马铃薯蛋白与蛋清蛋白混合凝胶特性分析

以马铃薯蛋白(potato protein,PP)和蛋清蛋白(egg white protein,EWP)为原料制备热诱导混合凝胶,分析不同比例PP-EWP混合凝胶的质构、蛋白质二级结构、分子间作用力、游离巯基及流变性质的变化规律.结果 表明,随着PP含量的增加,混合凝胶的保水性由(73.5±0.71)％升高至(97....     

NaCl添加量对发酵牦牛肉灌肠成熟过程中理化品质及挥发性风味物质的影响

研究添加0.0％、1.5％、3.0％、4.5％NaCl的发酵牦牛肉灌肠成熟过程中理化性质、菌落总数以及挥发性风味物质的变化.结果表明,NaCl添加量4.5％的发酵牦牛肉灌肠pH值和亮度值显著高于其余3组(P＜0.05);随着NaCl添加量的减少,硬度、胶着性、咀嚼性呈下降趋势,而储能模量、菌落总数呈上升趋势;此外,Na...     

Improvement of Foaming Property of Egg White Protein by Phosphorylation through Dry-Heating in the Presence of Pyrophosphate

ABSTRACT:  Egg white protein (EWP) was phosphorylated by dry-heating in the presence of pyrophosphate at pH 4 and 85 °C for 1 d, and the foaming properties of phosphorylated EWP (PP-EWP) were investigated. The phosphorus content of EWP increased to 0.71% as a result of phosphorylation. To estimate the foaming properties of EWP, the foams were prepared by 2 methods: bubbling of the 0.1% (w/v) protein solution and whipping of the 10% (w/w) protein solution with an electric mixer. The foaming power, which was defined as an initial conductivity of foam from 0.1% (w/v) protein solution, was a little higher in PP-EWP than in native EWP (N-EWP), and the foaming stability of PP-EWP was much higher than that of dry-heated EWP (DH-EWP) and N-EWP. The microscopic observation of foams from the 10% (w/w) solution showed that the foams of PP-EWP were finer and more uniform than those of N- and DH-EWP. Although there were no significant differences in the specific gravity and overrun of the foams between PP- and DH-EWP ( P  < 0.05), the specific gravity and overrun of the foams from PP-EWP were smaller and higher, respectively, than that of the foams from N-EWP. The drainage volume was smaller in the foams from PP-EWP than in those from N- and DH-EWP. These results demonstrated that phosphorylation of EWP by dry-heating in the presence of pyrophosphate improved the foaming properties, and that it was more effective for the foam stability than for the foam formation.     

羧甲基壳聚糖与NaCl组合漂洗制备白鲢鱼糜工艺条件优化

目的：探讨羧甲基壳聚糖（carboxymethyl chitosan,CBC）与NaCl组合漂洗白鲢鱼糜对凝胶品质、鱼糜收率及蛋白损失率等的影响。方法：以鲜白鲢鱼为原料,分别采用去离子水、0.25%、0.5%、0.75%、1.0%的NaCl溶液,0.5%、1.0%、1.5%、2.0%的CBC溶液,1.0% CBC＋1.0% NaCl、1.0% CBC＋0.75% NaCl、1.5% CBC＋1.0% NaCl、1.5% CBC＋0.75% NaCl,对鱼糜进行一次漂洗（鱼肉与漂洗液质量比1∶5）,测定不同漂洗处理对鱼糜凝胶强度、白度、蛋白质组成及流变特性的影响。结果：单独采用NaCl漂洗时,随着其用量的增大,鱼糜凝胶强度、白度呈现增加趋势（P＜0.05）,总蛋白含量呈现先增加后下降的趋势,过高或过低的NaCl质量分数,均不利于提高鱼糜得率。单独采用CBC溶液漂洗时,凝胶强度、白度、水溶性蛋白含量随着CBC质量分数的增大呈上升趋势（P＜0.05）。采用NaCl和CBC组合漂洗时,1.5% CBC＋0.75% NaCl组合得到的鱼糜凝胶强度最高,达232.05 g•cm,显著高于对照的142.22 g•cm（P＜0.01）,此时的盐溶性蛋白含量10.53%和水溶蛋白含量4.91%,显著高于空白对照的9.36%（P＜0.05）及4.06%（P＜0.01）。1.5% CBC＋0.75% NaCl组合漂洗,获得良好的鱼糜凝胶强度、白度及粗蛋白含量。结论：采用1.5% CBC＋0.75% NaCl漂洗可以改善鱼糜的凝胶品质,蛋白损失率比对照组降低10.56%,从而提高鱼糜得率,并降低废水排放。     

