Effect of pH and of Succinylation on the Water Retention Properties of Coagulated, Frozen and Thawed Egg Albumen

Egg albumen was modified to improve water retention properties of the coagulated, frozen and thawed product. Albumen was found to contribute more to expressible moisture (%EM) of coagulated whole egg mixture than yolk. For frozen and nonfrozen treatments, albumen (pH gt; 9.5) reduced %EM in both the coagulated albumen and whole egg mixtures made with pH-adjusted albumen. Succinylated albumen (≤0.2% g anhydridelg albumen) reduced %EM for frozen and nonfrozen treatments. Albumen at pH 10.5 and 11.0 required less time to attain an equivalent cook value than at pH 7.0,8.0,9.0, and 10.0.     

马铃薯淀粉废水蛋白的功能特性

以碱提酸沉法制备的马铃薯淀粉废水蛋白为原料,分别考察了pH值、NaCl浓度和温度对蛋白功能特性（溶解性、持水能力、乳化性及乳化稳定性、起泡性及泡沫稳定性）的影响。结果表明,pH值、NaCl浓度和温度对蛋白的功能特性产生不同程度的影响。在等电点（pH 4.0）时,马铃薯蛋白表现出最低的溶解性、持水性、乳化性、乳化稳定性及起泡性,而泡沫稳定性最好。在较低NaCl浓度（＜0.2 mol/L）时,蛋白溶解性、持水能力、乳化性和乳化稳定性随NaCl浓度的增加而提高,而高浓度的NaCl（＞0.2 mol/L）对上述性质具有抑制作用;蛋白的起泡性和泡沫稳定性在NaCl浓度为0.4 mol/L时具有最大值。在4～80 ℃范围内,蛋白质的各项功能性质随温度的升高均呈现先增加后降低的趋势,且溶解性、持水性、乳化稳定性、起泡性及泡沫稳定性在40 ℃时最佳,乳化性在60 ℃最佳。     

Isolation of Lysozyme from Hen Egg Albumen by Alcohol-Insoluble Cross-Linked Pea Pod Solid Ion-Exchange Chromatography

ABSTRACT: Albumen from hen eggs was diluted 3-fold with 0.05 M NaCl solution at pH 4.0 and was further treated with 30% ethanol for 8 h. The supernatant (77900 U/mg protein) thus obtained was further diluted (2.5-fold) with distilled water and its pH value was adjusted to 8.0 before being subjected to alcohol-insoluble cross-linked pea pod solid (AICLPPS) ion-exchange chromatography for lysozyme isolation. Results showed that AI-CLPPS ion-exchange chromatography increased the purification to 68-fold with a 72% lysozyme recovery from the starting albumen.     

EFFECT OF HEN EGG PRODUCTION AND PROTEIN COMPOSITION ON TEXTURAL PROPERTIES OF EGG ALBUMEN GELS

The effect of hen age, strain and dietary amino acid intake on the egg albumen gel textural properties was studied in two experiments by textural profile analysis (TPA) and uniaxial compression (UC) tests. In experiment 1, eggs from 4 different hen flocks were heat processed industrially. Egg rejection due to poor albumen gelling was correlated to hen age (r = 0.502), albumen dry matter (r =−0.632), gel hardness of 1^st compression (r =−0.765), and gel work of 1^st compression (r =−0.740) in TPA. In experiment 2 two hen strains, representing two levels of egg production, were fed diets with supplementation of L-lysine, methionine or both amino acids compared to a control diet. The lysine intake ranged from 818–1272 mg/hen/day and methionine intake from 377–575 mg/hen/day among hen groups, but without significant effect on the albumen gel texture parameters. The hen strains differed significantly in egg production (P<0.001), physical (P<0.001), chemical (P<0.05) and gel textural parameters of egg albumen (P<0.01). Hen age was essential, and correlated to the industrial egg rejection (r = 0.729), albumen dry matter (r =−0.902) and gel stress at fracture (r =−0.884). Albumen gels with high fracture stress values were found to contain a modified form of ovofransferrin.     

