Selective Solubilization of α- Lactalbumin and β-Lactoglobulin into Reversed Micelles from Their Mixtures

Phase transfer experiments were performed, involving contact between an aqueous 1:1 solution of α-lactalbumin and β-lactoglobulin and an AOT-in-isooctane reversed micellar phase. The resulting extraction and separation of the two proteins were analyzed as functions of pH, ionic strength and total protein concentration using SDS-PAGE, and compared with extractions from pure solutions. At low protein concentrations, the extent of reversed micellar solubilization of the two pure proteins predicted well the extraction from mixtures. However, at higher protein concentrations β-lactoglobulin appeared to be excluded from the micellar droplets. Because of the significantly different partitioning behavior of the two proteins, reversed micellar extraction from an initially equal weight mixture led to an effective separation of the proteins.     

Hydration of Whey Powders as Determined by Different Methods

Four methods for evaluating water hydration of 15 whey derivative powders were compared, and results are discussed with respect to the chemical composition of the powders. Hydration capacities between 0.21 and 4.64 mL water/g of powder were obtained, depending on the method used. The filtration/centrifugation method gave the highest hydration capacity, whereas the paste-water retention method gave the lowest. The Baumann test and the paste-water retention method were well correlated with protein and lactose content of the powders, enabling differentiation between hydration capacities of whey protein concentrates (35% proteins) and electrodialyzed whey powders (12% proteins). Reliable characterization of hydration required a combination of methods.     

Buttermilk Properties in Emulsions with Soybean Oil as Affected by Fat Globule Membrane-Derived Proteins

The potential utilization of buttermilk from an industrial source was studied in this research, focusing primarily on its composition and use as ingredient in oil-in-water emulsions. Buttermilk contained not only large amounts of caseins and whey proteins, but also material derived from the natural milk fat globule membrane (MFGM). Emulsions made with soybean oil (10% w/w) and buttermilk were stable with a low concentration (about 1% w/w) of buttermilk solids. MFGM-proteins and skim milk proteins did not seem to compete for adsorption at the emulsion interface. The protein adsorbed at the interface was present in an aggregated form and gave a maximum surface coverage of about 8 mg/m².     

The effect of mechanical harvesting and transport of grapes, and juice oxidation, on the protein stability of wines

The concentration of haze-forming protein was determined in wines made from Sauvignon Blanc grapes harvested by hand or machine and transported for up to 400 km. The effect of oxidation of juice from mechanically harvested fruit on the concentration of haze-forming proteins was also investigated. Wines made from mechanically harvested, long-distance transported fruit contained more heat-unstable protein, and required fining with twice as much bentonite to ensure heat stability as wines made from hand-picked fruit. Juice oxidation had little effect on protein content of the juice or of the wine made from it.     

Investigations on the extractability of gluten proteins from wheat bread in comparison with flour

 Immunochemical methods are recommended for the quantitation of small amounts of gluten in food produced for those with coeliac disease. A major problem, however, is the reduced extractability of gliadin, the toxic factor of gluten, with aqueous alcohol, when foods have been heat-processed. A combined extraction/HPLC procedure was used to study the extractability of all gluten protein types from wheat flour and bread under both non-reducing and reducing conditions. Gliadin isolated from wheat flour was used as a reference protein for quantitation. The results indicate that the extractability of gliadin from bread with 60% ethanol under non-reducing conditions is strongly reduced. α- and γ-gliadins are much more affected than ω-gliadins, and less gliadin was extracted from the crust than from the crumb. For a complete extraction of gliadins from bread, reducing conditions and increased temperature are required. However, glutenin subunits are coextracted with the gliadins. This extract can be used for the quantitation of total gluten proteins by RP-HPLC. The recovery of gliadin added to flour before dough-mixing and bread-making is 98%. Received: 16 February 1998     