The effects of fish meat and fish bone addition on nutritional value,texture and microstructure of optimised fried snacks

The aim of present study was to prepare the micro size fish bone dispersion (F.B) by a novel method and fortified in snacks based on wheat flour (W.F) with fish meat (F.M) addition. A formulation blend of W.F 10–50 g, potato powder (P.P) 0–40 g, F.M 0–30 g and F.B 0–20 g was used to investigate different responses using response surface methodology (RSM). The results revealed that F.M significantly (P < 0.05) influenced on protein content and inverse relation with water holding capacity (WHC) and hardness. Whereas, F.B increased hardness, ash and calcium contents but decreased WHC, expansion and colour parameters. Furthermore, scanning electron microscopy (SEM) confirmed the effect of independent variables on morphology of the product. Optimised formulation (w/w) was W.F 35.71%, P.P 28.57%, F.M 21.42% and F.B 14.28% with 37% bioavailable calcium, improved texture and nutritional value.     

Structural characterization and functional properties of egg white protein treated by electron beam irradiation

This study investigated the functional properties and structural characteristics of egg white protein (EWP) powder treated by electron beam irradiation (EBI) at the doses of 5, 10, 20, 30, 50, 70 and 100 kGy. In comparison with the untreated sample (0 kGy), the EBI-induced EWP showed generally better solubility and higher antioxidant capacity by ABTS•⁺ radical scavenging assay. Furthermore, the emulsifying activity index of EBI-induced EWP increased with increased EBI dose, reaching the maximum value of 15.8 ± 0.4 m²/g at 100 kGy. The emulsifying stability index and ϛ-potential of EBI-induced EWP showed fluctuating tendencies. These functional property changes of protein were attributed to the conformational changes caused by EBI. SDS-PAGE patterns confirmed that high-dose EBI would result in protein depolymerization to low-mass molecules at 11 kDa, contributing to the increased solubility. Circular dichroism data demonstrated that EBI-induced EWP exhibited partial denaturation and a flexible structure, which was responsible for the improved emulsifying properties. Fluorescence spectra revealed that high EBI doses led to an increase in the polar environment around tryptophan, which could enhance the solubility and antioxidant activity of EWP. In addition, high EBI doses decreased the content of free and total sulphydryl groups, and changed the intermolecular forces of protein, including ionic bonds, hydrogen bonds, hydrophobic interactions, and disulfide bonds. These findings can provide solid support for practical applications of EBI technology in EWP food processing.     

