RHEOLOGICAL STUDY OF O/W EMULSIONS CONTAINING DRIED WHOLE EGG AND LOCUST BEAN GUM

The influence of sucrose addition and type of salt (NaCl; Morton Lite salt: 50% NaCl and 50% KCl, and Mineral salt: 65% NaCl, 25% KCl and 10% MgSO₄) on the rheological properties of O/W emulsions containing locust bean gum was analyzed. Flow curves over the range 0.1 to 100 s⁻¹ and transient flow curves at 0.2 s⁻¹, at 20 and 30C were obtained for 12 different emulsions, containing 30% (w/w) of sunflower oil. The K and n power law parameters and the hysteresis loop area (HL) were evaluated from the flow curve. So were the Hahn parameters from time-dependent stress decay fitting. Rheological behaviour of emulsions was affected by the type of salt and the presence of sucrose. Changes in solvent properties of the continuous phase in the emulsions on the macromolecules present could be responsible for the different behaviour. The ageing effect on flow behaviour parameters and on the hysteresis loop area was also studied. Evolution of rheological parameters during emulsion storage suggests that increase of ionic strength and polar solutes concentration decrease the stabilizing properties of locust bean gum.     

MASKING OF THE BITTER TASTE OF SALT SUBSTITUTES WITH LACTOSE IN FOOD EMULSIONS

The forced-choice triangle test was used in the sensory evaluation of two emulsions containing salt mixtures similar to Morton Lite Salt or Mineral Salt against the same emulsions containing NaCl with an equal level of saltiness. 1%–2% wt/wt of lactose either in combination with sucrose or glucose and galactose produced a flavor which was not distinguished from that of 1.00% of NaCl. Sucrose alone was not able to mask the bitter taste of the mixtures in mayonnaise, nor were the other sugars in combination with 0.3% of lactose and 3.0% of vinegar in a simple emulsion. Doubling the vinegar concentration produced a complicated masking behavior with increasing concentration of lactose.     

DENATURATION OF PLANT PROTEINS RELATED TO FUNCTIONALITY AND FOOD APPLICATIONS. A Review

Proteins can be denatured by heat, changes in pH, organic solvents, detergents, urea, guanidine hydrochloride or other methods that modify the secondary, tertiary or quaternary structure, without breaking any covalent bonds. Physical-chemical measurements or functionality related to denaturation include solubility, viscosity, dissociation into subunits, sedimentation constant, optical rotation, association and ultraviolet spectra. The relationship between pH, temperature and rate of denaturation of wheat and soy proteins is complex. Optimum heat treatment of soy flakes, for example, inactivates nearly all biologically active components, but the protein retains most of its functionality. Knowledge about protein denaturation helps to produce food products with desirable functional properties.     

INFLUENCE OF GEL NETWORKS IN CONTROLLING CONSISTENCY OF O/W EMULSIONS STABILISED BY MIXED EMULSIFIERS

A coherent explanation is presented of the mechanisms by which mixed emulsifiers of the surfactant/fatty alcohol type both stabilise and control the consistencies of oil-in-water emulsions. Original and published data are used to develop a theory in which the semisolid and other flow properties of emulsions are related to the nature, strength and extent of viscoelastic networks present in the continuous phases. These networks form from the interaction of surfactant solution with fatty alcohol and have similar properties to ternary system gels formed when the mixed emulsifiers disperse in water, in the absence of an oil. The theory is discussed with particular reference to liquid paraffin-in-water emulsions prepared with the surfactants anionic sodium dodecyl sulphate, cationic alkyltrimethylammonium bromides or non-ionic cetomacrogol and fatty alcohols cetyl and stearyl and their mixtures, especially cetostearyl. It may be used also to explain the properties of emulsions prepared with a variety of oils, surfactants and amphiphiles. The effects of variation in storage time, surfactant type (ionic or non-ionic), temperature, mixed emulsifier concentration, and alcohol and surfactant chain lengths on the rheological and microscopical properties of ternary systems and emulsions support this theory. The importance of small strain experiments (creep and oscillatory) in providing a true measure of consistency is emphasized. Continuous shear experiments, although theoretically less satisfactory, provide useful additional information when correlated with the small strain data.     