蛋白质纤维分散染料助剂增溶染色研究

工艺参数对羊毛分散染料助剂增溶染色性能的影响作了研究。所推荐的最佳工艺适用于多数分散染料对羊毛、蚕丝的染色,匀染性及色泽俱佳,织物的皂洗及干湿摩擦牢度分别在2～5级和3～5级,这种分散染料染蛋白质纤维的新方法值得进一步研究。     

Effect of pH,temperature and storage time on the stability of bovine myelin basic protein

Bovine central nervous system tissue (CNT) harboring highest levels of the infectious agent for prion diseases, has been banned from food and feed supplies. Effective detection of CNT in excessively processed meat and feedstuffs requires the assay based on a stable marker in CNT as the analyte. Myelin basic protein (MBP), the major central nervous system (CNS) myelin protein, was reported to be detectable up to 115 °C in the literature. This study further investigated the effects of pH, temperature and storage time on the stability of purified bovine MBP (18.5 kDa) in solutions. Purified MBP dissolved in 10 mM PBS was adjusted to pH 3.0, 7.2 and 10.5, respectively. Sample at each pH was subjected to three heat treatments, 100 °C, 121 °C, and 133 °C for 30 min. The unheated and 100 °C heated samples at pH 7.2 were stored at 4 °C for 19 days to study the storage stability of bovine MBP. The immunoreactivity of all samples was examined using indirect non-competitive enzyme-linked immunosorbent assay and immunoblotting with an anti-MBP monoclonal antibody. The protein degradation was observed by analyzing samples using SDS-PAGE. Results show that bovine MBP was most stable at pH 7.2 while the protein was least stable at pH 10.5. MBP started to degrade after heating at 121 °C for 30 min at pH 7.2. Storage up to 19 days at 4 °C did not significantly affect the immunoreactivity of unheated and heated samples. However, unheated MBP samples started to show degradation from day 8 of storage; while no degradation was observed in 100 °C heated samples over the storage time. This study demonstrated that bovine MBP can be a suitable marker for the detection of bovine CNT in highly processed food and feed supplies.     

Thermal markers arising from changes in the protein component of milk

Classification of heat load applied to milk requires the detection of parameters appropriately related to the intensity of the heat treatment. Current analytical methods based on heat-induced changes in the protein component of milk have been directed either to determine the amount of protein-derived products arised from heat treatments or to evaluate the extent of thermal denaturation of milk proteins. Lately, a new analytical strategy has been developed according to the occurrence of three major whey proteins, namely bovine serum albumin (BSA), beta-lactoglobulin (βlg) and alfa-lactalbumin (αla), normally soluble at pH 4.6 in raw milk, in the pH 4.6 insoluble protein fraction recovered from heat-treated milk. The results have shown that pH 4.6 insoluble BSA, βlg and αla, as detected by ELISA in milk, can be regarded as thermal markers suited for either dairy process control or regulation purposes.     

臭氧氧化法分解聚驱采油废水中水解聚丙烯酰胺的过程分析

对含水解聚丙烯酰胺(HPAM)的模拟废水分别采用单独臭氧氧化和电絮凝耦合臭氧氧化两种方法进行处理。考察处理方法对HPAM降解的影响,采用GC-MS和FTIR方法对HPAM降解物进行表征以分析HPAM降解的过程。实验结果表明,单独臭氧氧化处理模拟废水时,在臭氧用量4.2 mg/L、废水pH=10、反应120 min的条件下,COD和HPAM的去除率分别为37.1%和83.4%;电絮凝耦合臭氧氧化处理模拟废水时,经电絮凝30 min后,再臭氧氧化120 min,COD和HPAM的去除率分别为82.2%和94.4%。臭氧氧化降解HPAM的过程可推断为:HPAM分子经断链分解为低相对分子质量的聚合物,低相对分子质量的聚合物继续氧化生成丙烯酸和丙烯酰胺的中间体,中间体再进一步氧化为烷烃、醛酮类、酯类等物质,最终彻底矿化。