Effect of ohmic heating on the structure and properties of flexible multilayer packaging.

Food-packaging-processing interactions define packaging materials' performance properties and product quality. This study evaluated the effect of ohmic heating (OH) processing and different food simulants on the properties of four multilayer flexible packaging materials (PETmet/PE, PETmet/PP, PET/Al/PE, and PET/Al/PA/PP). OH treatment was applied to the sealed packages containing the food simulants using a voltage gradient of 3.7 V/cm at a frequency of 20 kHz, resulting in a thermal process of at 80 °C for 1 min. The structure and performance of the different packages were then evaluated. The materials did not show changes in chemical groups nor thermal properties. However, the simulant-packaging-processing interaction resulted in changes in crystallinity, morphology, mechanical and barrier properties (water and oxygen), especially for metallized films in contact with acidic food simulants. The results indicate that although OH resulted in changes in packaging materials, these materials can be used under the conditions applied in this study.

Tackling food allergens-The role of food processing on proteins' allergenicity.

This chapter examines how innovative and emerging food processing technologies, such as those that use heat, electricity, electromagnetic waves, and pressure, can modify protein denaturation, aggregation, and intermolecular interactions pathways, which can result in varying immunoreactive responses. It emphasizes the need to understand how these processing methods affect the protein epitopes recognized by antibodies and their respective priming pathways, especially during the sensitization stage that precedes an allergic response. Although traditional processing methods have been investigated, the impact of novel technologies on food protein allergenicity remains largely unknown. The chapter specifically focuses on milk proteins, which have clinical significance and are associated with cow's milk allergy, one of the most common food allergies in young children. Additionally, it examines potential scientific advancements that novel processing methods may bring to this field.

Emergent Proteins-Based Structures-Prospects towards Sustainable Nutrition and Functionality.

The increased pressure over soils imposed by the need for agricultural expansion and food production requires development of sustainable and smart strategies for the efficient use of resources and food nutrients. In accordance with worldwide transformative polices, it is crucial to design sustainable systems for food production aimed at reducing environmental impact, contributing to biodiversity preservation, and leveraging a bioeconomy that supports circular byproduct management. Research on the use of emergent protein sources to develop value-added foods and biomaterials is in its infancy. This review intends to summarize recent research dealing with technological functionality of underused protein fractions, recovered from microbial biomass and food waste sources, addressing their potential applications but also bottlenecks. Protein-based materials from dairy byproducts and microalgae biomass gather promising prospects of use related to their techno-functional properties. However, a balance between yield and functionality is needed to turn this approach profitable on an industrial scale basis. In this context, downstream processing should be strategically used and properly integrated. Food solutions based on microbial proteins will expand in forthcoming years, bringing the opportunity to finetune development of novel protein-based biomaterials.

Ohmic heating as a new tool for protein scaffold engineering.

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 Ca2+. 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.

Electric field effects on proteins - Novel perspectives on food and potential health implications.

Electric fields (EF) technologies have been establishing a solid position in emergent food processing and have seen as serious alternatives to traditional thermal processing. During the last decades, research has been devoted to elucidation of technological and safety issues but also fundamental aspects related with interaction of electric fields (EF) with important macromolecules, such as proteins. Proteins are building blocks for the development of functional networks that can encompass health benefits (i.e. nutritional and bioactive properties) but may be also linked with adverse effects such as neurodegenerative diseases (amyloid fibrils) and immunological responses. The biological function of a protein depends on its tridimensional structure/conformation, and latest research evidences that EF can promote disturbances on protein conformation, change their unfolding mechanisms, aggregation and interaction patterns. This review aims at bringing together these recent findings as well as providing novel perspectives about how EF can shape the behavior of proteins towards the development of innovative foods, aiming at consumers' health and wellbeing.

Effects of ohmic heating on the immunoreactivity of ß-lactoglobulin - a relationship towards structural aspects.

