EFFECTS OF OIL DROPLETS ON PHYSICAL AND SENSORY PROPERTIES OF O/W EMULSION AGAR GEL

Effects of oil droplets in an agar gel matrix were investigated by mechanical analyses and sensory evaluation. The results for compressive and puncture properties were expressed in terms of relative values. All compressive properties; stress, strain and compressive energy of emulsion gels, as obtained by compression tests, decreased with both increases of oil droplet size and oil volume fraction. The stress, strain and energy of the emulsion gels obtained by puncture tests did not change with an increase in oil droplet size. Results of sensory evaluation showed that the sample containing small oil droplets was harder than that with large oil droplets. On the other hand, the large oil droplet sample was oilier than that with small oil droplets. The sensory evaluations for hardness and oiliness of emulsion gels did not exhibit significant relations to most of the properties of mechanical analyses.     

COMPARISON OF PHYSICAL PROPERTIES OF AGAR, LOW GEL STRENGTH AGAR AND GELATIN, AS SUPPLEMENTARY FOOD FOR PEOPLE WITH SWALLOWING DIFFICULTY

Low gel strength agar (LGSA), recently developed as a supplementary food for swallowing was compared with ordinary agar and gelatin. LGSA was developed to have physical properties close to that of gelatin, while keeping one property of agar, i. e. its setting temperature which can be controlled comparatively easier than gelatin. Each specimen was prepared with and without orange flavor. After determination of their basic properties, i. e. hardness, adhesiveness, cohesiveness and gumminess, three samples of two flavors, six in all, were studied for ease of swallowing using electromyography and sensory evaluation, on middle age (40 to 60 years old) and senior age (60 to 70 years old) subjects. Those experiments revealed nearly the same results with all samples, except for a slight difference in gumminess in LGSA and gelatin. No significant difference in electromyograms were noted in six samples or with age of subjects. It is feasible to employ agar materials together with gelatin in institutions whose members have swallowing disorders.     

EFFECTS OF DIMENSIONS OF AGAR AND GELATIN GELS ON PALATAL PRESSURE PATTERNS

Eating of agar and gelatin gels in the mouth was studied dynamically in detail. The palatal presures on agar and gelatin gels of various concentrations and dimensions were detected by pressure transducers installed at three locations of the palate. For each of the gels, Pm (the maximum palatal pressure at the initial stage of mastication), P (the mean palatal pressure), W (work), and T (retaining time in the mouth) changed significantly when their concentrations increased. Moreover, gel dimensions also affected Pm, P and W. For a bite-size gel, Pm, P and W increased or remained constant, while for a finer sized gel, Pm, P and W were nearly constant regardless of the increase in rupture strength or gel concentration.     

INFLUENCE OF GLUCOSE AND FRUCTOSE ON HIGH-METHOXYL PECTIN GEL STRENGTH AND STRUCTURE DEVELOPMENT

High-methoxyl (HM) pectin/sugar gels are viscoelastic materials whose elastic (storage modulus, G′) and viscous (loss modulus, G″) characteristics can be measured by dynamic rheological technique. At 10C, over the frequency range 0.1–10 Hz, magnitudes of G′ and G″ of glucose gels were higher than those of fructose gels. Magnitudes of G′ and G″ of both sugar gels increased with pectin concentration according to power laws; the increase in G′ was higher than that of G″. Much useful information on food gels can also be obtained by following the sol-gel transition process. Complex viscosity (η*) at 1 Hz was used to follow structure development (SD) and SD rate during sol-gel transition of pectin-fructose/glucose dispersions. Integrated average viscosities and SD rates were also higher for glucose gels than for fructose gels.     

挤压及热处理工艺对Mg-Zn-Y组织及力学性能的影响

通过金相显微分析、X射线衍射、扫描电镜及拉伸试验等研究Mg-Zn-Y合金铸态、挤压态及热处理后显微组织及其力学性能的变化.结果表明,挤压后直接时效处理可使沉淀相大量析出,强化效果明显,可提高材料的力学性能.     

菜籽多酚与VC在棉籽油中的抗氧化效果与协同增效作用

以过氧化值(POV)为指标,采用Schaal烘箱法研究菜籽多酚与VC在棉籽油中的抗氧化效果及其在棉籽油中的抗氧化协同增效作用.结果表明:菜籽多酚与VC在棉籽油中具有抗氧化作用,且菜籽多酚强于VC.抗氧化剂添加量在0.01%～0.10%范围内,单独使用以0.05%菜籽多酚与0.08%VC的效果最好,复合使用以0.05%(菜籽多酚与VC按3:7复配)的效果最好.菜籽多酚与VC按比3:7复配,在棉籽油中具有非常明显的协同增效作用.     

翅果油甾醇对大鼠前脂肪细胞增殖与分化的影响

体外培养大鼠前脂肪细胞,分别以2μmol/L、4μmol/L、8μmol/L的翅果油甾醇对其进行处理.采用MTT比色法检测细胞增殖情况;油红O染色化学比色法定量分析细胞内脂肪生成及细胞分化程度;逆转录-聚合酶链式反应（RT-PCR）分析过氧化物酶增殖物激活受体γ2（PPARγ2）mRNA表达情况,探讨翅果油甾醇对前脂肪细胞增殖分化的影响及其可能的机制.结果显示：各组细胞MTT测试OD值均低于对照组,4μmol/L及8μmol/L组细胞油红O染色的OD值及PPARγ2mRNA的表达量均显著下降.     

EFFECTS OF PROCESSING AND SQUALENE ON COMPOSITION AND OXIDATIVE STABILITY OF SEAL BLUBBER OIL

Effects of processing on constituents of seal blubber oil and that of squalene on oxidative stability of several oils were monitored. The content of α-tocopherol in oil decreased during processing, especially at the bleaching and deodorization steps. There was also a concurrent reduction in the contents of squalene and free fatty acids, especially during deodorization. Oils treated with squalene did not show any improved oxidative stability and in some cases were even less stable.     

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.     

A RESEARCH NOTE EFFECTS OF PRESSURIZATION AND REFRIGERATED STORAGE ON MICROSTRUCTURE OF FISH MUSCLE TISSUE

Fish muscle tissues were subjected to high hydrostatic pressures in the range of 1,000 - 3,000 atm and the tissues subsequently observed using transmission electron microscopy. Pressurization at 1,000 atm caused contraction of the sarcomere with the I-band thin filaments being lost while the A-band was unaffected. On pressurizing the tissues at 2,000 atm, the I-band region became more visible with breakdown of the thin filaments in this region as well as the Z-disks. There was gross disintegration ofmyofibrillar structure with collapse of A-band structure and T-tubular system on subjecting muscle tissue to 3,000 atm of pressure. However, there were no observable changes in myofibrillar structure beyond these initial changes during the subsequent 21 days of storage under refrigerated conditions (4–7C). The results provide the structural basis for pressure-induced changes in fish texture.