RHEOLOGICAL PROPERTIES AND APPLICATIONS OF MESQUITE TREE (PROSOPIS JULIFLORA) GUM 2. RHEOLOGICAL PROPERTIES AND STABILITY OF O/W EMULSIONS CONTAINING MESQUITE GUM

Oil-in-Water emulsions stabilised by mesquite gum have been examined by their creep compliance-time response at a constant low shear stress and by shear stress-shear rate studies. The Theological data were influenced by pH, electrolyte (NaCl, CaCl₂) and aging time. Both pH and electrolyte altered the degree of compactness of the mesquite molecules adsorbed on the oil drops. Aging produced changes in the rheological properties, the general trend depending on the rate of drop coalescence and the ability of adsorbed mesquite layers on adjacent flocculated drops to interpenetrate and form new linkages. The drop coalescence rate was highest at pH 7.0, but this was offset by greater interpenetration so that the rheological parameters increased substantially during aging.     

A MODIFIED RIGIDITY MODULUS TECHNIQUE FOR STUDYING THE RHEOLOGICAL PROPERTIES OF W/O EMULSIONS CONTAINING MICROCRYSTALLINE WAX

The creep compliance-time responses at constant pressure of W/O emulsions containing microcrystalline wax were determined by subjecting them to air pressure in a glass U-tube and measuring the resultant volume deformations. The constant stress at the tube wall was 2.52 times 10² dyn cm^-2. Sample slippage along the tube was avoided by blowing protuberances in the wall. Owing to the dynamic nature of the emulsions data reproducibility on a single sample could not be ascertained; with 4.0% gelatine gels reproducibility of the data was very satisfactory.     

INFLUENCE OF EGG YOLK LIPOPROTEINS ON THE RHEOLOGY AND STABILITY OF O/W EMULSIONS AND MAYONNAISE 1. VISCOELASTICITY OF GROUNDNUT OIL-IN-WATER EMULSIONS AND MAYONNAISE

Viscoelastic properties of groundnut oil-in-water emulsions stabilized by egg yolk and of mayonnaise have been deduced from their creep compliance-time response to a constant low shear stress. The viscoelastic parameter values, emulsion stability and initial mean drop size were influenced by pH and NaCl, due to disruption of the egg yolk components. When carboxymethylcellulose was incorporated in the continuous phase of the O/W emulsions an egg yolk-carboxymethylcellulose complex was formed and this affected the rheological properties of the emulsions and also their stability. Mayonnaises exhibited more pronounced viscoelasticity and greater stability than the O/W emulsions. At elevated temperature the micelles adsorbed around oil drops degrade. Their lipoprotein structure unfolds so that more segments on adjacent drops are then available for interlinking and network formation.     

EFFECT OF POLYSORBATE-60 ON THE STABILITY OF O/W EMULSIONS STABILIZED BY PROPYLENE GLYCOL ALGINATE AND XANTHAN GUM

The effect of polysorbate-60 in improving the stability of model oil-in-water emulsions formulated with xanthan gum and propylene glycol alginate was studied at two levels of the surfactant; 0.15% and 0.30%. Creep measurements and steady shear measurements as well as surface tension and oil droplet size measurements were conducted to relate rheological and surface properties to improved stability. Higher polysorbate-60 concentration resulted in lower surface tension values which shifted the oil droplet size distribution to a smaller size range; this distribution was a function of aging time at 0.15% weight concentration PS-60. The decay in rheological parameters, particularly Newtonian viscosity, was slower at 0.30% surfactant concentration.     

THE STUDY OF OPTIMUM OPERATING CONDITIONS OF EXTRUDED SNACK FOOD WITH TOMATO POWDER

Tomatoes are an integral part of diets worldwide. Many population studies have established a link between dietary intake of tomato, a major source of a carotenoid antioxidant, lycopene, and reduced risk of chronic diseases. Response surface methodology was used to analyze the effect of screw speed (X₁), moisture content (X₂) and tomato powder content (X₃) on the objective attributes (radial expansion ratio [Y₁], bulk density [Y₂], degree of gelatinization [DG], water absorption index [WAI] and hardness [Y₅]) of an extruded snack food with tomato powder. A Box‐Behnken design was used to develop models for the objective responses. The experiments were performed at 100C with the following: feed rate, 19.2 kg/h; X₁, 250 rpm; and die diameter, 3.98 mm. Individual contour plots of the different responses were overlaid. Regions meeting 3.22 optimum Y₁, 0.13‐g/cm Y₂, 81.25% DG, 5.12‐g gel/g dry weight WAI and 35.43‐N Y₅ were identified at 12.5 and 25% X₂ and X₃, respectively.     

