Heat-induced Gelation Properties of Salt-Soluble Muscle Proteins as Affected by Non-Meat Proteins

Addition of whey protein concentrate (WPC), whey protein isolate (WPI) or soy protein isolate (SPI) to salt-soluble muscle proteins (SSP) decreased the gel strength. WPI:SSP gels had higher water-holding capacity than SSP, SSP:WPC or SSP:SPI gels. Myosin heavy chain was a principal contributor to gel network formation in SSP, SSP:WPC, SSP:WPI and SSP:SPI systems. The characteristic fibrous network formed by SSP was the dominant feature of the microstructure of SSP:WPC and SSP:WPI gels. SSP:SPI gels had a more aggregated appearance due to the occurrence of clusters of SPI throughout the gel matrix.     

Foaming and Emulsifying Properties of Whey Protein Concentrates As Affected by Lipid Composition

Freeze-dried WPC, containing 35 and 75% protein were manufactured by pretreating whey with calcium chloride and heat. These and commercial WPC were subjected to proximate analysis and lipid classes, phospholipid classes, free fatty acids (FFA), and monoacylglycerols (MAG) composition were determined. Solubility, thermal, foaming, and emulsifying properties of the WPC were studied. Pretreatment increased calcium and phosphorus contents and decreased the contents of all other minerals. The pretreatment had no effect on solubility, denaturation enthalpy, and onset temperature of denaturation of WPC. These values were comparable to those of commercial WPC. Foaming capacity and emulsion stability were unaffected, but foam stability increased and emulsifying capacity decreased due to pretreatment. Overall, total lipids and lipid class contents of experimental WPC were too low to affect surface properties of WPC.     

Emulsion Stability as Affected by Competitive Adsorption Between an Oil-Soluble Emulsifier and Milk Proteins at the Interface

The effect of an oil-soluble emulsifier upon adsorption properties of β-casein and β-lactoglobulin at the oil-water interface was studied. Addition of emulsifier improved the emulsification properties, but lowered emulsion stability. Higher concentrations decreased emulsification capacity, due to an increase in oil phase viscosity, and interfered with several protein assays, except the o-phthaldialdehyde (OPA) assay. Depletion measurements revealed that the emulsifier displaced β-casein more readily than β-lactoglobulin from the surface of droplets, which correlated with emulsification and stability measurements. Displacement of proteins was not complete due to emulsifier-induced formation of a multiple w-o-w emulsion, which accounted for the missing protein in the continuous phase.     

淘汰蛋鸭盐溶蛋白的乳化和起泡性质

研究淘汰蛋鸭的胸肉和腿肉组织的总蛋白质和盐溶蛋白含量及盐溶蛋白的功能性质,并与肉鸭进行比较。采用微量凯氏定氮法测定肉鸭和淘汰蛋鸭的胸、腿部肌肉组织的总蛋白质和盐溶蛋白含量,并测定盐溶蛋白的乳化活性和起泡性。结果发现,肉鸭和淘汰蛋鸭的胸部肌肉和腿部肌肉中的总蛋白质含量在22%左右,胸部肌肉的总蛋白质含量稍大于腿部的肌肉总蛋白质含量;肉鸭的胸、腿肌肉中的盐溶蛋白含量分别为(24.61±1.19)%和(28.90±1.57)%,而淘汰蛋鸭的分别为(29.09±1.23)%和(27.27±1.63)%;肉鸭的胸、腿肌肉盐溶蛋白的乳化活性分别为(51.13±2.27)%和(46.53±2.16)%,而淘汰蛋鸭的分别为(50.00±0.73)%和(43.69±2.08)%;肉鸭的胸、腿肌肉盐溶蛋白的起泡性分别为(52.25±2.50)%和(47.67±0.93)%,而淘汰蛋鸭的分别为(54.38±4.27)%和(42.98±1.89)%。     