ß-Lactoglobulin (ß-LG) encompasses important biological functions, but it is also a major milk allergen, being responsible for the high incidence of cow's milk allergy in childhood. Despite numerous studies addressing the effect of thermal processing on the immunoreactivity of ß-LG, little is known about the impact of emergent food processing technologies, such as ohmic heating (OH), on its immunoreactivity. This study describes, for the first time, the effects of thermal and electric effects of OH on the immunoreactivity of ß-LG. The influence of high-temperature short time (HTST; 72.5 °C for 15 and 90 °C for 1 s) and low-temperature long time (LTLT; 65 °C for 30 min) pasteurization binomials combined with different electrical variables (electric field intensity and electrical frequency) was evaluated and compared with that of conventional heating. HTST at 90 °C for 1 s extensively affects the protein secondary structure and increases the levels of reactive aggregates, resulting in increased total immunoreactivity (assessed by ELISA and immunoblotting). OH at 4 V cm-1 and a frequency of 25 kHz reduced the immunoreactivity of monomeric ß-LG and its resultant aggregates, compared with conventional heat treatments. In contrast, the presence of electric fields (4 V cm-1 and 25 kHz) during LTLT increased the immunoreactivity of monomeric ß-LG. The thermal and electrical variables of OH change the balance between monomeric and aggregated forms of ß-LG, affecting their ability to bind specific antibodies. These outcomes bring novel insights into how to modulate OH aiming at reducing the allergenic potential of ß-LG based products.

Ohmic heating as an innovative approach for the production of keratin films.

Ohmic heating is a thermal processing method based on the application of electric fields directly into a semi-conductive medium. In this study, we explored for the first time the use of ohmic heating to obtain keratin films. The properties of the films prepared by ohmic heating and conventional heating were evaluated and compared under similar thermal profiles. A lower increase in free thiols' concentration was obtained for the keratin solutions and keratin films submitted to ohmic heating (16% increase for the keratin solution extracted from virgin hair, pH 9, submitted to ohmic heating and 23% when submitted to conventional heating). Significant differences in the swelling results were observed for the films prepared with keratin extracted from virgin hair, with a swelling decrease in about 55% for the films prepared by ohmic heating. Generally, the keratin films obtained by ohmic heating showed distinct properties comparatively to the films produced by conventional methods. The application of a fusion protein on the keratin films demonstrated their capacity to be used as substitutes to hair fibers when evaluating the potential of new cosmetic products. This work suggests that ohmic heating show potential to tailor keratin films properties depending on an intended application or functionality.

Electrosprayed whey protein-based nanocapsules for ß-carotene encapsulation.

In this work an electrohydrodynamic process (electrospray) was used to produce ß-carotene loaded nanocapsules based on whey protein isolate (WPI). WPI solutions were prepared in aqueous solutions with different concentrations of ethanol (5, 10 and 15%) which were used for ß-carotene solubilization. Different electrospray conditions were tested and the morphology and molecular organization of the nanocapsules were studied on dried and hydrated state. The size of the dried nanocapsules ranged between 227 and 283 nm. After hydration, there was a significant increase in the mean size of the nanocapsules, being the sizes higher for nanocapsules produced with increasing concentrations of ethanol. Results, obtained from the reactivity of free sulfhydryl groups and fluorescence analysis, showed that the increase of ethanol concentration had a destabilizing effect on the protein unfolding. Electrosprayed WPI-based nanocapsules can be used for the encapsulation of ß-carotene answering the industrial demand for novel encapsulation technologies to protect sensitive bioactive compounds.

Influence of moderate electric fields in ß-lactoglobulin thermal unfolding and interactions.

