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Research Project
INNOVATIVE FOOD-GRADE NANOSYSTEMS FOR THERAPEUTICAL FOOD PRODUCTS
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Publications
Physicochemical characterisation and release behaviour of curcumin-loaded lactoferrin nanohydrogels into food simulants
Publication . Araújo, João F.; Bourbon, Ana I.; Simões, Livia S.; Vicente, António A.; Coutinho, Paulo J. G.; Ramos, Oscar. L.
Whey protein nanostructures can be used as vehicles for the incorporation of nutraceuticals (e.g., antioxidants or vitamins) aimed at the development of functional foods, because nanostructures provide greater protection, stability and controlled release to such nutraceuticals. Fundamental knowledge is required regarding the behaviour of nanostructures when associated with nutraceuticals and their interactions with real food matrices. In this study, a lactoferrin (LF) nanohydrogel was developed to encapsulate curcumin (nutraceutical model) and its behaviour was evaluated in terms of the LF structure and the interaction with curcumin. The release kinetics of curcumin from LF nanohydrogels was also assessed using food simulants with a hydrophilic nature (10% ethanol) and lipophilic nature (50% ethanol). This system was able to encapsulate curcumin at 80 μg mL−1 with an efficiency of ca. 90% and loading capacity of ca. 3%. Through spectroscopic characterisation, it is suggested that LF and curcumin bind via hydrophobic interactions and the average binding distance between LF and curcumin was found to be 1.91 nm. Under refrigerated conditions (4 °C), this system showed stability for up to 35 days, while at room temperature (25 °C) it was shown to be stable for up to 14 days of storage. The LF nanohydrogel presented higher release rates of curcumin in a lipophilic food simulant (stable after ca. 7 h) as compared to a hydrophilic simulant (stable after ca. 4 h). LF nanohydrogels were successfully incorporated into a gelatine matrix and showed no degradation in this process. The behaviour of this system and the curcumin release kinetics in food stimulants make the LF nanohydrogel an interesting system to associate with lipophilic nutraceuticals and to incorporate in refrigerated food products of a hydrophilic nature.
Design of β-lactoglobulin micro- and nanostructures by controlling gelation through physical variables
Publication . Simões, Lívia S.; Araújo, João F.; Vicente, António A.; Ramos, Oscar L.
β-lactoglobulin (β-Lg) is the major protein fraction of bovine whey serum and its principal gelling agent. Its gelation capacity enables conformational changes associated with protein-protein interactions that allow the design of structures with different properties and morphologies. Thus, the aim of this work was to successfully use β-Lg, purified from a commercial whey protein isolate, to develop food-grade micro- (with diameters between 200 and 300 nm) and nano- (with diameters ≤ 100 nm) structures. For this purpose, the phenomena involved in β-Lg gelation were studied under combined effects of concentrations (from 5 to 15 mg mL−1), heating temperature (from 60 to 80 °C) and heating time (from 5 to 25 min) for pH values of 3, 4, 6 and 7. The effects of such conditions on β-Lg structures were evaluated and the protein was fully characterized in terms of size, polydispersity index (PDI) and surface charge (by dynamic light scattering – DLS), morphology (by transmission electron microscopy - TEM) and conformational structure (circular dichroism, intrinsic and extrinsic fluorescence). Results have shown that β-Lg nanostructures were formed at pH 3 (with diameters between 12.1 and 22.3 nm) and at 7 (with diameters between 8.9 and 35.3 nm). At pH 4 structures were obtained at macroscale (i.e., ≥ 6 μm) for all β-Lg concentrations when heated at 70 and 80 °C, independent of the time of heating. For pH 6, it was possible to obtain β-Lg structures either at micro- (245.0 – 266.4 nm) or nanoscale (≤ 100 nm) with the lowest polydispersity (PDI) values (≤ 0.25), in accordance with TEM analyses, for heating at 80 °C for 15 min. Intrinsic and extrinsic fluorescence data and far-UV circular dichroism spectra measurements revealed conformational changes on β-Lg structure that support these evidences. A strict control of the physical and environmental conditions is crucial for developing β-Lg structures with the desired characteristics, thus calling for the understanding of the mechanisms of protein aggregation and intermolecular interaction when designing β-Lg structures with novel functionalities.
Evaluation of antimicrobial edible coatings from a whey protein isolate base to improve the shelf life of cheese
Publication . Ramos, Ó. L.; Pereira, J. O.; Silva, S. I.; Fernandes, J. C.; Franco, M. I.; Lopes-da-Silva, J. A.; Pintado, M. E.; Malcata, F. X.