小麦面筋蛋白质酶解产物用作啤酒发泡蛋白的研究

为改善啤酒的泡沫性能,作者分别采用木瓜蛋白酶、胃蛋白酶以及碱性蛋白酶对小麦面筋蛋白进行适度酶解改性,并对其产物用作啤酒发泡蛋白的可行性进行了研究.结果表明,经适度酶解作用后,小麦面筋蛋白在pH 4.5条件下溶解性和泡沫性能得到显著改善(P<0.05),且小麦面筋蛋白酶解产物在啤酒环境中热稳定性较好,经30 min的热处理,含100 mg/L小麦面筋蛋白酶解产物的啤酒浊度与加热前相比增加不显著(p>0.05).小麦面筋蛋白胃蛋白酶酶解产物和碱性蛋白酶酶解产物对啤酒初始泡持性的改善效果都较好,但胃蛋白酶酶解产物对酵母蛋白酶A作用较敏感,对纯生啤酒货架期内泡持性的改善效果不太理想,而碱性蛋白酶酶解产物可明显改善纯生啤酒货架期内的泡沫稳定性.     

Physicochemical Properties of Dry Red Kidney Bean Proteins and Natural Microflora as Affected by Gamma Irradiation

Gammaγ-irradiation affected (p≤0.05) the physicochemical properties of dry red kidney beans (Phaseolus vulgaris.) Protein deamidation, solubility and hydrophobicity increased and the number of sulfhydryl groups was reduced after irradiation. Irradiation also affected the outgrowth of natural mold contaminants. A dose of 1.5 kGy reduced the number of molds by 2 log cycles immediately after the treatment. However, incomplete inhibition was observed with the highest irradiation dose (3 kGy). Species of Aspergillus and Penicillium. were completely inhibited at 1.5 and 3 kGy respectively.     

Improving Foaming Properties of Yolk-Contaminated Egg Albumen by Basic Soy Protein

ABSTRACT:  Yolk contamination of egg white is a common problem in the egg breaking industry. Foaming properties of egg white protein are affected by such contamination, but proteins of basic nature may restore the foaming properties of the yolk-contaminated egg white protein. The purpose of this study was to chemically modify a soy protein, that is, to esterify the acidic groups on the protein and to study the potential of such modified protein in improving foaming. We showed that the modification changed the isoelectric point of soy protein isolate (SPI) from 4.5 to about 10. Sonication was proven to be a very effective means to redisperse the methanol-denatured soy protein during reaction, as shown by the improved solubility profile. Such modified basic protein, that is, the sonicated-modified SPI (SMSPI), when added to the yolk-contaminated (at 0.4% level, as-is basis) egg white, gave significantly improved foaming properties. We have shown that the slight change in pH due to the addition of SMSPI was not the reason for improved foaming performance; instead, the modified protein itself was the main reason for such improvement. Addition of SMSPI increased the foaming performance of both pure egg white and yolk-contaminated egg white. SMSPI consistently performed better than the unmodified SPI for improving foaming. Addition of SMSPI (16%, based on dry egg white, and 1.6% based on liquid egg white) fully restored foam expansion and foam liquid stability of 0.4% yolk-contaminated egg white, and it even out-performed the foaming of pure white protein. Therefore, a feasible solution to restore the foaming properties of yolk-contaminated egg white has been identified. It is expected that such modified SPI can be used as an additive or ingredient in foaming formulation, especially when the egg white protein is suspected of lipid contamination.     

Modified Soy Proteins with Improved Foaming and Water Hydration Properties

Soy proteins were modified by alkali treatment at pH 10.0, followed by papain hydrolysis. Solubility, water hydration capacity (WHC), surface hydrophobicity, foaming and emulsifying properties of unmodified, alkali-treated, and papain-modified soy protein (PMSP) were compared. PMSP exhibited higher solubility (100% at pH > 7.0), WHC (3.13) and hydrophobicity (40.8) than unmodified soy protein which had solubility 68.5%, WHC 0.21, and hydrophobicity 8.1. The PMSP had foaming capacity (22.0 mL) similar to egg white (21.2 mL) at pH 7.0; and enhanced foam stability (36.4) compared to the unmodified control (32.9). In general, alkali-treated soy had lower functional properties. Emulsifying properties of PMSP and alkali treated soy were unchanged by the modification. PMSP could be used as an egg white substitute in foaming applications at neutral pH.     