In this study, the effects of moderate electric fields during thermal denaturation of ß-lactoglobulin were examined through an in situ circular dichroism approach, complemented by intrinsic extrinsic fluorescence analysis. Results have shown that the effects of electric fields in protein unfolding were linearly dependent on the applied electric field intensity (V/cm) and increased by the use of low electric frequencies - i.e. 50 to 200 Hz. These electric effects caused significant changes on ß-lactoglobulin melting temperature, unfolded conformation and subsequent intermolecular interactions, revealed by the increase of surface hydrophobicity (ANS affinity) and higher conservation of retinol binding. The obtained data provides a clear evidence that moderate electric fields contribute to distinct folding/unfolding of ß-lactoglobulin, resulting in structural modifications. These findings are relevant for (bio)-technological applications involving electric fields processing, bringing new insights for the development of innovative strategies to control protein function and tune production of functional protein systems.

Electric Field Processing: Novel Perspectives on Allergenicity of Milk Proteins.

Milk proteins are being widely used in formulated foods as a result of their excellent technological, functional, and biological properties. However, the most representative proteins from casein and whey fractions are also recognized as major allergens and responsible for the prevalence of cow's milk protein allergy in childhood. Electroheating technologies based on thermal processing of food as a result of application of moderate electric fields, also known by ohmic heating (OH) or Joule effect, are establishing a solid foothold in the food industry. Currently, the influence of OH on allergenic aspects of milk proteins is under debate but still undisclosed. The occurrence of electrical effects on the protein structure and its function has already been reported; thus, the impact of OH over allergenicity should not be overlooked. On the basis of these recent findings, it is then relevant to speculate about the impact of this emergent technology on the potential allergenicity of milk proteins.

Development of iron-rich whey protein hydrogels following application of ohmic heating - Effects of moderate electric fields.

The influence that ohmic heating technology and its associated moderate electric fields (MEF) have upon production of whey protein isolate cold-set gels mediated by iron addition was investigated. Results have shown that combining heating treatments (90°C, 5min) with different MEF intensities let hydrogels with distinctive micro and macro properties - i.e. particle size distribution, physical stability, rheological behavior and microstructure. Resulting hydrogels were characterized (at nano-scale) by an intensity-weighted mean particle diameter of 145nm, a volume mean of 240nm. Optimal conditions for production of stable whey protein gels were attained when ohmic heating treatment at a MEF of 3V∙cm-1 was combined with a cold gelation step using 33mmol∙L-1 of Fe2+. The consistency index of hydrogels correlated negatively to MEF intensity, but a shear thickening behavior was observed when MEF intensity was increased up to 10V∙cm-1. According to transmission electron microscopy, ohmic heating gave rise to a more homogenous and compact fine-stranded whey protein-iron microstructure. Ohmic heating appears to be a promising technique, suitable to tailor properties of whey protein gels and with potential for development of innovative functional foods.

Antimicrobial nanostructured starch based films for packaging.

Montmorillonite modified with a quaternary ammonium salt C30B/starch nanocomposite (C30B/ST-NC), silver nanoparticles/starch nanocomposite (Ag-NPs/ST-NC) and both silver nanoparticles/C30B/starch nanocomposites (Ag-NPs/C30B/ST-NC) films were produced. The nanoclay (C30B) was dispersed in a starch solution using an ultrasonic probe. Different concentrations of Ag-NPs (0.3, 0.5, 0.8 and 1.0mM) were synthesized directly in starch and in clay/starch solutions via chemical reduction method. Dispersion of C30B silicate layers and Ag-NPs in ST films characterized by X-ray and scanning electron microscopy showed that the presence of Ag-NPs enhanced clay dispersion. Color and opacity measurements, barrier properties (water vapor and oxygen permeabilities), dynamic mechanical analysis and contact angle were evaluated and related with the incorporation of C30B and Ag-NPs. Films presented antimicrobial activity against Staphylococcus aureus, Escherichia coli and Candida albicans without significant differences between Ag-NPs concentrations. The migration of components from the nanostructured starch films, assessed by food contact tests, was minor and under the legal limits. These results indicated that the starch films incorporated with C30B and Ag-NPs have potential to be used as packaging nanostructured material.