The influence of food emulsifiers on fat and sugar dispersions in oils. III. Water content,purity of oils

The influence of water on the interactions between fat and sugar crystals dispersed in triglyceride (vegetable) oils was qualitatively estimated from sedimentation and rheological experiments. The experiments were performed both with and without food emulsifiers (monoglycerides and lecithins) present in the oil. The effects of minor natural oil components (nontriglycerides) on the interactions and on emulsifier adsorption to the crystals were examined by comparing a commercial refined oil and a chromatographically purified oil. The results show that water generally increases the adhesion between fat and sugar crystals in oils and also increases the surface activity of the oil-soluble food emulsifiers. Minor oil components give a small increase in the adhesion between fat and sugar crystals in oils, but do not influence the adsorption of food emulsifiers in any systematic way.     

Iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions: effect of emulsifier type and pH

The objective of this study was to investigate the protective effect of five different emulsifiers on iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions. The emulsifiers were either based on protein (whey protein isolate and sodium caseinate) or based on phospholipid (soy lecithin and two milk phospholipids with different phospholipid contents, MPL20 and MPL75). Lipid oxidation was studied at pH 4.5 and 7.0, and results were compared to lipid oxidation in neat fish oil. Results showed that all emulsions oxidised more than neat oil. Furthermore, emulsions prepared with proteins oxidised more at low pH than at high pH, and casein emulsions oxidised the least (Peroxide value (PV) at day 7 was 0.5–0.7 meq kg^?1). Among emulsions prepared with phospholipids, emulsions with MPL75 were the most oxidised followed by emulsions prepared with lecithin and MPL20. Thus, PV in MPL75 emulsions was 5.0–5.5 meq kg^?1 at day 7 compared with 0.9–1.9 meq kg^?1 in MPL20 emulsions.     

HRV系列降粘剂在冀中南部稠油开采中的应用

为解决冀中南部１０多个稠油油藏原油粘度高,开采难度大的问题,开发了应用ＨＲＶ系列乳化降粘剂开采此类油藏的新方法,解决了稠油在地层,井筒难以流动的问题,而且使稠油的地面输送简单化现场应用表明,ＨＲＶ系列稠油乳化降粘剂使用浓度小,乳化效率高,降粘效果好,同时不影响原油破乳,具有较大的推广使用价值。     

原油碱水乳化活性组分研究

对河南油田三种原油中的有机酸和非酸含氧化合物进行了分离鉴定并研究了它们在碱水乳化中的作用。有机酸是引起各原油碱水乳化的活性物质，非酸含氧化合物本身无碱水乳化活性，但对有机酸的乳化活性有协同作用。     

Oxidation in fish-oil-enriched mayonnaise

 Oxidative protection of mayonnaises with 16% fish oil was studied during cold storage (5  °C) after supplementation with different tocopherol systems: the ternary antioxidant system ascorbic acid, lecithin and tocopherol (A/L/T), and two commercial mixtures, an oil-soluble (Toco 70) preparation and a water-soluble (Grindox 1032) preparation. The physical structure of the fish-oil-enriched mayonnaise was manipulated by adding extra emulsifier (Panodan TR) with the purpose of investigating whether or not this affected the antioxidative activity of the tocopherol mixtures. A number of different analytical techniques HPLC (high-performance liquid chromatography, gas chromatography mass spectrometry (GC-MS), sensory analysis, confocal laser scanning microscopy and rheological measurements) were employed to elucidate the chemical, sensory, structural and rheological aspects of the oxidation process. Discriminant partial least squares regression was used to analyse the data obtained. The three tocopherol preparations not only affected the oxidative stability of the mayonnaises differently, they also influenced the rheological and structural properties of the mayonnaises in different ways. The rheological and structural properties of the mayonnaise were also affected by the addition of extra emulsifier, but this did not influence the formation of fishy and rancid off-flavours. Addition of the A/L/T system caused the immediate formation of distinct fishy and rancid off-flavours in the fresh mayonnaises. The volatile compounds trans-2-heptenal, 4-octen-3-one, 1-octen-3-ol, trans,cis-2,4-heptadienal, trans,trans-2,4-heptadienal, trans-2-octenal, nonanal and trans,cis-2,6-nonadienal were thought to contribute to the fishy and rancid flavours. Addition of Toco 70 did not affect the sensory perception of mayonnaise nor the development of volatile off-flavour compounds as evaluated by GC-MS, but the peroxide values were slightly increased in mayonnaise containing Toco 70 as compared to the other mayonnaises. Mayonnaise with Grindox 1032 seemed to have fewer fishy and rancid off-flavours than mayonnaises without antioxidant. This flavour-protective effect of Grindox 1032 was correlated to an increase in the size of the droplet diameter of mayonnaises supplemented with Grindox 1032. Received: 12 April 1999 / Revised version: 11 June 1999     

