Papers by Ricardo Pereira
LWT, 2021
Ohmic heating (OH) encompasses interesting benefits towards thermal processing. Envisaging an inc... more Ohmic heating (OH) encompasses interesting benefits towards thermal processing. Envisaging an increasing relevance of soybean protein as an alternative non-animal protein, it is important to understand how OH can contribute to the quality and immunoreactivity of soybean-derived products. This study describes, for the first time, the impact of OH when applied at different electrical frequencies (50 Hz-20 kHz) and moderate electric field intensities (up to 20 V/cm), on the leakage of metals from the electrodes and immunoreactivity aspects of soybean protein isolate (SPI). This was achieved by monitoring the occurrence of electrochemical reactions and evaluating IgG-binding capacity. OH performed at 50 Hz and 95 • C induced significant alterations on the intrinsic fluorescence of SPI (p ≤ 0.05) and the release of detectable amounts of Fe/Ni, with a subsequent reduction of 36% in the immunoreactivity of Gly m TI. The occurrence of non-thermal effects, as well as the interaction between protein and trace metals, may result in a partial blockage of protein epitopes, thus impairing specific antibody binding. These findings present novel information about the importance of OH parameters, such as electrical frequency and occurrence of electrochemical reactions, which can affect the structure and immunoreactivity of SPI fractions.
Advances in Processing Technologies for Bio-based Nanosystems in Food
CRC Press eBooks, Jul 25, 2019
Food Research International, Dec 1, 2014
Production of edible nanostructures constitutes a major challenge in food nanotechnology, and has... more Production of edible nanostructures constitutes a major challenge in food nanotechnology, and has attracted a great deal of interest from several research fields including (but not limited to) food packaging. Furthermore, whey proteins are increasingly used as nutritional and functional ingredients owing to their important biological, physical and chemical functionalities. Besides their technological and functional characteristics, whey proteins are generally recognized as safe (GRAS). Denaturation and aggregation kinetics behavior of such proteins are of particular relevance toward manufacture of novel nanostructures possessing a number of potential uses. When these processes are properly engineered and controlled, whey proteins may form nanostructures useful as carriers of bioactive compounds (e.g. antimicrobials, antioxidants and nutraceuticals). This review discusses the latest advances in nanoscale phenomena involved in protein thermal aggregation aiming at formation of bio-based nanocoating networks. The extent of aggregation is dependent upon a balance between molecular interactions and environmental factors; therefore, the impact of these conditions is addressed in a critical manner. A particular emphasis is given to the effect of temperature as long as being one of the most critical variables. The application of moderate electric fields (MEF), an emergent approach, as such or combined with conventional heating is considered as it may inhibit/prevent excessive denaturation and aggregation of whey proteinsthus opening new perspectives for development of innovative protein nanostructures (i.e. nanocoatings). A better understanding of the mechanism(s) involved in whey protein denaturation and aggregation is crucial as it conveys information relevant to select methods for manipulating interactions between molecules, and thus control their functional properties in tailor-made applications in the food industry.
Bio-Based Nanocomposites for Food Packaging and Their Effect in Food Quality and Safety
Elsevier eBooks, 2018
Oscar L. Ramos, Ricardo N. Pereira, and Joana T. Martins gratefully acknowledge their post-doctor... more Oscar L. Ramos, Ricardo N. Pereira, and Joana T. Martins gratefully acknowledge their post-doctoral grants (SFRH/BPD/80766/2011, SFRH/BPD/81887/2011, and SFRH/BPD/89992/2012, respectively) to the Fundacao para a Ciencia e Tecnologia (FCT, Portugal). The authors thank the FCT Strategic Project of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684), and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte, as well as the project POCI-01-0145-FEDER-006939 (Laboratory for Process Engineering, Environment, Biotechnology and Energy—LEPABE) funded by FEDER funds through COMPETE2020—Programa Operacional Competitividade e Internacionalizacao (POCI)—and by national funds through FCT.
Whey and Whey Powders: Production and Uses
Elsevier eBooks, 2016
Whey, a by-product of the dairy industry, contains many valuable constituents, especially soluble... more Whey, a by-product of the dairy industry, contains many valuable constituents, especially soluble proteins, for example, β-lactoglobulin, α-lactalbumin, immunoglobulin, bovine serum albumin, lactoferrin, and lactoperoxidase. They are widely accepted as food ingredients in several food formulations (e.g., confectionery, bakery, health, and sport supplements), normally in dry form. Whey products possess relevant nutritional (e.g., high content of essential amino acids), functional (e.g., gelation, foaming, and emulsifying agent), and biological (e.g., antimicrobial, anticarcinogenic, and immunomodulatory activities) properties for health. Advances in processing technologies of whey protein powders, their major functional and biological properties, and the most promising applications will be briefly reviewed.