年龄对舍饲育肥牦牛肉营养价值和抗氧化活性的影响

本实验旨在研究年龄对舍饲育肥牦牛肉营养价值和抗氧化活性的影响,为优质牦牛肉的生产提供指导。选取18 头健康麦洼公牦牛,根据年龄分为1.5、2.5 岁组和4.5 岁组,每组6 个重复,预饲期15 d,正式实验期180 d。结果表明：1）年龄对牦牛肉中粗蛋白质和粗灰分有显著影响（P＜0.05）,其中4.5 岁组牦牛肉中粗蛋白质量分数为23.50%,2.5 岁组粗灰分质量分数为1.36%,均在3 组中最高;2）不同年龄牦牛肉中必需氨基酸占总氨基酸比例（the ratio of essential amino acids to total amino acids,EAA/TAA）和EAA占非必需氨基酸比例差异显著（P＜0.05）,其中2.5 岁组最高,4.5 岁组其次,1.5 岁组最低,但2.5 岁组鲜味氨基酸占TAA比例仅为42.88%,显著低于1.5 岁组的43.49%和4.5 岁组的43.43%（P＜0.05）;3）年龄对脂肪酸质量分数影响较小,仅2.5 岁组二十一烷酸（C21:0）质量分数显著高于1.5 岁组和4.5 岁组（P＜0.05）,而其他脂肪酸质量分数和比例差异不显著（P＞0.05）,另外山嵛酸（C22:0）和11,14-二十碳烯酸（C20:2）仅在1.5 岁组中检出,在2.5 岁组和4.5 岁组均未检出;4）随着年龄的增长,牦牛肉中丙二醛含量不断升高,4.5 岁组比1.5 岁组升高了53.80%,但不同年龄牦牛肉中过氧化氢酶、总超氧化物歧化酶、谷胱甘肽过氧化物酶活力和总抗氧化能力无显著差异（P＞0.05）。综上所述,年龄能够影响牦牛肉的营养成分,但对其抗氧化活性无明显影响。     

氯化钠对鸡肉冷藏过程中肌原纤维蛋白氧化的影响

为探究氯化钠对鸡肉腌制冷藏过程中肌原纤维蛋白氧化的影响,采用不同添加量（0.0%、1.5%、3.0%、4.5%、6.0%、7.5%）的氯化钠处理鸡胸肉,冷藏不同时间（0、2、4 d）后提取肌原纤维蛋白,通过测定其表面疏水性、粒径、羰基、巯基含量等判断肌原纤维蛋白氧化程度。结果表明：随着氯化钠添加量的增加及贮藏时间的延长,鸡肉肌原纤维蛋白羰基含量逐渐增加,巯基含量则显著减少（P＜0.05）;肌原纤维蛋白产生一定的聚集交联现象,平均粒径呈增大趋势;肌原纤维蛋白中α-螺旋相对含量随着氯化钠添加量的增加而降低,而色氨酸荧光强度随氯化钠添加量的增加先升高后降低。综上所述,氯化钠对鸡肉腌制冷藏过程中的肌原纤维蛋白氧化有一定促进作用,其中氯化钠添加量4.5%时对鸡肉肌原纤维蛋白的氧化效果最为明显。     

Influence of whey protein concentrate, additives, their combinations on the quality and microstructure of vermicelli made from Indian T. Durum wheat variety

Effect of whey protein concentrate (5%, 7.5%, 10%) and additives on the quality of vermicelli made from Indian durum wheat was studied. The results revealed that with increase in whey protein concentrate (WPC) from 0% to 10%, cooked vermicelli weight increased from 82.5 to 88 g/25 g, cooking loss increased from 6.0 to 8.4%, L values indicating lightness increased (47.42–52.9); b values indicating yellowness decreased (7.0–3.80) and shear force decreased (66–45 g). Sensory evaluation of vermicelli with 5%, 7.5%, 10% WPC showed that addition of above 5% WPC resulted in whitish colour vermicelli with mashy strand quality and sticky mouthfeel. Studies on the effect of additives namely ascorbic acid (0.01% and 0.015%), gluten (1.5% and 3.0%) and glycerol monostearate (GMS) (0.25% and 0.5%) individually as well as in combination on the quality of vermicelli with 5% WPC indicated that combination of 0.01% ascorbic acid, 3% gluten and 0.5% GMS resulted in vermicelli having lower cooking loss, creamy yellow colour, firm, discrete strands and non-sticky mouthfeel. The protein content of vermicelli with 5% WPC and combination of additives was 16% as against 11.5% of control vermicelli. Scanning electron microscopy study of control vermicelli, vermicelli with 5% WPC and vermicelli with 5% WPC and combination of additives revealed that vermicelli with 5% WPC showed a rough surface with a prominent rupture while vermicelli with 5% WPC and combination of additives showed a continuous, rupture free structure.     