VIEWS ON RELATING INSTRUMENTAL TESTS TO SENSORY ASSESSMENT OF FOOD TEXTURE. APPLICATIONS TO PRODUCT DEVELOPMENT AND IMPROVEMENT 1,2

Well-defined measurements of the mechanical properties of food and the reduction of sensory attributes to the fundamental primary entities, together with the definition of their correlation functions, provide the basis for the eventual development of instruments calibrated in terms of human sensory response and having a high probability of predicting the consumer reaction. Since mechanical measurements of most foods are time-dependent, the understanding of conditions prevailing during sensory testing (rate of shear, etc.) will aid in selecting the optimum conditions for instrumental testing. Recent progress in this area has been made with fluids and some solid foods. The method of magnitude estimation assists the researcher in discovering the underlying laws relating physical product changes to perceived textural changes. At the same time, magnitude estimation also aids the product developer to determine empirical, ad hoc relations between physical levels of mechanical variables and textural perceptions, even if the true, underlying relationships are not known. Ad hoc equations can be used (in conjunction with optimization techniques) to determine the combination of mechanical variables that (a) produce a specific sensow texture profile, and (b) maximize texture/product acceptability.     

MEASUREMENT OF FLOW PROPERTIES OF FOOD SUSPENSIONS WITH A MIXER

Abstract. Flow properties of selected food suspensions (tomato puree, apple sauce, and apple pulp) were studied with a mixer. Power law constants for the suspensions were determined by employing an approximate method based on power correlations for mixers in the laminar flow regime. The studied suspensions cannot be characterized with narrow gap viscometers because of the size and segregation of the particles (formation of a dilute phase next to the rotor).     

A very stable W/O/W multiple emulsion

Synopsis
The comparison of the results of microscopic, conductimetric and rheologic analyses carried out on the same triple W/O/W emulsion, immediately following its manufacture and 10 years later, indicates the remarkable stability of such system. This stability illustrates the great potential of this formula in the protection of unstable ingredients, with regard to external stress, when encapsulated with a high yield.
Résumé
La comparison des résultats des analyses microscopiques effectuées sur une même fomule d'émulsion multiple H/L/H, juste après sa fabrication et après 10 ans de conservation, ont permis de mettre en évidence la remarquable stabilité de ce système. Cette stabilité démontre les grandes possibilités de cette formule dans la protection, vis à vis des milieux extérieurs, des substances fragiles incorporés avec un haut rendement d'encapsulation.     

A PRELIMINARY INVESTIGATION OF THE MEMBRANE LIPID OF Halobacterium halobium AS A FOOD ADDITIVE1

A preliminary investigation of the membrane lipid of Halobacterium halobium as a food additive. F. J. Post and N. F. Collins, Biology Department, Utah State University, Logan, Utah 84322. A study was made of the suitability of the diether phytanyl phosphatidyl glycerol phosphate lipid component of the cell membrane of Halobacterium halobium NRC 34003 as a potential food additive. The lipid was shown to be a possible emulsifier with a hydrophile-lipophile balance (HLB) of 7–8 producing a water in oil emulsion. Its use as a possible noncaloric fat substitute is also discussed. The lipid had a melting point at -12⁰ to -15⁰ C and was nontoxic at an 0.8 g kg^-1, one-dose exposure to mice either by feeding or by intraperitoneal injection. Some methods for increasing the yield of lipid are proposed.     

大豆蛋白酶法水解制取食用发泡剂的研究

为利用大豆蛋白制取食用发泡剂，比较了大豆分离蛋白和脱腥大豆蛋白粉水解前后的发泡性能。通过正文实验法，确定了以大豆分离蛋白为原料，酶法制取发泡剂的最佳工艺条件为：在浓度为５％的大豆蛋白中添加０．５％酶制剂反应１５ｍｉｎ。该工艺条件下所制得的发泡剂的发泡力可达（３９０±２）ｍｌ，且样品经减压干燥后仍能保持较好的发泡能力．     

THE COMPRESSIVE BEHAVIOR OF SOLID FOOD SPECIMENS WITH SMALL HEIGHT TO DIAMETER RATIOS2

Cylindrical specimens of height to diameter ratios between 0.12 to 1.0 of potato flesh, bologna sausage and process American cheese were uniaxially compressed to failure. The flatter the specimen the stiffer it appeared. This was also true with respect to strength. The magnitude of strain at failure also increased with the specimen's flatness. Application of two correction procedures for the calculation of a dimensionally independent modulus did not always yield consistent results, demonstrating that the stiffness-strength-shape relationships can depend not only on the material but also on the particular character of the end constraints.     

一种野生麻纤维染色初探

初步探讨了不同蓟处理的新疆野生麻散纤维的活性染料染色。实验结果表明：采用双活性基染料染该野生麻，染色效果较好。