Food Research International, Nov 1, 2019
There is an increasing demand for alternative and sustainable protein sources, such as vegetables... more There is an increasing demand for alternative and sustainable protein sources, such as vegetables, insects and microorganisms, that can meet the nutritional and sensory pleasantness needs of consumers. This emergent interest for novel protein sources, allied with "green" and cost-effective processing technologies, such as high hydrostatic pressure, ohmic heating and pulsed electric fields, can be used as strategies to improve the consumption of proteins from sustainable sources without compromising food security. In addition to their nutritional value, these novel proteins present several technological-functional properties that can be used to create various protein systems in different scales (i.e., macro, micro and nano scale), which can be tailored for a specific application in innovative food products. However, in order for these novel protein sources to be broadly used in future food products, their fate in the human gastrointestinal tract (e.g., digestion and bioavailability) must be assessed, as well as their safety for consumers must be clearly demonstrated. In particular, these proteins may become novel allergens triggering adverse reactions and, therefore, a comprehensive allergenicity risk assessment is needed. This review presents an overview of the most promising alternative protein sources, their application in the production of innovative food systems, as well as their potential effects on human health. In addition, new insights on sustainable processing strategies are given.
Ohmic heating has often been said to improve the sensorial quality of foodstuffs, which has been ... more Ohmic heating has often been said to improve the sensorial quality of foodstuffs, which has been attributed mainly to its volumetric heating mechanism and (eventually) to the presence of an electric field. This is still subject to doubts and questions from the scientific community, and it is therefore important to determine the effect of ohmic heating on food constituents. We have investigated whether ohmic heating technology would give rise to changes on the denaturation of whey proteins from bovine milk. Whey protein solutions samples were heated at 85 ºC (up to 30 min) and ohmic heating experiments were also adapted to simulate the sample temperature changes during conventional (indirect heating) experiments. Our results show that ohmic heating seems to reduce protein unfolding and denaturation, when compared with conventional heating.
New Insights on Bio-Based Micro- and Nanosystems in Food
Encyclopedia of Food Chemistry, 2019
The application of micro- and nanotechnologies in the food industry have been widely studied and ... more The application of micro- and nanotechnologies in the food industry have been widely studied and reported due to an increasing growth of public awareness for the consumption of healthy food products. Consequently, food industry players have become highly interested in the development and application of innovative food-grade micro- and nanosystems intended for the protection and controlled delivery of bioactive compounds. This can be achieved by resorting to novel state of the art methodologies (i.e., top-down and bottom-up strategies) that take advantage of the functional properties of such ingredients, so that they can be used to protect and release, in a controlled manner, bioactive compounds. To evaluate effectiveness of these micro- and nanosystems it is of utmost importance to evaluate their behavior when incorporated in food products, in order to perceive potential interactions with biomolecules, as well as under gastrointestinal (GI) digestion. In vitro GI models have been used since they provide accurate results, are relatively inexpensive, and do not raise ethical issues, and most of all can be correlated with those obtained in vivo.
Nanostructures of whey proteins for encapsulation of food ingredients
Biopolymer Nanostructures for Food Encapsulation Purposes, 2019
Abstract The most current and high-level research is being taken on the use of nanoscience and na... more Abstract The most current and high-level research is being taken on the use of nanoscience and nanotechnology due to its varied application in numerous fields of science. Food nanotechnology, and in particular, the development and application of bio-based nanostructures are an emerging area having a high potential to engender new products and processes in the food industry. This chapter intends to discuss whey protein-based nanostructured systems (i.e., whey protein isolate, whey protein concentrate, β-lactoglobulin, and α-lactalbumin) for encapsulation of food ingredients. These protein nanostructures have unique properties, such as a high nutritional value, GRAS nature, gelling capability, and can be easily prepared and controlled. They have also the ability to conjugate a large variety of food ingredients (e.g., antioxidants, vitamins, minerals, flavors, and odors) via amino groups or ionic and hydrophobic interactions. This behavior will prevent the degradation of sensitive bioactives, while permitting a site-specific action and controlled delivery rate due to the swelling behavior of the gel in reaction to external and physical stimuli such as temperature, enzymes, pH, or ionic strength), thus contributing to an improved bioavailability of such ingredients. The potential of whey protein nanostructures for encapsulation and controlled delivery of food ingredients will be addressed in a critical manner in this chapter. Moreover, various techniques used for their nanoencapsulation and evaluation of their stability during storage will also be discussed. The behavior and bioavailability of whey nanostructures and their associated/encapsulated food ingredients will be discussed using insights from in vitro and in vivo gastrointestinal systems together with potential cytotoxicity, cellular uptake, and allergenicity via in vitro cell lines. Finally, examples of such nanostructures applied in food matrices will be described, as well as the main challenges for their commercial use.
