Food processing strategies to enhance phenolic compounds bioaccessibility and bioavailability in plant-based foods.

Phenolic compounds are important constituents of plant-based foods, as their presence is related to protective effects on health. To exert their biological activity, phenolic compounds must be released from the matrix during digestion in an absorbable form (bioaccessible) and finally absorbed and transferred to the bloodstream (bioavailable). Chemical structure and matrix interactions are some food-related factors that hamper phenolic compounds bioaccessibility and bioavailability, and that can be counteracted by food processing. It has been shown that food processing can induce chemical or physical modifications in food that enhance phenolic compounds bioaccessibility and bioavailability. These changes include: (i) chemical modifications into more bioaccessible and bioavailable forms; (ii) cleavage of covalent or hydrogen bonds or hydrophobic forces that attach phenolic compounds to matrix macromolecules; (iii) damaging microstructural barriers such as cell walls that impede the release from the matrix; and (iv) create microstructures that protect phenolic compounds until they are absorbed. Indeed, food processing can produce degradation of phenolic compounds, however, it is possible to counteract it by modulating the operating conditions in favor of increased bioaccessibility and bioavailability. This review compiles the current knowledge on the effects of processing on phenolic compounds bioaccessibility or bioavailability, while suggesting new guidelines in the search of optimal processing conditions as a step forward towards the design of healthier foods.

Effects of pulsed light treatments and pectin edible coatings on the quality of fresh-cut apples: a hurdle technology approach.

BACKGROUND: Pulsed light (PL) treatments stand as an alternative for the shelf-life extension of fresh-cut products. The antimicrobial effects of PL are well known; however, its influence on quality attributes needs to be assessed. This study was aimed at evaluating the application of PL treatments in combination with pectin-based edible coatings enriched with dietary fiber for the preservation of fresh-cut apples. RESULTS: Dipping of fresh-cut apples in ascorbic acid/calcium chloride solution prior to pectin coating and PL treatments was effective to minimize browning and softening of apple surfaces. Incorporation of fiber in the pectin coating did not cause any change in microbial loads and sensory acceptability of apple cubes. Pectin-coated PL-treated apple pieces exhibited significantly higher antioxidant activity values than fresh and PL control samples. At the end of storage, the combination of both treatments resulted in an almost 2 log CFU g-1 reduction of microbial counts. Sensory attribute scores did not fall below the rejection limit throughout 14 days, although the presence of off-odors limited the acceptability of the pectin-coated samples. CONCLUSION: The results demonstrate that PL treatments applied to pectin-coated fresh-cut apples may be used to maintain quality attributes, thus conferring prebiotic potential and extending the shelf-life of the product. © 2016 Society of Chemical Industry.

Influence of Cooking Conditions on Carotenoid Content and Stability in Porridges Prepared from High-Carotenoid Maize.

Maize is a staple food crop in many developing countries, hence becoming an attractive target for biofortification programs toward populations at risk of micronutrient deficiencies. A South African white endosperm maize inbred line was engineered with a carotenogenic mini-pathway to generate high-carotenoid maize, which accumulates ß-carotene, lutein and zeaxanthin. As maize porridge is a traditional meal for poor populations in sub-Saharan African countries, high-carotenoid maize was used as raw material to prepare different maize meals. The objective of this work was to assess the impact of popular home-cooking techniques and different cooking parameters (temperature, time and pH) on the final carotenoid content in the cooked product, using a spectrophotometric technique based on the mean absorption of carotenoids at 450 nm. Carotenoid levels were not only preserved, but also enhanced in high-carotenoid maize porridges. The carotenoid content was increased when temperatures ≤95 °C were combined with short cooking times (10-60 min). The most optimum thermal treatment was 75 °C/10 min. When treated under those conditions at pH 5, high-carotenoid maize porridges doubled the initial carotenoid content up to 88 µg/g dry weight. Regarding to cooking techniques, the highest carotenoid content was found when unfermented thin porridges were prepared (51 µg/g dry weight of high-carotenoid maize porridge). We conclude that high-carotenoid maize may contribute to enhance the dietary status of rural populations who depend on maize as a staple food.

Modulating Biopolymer Electrical Charge to Optimize the Assembly of Edible Multilayer Nanofilms by the Layer-by-Layer Technique.

