Oxymyoglobin and Lipid Oxidation in Phosphatidylcholine Liposomes Retarded by α-tocopherol and β-carotene

An n-3 fatty acid-constructed oxymyoglobin liposome model was used to study the effects of 10 μM α-tocopherol and/or various concentrations of β-carotene on oxymyoglobin and lipid oxidation. Oxidation was delayed by α-tocopherol or β-carotene treatments alone (p < 0.05). β-Carotene at 1.5 μM and 2μM caused greater delay in oxymyoglobin oxidation than α-tocopherol (p < 0.05). For lipid oxidation inhibition, 2 μM β-carotene was similar in effect to α-tocopherol. With α-tocopherol plus 1.5 or 2 μM β-carotene, greater oxidation delaying effect resulted for both oxymyoglobin and lipid oxidations than with 1.5 or 2 μM β-carotene treatment alone (p < 0.05).     

α-Tocopherol, β-Carotene and Ascorbic Acid as Antioxidants in Stored Poultry Muscle

Broilers were fed α-tocopherol or β-carotene for 3 wk or L-ascorbic acid for 24 hr prior to slaughter. α-Tocopherol maintained the redness of unheated meat stored for 8 wk (—20°C). Values for thiobarbituric acid reactive substances in ground, stored meat showed that L-ascorbic acid produced results similar to the control while a-tocopherol produced results lower than the control. Panelists rated meat with added α-tocopherol as different from the control for smell and flavor. β-Carotene was a pro-oxidant compared to the control and other additives. Meat from broilers fed β-carotene had lower α-tocopherol content than the control. Vitamin A in livers of birds fed β-carotene was 64% higher than that of the control.     

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.     

β-Lactoglobulin – a three-dimensional perspective

Summary Bovine β-lactoglobulin has been the subject of intense study over the past 60 years by, effectively, every available physicochemical technique, of which one of the most powerful is X-ray crystallography. We present a short review of the X-ray crystallographic work on milk protein together with an overview of the properties as they are seen from the current state of crystallographic analyses. At the present time, structural analyses do not provide any further insights into the possible function of the protein.     

Optimization of Thermal Pretreatment Conditions for the Separation of Native α-Lactalbumin from Whey Protein Concentrates by Means of Selective Denaturation of β-Lactoglobulin

ABSTRACT: In this study a method to obtain native α-lactalbumin with a high degree of purity of 98% (m/m) and recovery of 75% (m/m) by selective denaturation of β-lactoglobulin was developed. To achieve this goal, the thermal pretreatment of whey protein concentrate was optimized varying the composition of the liquid whey protein concentrate in terms of total protein, lactose and calcium content, and pH value. The kinetics of the thermal denaturation of α-la and β-lg were then investigated at predetermined optimal composition (protein content 5 to 20 g/L, lactose content 0.5 g/L, calcium content 0.55 g/L, and pH 7.5). Using the activation energies and reaction rate constants obtained, lines of equal effects for targeted denaturation degrees of α-la and β-lg were calculated. Depending on total protein content, an area of optimal heating temperature/time conditions was identified for each protein concentration level.     

Quenching Mechanisms and Kinetics of α-Tocopherol and β-Carotene on the Photosensitizing Effect of Synthetic Food Colorant FD&C Red No. 3

ABSTRACT: Effects of FD&C Red No. 40, Red No. 3, Yellow No. 5, Yellow No. 6, Green No. 3, Blue No. 1 and Blue No. 2 on 0.03M soybean oil oxidation in acetone at 25 °C under light were studied by measuring headspace oxygen depletion. As Red No. 3 increased from 0 to 5, 20, 100 and 200 ppm, the headspace oxygen was reduced by 2 to 70, 73, 77 and 77%, respectively, for 4 h. Only Red No. 3 acted as a photosensitizer to produce singlet oxygen in the oil. The quenching rates of α-tocopherol and β-carotene for the singlet oxygen by Red No.3 were 4.1 × 10⁷ M⁻¹s⁻¹ and 7.3 × 10⁹ M⁻¹s⁻¹, respectively. When β-carotene was below 1.86 × 10⁻⁶ M, β-carotene quenched singlet oxygen, but it quenched both singlet oxygen and Red No. 3 at or above 3.72 × 10⁻⁶ M. However, α-tocopherol quenched singlet oxygen only.     