酶法改善卵白蛋白起泡性

采用碱性蛋白酶对卵白蛋白进行酶法改性处理以改善其起泡性。探讨酶解时间、底物质量分数、酶用量因素对卵白蛋白起泡性和泡沫稳定性的影响,在单因素试验基础上采用Box-Behnken中心组合试验设计优化酶法改性条件。结果表明,碱性蛋白酶酶法改性卵白蛋白改善其起泡性的最佳条件为：酶用量144 000 U/g、底物质量分数1.90%、酶解时间34 min。在此条件下酶法改性后卵白蛋白起泡性达202.0%,为未改性（120%）的1.683 倍。     

胡麻籽分离蛋白的溶解性与起泡性研究

为促进胡麻籽分离蛋白在食品工业中的应用,研究了pH值、盐浓度、蛋白质浓度等因素对其水溶性、起泡性和泡沫稳定性的影响。pH值对胡麻籽分离蛋白溶解度的影响呈典型的V形曲线。NaCl浓度为0.4mol/L前后胡麻籽分离蛋白表现出明显的盐溶与盐析效应。在0.1%～0.8%范围内,提高蛋白质浓度能增强起泡性与泡沫稳定性。在等电点附近,胡麻籽分离蛋白的起泡性最差但却具有最强的泡沫稳定性。NaCl对胡麻籽分离蛋白的起泡性的影响与其对溶解性的影响有相同的趋势。蔗糖能提高胡麻籽分离蛋白的泡沫稳定性,但当浓度高于5%时,对起泡性有负面影响。     

丝素的发泡性和胶凝性

丝素的起泡能力低于酪蛋白酸钠,但泡沫稳定性明显优于酪蛋白酸钠.丝素溶液直接或经剪切后放置均易形成凝胶,经高速剪切作用后形成凝胶的速度明显加快;随着丝素浓度增加,丝素凝胶的弹性增加;丝素经复合风味蛋白酶水解后形成凝胶,动态实验结果表明,其胶凝点在酶解进行至9min左右.用SEM和TEM观察丝素凝胶的超微结构发现,直接放置形成的丝素凝胶的网孔小于剪切作用后形成的凝胶.     

绿茶提取物对乳清蛋白发泡特性、流变特性和热力学特性的影响

本文选用三种不同的绿茶提取物(CGT、NGT和UGT,分别来自中国、日本和肯尼亚),探讨绿茶提取物对乳清蛋白的发泡特性、流变特性和热力学特性的影响。研究结果表明:绿茶提取物可以显著提高乳清蛋白的发泡能力、发泡稳定性及胶体强度;绿茶提取物不影响乳清蛋白变性温度,但可以使其热焓值显著下降。研究结果暗示乳清蛋白与绿茶提取物中的一些主要组分发生了协同相互作用。     

Flow Properties Of Encapsulated Milkfat Powders as Affected by Flow Agent

Food powders containing softer cores of fatty or flavor components present handling problems, as such powders are generally of very low density and mostly non free-flowing. Three classes of flow conditioners [silica, silicate and stearate], at three levels of concentration, were evaluated to determine effects on bulk and flow properties of sucrose, lactose and modified corn starch as well as butter oil powders encapsulated with the same materials. Silica and silicate were generally effective in improving bulk properties but only silica was effective in improving flow-ability of unencapsulated powders as well as lactose-encapsulated butteroil powder. Washing with isopropanol was effective in improving flow only with the lactose-encapsulated butteroil powder. Butteroil encapsulated in lactose had flow characteristics similar to lactose.     

