154 research outputs found
Macromolecular crowding affects protein photosensitivity: the case of egg white immunoreactivity.
No full textAn aqueous solution containing 0.1 g/l egg white proteins was exposed to increasing irradiance (0, 1.6, 7.2, 10.5, 17.0 and 29.1 W m -2) UV-C light for up to 30 min at 8 °C. In all cases, a decrease in immunoreactivity was detected. A 10-fold decrease of immunoreactivity was obtained in circa 7 min at 29.1 W/m 2 and in more than 4 h at 1.6 W/m 2. The loss of immunoreactivity was attributed to denaturation phenomena leading to the formation of protein fragments partially retaining the original epitopes. A progressive decrease in protein photosensitivity was observed by increasing its concentration. Above a limit concentration of 2.2 g/l, egg white proteins became extremely resistant to UV-light, even prolonging exposure time at 29.1 W/m 2 to 3 h. Photostability of egg white proteins was attributed to the occurrence of crowding effects which favoured protein folding and hindered photolysis. © 2011 Elsevier Ltd. All rights reserved
High-pressure homogenisation combined with blanching to turn lettuce waste into a physically stable juice
No full textLettuce waste was blanched, ground, pre-homogenised at 40 MPa and subjected to high pressure homogenisation (HPH) at 80 (1 pass) and 150 MPa (1, 10 passes) to obtain an ingredient intended for blended juice formulation. When lettuce was subjected to HPH without previous blanching, physically unstable juices were obtained. By contrast, the combination of HPH with a blanching pre-treatment allowed obtaining juices showing no physical separation and characterised by a bright green colour. This high stability was attributed to the modification of lettuce fibrous structure and to a 90% and 60% inactivation of polyphenoloxidase and pectin methylesterase, respectively. Juices presented a phenolic content of 3.5 ± 1.3 mg GAE/100 g and a microbial count at least 1 Log lower than that of corresponding not-blanched samples and below limits usually indicated for juice quality (4.7 Log CFU/g). During storage (4 °C), no phase separation was observed but microbial counts rapidly increased, suggesting the need for a further stabilization step.
Industrial application
Solid waste generated by fresh-cut processing of lettuce could be valorised by the application of blanching and HPH, leading to an innovative ingredient potentially exploitable in the formulation of healthy blended juices, smoothies and comminuted food. This effort is worth making considering that HPH is being increasingly introduced as processing operation in various industrial contexts, showing good feasibility and cost effectiveness, and could allow valorisation of different leaf discards
High-Pressure Carbon Dioxide Treatment of Fresh Fruit Juices
No full textFresh fruit juices consumption has greatly risen over the last years, due to the increasing demand for fresh-like foods. Microbial growth and enzymatic activity as well as physical and chemical changes can contribute to quality depletion of these juices. High-pressure carbon dioxide (HPCD) is a promising nonthermal technology for the stabilization of fresh juices. During the treatment, juice is in contact with carbon dioxide at temperature-pressure conditions approaching the critical point. HPCD pressures rarely exceed 50MPa. Temperature is generally between 20°C and 50°C, low enough to maintain the product fresh-likelihood. This chapter reviews the effects of HPCD treatment on liquid food, with particular focus on fruit juices. To this aim, a description of the basic principles of this technology and of its effects on microorganisms, enzymes and sensory, physicochemical, and physical properties of fruit juices is presented. Finally the description of combined strategies and plants nowadays available for HPCD treatment is reported
shelf life prediction by integration of sensory acceptability data into classic kinetic modelS
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Optimising Soy and Pea Protein Gelation to Obtain Hydrogels Intended as Precursors of Food-Grade Dried Porous Materials
No full textDried porous materials based on plant proteins are attracting large attention thanks to their potential use as sustainable food ingredients. Nevertheless, plant proteins present lower gelling properties than animal ones. Plant protein gelling could be improved by optimising gelation conditions by acting on protein concentration, pH, and ionic strength. This work aimed to systematically study the effect of these factors on the gelation behaviour of soy and pea protein isolates. Protein suspensions having different concentrations (10, 15, and 20% w/w), pH (3.0, 4.5, 7.0), and ionic strength (IS, 0.0, 0.6, 1.5 M) were heat-treated (95 °C for 15 min) and characterised for rheological properties and physical stability. Strong hydrogels having an elastic modulus (G′) higher than 103 Pa and able to retain more than 90% water were only obtained from suspensions containing at least 15% soy protein, far from the isoelectric point and at an IS above 0.6 M. By contrast, pea protein gelation was achieved only at a high concentration (20%), and always resulted in weak gels, which showed increasing G′ with the increase in pH and IS. Results were rationalised into a map identifying the gelation conditions to modulate the rheological properties of soy and pea protein hydrogels, for their subsequent conversion into xerogels, cryogels, and aerogels
Antiossidanti alimentari: enzimi e microrganismi ad azione antiossidante. In: 2007, p. 313-322
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