Expression of recombinant wild-type and mutant β-Lactoglobulins in the yeast Pichia pastoris

Summary We have produced β-lactoglobulin gene constructs in the pGAPZαA vector for over expression of recombinant wild-type and a putative monomeric mutant protein in Pichia pastoris . Levels of expression of at least 150 mg L⁻¹ of the wild-type were achieved in shake flask culture. Ion exchange chromatography showed that the expressed recombinant wild-type β-Lg eluted as a heterogeneous mixture of species, some of which may be owing to small variations in the N-terminus and some to ligand binding. The putative monomeric β-lactoglobulin construct gave an expressed protein that was recognized by anti bovine β-lactoglobulin antibody, but we do not know yet if it forms monomers rather than dimers.     

Caustic-induced gelation of β-lactoglobulin

The gelation kinetics of β-lactoglobulin (βLg) solutions has been determined in the alkaline regime over a wide range of protein concentrations, gelling temperatures and gelation pH (pH_gel), set using NaOH. The behaviour is compared with caustic-induced gelation of whey protein concentrate and the alkaline dissolution of heat-induced whey gels. The gelation time decreases significantly between neutral conditions and pH_gel 9, because of the activation of the free cysteine groups and displacement to the monomeric form, and between pH_gel 10 and 11, due to the base denaturation of βLg. Both transitions are associated with a significant decrease in the activation energy of gelation. At pH_gel >11.5 the gelation time is observed to increase with pH_gel, owing to destruction of interprotein crosslinks. These results are consistent with the recently reported observation that a minimum pH for the dissolution of βLg gels and aggregates exists around 11.6 [ Biomacromolecules 8 (2007) 1162]. This phenomenon has been assigned to the destruction of non-covalent interactions that would inhibit the final percolation of the gel.     

Determination of α-bisabolol and d-panthenol in cosmetic products by gas chromatography

α-bisaboloi and d -panthenol are used in many cosmetic preparations, respectively, for their anti-inflammatory and regenerating properties. Their quantitative determination was an important element of their evaluation in these emulsions. Their concentration has been determined by gas chromatographic techniques, using a flame ionization detector. In both cases, the internal standards have been chosen for their compatibility with the analysis of extracted substances.
Owing to the complexity of the cosmetic formulations, a preliminary extraction of α-bisabolol and d -panthenol was necessary. For the two substances the preparative separation was based on a liquid–liquid extraction. After dissolving the emulsion in methanol and diluting it with an aqueous buffer solution α-bisabolol was then extracted by ethyl acetate and d -panthenol by ethyl formate.     

Specific Anosmia Observed for β-Ionone, but not for α-Ionone: Significance for Flavor Research

ABSTRACT:  In the context of measuring thresholds of orange flavor compounds in a deodorized orange juice matrix, it was found that 50% of panelists could not perceive β-ionone or β-damascenone as well as the other panelists. Orthonasal and retronasal thresholds for β-ionone were, respectively, 985 and 490 times higher for nonperceivers than perceivers. For β-damascenone, the ratios were 690 and 390 times higher for ortho- and retronasal thresholds, respectively. Panelists who could not perceive β-ionone were otherwise good perceivers of most compounds tested. There were no such differences for α-ionone, a constitutional isomer of β-ionone. All 3 compounds were retested in water using the same panelists. Differences between nonperceivers and perceivers of β-ionone were 4900 and 4600 times higher for ortho- and retronasal thresholds for nonperceivers, respectively. However, for β-damascenone, no such differences were found when measured in water. The same panelists could be classified as "perceivers" or "nonperceivers" when β-ionone was tested in deodorized orange juice or in water. A different panel was used to confirm β-ionone and β-damascenone thresholds in water. A greater difference between perceivers and nonperceivers was found for β-ionone; as with the first panel, there were no differences in sensitivity to β-damascenone between panelists when the compound was tested in water.     

