Enrichment of Genistein in Soy Protein Concentrate with Hydrocolloids and β-glucosidase

ABSTRACT: The effects of hydrocolloid (propylene glycol alginate, K-carrageenan, citrus pectin, and xanthan gum) additions in soy protein concentrate (SPC) preparation on genistin and genistein retentions were investigated. Additions of xanthan, alginate, pectin, and carrageenan in SPC prepared with the acid leach method gave 0.711, 0.760, 0.792, and 0.825 mg/g genistein, respectively, whereas control SPC prepared without hydrocolloid gave 0.721 mg/g genistein. SPC prepared under optimum conditions for (β-glucosidase hydrolytic activity with xanthan, alginate, carrageenan, and pectin had 0.943, 0.975, 1.015, and 1.132 mg/g genistein, respectively, compared to genistein in control SPC (0.845 mg/g) under the optimum conditions. Combined (β-glucosidase and pectin treatment in SPC preparation resulted in high genistein SPC (1.551 mg/g).     

Anthocyanin Analysis as a Measure of Glycosidase Activity in Enzymes for Juice Processing

A screening procedure combining HPLC and spectrophotometric analyses was developed to measure glycosidase activity of enzyme preparations used for juice processing. Enzyme preparations (27) were evaluated; several contained β-galactosidase activity which can decompose cranberry juice pigments. β-galactosidase and α-arabinosidase activities were also determined using standard procedures (nitrophenol glycosides as substrates). Comparative results showed inconsistencies between the two procedures. Cranberry juice processing demonstrated that some enzyme preparations could decompose anthocyanin pigments under processing conditions. Pigment loss was much higher when enzymes were used with juice than with crushed fruit.     

Characterization of the β-Glucosidase Activity Produced by Enological Strains of Non-Saccharomyces Yeasts

ABSTRACT: The β-glucosidase activities of 20 wine-related non- Saccharomyces yeasts were quantified, characterized, and assessed for their efficiency in releasing aroma-enhancing compounds during the winemaking process. Of these enzymatic activities, the β-glucosidase activity of Debaryomyces pseudopolymorphus revealed the most suitable combination of properties in terms of functionality at wine pH, resistance to wine-associated inhibitory compounds (glucose, ethanol, and sulfur dioxide), high substrate affinity, and large aglycone-substrate recognition. Its potential as a wine aroma-enhancing enzyme was confirmed by the significantly increasing concentrations of free volatiles (citronellol, nerol, and geraniol) during the fermentation of Chardonnay juice inoculated with both D. pseudopolymorphus and a widely used commercial starter culture strain of Saccharomyces cerevisiae , VIN13.     

Enzymic Transformation of Isoflavone Phytoestrogens in Soymilk by β-Glucosidase-Producing Bifidobacteria

ABSTRACT: Five strains of bifidobacteria were screened for β-glucosidase activity using p-nitrophenyl-β-D-glucopyranoside as the substrate, and selected strains were used to ferment soymilk. Enumeration of viable bifidobacteria and quantification of isoflavones using HPLC were performed at 0, 12, 24, 36, and 48 h of incubation. Four strains produced β-glucosidase. B. pseudolongum and B. longum -a displayed the best growth in soymilk, with an increase of 1.3 log₁₀ CFU/mL after 12 h. B. animalis, B. longum -a, and B. pseudolongum caused hydrolysis of isoflavone malonyl-, acetyl- and β-glucosides to form aglycones, and transformed daidzein to equol in soymilk. Fermentation of soymilk with Bifidobacterium sp. resulted in a significant increase (p < 0.05) in the concentration of aglycones.     

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.     

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.     

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.     

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.     

Quantitative X-Ray Diffraction Determination of α-Lactose Monohydrate and β-Lactose in Chocolate

ABSTRACT:  Lactose is a constituent of milk chocolate. During processing and cooling, lactose may precipitate as α-lactose monohydrate and β-lactose. The presence of α-lactose monohydrate has a deleterious effect on the quality of milk chocolate. A quantitative X-ray diffraction method for determination of α-lactose monohydrate and β-lactose in chocolate is described. The α-lactose monohydrate signal at 19.9°2θ with Cu-Kα X-rays is a cubic function of concentration. The β-lactose signal at 20.9°2θ is a linear function of concentration. α-Lactose monohydrate is detectible at about 0.1 weight% and can be quantified at >0.5 weight%. β-Lactose is detectible at about 1 weight% and can be quantified at >3 weight%. About 10 min is required to prepare and run a sample.
Practical Application: The crystalline form of lactose affects the quality of chocolate. A rapid method for quantifying crystalline forms of lactose in chocolate is described. The method can be used for quality control and for improving chocolate quality.     