乳清浓缩蛋白与卵清蛋白复合膜的制备及其性能

本文以乳清蛋白（Whey protein concentrate,WPC）和卵清蛋白（Egg white protein,EWP）为成膜基质,添加5 U/g_蛋白转谷氨酰胺酶（Transglutaminase,TG）制备WPC/EWP复合膜,分别研究WPC和EWP质量比、膜液pH、甘油添加量对WPC/EWP复合膜结构及性能的影响。结果表明,当WPC/EWP质量比为1:3,成膜液pH为8,甘油添加量为35%时,电镜结果表明形成的复合膜结构致密无孔隙,红外结果显示WPC和EWP有较好的相容性。WPC/EWP复合膜的水蒸气透过率为2.08×10?10 g·s?1m?1Pa?1,透光率为73.90%,抗拉强度为1.60 MPa,断裂伸长率为151.96%。WPC、EWP和甘油在膜液pH为8时具有良好的融合性,能显著（P<0.05）提高WPC/EWP复合膜的机械性能。     

Foams Prepared from Whey Protein Isolate and Egg White Protein: 2. Changes Associated with Angel Food Cake Functionality

ABSTRACT:  The effects of sucrose on the physical properties and thermal stability of foams prepared from 10% (w/v) protein solutions of whey protein isolate (WPI), egg white protein (EWP), and their combinations (WPI/EWP) were investigated in wet foams and angel food cakes. Incorporation of 12.8 (w/v) sucrose increased EWP foam stability (drainage 1/2 life) but had little effect on the stability of WPI and WPI/EWP foams. Increased stability was not due to viscosity alone. Sucrose increased interfacial elasticity ( E  ') of EWP and decreased E' of WPI and WPI/EWP combinations, suggesting that altered interfacial properties increased stability in EWP foams. Although 25% WPI/75% EWP cakes had similar volumes as EWP cakes, cakes containing WPI had larger air cells. Changes during heating showed that EWP foams had network formation starting at 45 °C, which was not observed in WPI and WPI/EWP foams. Moreover, in batters, which are foams with additional sugar and flour, a stable foam network was observed from 25 to 85 °C for batters made from EWP foams. Batters containing WPI or WPI/EWP mixtures showed signs of destabilization starting at 25 °C. These results show that sucrose greatly improved the stability of wet EWP foams and that EWP foams form network structures that remain stable during heating. In contrast, sucrose had minimal effects on stability of WPI and WPI/EWP wet foams, and batters containing these foams showed destabilization prior to heating. Therefore, destabilization processes occurring in the wet foams and during baking account for differences in angel food cake quality.     

Nutritional,physicochemical, and textural properties of gluten-free extruded snacks containing cowpea and whey protein concentrate

Ready-to-eat extruded snacks with high protein and fibre were developed from a composite flour comprising rice flour, cowpea flour and whey protein concentrate (WPC). Nutritional, physicochemical, and textural properties of extrudates were evaluated, at five ratios of cowpea: WPC (10:0, 15:05, 20:10, 25:15, 30:20); rice flour was used as a control. The protein and fibre content in the extrudates significantly increased (P ≤ 0.05) with cowpea (10%–30%) and WPC (5%–20%) incorporation compared to the control. The extrudates with higher levels of cowpea and WPC showed a significant increase in bulk density and hardness. A slight decrease of 12% was observed in the expansion of 15% cowpea and 5% WPC fortified extrudates compared to the control. The number of peaks during compression increased with incorporations of cowpea and WPC. All cowpea and WPC containing snacks were darker than the control. Significant correlations were found between the protein, fibre, colour values and textural properties. The essential and non-essential amino acid profiles increased in the extrudates, proportionally to the cowpea and WPC fortification.     

Effect of pH and Salts on the Solubility of Egg White Protein

The solubility of 1% dispersions of freeze-dried (FD) and commercial spray-dried (SD) (containing less than 0.1% SDS) egg white protein (EWP) was determined in water and in 0.1, 0.3, and 0.5M NaCl and NaI, and 0.01, 0.05, and 0.1M Na₄P₂O₇ at pH 3, 5, 7, and 9. Protein solubility generally increased at higher pH and salt concentrations over the ranges studied. Both I and P₂0₇ ions, but not Cl, substantially increased the apparent solubility of FDEW, but had less effect upon the solubility of SDEW. Both NaI and Na₄P₂0₇ changed the character of the solvent in a way similar to that of SDS, a known protein denaturant and solubilising agent. The effect of these two salts upon EWP solubility was more pronounced than for bovine serum albumin.     