Specific Disulfide Bond in α-Lactalbumin Infiuences Heat- Induced Gelation of α-Lactalbumin-Ovalbumin-Mixed Gels

The gel strength of ovalbumin mixed with α-lactalbumin (α-La) was determined after heating at 80°C for 15 min at pH 7.0 Gel strength of the mixture of 4%α-La and 4% ovalbumin was two times that of 8% ovalbumin. Modified α-La at Cys6-Cys120 (3 SSα-La) had low enhancement effects on ovalbumin gelation. Competitive ELISA using monoclonal antibody to α-La showed decreased binding reactivities after heating α-La with ovalbumin at specific concentrations. The decrease of total SH groups in the gel mixed with 3SS α-La was much less than when mixed with α-La. A disulfide bond of Cys6-Cys120 in α-La contributed to interactions between ovalbumin and α-La in heat-induced gels.     

α-Tocopherol Content and Oxidative Stability of Egg Yolk as Related to Dietary α-Tocopherol

Hens fed diets with 0.0, 7.5, 15.0, 30.0, 60.0 and 120.0 mg supplemental α-tocopherol/kg feed produced egg yolks with 25,30,35,45,50 and 75 μg/g yolk, respectively. The correlation coefficient between dietary α-tocopherol (mg/kg diet) and egg yolk α-tocopherol (μg/g egg yolk) after 28 days feeding was 0.99. The supplemented dietary α-tocopherol had an effect on the α-tocopherol in egg yolk (p<0.05). The oxidative stability of yolk was determined by measuring the oxygen and volatile compounds in the headspace of bottled yolk. α-Tocopherol had an effect on the stability of yolk as an antioxidant at 25, 45 and 50 μg/g yolk and a prooxidant at 75 μg/g or above (p<0.05). The addition of 60.0 mg α-tocopherol/kg diet resulted in the best egg yolk stability. The correlation coefficient between headspace oxygen disappearance and volatile compound formation in the headspace of bottled egg yolk was 0.84.     

Composition and Structure of Fat Bloom in Untempered Chocolate

It is generally accepted that visual fat bloom is caused by the separation of cocoa butter toward the surface. However, this is not always true for all types of bloom. One type of fat bloom, which can occur due to lack of tempering, has still not been completely elucidated. We performed a compositional and structural study of this type of fat bloom in plain chocolate. More specifically, we performed (1) an investigation of its crystallographic properties, (2) investigation of fat content, (3) analysis of the composition of triacylglycerol (TAG), (4) stereomicroscopic observations, and (5) observation and elemental analysis using a scanning electron microscope with an energy‐dispersive X‐ray spectrometer (SEM‐EDS). In the bloomed chocolate, the fat content in the light brown phase was lower than that in the black phase. Concerning fat composition, the content of sn‐1,3‐saturated acyl, sn‐2‐oleoyl glycerols (Sat‐O‐Sat type TAGs) in the light brown phase was lower. The lower fat content is thought to result in its lighter color. The results of our composition analysis and morphological observations suggest that the mechanism of the bloom generation due to nontempering involves not the separation of fat toward the surface but the crystallization of fat which leads to withdrawal of fat from the vicinity of the growing crystal, leading to differences in fat content.     

Cholesterol Reduction in Liquid Egg Yolk using β-Cyclodextrin

A process to reduce cholesterol in liquid egg yolk using β-cyclodextrin (CD) was optimized by response surface methodology, based on cholesterol reduction and yield. The most important factors influencing cholesterol reduction were dilution of egg yolk to a defined water:solid ratio and CD concentration. In the final process, egg yolk was adjusted to pH 10.5, diluted to a water:solid ratio of 2.9, heated to 50°C, and CD added at a CD:cholesterol molar ratio of 4.0. The slurry was mixed for 6.5 min at 1800 rpm, cooled to 4°C and centrifuged. Cholesterol in the supernatant was reduced by 89.2%. The yield, cholesterol and CD in the final product were adjusted by varying centrifugal force and CD concentration.     

