Effect of high-pressure homogenization on droplet size distribution and rheological properties of ice cream mixes.

The effect of different homogenization pressures (15/3 MPa and 97/3 MPa) on fat globule size and distribution as well as on structure-property relationships of ice cream mixes was investigated. Dynamic light scattering, steady shear, and dynamic rheological analyses were performed on mixes with different fat contents (5 and 8%) and different aging times (4 and 20 h). The homogenization of ice cream mixes determined a change from bimodal to monomodal particle size distributions and a reduction in the mean particle diameter. Mean fat globule diameters were reduced at higher pressure, but the homogenization effect on size reduction was less marked with the highest fat content. The rheological behavior of mixes was influenced by both the dispersed and the continuous phases. Higher fat contents caused greater viscosity and dynamic moduli. The lower homogenization pressure (15/3 MPa) mainly affected the dispersed phase and resulted in a more pronounced viscosity reduction in the higher fat content mixes. High-pressure homogenization (97/3 MPa) greatly enhanced the viscoelastic properties and the apparent viscosity. Rheological results indicated that unhomogenized and 15/3 MPa homogenized mixes behaved as weak gels. The 97/3 MPa treatment led to stronger gels, perhaps as the overall result of a network rearrangement or interpenetrating network formation, and the fat globules were found to behave as interactive fillers. High-pressure homogenization determined the apparent viscosity of 5% fat to be comparable to that of 8% fat unhomogenized mix

A simple and portable method for on-line texture measurement of Italian “Speck Alto Adige"

Texture is a relevant parameter for the assessment of cured ham's quality. In this study a rapid on-line instrumental technique for the measurement of the texture of pieces of cured smoked ham intended for sale as “Speck Alto Adige” PGI was developed. Speck samples were subjected to a compression test using a portable Shore A tester, and instrumental data were compared with conventional texture analyses (texture profile analysis and stress relaxation test) and with sensory evaluations. First, a hardness range in which a threshold value could be identified for the eligibility of 120 speck samples for the “Speck Alto Adige” PGI indication was established; afterwards, a Shore A hardness threshold value of 48 was defined based on measurements of more than 1000 samples. These findings may help manufacturers to determine the textural properties of Speck, based on a simple and rapid instrumental analysisinfo:eu-repo/semantics/publishedVersio

Potential of hardy kiwifruit (Actinidia arguta) for fruit spread production: a first insight

Hardy kiwifruits represent an unexplored agricultural resource for South Tyrol which could be of particular interest to the region by contributing to agricultural biodiversity and the valorisation of minor crops in the area. The main limitation of this crop is its short shelf-life as a fresh raw material, which is related to its intrinsic perishability. Processing hardy kiwis into canned products could be a valid strategy for encouraging the production and spread of this crop throughout the territory, enabling food products derived from it to be available all year round. This study evaluated the suitability of hardy kiwifruits for processing into spreads. Results indicate that no pectin needs to be added to ensure that the fruit spread has a pleasant texture, and browning over time occurred slowly, despite the preserve not being stabilised with antioxidant agents, suggesting that the shelf-life of such a preserve might be quite long. Finally, from a preliminary sensory evaluation, consumers rated the preserve positively with regard to its texture, sweetness and flavour, and it obtained a positive overall evaluation from an organoleptic point of view, indicating that this crop has potential for use in the production of fruit spreads

Quality of raspberries preserves obtained from different varieties

The aim of this work was to qualitatively evaluate four different raspberry varieties in order to identify the most suitable for processing into fruit spread. The study, which consisted of two years of experimentation, included agronomic evaluations (choice of varieties, cultivation under uniform conditions, harvesting and analysis of fruit quality parameters), technological evaluations (standardisation of the fruit spread preparation procedure, evaluation of the finished product in terms of chemical and physical properties and the evolution of the colour of the preserves over time) and sensory evaluations (consumer test aimed at identifying preferences between fruit spreads). The results obtained can support local producers by providing information on the characteristics of the varieties under investigation and the processed products obtained from them

