Binding of Taurocholate by Pectin in the Presence of Calcium Ions

Binding of taurocholate by pectin was examined in vitro, using low-methoxyl pectin and calcium lactate. Water in calcium pectate gel was partially separated from the gel by filtration through a glass-filter. Taurocholate bound by pectin was calculated after measurement of taurocholate in the filtrate by the UV absorption method. The amount of taurocholate bound by pectin increased linearly with increase in pectin concentration but independent of time. One gram pectin bound a maximum of 6.0 μmole of taurocholate.     

Comparison of Transparent Gels with Turbid Gels Prepared from Egg White: Creep Analysis of Gels

Egg white from which the precipitate occurring during dialysis against water had been removed gave a transparent gel on heating at lower salt concentrations and pH 3.54. The addition of NaCl or a shift of pH from 3.54 to 4.50 brought about the turbid gels. Creep analyses of these transparent and turbid gels were done using a four-element mechanical model. The instantaneous elastic modulus, E₀, Newtonian modulus, ηn and retarded viscoelastic moduli, E₁ and η₁ increased with NaCl up to 125 mM and then decreased with increase in NaCl concentration at pH 3.54. At 125 mM NaCl and pH 3.54, a translucent gel was obtained. E₀ and η₁ decreased with the temperature of the gel, while E₁ and η₁did not change depending of temperature.     

Gel-Forming Characteristics and Rheological Properties of Kefiran

A water soluble polysaccharide “kefiran” produced by Lactobacillus kefiranofaciens was examined for its gel-forming and rheological properties. Kefiran (3%) formed gel in the presence of ethanol (4–10%). The gel strength in 8% ethanol was comparable to that of 3% gelatin gel in water. Addition of casein (3%) increased gel strength 1.5–2.0 fold. The unique properties of kefiran may make it a useful food additive.     

Toxic Compounds Formed on Prolonged Heating of Citrinin under Watery Conditions

Citrinin was partially decomposed by heating under aqueous conditions at 90°C for > 10 min and a group of degraded compounds (Group I) was detected by TLC. At 100°C and 110°C, citrinin disappeared rapidly, and the cytotoxicity of the samples increased with prolonged heating. At 120°C, citrinin disappeared more rapidly while TLC spots of Group I compounds also diminished upon >20 min heating and a new group of compounds (Group II) appeared. Cytotoxicity decreased rapidly at > 120°C and was eliminated after 10 min at 130°C. Group I appeared to contain toxic compound(s) but Group II did not. Heating citrinin under conditions similar to cooking may cause formation of additional cytotoxic compounds.     

Changes of Aldehyde Levels in Defatted Soybean Extract

Aldehyde levels in defatted soybean extracts were measured by using aldehyde dehydrogenase. The level increased during incubation of flour-water suspension and its centrifuged extract at pH 6.5, while it decreased markedly at alkaline pHs. This aldehyde-eliminating activity was observed in 1:5 flour:water ratio, but was not in 1:20 flour:water ratio. ¹⁴C-labelled acetaldehyde added to 1:5 flour:water extract was converted into acetic acid. Fractionation of the extract indicated that a heat-labile protein and a heat-stable compound with low molecular weight were required for the aldehyde-eliminating activity.     

Continuous Gel Formation by HTST Extrusion-Cooking: Soy Proteins

The continuous production of gels of high moisture content is carried out by extrusion-cooking, with a residence time of 30-100 sec, using soy protein isolate as a model ingredient. The hot viscous extrudate can be collected in a mold, and gels upon cooling. The best texture characteristics are obtained with protein and water concentrations of 18 and 80% (wet basis), respectively, and extrusion temperatures of 150-160°C. The effects of acidification, addition of NaCl, CaCl₂ or sucrose on gel texture are investigated. Extrusion-prepared soy gels melt reversibly upon further heating (120°C) and withstand frozen storage. Their texture and micro-structure are compared to those of soy gels prepared by conventional batch heating at 100-120°C.     

Continuous Restructuring of Mechanically Deboned Chicken Meat by HTST Extrusion-Cooking

The continuous restructuring of mechanically deboned chicken meat (MDM) was attempted using twin-screw extrusion-cooking at high moisture contents (50-80%), high temperatures (ca 150°C), short residence times (30-240 sec) and low pressures (below 6 bars). The hardness, cohesiveness and water-holding capacity of the nonexpanded moist extruded samples are optimal and resemble those of meat-loaf when 10-20% wheat flour or pregelatinized corn starch are added to MDM. Incorporation of 25% soy protein isolate gives a solid gel matrix containing dispersed meat particles. Scaling up this process could lead to the continuous production of simulated meat chunks or slices for use in canned or frozen dishes.     

Rheological Properties of Heat-Induced Ovalbumin Gels Prepared by Two-step and One-step Heating Methods

Ovalbumin gave a transparent solution, transparent gel, or opaque gel on heating at low ionic strength, but a turbid gel, or turbid suspension at high ionic strength (one-step heating). The ovalbumin solution, once heated at low ionic strength, gave a transparent gel with a second heating at high ionic strength (two-step heating). Textural parameters of hardness and adhesiveness, viscoelastic parameters from creep curves, breaking energy and water-holding capacity of these gels were measured. Transparent gels by the one- or two-step heating were firm and elastic and had high water-holding capacity. Turbid gels by one-step heating were soft and less elastic and had low water-holding capacity. The relationship between gel properties and structure was discussed.     

Thermally Induced Epitope Regions of Ovalbumin Identified with Monoclonal Antibodies

To identify the structural regions of the ovalbumin molecule that change during heat denaturation, we used monoclonal antibodies that reacted specifically with the soluble heat-denatured ovalbumin as probes. Five monoclonal antibodies recognizing different epitopes of the denatured ovalbumin were produced. Through the isolation and sequence analysis of the peptides derived from ovalbumin that reacted with the monoclonal antibodies, five parts of the ovalbumin molecule were identified as the regions that change structurally and provide new epitopes during heat denaturation. These findings could be useful information in understanding the structural properties of heat-denatured ovalbumin.     

Preparation of Heat-induced Transparent Gels from Egg White by the Control of pH and Ionic Strength of the Medium

Egg white was dialyzed against distilled water or diluted with water, and the precipitates formed were removed by centrifugation. The supernatant gave a transparent gel after being heated at an acidic pH (2–4). At other regions of pH, except for the highly alkaline region, the gel or suspension was turbid upon heating. Insufficient centrifugation of the dialyzed egg white or the addition of NaCl to the supernatant after centrifugation resulted in a turbid gel on heating at even acidic pH. The removal of the slight precipitate formed at low ionic strength and the maintenance of low ionic strength during heating were both necessary for production of a transparent gel.