Interactions of (β-Lactoglobulin and High-methoxyl Pectins in Acidified Systems

The interactions that occur when β-lactoglobulin (β-lg) is mixed with a high-methoxyl pectin (HMP) and a modified pectin (mHMP, modified using plant pectinesterase) were examined at pH 3.8. Whereas soluble aggregates formed in β-lg-HMP, β-lg-mHMP precipitated upon mixing. β-lg-HMP mixtures showed soluble aggregates with larger hydrodynamic diameters when heated at 65°C than when heated at 90°C. β-lg-HMP mixtures adjusted to pH 6.0 after heating showed that the aggregates formed at 65°C could be dissociated, but the complexes were not reversible after heating at 90°C. A similar effect also was observed when resuspending the°-lg-mHMP precipitates at pH 6.0. The behavior of the 2 pectins was attributed to their differences in charge distribution.     

Stability of α-, γ-, or δ-Tocopherol during Soybean Oil Oxidation

ABSTRACT:  The decomposition of α-, γ-, or δ-tocopherol in soybean oil during 24 d of storage at 50 °C was determined by high performance liquid chromatography (HPLC). The initial contents of α-, γ-, and δ-tocopherol in soybean oil were 53, 750, and 268 ppm, respectively. The degradation rates of α-, γ-, and δ-tocopherol for the first 10 d were 5.6%, 1.2, and 0.5% per day, respectively. The α-tocopherol was completely destroyed in 16 d. The destructions of γ- and δ-tocopherol were 28% and 17% after 24 d. The induction period of soybean oil determined by headspace oxygen, conjugated diene, and peroxide value was 8 d. As the degradations of α-, γ-, and δ-tocopherol increased, the headspace oxygen disappearance, conjugated diene formation, and peroxide value of soybean oil increased. The correlation coefficient between the degradation of tocopherols and the oxidation of soybean oil was about 0.95. The degradation of tocopherols in soybean oil during storage was due to the oxidation.     

β-Glucosidases from Soybeans Hydrolyze Daidzin and Genistin

β-Glucosidases which hydrolyze isoflavone glucosides, daidzin and genistin, were partially purified from soybean cotyledon. Three iso-forms of β-glucosidases (A,B,C) were separated on a CM-Sephadex C-50 ion exchange column. β-Glucosidase-B and C brought about nearly all of the hydrolyzing action on daidzin and genistin. β-Glu-cosidase-B and C were further purified with gel-filtration chromatog-raphy, and the partially purified enzymes were characterized at pH 5.0 and 45°C, (optimum conditions). Adding the β-glucosidase-B and C to soymilk at 45°C, both enzymes hydrolyzed daidzin and genistin and caused an increase in aglycones daidzein and genistein.     

β-Galactosidase Activity and Cell Wall Breakdown in Apricots

ABSTRACT: Apricots ( Prunus armeniaca L., cultivars Magyar and Bergeron ) were harvested 3 d apart (1st, 2nd and 3rd harvest). Fruits were stored at 4 to 6 °C, 90 % relative humidity, for 3 to 25 d. (β-Galactosidase activity, pectin degradation, and softening were studied as a function of harvest and storage time. (β-Galactosidase activity increased as a function of harvest; it increased continuously during storage in the case of cv. Bergeron. With Magyar enzyme activity reached a maximum value during storage in the case of 2nd and 3rd harvest fruits, then it declined. Total pectin and that solubilized neutral carbohydrate contents decreased as a function of storage. Solubilized pectin quantity did not depend either on harvest or on storage.     

Optimizing Cholesterol Removal in Cream Using β-Cyclodextrin and Response Surface Methodology

Average cholesterol reduction increased as β-cyclodextrin concentration increased, regardless of other factors. The process was optimized using RSM. When β-cyclodextrin addition was 10%, the effect of stirring speed was more noticeable than that of stirring time. When stirring speed was at 1,600 rpm, 94.2% of cholesterol was reduced in 30 min. When stirring time was 20 min, the cholesterol was reduced 97.99% using 15%β-cyclodextrin. When stirring speed was 1,200 rpm, the effect of β-cyclodextrin addition was greater than that of stirring time. Although the percentage of cholesterol reduction varied with different factors and conditions, about 94% of cholesterol was removed from cream.