Relevance of physical properties in the stability of plant-based food products

895-904Plant tissues are composed of a watery solution of low molecular weight species, mainly sugars, salts and organic acids, and of high molecular weight hydrocolloids, contained in a water insoluble matrix of macromolecules, mostly carbohydrates. All these constituents interact with water, thus reducing its thermodynamic vapour pressure (aw), with small molecules interacting through polar binding, and large biopolymers through surface and capillary effects. Similarly, some constituents will greatly affect kinetic glass transition temperatures (Tg), while others will not. As regards stability, while microbial and chemical changes are mainly related to aw, structure-related changes such as collapse are dependent on the glass transition temperature, Tg. In simple systems such as juices, both thermodynamic and kinetic approaches, employed respectively for high and low moisture systems, have predictive ability, which can be unified in the concept of “critical aw”. However, in complex, multidomain, multiphase systems, such as vegetables and fruits, where insoluble polymeric phases are present, hydrocolloids such as soluble pectins will only slightly affect Tg and aw, but significantly increase the macro viscosity of the soluble fraction, thereby reducing the tendency to collapse. In such cases the use of Tg as a predictive tool must be considered with care. The interrelationships among these aspects are discussed in detail below. </span

Rheological properties of model dairy emulsions as affected by high pressure omogenization

The aim of this work was to evaluate the effect of different homogenization pressures on the rheological properties of model dairy emulsions. Solutions of sodium caseinate and whey protein concentrate at 2% + 1% and 2% + 2% (w/v) were emulsified with milk fat at the final contents of 5%, 8% and 15% (w/v). Raw and pasteurized emulsions were subjected to conventional (15/3 MPa) and high pressure (97/3 MPa and 147/3 MPa) homogenization. Differences in viscosity were observed according to fat content, protein ratio, heat treatment and pressure homogenization conditions. Gel networks formed in 8% and 15% fat content emulsions after pasteurization and high pressure homogenization. Gel strength was mostly affected by protein and fat contents. Dynamic high pressure may be used to produce emulsion gels with modulated structures which could be exploited low fat formulations. Industrial relevance: Texture influences people's acceptance of food and may be more important than the flavor in some products. Gelation of emulsions was observed after pasteurization and high pressure homogenization treatments, depending on fat and protein contents. Dynamic high pressure may be an alternative tool to improve viscoelastic properties and mouth feel of emulsions by providing a weak gel structure in the system. These characteristics can be exploited for low fat and low additive formulations. \ua9 2010 Elsevier Ltd

Dynamic high pressure induced gelation in milk protein model systems

The structure-functional properties of milk proteins are relevant in food formulation. Recently, there has been growing interest in dynamic high-pressure homogenization effects on the rheological-structural properties of food macromolecules and proteins. The aim of this work was to evaluate the effects of different homogenization pressures on rheological properties of milk protein model systems. For this purpose, sodium caseinate (SC) and whey protein concentrate (WPC) were dispersed at different concentrations (1, 2, and 4%), pasteurized, and then homogenized at 0, 18. MPa (conventional pressure, CP), 100. MPa (high pressure, HP), and 150. MPa (HP+). Differences in viscosity were observed between WPC and casein dispersions according to concentration, heat treatment, and homogenization pressure. Mechanical spectra described the characteristic behavior of solutions except for the WPC 4% pasteurized sample, in which a network formed but was broken after homogenization. Dispersions with different ratios of WPC and SC were also made. In these systems, pasteurization alone did not determine network formation, whereas homogenization alone promoted cold gelation. A total concentration of at least 4% was required for homogenization-induced gelation in pasteurized and unpasteurized samples. Gels with higher elastic modulus (G\u2032) were obtained in more concentrated samples, and a bell-shaped behavior with the maximum value at HP was observed. The HP treatment produced stronger gels than the CP treatment. Similar G\u2032 values were obtained when different concentrations, pasteurization conditions, and homogenization pressures were combined. Therefore, by setting appropriate process conditions, systems or gels with tailored characteristics may be obtained from dispersions of milk proteins. \ua9 2010 American Dairy Science Association

Effects of high pressure homogenisation of ice cream mix on the physical and structural properties of ice cream

This study investigated the effect of high pressure homogenisation (HPH) on the physical and structural properties of ice cream. Samples were produced from mixes differing in fat content (5% and 8%) and subjected to different homogenisation pressures (15/3MPa and 97/3MPa). Ice creams were compared for fat globule size distribution, overrun, melting behaviour, and hardness. No influence of HPH on fat structure destabilisation with respect to the conventional homogenisation (CH) was observed. The HPH ice cream samples with high fat content were characterised by the lowest overrun, the highest hardness and improved resistance to melting; the HPH ice creams with low fat content showed higher resistance to meltdown, but were not clearly differentiated for hardness with respect to the CH samples. \ua9 2013 Elsevier Ltd