Foaming Properties of Selected Plant and Animal Proteins

The foaming properties of proteins are important in predicting their fnnctionality in aerated foods. In model aqueous systems, foam expansion (FE) and foam stability (FS) of commercial plant proteins, wheat germ protein flour (WGPF), corn germ protein flour (CGPF), and soy flour (SF), were compared with those of nonfat dried milk (NFDM) and egg white powder (EWP) at 1, 2, 4, 6, and 8% using one- and two-way analyses of variance. The effects of pH 4, 5, 6, 7, and 8 on FE and FS of WGPF were also measured. The highest overall FE and FS were obtained for EWP. Among plant proteins, FE and FS were maximum for CGPF and SF, respectively. FS was lowest for NFDM. Except for SF, FE and FS increased with increasing protein concentration. The FE and FS of WGPF were highest at pH 8, lowest at pH 7, and intermediate at pH 4–6.     

Effect of Albumen on TBA Values of Comminuted Poultry Meat

Fresh ground broiler meat was prepared and thoroughly mixed with 0, 5 and 10% raw or cooked albumen. The changes in TBA values for these ground meat-albumen mixtures were determined following storage at 2–4°C. Albumen reduced (P < 0.05) the TBA values of raw ground poultry meat but did not prevent carbonyl formation during storage. Raw albumen was more effective than cooked albumen. Adding albumen to ground poultry meat before oxidative cooking also decreased (P < 0.05) the amount of carbonyl volatiles produced.     

Surimi from Fillet Frames of Channel Catfish

Surimi was prepared with channel catfish mince recovered from fillet frames. The deboned meat was washed once, twice, or three times with water for surimi processing. Unwashed mince was also blended with cryoprotectants for surimi processing. Heat-induced gels were prepared using washed or unwashed catfish surimi with or without starch. Results indicated no differences (P>0.05) in textural properties and Hunter color values due to number of washes in those gels prepared with washed surimi. Differences (P<0.05) in proximate composition, textural properties and Hunter color values were found between gels prepared with washed and unwashed surimi.     

Storage of Shell Eggs Influences the Albumen Gelling Properties

Eggs from hens at 42 and 65 wk of age, respectively, were stored for time and temperature combinations of 0, 7, 10, and 14 d at 4, 12, 20, 28, and 37 °C in two experiments. The egg albumen was analysed for raw albumen quality parameters and dry matter content. Albumen gels prepared at either 85 °C or 90 °C were analysed for the textural properties corrected stress σ and Hencky strain ε at fracture point, σ_fandε_f , respectively, by uniaxial compression. The denaturation temperature, T_D, of ovalbumin in albumen samples was analysed by differential scanning calorimetry, DSC, and related to standards of N-ovalbumin and S-ovalbumin. Fresh egg albumen was characterised by the formation of gritty gels of poor water-holding capacity with lowσ_f and ε_fvalues. The stress and strain of gels at fracture were maximal after 14 d at 4 °C, and ε correlated significantly with ovalbumin T_Dfor gels prepared at 85 and 90 °C. The grouping of egg albumen samples with respect to the form of ovalbumin present (N-, intermediate, or S-) correlated with the egg mass loss during storage. Within the study, the storage temperature was more determining for the conversion of N-ovalbumin into S-ovalbumin than storage time.     

Storage Stability of Vacuum Packaged Frozen Pork Sausage Containing Soy Protein Concentrate, Carrageenan or Antioxidants

Fresh pork sausage patties containing carrageenan, without or with soy protein and an antioxidant were packaged with or without vacuum. They were evaluated for sensory properties, visual color, thiobarbituric acid reactive substances (TBARS), and Hunter color ‘L’, ‘a’, ‘b’ values at 4-wk intervals during 16 wk frozen storage. Rosemary extract was as effective as butylated hydroxytoluene (BHT)/propyl gallate (PG)/citric acid (CA) in antioxidant properties, but patties with BHT/PG/CA showed less surface discoloration (P < 0.05). In fat-control (FC) products, antioxidants combined with vacuum packaging provided optimum protection against rancidity. With vacuum packaging (VP), reduced-fat products maintained acceptable quality (TBARS and sensory properties) during 16 wks frozen storage.     

