Effect of high pressure homogenization (HPH) on the rheological properties of tomato juice: Creep and recovery behaviours

AbstractHigh pressure homogenization (HPH) is a non-thermal technology that has been proposed as a partial or total substitute for the thermal processing of food. Although its effect on microbial inactivation has been widely studied, the rheological changes occurring in fruit products need better describing. The present work evaluated the effect of HPH (up to 150MPa) on the creep and recovery properties of tomato juice. The mechanical Burger's model explained juice creep compliance well, and its parameters (Newtonian dashpots and Hookean springs) were evaluated as a function of the homogenization pressure. HPH processing increased both tomato juice elastic and viscous behaviours, which could be attributed to the disruption of suspended particles during processing. Moreover, each Burger's model constituent could be related to the product internal structure. The results obtained highlighted the possible applications of the HPH process as a valuable tool to promote physical changes in food products

Effect of high pressure homogenization (HPH) on the rheological properties of tomato juice: Time-dependent and steady-state shear

AbstractHigh pressure homogenization (HPH) is a non-thermal technology that has been widely studied as a partial or total substitute for the thermal processing of food. Although microbial inactivation has been widely studied, there are only a few works in the literature reporting the physicochemical changes caused in fruit products due to HPH, especially those regarding the rheological properties. The present work evaluated the effect of HPH (up to 150MPa) on the time-dependent and steady-state shear rheological properties of tomato juice. HPH reduced the mean particle diameter and particle size distribution (PSD), and increased its consistency and thixotropy. The rheological results were in accordance with the PSD observed. The rheological properties of the juice were evaluated by the Herschel–Bulkley and Falguera–Ibarz models (steady-state shear) and Figoni–Shoemaker and Weltman models (time-dependent). The parameters of these equations were modelled as a function of the homogenization pressure. The models obtained described the experimental values well, and contributed to future studies on product and process development

Effect of ozonation on the sensory characteristics and pasting properties of cassava starch

AbstractThe effects of different ozone treatments on the sensory characteristics and pasting properties of cassava starch were studied. Cassava starch was humidified to obtain a final moisture content of approximately 30% and the product was exposed to ozone in gas form (14m3/hr) pumped into a horizontal dry mixer at approximate concentrations of 40ppm for 30, 60, 90 and 120min and 118ppm for 30 and 60min. The ozonized samples presented higher peak viscosities and lower cooking stability under agitation than the untreated and control samples. The treatments that affected the greatest number of viscoamylographic characteristics were at 40ppm/90min. and 118ppm/60min. On the other hand, the sample treated at 40ppm/30min. did not present any significant change on its pasting properties. For the sensory characteristics, the samples treated at 40 and 118ppm for 30min were scored as different from the untreated sample regarding the color and odor, and the sample treated at 40ppm for 90min was scored as different only regarding the odor. Previous work showed that ozone can be efficient to decrease starch microbial contamination. However, the ozone treatment partially changed the pasting properties and sensory characteristics of cassava starch

Editorial

A Revista Segurança Alimentar e Nutricional-SAN inaugura a sua edição exclusivamente on line, reunindo 10 artigos científicos elaborados por autores de diversas regiões do País, que abordam distintos aspectos da SAN, com ênfase nas politicas e programas públicos de alimentação e nutrição e na área de ciência e tecnologia de alimentos

Effects Of High Pressure Homogenization On The Activity, Stability, Kinetics And Three-dimensional Conformation Of A Glucose Oxidase Produced By Aspergillus Niger.

High pressure homogenization (HPH) is a non-thermal method, which has been employed to change the activity and stability of biotechnologically relevant enzymes. This work investigated how HPH affects the structural and functional characteristics of a glucose oxidase (GO) from Aspergillus niger. The enzyme was homogenized at 75 and 150 MPa and the effects were evaluated with respect to the enzyme activity, stability, kinetic parameters and molecular structure. The enzyme showed a pH-dependent response to the HPH treatment, with reduction or maintenance of activity at pH 4.5-6.0 and a remarkable activity increase (30-300%) at pH 6.5 in all tested temperatures (15, 50 and 75°C). The enzyme thermal tolerance was reduced due to HPH treatment and the storage for 24 h at high temperatures (50 and 75°C) also caused a reduction of activity. Interestingly, at lower temperatures (15°C) the activity levels were slightly higher than that observed for native enzyme or at least maintained. These effects of HPH treatment on function and stability of GO were further investigated by spectroscopic methods. Both fluorescence and circular dichroism revealed conformational changes in the molecular structure of the enzyme that might be associated with the distinct functional and stability behavior of GO.9e10341

Effect of High-Pressure Technologies on Enzymes Applied in Food Processing

High isostatic pressure (HIP) and high-pressure homogenization (HPH) are considered important physical technologies that able to induce changes on enzymes. HIP and HPH are emerging food processing technologies that involve the use of ultra high pressures (up to 1200 MPa for HIP and up to 400 MPa for HPH), where the first process is based on the principle that the maintenance of a product inside vessels at high pressures induces changes in the molecules conformation and, consequently, in the functionality of polysaccharides, proteins and enzymes. To the contrary, for HPH process, the high shear and sudden pressure drop are the responsible phenomena for the changes on the processed product. This chapter aims to evaluate comparatively the effects of HIP and HPH on the activity of enzymes currently applied in food industry and to identify the main structural changes induced by each process. The overall evaluation of the results shows that mild conditions of both processes were recently highlighted as able to improve the activity and the stability of several enzymes, whereas extreme process conditions (pressure, time and temperature) induce enzyme denaturation with consequent reduction of biological activity. Considering the complexity and diversity involved in the enzyme structure and its ability to react, it is not possible to determine specific conditions that each process is able to promote increase or reduction of enzyme activity, being necessary to evaluate HIP and HPH for each enzyme. Finally, in terms of molecular structure, the effect of HIP and HPH on enzymes can be explained by the alterations in the quaternary, tertiary and secondary structures of enzymes, which directly affects its active site configuration

Influence of high pressure homogenization on commercial protease from Rhizomucor miehei: Effects on proteolytic and milk-clotting activities

AbstractThis work studied the influence of high pressure homogenization (HPH) on a commercial fungal protease. The enzyme solutions (2 and 20 g/100 mL) were processed up to 190 MPa and the proteolytic activity (PA), milk-clotting activity (MCA) and the rheological behavior of the milk coagulation phase were evaluated. The effects of multi-pass (three cycles) HPH at 25 and 190 MPa was evaluated for enzyme processed at concentration of 2 g/100 mL. No differences in PA and MCA were observed for the samples of 2 g/100 mL of enzyme concentration processed by HPH. On the other hand, increase in PA (∼3%) and MCA (∼10%) were observed for the enzymes processed at 190 MPa at high concentration, which consequent faster clotting and higher consistency of the milk gel. The multi-pass increased PA (≤6%) but did not alter MCA nor improved the milk coagulation phase. The results highlight that the energy supplied from HPH to enzyme at low concentration is not enough to promote positive changes in the enzyme coagulant profile; however, the HPH of solution with high enzyme concentration showed a positive effect, indicating that the collisions between enzymes during the process was important to reach the observed changes