Green banana starch enhances physicochemical and sensory quality of baru almond-based fermented product with probiotic bacteria

This study aimed to isolate and characterise green banana starch (GBS) and to investigate the effect of adding 0%, 1.5%, 3.0%, 4.5% and 6.0% GBS on physicochemical and sensory properties of a fermented product based on baru almond (Dipteryx alata Vogel) water extract with probiotic bacteria. GBS showed high gelatinisation temperature (73.37 °C), enthalpy (16.61 J g⁻¹) and final viscosity (239.6 RVU). On the contrary, it showed a low tendency to retrograde (67.53 RVU), water solubility (0.02%), water absorption (1.85 g g⁻¹) and gel hardness (6.7 N). Higher addition levels of GBS increased firmness, reduced syneresis and positively affected pH, titratable acid, soluble solids and colour of baru almond-based fermented products. The incorporation of 4.5% GBS was well accepted and preferred over the control sample (no GBS addition). GBS can be used as a natural thickener. The baru almond-based fermented product with 4.5% GBS stands out for having potential probiotic properties and for being a promising dairy alternative.     

LOW-FAT, NO ADDED SALT IN RESTRUCTURED BEEF STEAKS WITH VARIOUS BINDERS

This research investigated technology for the development of a low-fat restructured beef steak devoid of added salt with texture similar to intact muscle. Low-fat (10%), low-sodium restructured beef steaks made from closely trimmed, flaked beef round muscles and tumbled with or without a binding agent were compared to boneless top loin steaks (5–6% fat). Boneless top loin steaks had greater (P < .05) shear resistance, cohesiveness, juiciness, overall desirability, percentage moisture (raw) and percentage protein (cooked) than restructured steaks. Steaks made with 3.0% modified potato starch had slightly more juiciness and moisture content (cooked) and lower expressible fluid content than all other restructured samples. Product made with 1.0% microcrystalline cellulose had lower (P < .05) juiciness scores than top loin steaks and restructured steaks made with no additives or modified potato starch. Use of 0.25% kappa-carrageenan or 1.5% surimi increased (P < .05) sensory scores for off-flavor. Steaks made with 1.5% surimi also had lower (P < .05) sensory scores for overall desirability.     

Date Bars Fortified with Soy Protein Isolate and Dry Skim Milk

Fortification of plain and chocolate coated date bars with soy protein isolate (SPI) and dry skim milk (DSM) in different proportions (1.5% SPI + 10.5% DSM; 3.0% SPI + 7.0% DSM and 4.5% SPI + 3.5% DSM) resulted in an increase of protein, fat, fiber, ash, Na, K, Ca, Mg, P, Zn, and all the essential amino acids. The chemical score increased from 48 to a range of 83–95. The in vitro protein digestibility (IVPD) values (77.8–81.8%) and calculated protein efficiency ratios (C-PERs) of the fortified bars (2.40–2.47) were close to the IVPD (90.0%) and C-PER (2.50) of ANRC-casein. In general, sensory evaluation indicated no difference in the control and fortified date bars, which were stored up to six months. 1.5% SPI + 10.5% DSM was the optimum level of supplementation in terms of nutritive benefit.     

Influence of protein isolate from lupin seeds (Lupinus albus ssp. Graecus) on processing and quality characteristics of frankfurters

Lupin protein isolate (92% protein) from seeds of Lupinus albus ssp. Graecus (LSPI) was used as powder ingredient for the manufacture of frankfurters at levels 0, 1, 2 and 3% of the formulation weight. Additional 1% water was added during batter formulation to each 1% protein used. LSPI increased (P < 0.05) the pH and viscosity of batter and reduced the jelly separation. Increasing the LSPI level resulted in higher (P < 0.05) processing yield and lower (P < 0.05) purge accumulation, redness and visual colour scores and hardness of frankfurters. Significant differences in overall acceptability were not found among the control and frankfurters with 1% and 2% LSPI. Frankfurters with 3% LSPI were judged as unacceptable. Incorporation of LSPI at 1% level either in hydrated form or as stabilizer in pre-emulsified fat improved the processing characteristics and overall acceptability of frankfurters made with LSPI as powder ingredient and did not affect the color and texture.     