Effect of heat treatment on foaming properties of ostrich (Struthio camelus) egg white proteins

The effect of heat-treatment on foaming properties of ostrich albumen was investigated. At pH 7.5, coagulation of ovotransferrin (OT) resulted in minimum foaming capacity (FC) and maximum foam density (FD). While both exposure of sulfhydryl groups of ovalbumin (OV) and OT-OV interactions improved FC at lower pH, neither of them had beneficial effect on FC at pH 9. At pH 9, FC and FD were mildly affected by heat-treatment because of less aggregation of OT, then FC decreased due to covalent aggregates composed of ovomucin and OV, but at higher temperatures, higher level of OV unfolding resulted in enhanced FC.     

The significance of critical processing steps in the production of dried egg albumen powder on gel textural and foaming properties

The purpose of the present work was to study the variation in egg albumen functional properties as a function of seven selected processing steps from the initially raw liquid albumen to the final dried egg albumen powder. Albumen samples in six replicates were analysed for dry matter, pH, glucose, triglycerides, albumen gel properties (ie textural stress and Hencky strain, water‐ and protein‐binding capacity and gel colour L*, a*, b*), foaming properties (ie overrun, stability against drainage and bubble breakdown) and surface tension. The gel texture and water‐holding capacity significantly decreased during the processing steps from raw albumen through storage, centrifugation and ion exchange, whereas the final dry‐pasteurisation resulted in increased gel properties. Covalently linked protein polymers formed during the dry‐pasteurisation, as revealed by SDS‐PAGE, may explain this improvement. The foam overrun increased twofold during the three final steps of ultrafiltration, spray‐drying and dry‐pasteurisation compared with the raw albumen; however, the foam stability decreased, ie drainage and foam volume breakdown rates increased. The surface pressure increase was positively correlated with the foam overrun. This paper reveals at which processing steps the control of functional properties of egg albumen powder can take place. Copyright © 2004 Society of Chemical Industry     

茶叶籽粕蛋白功能特性研究

以大豆分离蛋白为对照,研究碱法和酶法提取茶叶籽粕蛋白的功能特性。结果表明：酶法提取茶叶籽粕蛋白的溶解性、吸油性、乳化能力和乳化稳定性、起泡性、凝胶脆度优于碱法提取茶叶籽粕蛋白,而后者的吸水性、泡沫稳定性则优于前者,两者所形成蛋白凝胶的黏性和硬度相当。碱法和酶法提取的茶叶籽粕蛋白的乳化能力和乳化稳定性稍优于大豆分离蛋白,但起泡性和泡沫稳定性则不及大豆分离蛋白,溶解性与大豆分离蛋白相当,它们形成凝胶的最低质量分数分别为13%和15%,凝胶的黏性和硬度低于大豆分离蛋白。pH值、蛋白质量分数、NaCl浓度等因素对茶叶籽粕蛋白功能特性均有不同程度的影响。     

鲤鱼鱼肉蛋白酶水解物抗氧化性及功能特性

采用碱性蛋白酶对鲤鱼鱼肉蛋白进行酶解,制备不同水解度的水解物。测定水解物的抗氧化活性以及不同pH值条件下水解物的功能特性。结果表明:随着水解度的逐渐升高,水解物的抑制脂质氧化能力、D PP H自由基清除能力、还原能力以及金属离子(Cu2+和Fe2+)螯合能力逐渐增加(P<0.05);同时,水解物的溶解性、乳化性和起泡性都在pH值为4.0(等电点)时达到最低,而后溶解性和乳化性随着pH值升高而增大(P<0.05),而起泡性随着pH值的升高先上升后又下降。因此,鲤鱼鱼肉蛋白碱性蛋白酶水解物可以提高蛋白质的抗氧化活性和溶解性,但是较高的水解度会在一定程度上降低其乳化性和起泡性。     