The aim of this work was to study the influence of biopolymer (alginate, ALG; chitosan, CHI) charge on the formation of multilayer nanofilms by the layer-by-layer (LbL) technique. The electrical charge of ALG and CHI (high, medium, or low) was modulated by adjusting the pH of biopolymer solutions. The amount of biopolymer deposited in multilayers depended on the charge of ALG and CHI solutions. The lower the charge the higher the deposition rate due to the higher number of biopolymer molecules needed to neutralize the previous layer. Medium and low charge biopolymers led to a drastic change in the wettability of multilayers, with ALG layers being strongly hydrophilic and CHI layers strongly hydrophobic. The surface ζ-potential alternatively changed from negative to positive using ALG or CHI. This effect was more pronounced using highly charged biopolymers. Results obtained in this study evidenced that the multilayers properties can be tuned by controlling the biopolymer electrical charge.

Effects of polysaccharide-based edible coatings enriched with dietary fiber on quality attributes of fresh-cut apples.

Little information is available regarding the incorporation of dietary fiber into edible films and coatings. In this work, apple fiber and inulin were incorporated into polysaccharide-based (alginate, pectine and gellan gum) edible coating formulations and their effects on the quality attributes of fresh-cut apples were evaluated. Antioxidant properties, color, firmness, sensory quality and microbial growth of fresh-cut apple were studied during 16 days of storage at 4 °C. Results show that dietary fiber extracts incorporated to gellan gum, pectin and alginate-based coatings together with calcium chloride and ascorbic acid successfully maintained the firmness and color of coated fresh-cut apples in comparison with uncoated control samples, which presented severe texture softening and browning. The firmness of apple pieces coated with polysaccharide-based coating formulations incorporating apple fiber doubled, and sometimes tripled, that of uncoated samples. Any of the assayed coatings exhibited a positive effect on the sensory properties of fresh-cut apples. The incorporation of apple fiber, together with the use of ascorbic acid, contributed to keep the antioxidant potential of the fruit at least during the first week of storage. Furthermore, gellan gum coatings had a marked effect in reducing mesophilic and psychrophilic counts on fresh-cut apples throughout storage regardless the addition of dietary fibers. The results achieved demonstrate the feasibility of the addition of dietary fiber to edible coating formulations for increasing the nutritional value of fresh-cut apples without compromising their fresh-like quality attributes.

Pulsed light inactivation of naturally occurring moulds on wheat grain.

BACKGROUND: Pulsed light (PL) is emerging as a non-thermal technology with excellent prospects for the decontamination of foods and food contact surfaces. Its application for mould inactivation on cereal grains would allow a reduction of storage losses as well as the prevention of mycotoxin contamination at a post-harvest level. The potential of PL for the decontamination of naturally occurring moulds on wheat grain was investigated in this study. RESULTS: Treatments of up to 40 flashes of a fluence of 0.4 J cm⁻² per pulse were applied to both sides of the grain, with an overall energy release ranging from 6.4 to 51.2 J g⁻¹. The most powerful treatment applied to wheat in this study (51.2 J g⁻¹) resulted in a mould reduction of approximately 4 log cycles on samples displaying an initial mould contamination level of 2.2 × 105 CFU g⁻¹. At the same time, the seed germination percentage was only slightly affected. For PL treatments causing an inactivation of 3-4 log cycles, only 14-15% of the germination power of the wheat seeds was lost. CONCLUSION: The PL treatments attained greater microbial reductions for higher treatment times and lower initial mould loads. The absence of the UV portion of the radiation spectrum was found to significantly reduce the treatment effectiveness.

Tailoring the Techno-Functional Properties of Fava Bean Protein Isolates: A Comparative Evaluation of Ultrasonication and Pulsed Electric Field Treatments.

