El presente trabajo se ha centrado en el desarrollo de emulsiones alimentarias aceite-en-agua estabilizadas con proteínas de atún. Específicamente, se ha analizado la influencia del método de conservación de las proteínas aisladas (liofilización, congelación) y de las condiciones de procesado seleccionadas sobre el comportamiento reológico y la microestructura de dichas emulsiones. Se han preparado emulsiones aceite en agua (con un contenido del 70% en peso de aceite) estabilizadas con proteínas de atún. La concentración de emulsionante usada ha sido 0,50% en peso. El comportamiento reológico de estas emulsiones no depende significativamente del método de conservación de la proteína empleado. Por otra parte, un aumento de la velocidad de agitación durante el proceso de manufactura de la emulsión da lugar a una disminución continua del tamaño medio de gota y a un aumento de las funciones viscoelásticas dinámicas, menos significativo a medida que aumenta dicha velocidad de agitación. | This work is focused on the development of o/w salad dressing-type emulsions stabilized by tuna proteins. The influence of protein conservation methods after the extraction process (freezing or liofilization) on the rheological properties and microstructure of these emulsions was analyzed. Processing variables during emulsification were also evaluated. Stable emulsions with adequate rheological and microstructural characteristics were prepared using 70% oil and 0.50% tuna proteins. From the experimental results obtained, we may conclude that emulsion rheological properties are not significantly affected by the protein conservation method selected. On the contrary, an increase in homogenization speed favours an increase in the values of the linear viscoelastic functions. Less significant is the fact that as agitation speed increases further, mean droplet size steadily decreases.

Se ha realizado un estudio de la distribución del tamaño de gotas y de las propiedades viscoelásticas lineales de emulsiones concentradas de aceite en agua, estabilizadas con diferentes proteínas (cangrejo, gluten y soja). Los sistemas estudiados siempre presentan un comportamiento típico de emulsiones altamente concentradas con un alto grado de floculación. Se ha observado que un incremento de la velocidad de agitación empleada durante la preparación o de la concentración de emulsionante dan lugar a un aumento de los módulos viscoelásticos (G' y G") y a una disminución del tamaño de gotas. Por tanto se produce un reforzamiento del entramado formado por asociación de las gotas de fase dispersa y como consecuencia, un aumento en la estabilidad de las emulsiones. | Droplet Size Distribution (DSD) and linear viscoelastic properties of concentrated o/w emulsions stabilized by different proteins (crayfish, gluten and soybean) have been studied. A typical behaviour of highly concentrated emulsions with a high degree of flocculation has been found. An increase in energy input for the emulsification process or in emulsifier concentration leads to an increase in both viscoelastic moduli (G', G") as well as to a decrease in droplet size. Thus, an enhancement of the entanglement network produced by association of protein molecules that are surrounding oil droplets or are present in the continuous phase takes place, leading to a significant improvement of emulsion stability.

Water affects safety, stability, quality and physical properties of food. The influence of water on physical properties of food is dependent on the state of water in food. The state, expressed as water activity, is briefly discussed in the paper. Further, the influence of water on such physical properties as rheological, thermal, mass transfer, electrical, optical and acoustic is presented in details.

This work underlines that the role of water, its flow properties and its expulsion from the spatial network during oral processing, cannot be neglected in understanding the relation between gelled food structures and its sensory perception. It is shown that the properties of the included water phase of semi-solids are important as this phase can boost the water content in the oral cavity, and thereby increase taste sensations like sweetness. Moreover, the included water phase also plays a crucial role in how the energy exerted onto the gel during palating is used for either fracture, stored or dissipated in or by the network. To demonstrate this, a series of mixed whey protein/polysaccharide cold-set gels have prepared that were studied for a number of rheological and sensorial properties. Also, information on the expulsed serum volume during uniaxial compression and the breakdown pattern of these gels in the oral cavity was determined. It is shown that expulsion of serum from a gel during oral processing can be substantial and set by the morphology of the formed gel and the stiffness of the matrix. This expulsed serum volume is directly proportional to taste response. Moreover, it is found that both the viscous and elastic flow of serum through the gel upon deformation contribute to the perceived crumbliness of gels by lowering the recoverable energy. The elastic contribution of polysaccharides in the serum impairs with the energy available for fracture during oral processing, thereby affecting the sensory spreadability of the product.

This study was carried out to evaluate the effects of power ultrasound (US) on the molecular weight and rheological properties of a food polysaccharide, konjac glucomannan (KGM). Upon the exposure of KGM solution (1% w/v in water) to US at a relatively high power intensity (50 W/cm2), the apparent viscosity decreased rapidly from about 50 Pa s to a negligible level within 10–20 min. The intrinsic viscosity ([η]) of KGM solution decreased gradually during the US exposure with a time course closely fitted to the first-order polymer degradation kinetics (random chain scission). The US treatment also caused a significant reduction of particle size (Zavg) of KGM aggregates and changes in the rheological properties including the decrease of storage modulus (G′) and loss modulus (G″), and the increase in phase angle (tan δ = G″/G′). Nevertheless, no change in primary structure was detected by Fourier transformation infrared (FT-IR) analysis. The results suggested that high intensity US was an effective means for KGM degradation without significant structural destruction.

In this work, water-insoluble bamboo shoot dietary fiber (BSDF) was prepared, and used as plant food particle stabilizer for oil-in-water (O/W) Pickering emulsions. The obtained plant food particle had novel emulsification ability, the prepared emulsions were stable against coalescence for at least 4 weeks and also insensitive to pH, ionic strength and pasteurization conditions. The BSDF suspensions and BSDF-stabilized O/W emulsions both exhibited shear-thinning behaviors; moreover, both viscosity and module were increased with the increase of BSDF contents. The surface coverage of emulsions was positively correlated with the content of BSDF suspensions. It indicated that the dietary fibers from bamboo shoot had a soft nature and suitable shape to produce stable Pickering emulsions, which could be used as food-grade particles for applications of food and cosmetics industries.