Heat-induced Egg White Gels as Affected by pH

The functional properties of heat-induced egg white gels were investigated at five pH values. Textural characteristics were determined using the Instron Universal Machine. Hardness, elasticity, cohesiveness, chewiness, and fracturability were maximum at pH 11. Hunter L values were maximum at pH 5 and 7. Microstructure studied with electron microscopy was distinctly different at the five pH values. Alkaline gels showed a fine ordered network that might have contributed to excellent textural characteristics. Water-holding capacity (WHC) was high at alkaline pH, but decreased with addition of 2-mercaptoethanol, suggesting that disulfide bonds were important in egg white gels. Sodium dodecyl sulfate (SDS) improved WHC at pH 7 and 9. No significant correlation was observed between textural profiles and WHC.     

Effect of Muscle Condition Before Freezing and Simulated Chemical Changes During Frozen Storage on the pH and Colour of Beef

The effect of rigor temperature (RT, 35 versus 10°C), increased ionic concentration (MS, 0 versus 0·2% mixed salts), oxidized lipids (OL, 0 versus 1% added oxidized fat), increased free amino acids (FAA, 0 versus 0·3% added mixture of amino acids), fat content (FC, 0 versus 15% added fat) and excluding atmospheric gases (V, 0 versus 99·9% vacuum) on pH and colour of mince stored for one month at -20°C was studied using a complete 2(6) factorial design. Adding FAA increased the meat pH measured after storage (p<0·001). Meat lightness (Hunter L* value) was increased by increased fat content (p<0·001), higher rigor temperature (p<0·001) and oxidized lipids (p<0·05). Vacuum packing tended to preserve redness (Hunter a*) whereas the higher rigor temperature decreased redness (p<0·001). Vacuum packing (p<0·05) and increased fat content (p<0·001) increased yellowness (Hunter b*). The hue angle was lowered by increased salt concentration (p<0·01), increased free amino acids (p<0·01) and using vacuum packing (p<0·001), whereas it was raised (p<0·001) by increased fat content and higher rigor temperature. Various significant two-and three-way interactions are tabulated and discussed.     

鸡蛋内部品质与其呼吸强度的关系

贮藏期鸡蛋品质的变化与呼吸作用息息相关,为了进一步明确鸡蛋内部品质与其呼吸强度之间的关系,本研究选取同一品种的鸡蛋作为实验样本,利用呼吸测定仪测定鸡蛋的二氧化碳呼吸强度,通过SPSS 19.0软件分别分析鸡蛋哈夫单位、蛋白高度、pH值、黏度、蛋黄指数、蛋黄比例以及蛋黄色度与呼吸强度间的关系。结果表明：鸡蛋哈夫单位、蛋白高度及黏度与呼吸强度之间呈极显著正相关（P＜0.01）;pH值与呼吸强度之间呈极显著负相关（P＜0.01）;蛋黄指数、蛋黄色度与呼吸强度之间呈极显著正相关（P＜0.01）;而蛋黄比例与呼吸强度间相关性较小;此外,pH值与黏度、蛋黄指数、蛋黄色度间均存在极显著负相关（P＜0.01）;黏度与蛋黄指数、蛋黄色度之间呈极显著正相关（P＜0.01）;蛋黄比例与其他参数相关性较小。总之,在鸡蛋内部品质参数中,鸡蛋哈夫单位、蛋白高度、蛋黄指数、pH值、黏度及蛋黄色度对呼吸强度影响较大。     

Effect of some traditional processing operations on the functional properties of African breadfruit seed (Treculia africana) flour

