1,721,068 research outputs found
Prevention of enzymatic browning during freezing, storage and thawing of cherimoya (Annona Cherimola, Mill.) derivatives
No full textOptimising 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
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
Feasibility of protein aerogel particles as food ingredient: The case of cocoa spreads
Full text linkThe feasibility of aerogel particles made of whey protein isolate (WP) as food ingredient was studied for the first time. To this aim, cocoa spreads, which traditionally contain large amounts of solid fat, were prepared using sunflower oil as lipid phase instead of fats. Sunflower oil was mixed with sugar, cocoa powder and WP aerogel particles or unstructured WP (control). Two preparation methodologies were applied: (i) mixing ingredients all at once (one-step) and (ii) preliminary oil absorption into aerogel particles, and subsequent mixing with the other ingredients (two-step). WP aerogel spreads showed higher viscosity than control ones, demonstrating the peculiar functionality of porous aerogel particles in entrapping oil. However, the preparation procedure drove the inter-particle interactions among ingredients. In particular, preliminary oil absorption into aerogel particles (two-step procedure) allowed a stronger network to be obtained. Results open to the possibility of applying aerogel particles as food ingredients, highlighting the need for a dedicated process design to maximise the exploitation of their functionality
Structural characterization of oleogels from whey protein aerogel particles
No full textOleogels intended as fat substitutes were prepared by oil dispersion of aerogel particles obtained through freeze-drying (FD) or supercritical-CO2-drying (SCD) of whey protein isolate (WPI) hydrogels (20 g/100 g). SEM revealed that freeze-dried particles presented larger dimensions than supercritical-dried ones. The latter also showed higher oil dispersibility, forming aggregates with lower dimension (300 nm) than those formed by freeze-dried particles (700 nm). Both particles presented oil structuring capability. Freeze-dried particles gave a weak oleogel, while supercritical-dried ones gave a strong (G′ = 3.1 × 105 Pa) and plastic (critical stress = 723.2 Pa) oleogel, with rheological features comparable to those of traditional fats. These results can be explained based on the lower aggregation induced by SCD and on the higher capacity of supercritical-dried particles to form a network in oil through hydrophilic interactions, as suggested by FTIR. Therefore, WPI aerogel particles show the potentiality to be used as food ingredients to prepare oleogels with tailor-made physical properties
Exploring the potentialities of photoinduced glycation to steer protein functionalities: The study case of freeze-dried egg white proteins/carbohydrates mixtures
Full text linkThe capacity of UV-C light to induce glycation and modify functional properties of systems containing freeze-dried egg white proteins and carbohydrates with increasing molecular weight (i.e., glucose, maltose, trehalose and maltodextrin) was studied. Color changes induced by light exposure were taken as typical indicators of glycation. Samples were then analyzed for selected physical (critical concentration, particle size and viscosity), chemical (ovalbumin content) and technofunctional properties (gelling temperature and foaming capacity). The presence of sugars during exposure to UV-C light promoted intense browning and decreased ovalbumin content by circa 30%. Concomitantly, up to a 3-fold increase in critical concentration of the aqueous suspensions of the irradiated protein-carbohydrate powders and changes in particle size were detected. These modifications were consistent with the development of non-enzymatic browning reactions upon UV-C light irradiation. Photoinduced glycation was associated to a decrease in viscosity, a tendency to form gel at temperature lower by up to 8◦C and a better capacity of foam stabilization. The intensity of these changes seems to be affected by the nature of the carbohydrates reacting with proteins, with longer carbohydrates able to produce systems with higher foam stability capacity
Determination of the glass transition temperatures of "solution A" and high molecular weight melanoidins and estimation of viscosities by the WLF equation: a preliminary study
No full textAttività antiossidante del vino: influenza della modalità di vinificazione dell’invecchiamento
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