球磨处理对鸡蛋清蛋白结构、性质及起泡性的影响

蛋清因具有优良的起泡性而在焙烤等食品加工领域中被广泛应用,因此,提升蛋清蛋白的起泡性有重要意义.本实验对鸡蛋清蛋白进行球磨处理,通过测定球磨处理后蛋清蛋白的游离巯基含量、表面疏水性、水解度、Zeta-电位和粒径,并分析其热力学性质、二级结构、起泡特性和微观结构,以研究球磨处理对蛋清蛋白结构性质及其起泡性的影响.结果表明...     

Physical Properties of Extruded Products as Affected by Cheese Whey

Corn, rice and potato flour were extruded with sweet whey solids (SWS) or whey protein concentrate (WPC) using low and high shear extrusion processing conditions. WPC added at product content of 25% had minimal effect on the texture of extruded products. Expansion and breaking strength were improved in some processes through changes in extrusion shear and moisture. Whey product incorporation resulted in reduced specific mechanical energy input to the process. Increasing whey product concentration beyond 25% reduced expansion and water absorption indices significantly, affecting textural hardness. Product quality characteristics were directly related to the whey product content.     

Color in Concentrated Milk Proteins with High Sucrose as Affected by Glucose Replacement

A model system of sucrose, whole dry milk powder, and distilled water was used to evaluate color development during heating. Sucrose replacement by glucose and moisture were the selected variables in a second-order central composite design. The main color response was the Kubelka-Munk index K/S calculated from reflectance colorimetric measurement using the Self-Backing Reflectance Transformation (SBRT) procedure. Browning reached a zone of maximum K/S when sucrose replacement increased. Additional replacement in the maximum zone did not increase browning, but produced an opposite effect decreasing browning, depending on moisture content. Chromophore group formation was higher between 40 and 75% of sucrose replacement by glucose and at 20-30% moisture content.     

Determination of Foaming Properties of Proteins by Conductivity Measurements

A new method was established to estimate the foaming properties of proteins from the conductivity of foams using a simple apparatus that consisted of a glass column with the conductivity cell. A close correlation was observed between the initial conductivity of foams and the foam volumes of heat-denatured ovalbumins or 11 native proteins, suggesting that the initial conductivity of foams can be used as a measure of foaming power. In addition, a close correlation was obtained between the foam stability determined from changes in the conductivity and foam volume with time of heat-denatured ovalbumins or 11 native proteins, suggesting that foam stability also can be estimated from changes in the conductivity of foams. The advantages of the conductivity measurements are to determine the foaming properties more simply and accurately than the currently used methods.     

浮选法脱墨中表面活性剂起泡性能研究进展

表面活性剂的起泡性能对浮选法脱墨效果的影响很大,研究浮选过程中表面活性剂泡沫体系的影响因素,以及各因素之间的相关性,对优化脱墨剂配方、提高脱墨效率至关重要。对浮选法脱墨中表面活性剂起泡性能的影响因素进行了综述,分析了泡沫性能评价的多种测定方法。对表面张力、黏度、表面电荷等影响表面活性剂的起泡性能的重要因素及其相关规律作了阐述,对起泡性能的多种检测方法及其优劣性作了总结。     

Rheological Properties of Chitosan and its Interaction with Porcine Myofibrillar Proteins as Influenced by Chitosan's Degree of Deacetylation and Concentration

ABSTRACT Rheological and gelation characteristics of a specific degree of deacetylation (dd 50 to 99) and concentration (0.5% to 1.5%) of chitosan and chitosan/SSP (salt-soluble protein) mixtures were studied. Results suggested that SSP thermal gelation was interfered with by the positive charges of amino groups of the chitosan molecule. Regardless of degree of deacetylation, increasing chitosan concentration caused stronger interference on SSP gelation and lowered complex modulus [G*]. Loss tangent of chitosan/SSP gel decreased with increasing temperature. Higher level (1.5%) of dd 99 chitosan had the lowest G*, which resulted from ionic interaction with SSP. SDS-PAGE revealed protein aggregation, indicating possible covalent bond formation.