Effects of heating rate and pH on fracture and water-holding properties of globular protein gels as explained by micro-phase separation

The effect of heating rate and pH on fracture properties and held water (HW) of globular protein gels was investigated. The study was divided into 2 experiments. In the 1st experiment, whey protein isolate (WPI) and egg white protein (EWP) gels were formed at pH 4.5 and 7.0 using heating rates ranging from 0.1 to 35 °C/min and holding times at 80 °C up to 240 min. The 2nd experiment used one heating condition (80 °C for 60 min) and probed in detail the pH range of 4.5 to 7.0 for EWP gels. Fracture properties of gels were measured by torsional deformation and HW was measured as the amount of fluid retained after a mild centrifugation. Single or micro-phase separated conditions were determined by confocal laser scanning microscopy. The effect of heating rate on fracture properties and HW of globular protein gels can be explained by phase stability of the protein dispersion and total thermal input. Minimal difference in fracture properties and HW of EWP gels at pH 4.5 compared with pH 7.0 were observed while WPI gels were stronger and had higher HW at pH 7.0 as compared to 4.5. This was due to a mild degree of micro-phase separation of EWP gels across the pH range whereas WPI gels only showed an extreme micro-phase separation in a narrow pH range. In summary, gel formation and physical properties of globular protein gels can be explained by micro-phase separation. PRACTICAL APPLICATION: The effect of heating conditions on hardness and water-holding properties of protein gels is explained by the relative percentage of micro-phase separated proteins. Heating rates that are too rapid require additional holding time at the end-point temperature to allow for full network development. Increase in degree of micro-phase separation decreases the ability for protein gels to hold water.     

Soybean Flour/Oil and Wheat Bran Effects on Characteristics of Cassava (Manihot esculenta Crantz) Flour Extrudate

Adding soybean flour, soybean oil and wheat bran to cassava flour increased the percentage of crude protein/fat and crude fiber respectively in the blends. Crude protein or extrudate correlated negatively (P<0.01) with expansion, water solubility or total reducing sugars and positively (P<0.01) with bulk density, and water absorption. Crude fiber of extrudate correlated negatively (P<0.01) with expansion, bulk density and total reducing sugars. At 4% soybean oil addition, extrudate expansion and WSI were highest, while bulk density and WAI were lowest. Extrudates became more yellow in color on addition of soybean flour.     

Egg white proteins and β-cyclodextrin: effective cryoprotectant mixture against oxidative changes in the myofibrillar proteins of Culter alburnus

The effect of egg white protein (EWP) and β-cyclodextrin (β-CD) mixture was analysed on the myofibrillar proteins (MP) of Culter alburnus during a frozen storage at −18 °C for 60 days. Different proportions of EWP:β-CD mixture (0%, 2%, 4% and 6%) were added into MP to analyse their effect against oxidative changes. During the study, sulphydryl contents and Ca-ATPase activity (0.297 to 0.136 mmol g⁻¹) decreased. Moreover, protein denaturation also prompted the surface hydrophobicity (11.47 to 32.06 μg) and carbonyls (26.36 to 49 mg.28 nmol mg⁻¹) of control MP. A significant decline was observed in emulsifying properties. Besides, EWP:β-CD showed remarkable stability against oxidative changes, by significantly reducing the carbonyls (26.26 to 37.69 nmol mg⁻¹) and surface hydrophobicity (11.51 to 20.31 μg) and also the decline of Ca-ATPase activity (0.29 to 0.19 mmol g⁻¹). It can be concluded that EWP:β-CD (6%) is an efficient approach against oxidative changes in MP from Culter alburnus.