisted amylases in vitro unless solubilized in alkali, ie retrograded amylose. The fermentability of starch reaching the hind gut was high, about 90%. In-vitro digestibility figures varied depending on the method used and were in the ranges 91–93, 76–86 and 71–77% in the potato product, infant purée and pea product, respectively. One of the methods allowed simultaneous and accurate determination of the in-vivo resistant retrograded amylose fraction.     

Prediction of apparent heal protein digestibility in pigs with a two-step in-vitro method

The use of a two-step in-vitro method to predict the in-vivo ileal digestibility of proteins in pigs was investigated. It proved not possible to predict accurately the ileal protein digestibility with the in-vitro method. By dividing the samples into groups of closely related products, a good relationship (r² = 0.93) between in-vivo and in-vitro data was only obtained for wheat products, where only five samples were analysed. For beans, peas, rapeseed products and soya bean products it was still not possible to predict the in-vivo protein digestibility (r² = 0.03-0.60). The in vivo-in vitro relationship was mainly determined by the properties of the proteins and the presence of antinutritional factors, such as lectins and trypsin inhibitors. The first influences both the in-vitro and in-vivo protein degradability and the latter only reduces the in-vivo degradability by stimulating the secretion of endogenous protein. It is suggested that, with the in-vitro method, real ileal digestibility of proteins is predicted. The apparent ileal protein digestibility can only be predicted with the in-vitro method after making corrections for the influence of these antinutritional factors on the secretion of endogenous protein. Possibly corrections are also needed for microbial protein, and protein which is solubilised in the small intestine but not absorbed because of the physical state of the chyme.