Protein hydrogels are one of the most convenient and widely used matrix in food applications. Rec... more Protein hydrogels are one of the most convenient and widely used matrix in food applications. Recently, cold gelation ability of whey protein isolate (WPI) is taking interest in protection and delivery of value-added bioactive compounds through micro and nano-association techniques. This study aims to combine an electro-heating treatment at moderate electric fields (MEF) together with cold gelation ability of whey proteins in order to reduce size of protein aggregates at nano-scale and improve association efficiency of riboflavin. Divalent iron cation assisted cold gelation of electro-heated WPI and effects of MEF on the produced hydrogels were reported and encouraged during this experimental research. Particle size was characterized, through dynamic light scattering. While spectrofluorimetric analyses were performed in order to examine the effects of MEF and cold induced gelation on the association of riboflavin within WPI hydrogel network structure. Under MEF application smaller s...
Research on whey utilization is now being largely focused on exploiting their physiochemical and ... more Research on whey utilization is now being largely focused on exploiting their physiochemical and bioactive properties. Whey protein isolate (WPI) is among the most important whey-derived ingredients and consists of products purified to a high protein content (> 90%). The denaturation and aggregation kinetic behavior of WPI upon heating is of particular relevance; when properly engineered and controlled, it results in the production of novel nano-structures with many potential uses in food formulations (i.e. enhancement of textural properties, action as stabilizing agents and delivery of biologically active substances). Combination of heat and moderate electric fields (MEF) treatment interferes with unfolding and aggregation pathways of whey biopolymers [1].
Ohmic heating is one of the earliest applications of electricity in thermal processing of food an... more Ohmic heating is one of the earliest applications of electricity in thermal processing of food and is receiving increased attention because of its uniform heating of liquids with faster heating rates, which presumably enables obtaining products of a superior quality to those processed by conventional heating technologies. Given the biochemical structure of proteins, it is expectable that ohmic heating and its moderate electric fields will influence their properties and hence their behavior. The aim of this work was to evaluate the effects of moderate electric fields on denaturation and aggregation of whey proteins and its subsequent effects in whey-derived products. Results presented here show that ohmic heating led to lower whey protein denaturation at the early stages of heating, kinetically traduced by lower values of n and k, when compared to those from conventional heating (p < 0.05) under equivalent heating rate and holding times. Furthermore, whey protein aggregation (meas...
Materials Science and Engineering: C, 2021
Ohmic heating (OH) is recognised as an emerging processing technology which recently is gaining i... more Ohmic heating (OH) is recognised as an emerging processing technology which recently is gaining increasing attention due to its ability to induce and control protein functionality. In this study, OH was used for the first time in the production of scaffolds for tissue engineering. BSA/casein solutions were processed by OH, promoting protein denaturation and aggregation, followed by cold-gelation through the addition of Ca 2+ . The formation of stable scaffolds was mostly dependent on the temperature and treatment time during OH processing. The variations of the electric field (EF) induced changes in the functional properties of both gel forming solutions and final scaffolds (contact angle, swelling, porosity, compressive modulus and degradation rate). The scaffolds' biological performance was evaluated regarding their ability to support the adhesion and proliferation of human fibroblast cells. The production process resulted in a non-cytotoxic material and the changes imposed by the presence of the EF during the scaffolds' production improved cellular proliferation and metabolic activity. Protein functionalization assisted by OH presents a promising new alternative for the production of improved and tuneable protein-based scaffolds for tissue engineering.