The objective of this work was to evaluate the effectiveness
of antimicrobial edible coatings to wrap cheeses,
throughout 60 d of storage, as an alternative to commercial
nonedible coatings. Coatings were prepared using
whey protein isolate, glycerol, guar gum, sunflower oil,
and Tween 20 as a base matrix, together with several
combinations of antimicrobial compounds—natamycin
and lactic acid, natamycin and chitooligosaccharides
(COS), and natamycin, lactic acid, and COS. Application
of coating on cheese decreased water loss (~10%,
wt/wt), hardness, and color change; however, salt and
fat contents were not significantly affected. Moreover,
the antimicrobial edible coatings did not permit growth
of pathogenic or contaminant microorganisms, while
allowing regular growth of lactic acid bacteria throughout
storage. Commercial nonedible coatings inhibited
only yeasts and molds. The antimicrobial edible coating
containing natamycin and lactic acid was the best in
sensory terms. Because these antimicrobial coatings are
manufactured from food-grade materials, they can be
consumed as an integral part of cheese, which represents
a competitive advantage over nonedible coatings.
Effect of composition of commercial whey protein preparations upon gelation at various pH values
Publication . Ramos, Óscar S.; Pereira, Joana O.; Silva, Sara I.; Amorim, Maria M.; Fernandes, João C.; Lopes-da-Silva, José A.; Pintado, Manuela E.; Malcata, F. Xavier
The major goal of this research effort was to comprehensively characterize various whey protein products available in the market — including one whey protein isolate (WPI) and three whey protein concentrates (two forms of WPC 80, and WPC 50), with regard to the effects of specific components (e.g. lecithin and minerals) and concentration of β-lactoglobulin (β-Lg) and α-lactalbumin upon thermal and gelation properties at various pH values (using micro differential scanning calorimetry, μDSC, and oscillatory rheometry). At pH values far from the isoelectric point of whey proteins, denaturation and aggregation appeared as one single endothermic peak in the corresponding μDSC heating thermograms, for WPI and both WPC 80; however, they appeared as separate transitions at pH 5. Acidic conditions increased the temperature of occurrence of the dominant endothermic transition associated to β-Lg, thus increasing the thermal stability of WPI, WPC 80A and WPC 80B. Gelation took place at the lowest temperature when pH was set at 5. WPI, WPC 80A and WPC 80B exhibited the highest G′ values at pH 5 — whereas WPI led to stronger gels than WPC, irrespective of pH. In the case of WPC 50, gelation did not occur at all.
Effect of whey protein purity and glycerol content upon physical properties of edible films manufactured therefrom
Publication . Ramos, Óscar L.; Reinas, Isabel; Silva, Sara I.; Fernandes, João C.; Cerqueira, Miguel A.; Pereira, Ricardo N.; Vicente, António A.; Poças, M. Fátima; Pintado, Manuela E.; Malcata, F. Xavier
This manuscript describes the detailed characterization of edible films made from two different protein
products e whey protein isolate (WPI) and whey protein concentrate (WPC), added with three levels of
glycerol (Gly) e i.e. 40, 50 and 60%(w/w). The molecular structure, as well as barrier, tensile, thermal,
surface and optical properties of said films were determined, in attempts to provide a better understanding
of the effects of proteinaceous purity and Gly content of the feedstock. WPI films exhibited
statistically lower (p < 0.05) moisture content (MC), film solubility (S), water activity, water vapor
permeability (WVP), oxygen and carbon dioxide permeabilities (O2P and CO2P, respectively) and color
change values, as well as statistically higher (p < 0.05) density, surface hydrophobicity, mechanical
resistance, elasticity, extensibility and transparency values than their WPC counterparts, for the same
content of Gly. These results are consistent with data from thermal and FTIR analyses. Furthermore,
a significant increase (p < 0.05) was observed in MC, S, WVP, O2P, CO2P, weight loss and extensibility of
both protein films when the Gly content increased; whereas a significant decrease (p < 0.05) was
observed in thermal features, as well as in mechanical resistance and elasticity e thus leading to weaker
films. Therefore, fundamental elucidation was provided on the features of WPI and WPC germane to food
packaging e along with suggestions to improve the most critical ones, i.e. extensibility and WVP.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
Funding Award Number
SFRH/BPD/80766/2011