The effect of germination, fermentation, roasting and defatting on the proximate composition, water absorption capacity (WAC), oil absorption capacity (OAC), foaming capacity (FC), foaming stability (FS), emulsion capacity (EC), emulsion stability (ES), packed bulk density (PBD), least gelation concentration (LGC) and protein solubility (PS) of breadfruit seed flour (BSF) was investigated. WAC, OAC, FC, EC, PBD and LGC obtained are 190-380%; 130.3-200.5%; 2.3-60.4%; 12.4-52.9%; 0.4-0.6 g/ml; 6-12% (w/v) and 200-420%; 176.4-320.6; 4.2-70.8%; 20.2-60.4%; 0.5-0.7 g/ml; 0.5-0.8% (w/v) in the full fat and defatted flours respectively. Foams were more stable in the untreated; least in fermented and roasted samples. Defatting improved the FC, FS and EC; roasting and fermentation reduced EC of full fat BSF; Processing and defatting had no effect on the PBD; roasting and germination increased LGC while defatting and fermentation reduced it. Full fat flours had the lowest PS at pH 4 and the highest at pH 8. Fermented full fat BS flour had the highest PS at pH 5 and 8. Defatted germinated, raw dried and roasted BSF had lowest PS at pH 4; PS of fermented BSF is lowest at pH 3 and highest at pH 2.     

WATER-HOLDING AND COLOR CHARACTERISTICS OF BEEF FROM ELECTRICALLY STIMULATED CARCASSES

Electrical stimulation (ES) was applied to the right sides of 15 beef carcasses and the corresponding left sides were used as nonstimulated (NS) controls. Data collected included: postexsanguination pH (0.5, 3, 6, 24 h), L, a, and b color values, drip loss, and expressible moisture. Muscles from ES carcasses tended to have more accelerated postmortem pH declines than the corresponding muscles from NS carcasses. M. triceps brachii had a lower pH at 0.5 h (P < 0.05) , M. longissimus thoracis had a lower pH at 0.5 h (P = 0.055) and 3 h (P < 0.05), and M. semimembranosus had a lower pH at 0.5 and 3 h (P < 0.05), respectively. Hunter L, a, and b values did not differ within ES and NS treated muscles. Additionally, ES did not influence color values of the M. semimembranosus. ES did not affect drip loss or expressible moisture in beef muscles.     

DRY BEAN (PHASEOLUS VULGARJS) COLOR STABILITY AS INFLUENCED BY TIME and MOISTIJRE CONTENT

The color stability of 32 lines of beans to which different levels of moisture were added was evaluated in an accelerated shelf-life testing chamber for up to 10 weeks using Hunter values and National Bureau of Standard (NBS) unit of color difference (± E) techniques. With pinto beans, Hunter L values decreased as storage time increased. Also, Hunter a values increased with time. However, Hunter b values did not change with storage. With great northern beans, Hunter a and b values were more important than Hunter L value. Similar to pinto beans, along with prolonged storage, great northern bean color changed. Pinto and great northern beans having an extra 10% added moisture showed much more color change than those of control or 5% moisture added beans. Finally, bean genotype was closely related with color stability in stored pinto and great northern beans.     

Influence of konjac flour on foaming properties of milk protein concentrate and quality characteristics of gluten‐free cookie

The effects of konjac flour (KF) for modifying the foaming properties of milk protein concentrate (MPC) and characteristics of gluten‐free rice cookies were investigated. The three variables of konjac concentration (0.1–0.4%), pH (pH 5–9) and NaCl concentration (0.2–0.6 м) were studied. Both KF and pH had considerable effects on the foaming capacity (FC) and foaming stability (FS) of MPC. The NaCl had a negligible effect. Lowered FC and FS observed at pH 9 and pH 5 were increased with the increase in KF addition. Batter characteristics (flowability and consistency), cookie quality (moisture, yield, spread ratio, specific volume, hardness and colour) and sensory acceptance were evaluated in gluten‐free cookies with 0%, 0.25% and 0.4% KF. Konjac supplementation increased batter characteristics, yield, specific volume and hardness, but decreased lightness. Panellist acceptance, especially regarding texture and overall acceptability, increased in gluten‐free cookies with 0.4% KF. A higher purchasing decision was found for cookies with added KF.