酸性花生乳饮料稳定性的研究

酸性花生乳易引起脂肪上浮或凝集成团及蛋白质沉淀。本文从产品浓度、稳定剂、乳化剂选择及杀菌条件三方面进行试验。结果表明：产品浓度12％左右（其中乳固体4％）,混合乳化剂量为0．1％（单甘酯：蔗糖酯＝6：4）,CMC、果胶、六偏磷酸钠加入量分别为0．3％、0.1％和0．1％,可大大增加饮料的稳定效果。     

Effect of replacement of fat with sesame oil and additives on rheological, microstructural, quality characteristics and fatty acid profile of cakes

Effect of replacement of fat with 25, 50, 75 and 100% sesame oil (on fat basis); 50% sesame oil, hydrocolloids and emulsifiers on the rheological, microstructural, quality characteristics and fatty acid profile of cake was studied. Addition of increasing amount of sesame oil decreased viscosity, increased specific gravity of cake batter; decreased cake volume and overall quality score. Microstructure studies showed disrupted gluten matrix. Among the two different hydrocolloids [hydroxypropylmethylcellulose (HPMC) and xanthan] and emulsifiers [glycerol monostearate (GMS) and sodium stearoyl-2-lactylate (SSL)] tried, HPMC and SSL increased the batter viscosity, decreased the specific gravity, increased the volume and overall quality score. Use of combination of HPMC and SSL improved significantly the quality characteristics of cake with 50% sesame oil in such a way that the overall quality score was higher than that of the control cake with fat. The microstructure of cake crumb with 50% sesame oil and HPMC showed a smooth structure with less number of cavities and SSL showed a continuous protein matrix. On replacing the fat with 50% sesame oil, there was a decrease in saturated fatty acids and increase in unsaturated fatty acids, particularly linoleic acid. The fatty acid profile of cake with 50% sesame oil was better than the control cake as there was 2.4 times decrease in palmitic acid content and 5.9 times increase in essential fatty acids (EFA) content.     

Hydrocolloids as emulsifiers and emulsion stabilizers

We consider the essential molecular features of hydrocolloids having the ability to act as emulsifying agents and emulsion stabilizing agents. The criteria for effectiveness in protecting newly formed droplets against flocculation and coalescence are contrasted with the requirements to maintain long-term stability against aggregation, creaming and Ostwald ripening. To illustrate various aspects of stability behaviour, comparison is made between the physico-chemical characteristics of hydrocolloid emulsifying agents and those of other kinds of food emulsifying agents – surfactants, proteins and nanoparticles. Interfacial complexation between protein and polysaccharide may occur through covalent bonding or electrostatic bonding. For the case of electrostatic protein–polysaccharide complexes, the interfacial nanostructure and the stabilizing properties of the adsorbed layer are dependent, amongst other things, on the sequence of adsorption of the biopolymers to the emulsion droplet surface.     

Studies on interaction between stevioside,liquid sorbitol,hydrocolloids and emulsifiers for replacement of sugar in cakes

Studies were carried out on the replacement of sugar with stevioside and liquid sorbitol (SO); addition of hydrocolloids, emulsifiers with and without 10% debittered fenugreek seed powder (DFSP) to a mixture of stevioside and SO on the rheological, microstructural and quality characteristics of cake. Experimental data showed that addition of sugar increased the amylograph viscosity of wheat flour paste during heating and cooling while SO at different percentages decreased these viscosities, however addition of combination of hydrocolloid (xanthan, XA) and emulsifier (polysorbate-60, PS-60) increased the viscosity of wheat flour paste with 100% SO. Addition of combination of XA + PS-60 improved distribution pattern of air cells, increased batter viscosity, cohesiveness, overall quality score of cake with 100% SO and allowed incorporation of DFSP to improve the functional characteristics of cake. Evaluation of composition of developed cake showed negligible sucrose content, perceptible fenugreek flavor and increased dietary fiber as against cake with sugar.     

Emulsion gels: The structuring of soft solids with protein-stabilized oil droplets

Many food products can be categorized as emulsion gels. This is especially the case for protein-based oil-in-water emulsions which can be converted into soft-solid-like materials by common food processing operations such as heating, acidification, and enzyme action. This review article outlines how the rheological and structural properties of protein-stabilized emulsion gels are influenced by the dispersed oil volume fraction, the oil–water interfacial composition, and the colloidal interactions of the constituent emulsion droplets. For model systems of variable oil content and containing different food proteins, some general trends of rheological behaviour at small and large deformations are identified. Experimental rigidity data are considered in relation to: (i) material science theories of the reinforcement of solid materials by active and inactive filler particles, and (ii) Brownian dynamics simulations of aggregated particle networks containing bonded and non-bonded particles. Influences of interfacial composition and particle–matrix interactions on microstructure and rheology are explained with particular reference to the role of small-molecule surfactants. Compositional and structural factors affecting the large-deformation rheology and fracture properties are described. Finally, the practical relevance of the model system studies to the behaviour of real food products is critically assessed.