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.     

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).     

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.     

Entrapment of nutrients during cholesterol removal from cream by crosslinked β-cyclodextrin

This study was designed to elucidate the quantities of nutrients entrapped during cholesterol removal from cream by crosslinked β-cyclodextrin (β-CD, 4–12%, w/v) and to evaluate the amounts of the residual β-CD in cholesterol-removed cream treated by crosslinked β-CD. The content of lactose in the control cream (without the treatment by crosslinked β-CD) was 2.74%, and the amounts of lactose entrapped by crosslinked β-CD ranged from 0.00 to 0.03%. The total amounts of the entrapped short-chain free fatty acid (FFA) and free amino acid (FAA) ranged from 0.04 to 0.12 ppm and from 0.37 to 0.48 μmol/mL, respectively. The amounts of the entrapped water-soluble vitamins (L-ascorbic acid, niacin, thiamine and riboflavin) ranged from 0.01 to 0.05 ppm, from 0.01 to 0.05 ppm, from 0.00 to 0.04 ppm and from 0.02 to 0.05 ppm, respectively. The entrapped amounts of nutrients mentioned above were not remarkably affected by the concentrations of crosslinked β-CD (4–12%, w/v). The very small amounts of residual β-CD in the cholesterol-removed cream were measured (1.86–6.11 ppm). Based on the data obtained from the present study, it is concluded that the amounts of entrapped nutrients were negligible during cholesterol removal from cream by crosslinked β-CD, and the amounts of residual β-CD in cholesterol-removed cream were trace.     

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.     

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.     

Cholesterol Removal from a Lard-water Mixture with β-Cyclodextrin

The effect on removing cholesterol from a lard-water mixture by β-cyclodextrin (β-CD) increased with increasing level of β-CD (1–10%). About 90% of cholesterol was removed from lard by 5%β-CD with 1: 1 ratio of lard-to-water and stirrina at 150 rpm and 27°C for 1 hr. The acid value of β-CD treated lard was significantly decreased due to removal of free fatty acid. The peroxide value of β-CD treated lard was slightly increased whereas the fatty acid composition apparently was not changed.     

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 Separation from Whey Protein Isolate on a Large Scale

A method for obtaining large quantities of β-lactoglobulin (β-Lg) from commercial whey protein isolate (WPI) was developed. β-Lg was separated from the rest of the whey proteins in a solution of 15% (W:W) WPI in distilled water adjusted to pH 2 and 7% NaCl. β-Lg was then separated from NaCl using diafiltration. The results indicate that more than 65% of the β-Lg originally in the WPI solution was recovered. The purity of the β-Lg was greater than 95%.     

Properties of cholesterol-reduced ice cream made with cross-linked β-cyclodextrin

This study examined the properties of cholesterol-reduced ice cream stored at −12, −18 and −28°C. Over 90.0% cholesterol was removed, and ice crystal size decreased while viscosity increased as the freezing temperature decreased in the cholesterol-reduced ice cream. The melting time was slightly shorter in the cholesterol-reduced ice cream than in the control. A significant difference was found in the dull colour, and crumbly and unnatural flavour, especially when stored at −28°C, regardless of cross-linked β-cyclodextrin treatment. This study indicated that although some differences were observed, most of the properties of the cholesterol-reduced ice cream were comparable to the control ice cream.     

Cold Gelation of β-lactoglobulin in the Presence of Iron

ABSTRACT: To protect and transport iron, we investigated the trapping properties of a network formed from β-lactoglobulin. We studied the influence of different parameters—pH, iron, and protein concentrations—on gel properties (optical and mechanical properties, WHC, and microstructure). For all conditions tested, the results show the formation of a cold gel in the presence of iron. The mechanical properties reveal that the elastic behavior and the strength of rupture increase with higher protein concentrations and decrease with higher iron concentrations. The water-holding capacity is high for low iron concentrations. The microstructure shows that, at low iron/protein ratios, a homogeneous filamentous network is obtained whereas, at high iron/protein ratios, more random aggregated particles are present.