Gels, 2019
Proteins are receiving significant attention for the production of structures for the encapsulati... more Proteins are receiving significant attention for the production of structures for the encapsulation of active compounds, aimed at their use in food products. Proteins are one of the most used biomaterials in the food industry due to their nutritional value, non-toxicity, biodegradability, and ability to create new textures, in particular, their ability to form gel particles that can go from macro- to nanoscale. This review points out the different techniques to obtain protein-based nanostructures and their use to encapsulate and release bioactive compounds, while also presenting some examples of food grade proteins, the mechanism of formation of the nanostructures, and the behavior under different conditions, such as in the gastrointestinal tract.
Food Research International, 2019
Sodium caseinate (NaCAS) is widely used in the food industry to provide nutritional and functiona... more Sodium caseinate (NaCAS) is widely used in the food industry to provide nutritional and functional benefits. This work deals with the effects of applying moderate electric fields (MEF) of different intensity -ranging from 2 V•cm -1 to 17 V•cm -1 -on the physical and functional properties of NaCAS solutions during Ohmic heating (OH) at 95 °C. Self-standing gels were produced regardless the heating technique applied (i.e. conventional or OH), and these gels were much more prone to physical rupture when compared with the ones produced from unheated NaCAS. Interestingly, OH treatment formed gels with lower values of strain at rupture and water holding capacity than unheated samples; this pattern was not observed for gels obtained through the conventional heating treatment (at 0 V•cm -1 ). These effects may be linked with disturbances of the distribution of random coil structures and enhanced solubility of NaCAS at its isoelectric point, reducing aggregation and impairing the development of a more compact protein network. Results show that OH presents potential to be used as volumetric heating tool for NaCAS solubilization and for the production of distinctive acidified systems.
Bioresource technology, Jan 29, 2018
This review provides an overview of recent research on electrotechnologies applied to the valoriz... more This review provides an overview of recent research on electrotechnologies applied to the valorization of bioresources. Following a comprehensive summary of the current status of the application of well-known electric-based processing technologies, such as pulsed electric fields (PEF) and high voltage electrical discharges (HVED), the application of moderate electric fields (MEF) as an extraction or valorization technology will be considered in detail. MEF, known by its improved energy efficiency and claimed electroporation effects (allowing enhanced extraction yields), may also originate high heating rates - ohmic heating (OH) effect - allowing thermal stabilization of waste stream for other added-value applications. MEF is a simple technology that mostly makes use of green solvents (mainly water) and that can be used on functionalization of compounds of biological origin broadening their application range. The substantial increase of MEF-based plants installed in industries worldw...
Food Hydrocolloids, 2016
-Lactoglobulin ( -Lg) is the major protein fraction of bovine whey serum and a primary gelling ... more -Lactoglobulin ( -Lg) is the major protein fraction of bovine whey serum and a primary gelling agent. -Lg has a high nutritional value, is stable at low pH being highly resistant to proteolytic degradation in the stomach, besides, it has the ability of acting as an encapsulating agent. This study aims at assessing the ability of -Lg nanostructures to associate a nutraceutical -i.e. riboflavin -and release it in a controlled manner throughout an in vitro gastrointestinal (GI) system. For this reason -Lg nanostructures loaded with riboflavin were critically characterized in terms of their morphology (i.e. size, polydispersity, zpotential and shape) by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and efficiency to associate to riboflavin through spectrofluorimetry. Furthermore, these nanocomplexes were evaluated in an in vitro GI model, simulating the physiological conditions. Stable -Lg nanostructures were obtained at pH 6, of spherical shape, characterized by particle size of 172±1 nm, low polydispersity (i.e. PDI of 0.06±0.02), z-potential of -32±3 mV and association efficiency (AE) of 26±1 %. -Lg nano-structures showed to be stable upon their passage throughout stomach (i.e. particle size, PDI and z potential of 248±10 nm, 0.18±0.03 and 18±3 mV, respectively). Concerning their passage throughout the intestine, such nanostructures were mostly degraded in the duodenum. Regarding riboflavin, a release of about 11 % was observed after their passage through stomach, while 35 %, 38 % and 5 % were the released percentages of the total riboflavin associated observed after passage through duodenum, jejunum and ileum, respectively. Hence, -Lg nanostructures showed to be suitable carriers for riboflavin until the intestine, where their degradation occurs. -Lg also showed to be structurally stable, under food simulant conditions (yoghurt simulant, composed of 3 % acetic acid), over 14 days, with a protective effect upon riboflavin activity, releasing it in a 7 day period. 1.
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Papers by Ricardo Pereira