The fava bean protein isolate (FBPI) holds promise as a sustainable plant-based protein ingredient. However, native FBPIs exhibit limited functionality, including unsuitable emulsifying activities and a low solubility at a neutral pH, restricting their applications. This study is focused on the effect of ultrasonication (US) and pulsed electric fields (PEF) on modulating the techno-functional properties of FBPIs. Native FBPIs were treated with US at amplitudes of 60-90% for 30 min in 0.5 s on-and-off cycles and with PEF at an electric field intensity of 1.5 kV/cm with 1000-4000 pulses of 20 µs pulse widths. US caused a reduction in the size and charge of the FBPIs more prominently than the PEF. Protein characterization by means of SDS-PAGE illustrated that US and PEF caused severe-to-moderate changes in the molecular weight of the FBPIs. In addition, a spectroscopic analysis using Fourier-transform infrared (FTIR) and circular dichroism (CD) revealed that US and the PEF induced conformational changes through partial unfolding and secondary structure remodeling from an α-helix to a ß-sheet. Crystallographic and calorimetric determinations indicated decreased crystallinity and lowered thermal transition temperatures of the US- and PEF-modified FBPIs. Overall, non-thermal processing provided an effective strategy for upgrading FBPIs' functionality, with implications for developing competitive plant-based protein alternatives.

Emerging Chemical, Biochemical, and Non-Thermal Physical Treatments in the Production of Hypoallergenic Plant Protein Ingredients.

Allergies towards gluten and legumes (such as, soybean, peanut, and faba bean) are a global issue and, occasionally, can be fatal. At the same time, an increasing number of households are shifting to plant protein ingredients from these sources, which application and consumption are limited by said food allergies. Children, the elderly, and people with immune diseases are particularly at risk when consuming these plant proteins. Finding ways to reduce or eliminate the allergenicity of gluten, soybean, peanut, and faba bean is becoming crucial. While thermal and pH treatments are often not sufficient, chemical processes such as glycation, polyphenol conjugation, and polysaccharide complexation, as well as controlled biochemical approaches, such as fermentation and enzyme catalysis, are more successful. Non-thermal treatments such as microwave, high pressure, and ultrasonication can be used prior to further chemical and/or biochemical processing. This paper presents an up-to-date review of promising chemical, biochemical, and non-thermal physical treatments that can be used in the food industry to reduce or eliminate food allergenicity.

Relationship between Physicochemical, Techno-Functional and Health-Promoting Properties of Fiber-Rich Fruit and Vegetable By-Products and Their Enhancement by Emerging Technologies.

The preparation and processing of fruits and vegetables produce high amounts of underutilized fractions, such as pomace and peel, which present a risk to the environment but constitute a valuable source of dietary fiber (DF) and bioactive compounds. The utilization of these fiber-rich products as functional food ingredients demands the application of treatments to improve their techno-functional properties, such as oil and water binding, and health-related properties, such as fermentability, adsorption, and retardation capacities of glucose, cholesterol, and bile acids. The enhancement of health-promoting properties is strongly connected with certain structural and techno-functional characteristics, such as the soluble DF content, presence of hydrophobic groups, and viscosity. Novel physical, environmentally friendly technologies, such as ultrasound (US), high-pressure processing (HPP), extrusion, and microwave, have been found to have higher potential than chemical and comminution techniques in causing desirable structural alterations of the DF network that lead to the improvement of techno-functionality and health promotion. The application of enzymes was related to higher soluble DF content, which might be associated with improved DF properties. Combined physical and enzymatic treatments can aid solubilization and modifications, but their benefit needs to be evaluated for each DF source and the desired outcome.

Efficacy of Pectin-Based Coating Added with a Lemon Byproduct Extract on Quality Preservation of Fresh-Cut Carrots.

The effect of an edible pectin-based coating supplemented with a lemon byproduct extract on the quality attributes of fresh-cut carrots was studied. Color, hardness, microbial growth, respiratory activity, and antioxidant properties of fresh-cut carrots were studied during 14 days of storage at 4 °C. The application of a pectin-based coating containing a lemon byproduct extract preserved carrots' physiological parameters, reduced their physiological activity and, thus, delayed senescence. This aspect was also confirmed by the reduced O2 consumption of the coated carrots due to the slowing down of the product's metabolic reactions. Moreover, coated carrots were characterized by limited changes in colour (ΔE < 3) and white-blush development on both cortical tissue and vascular cylinder, and the presence of calcium chloride in the coating formulation helped to maintain carrots' hardness throughout storage. In addition, treatment with pectin-based coating and lemon byproduct extract improved microbiological stability of fresh-cut carrots, showing the lowest value of total bacterial count immediately after treatment (2.58 log CFU g−1). This kind of treatment also resulted in a significant preservation of valuable compounds (17.22 mg GAE 100 g−1) and antioxidant activity level (289.49 µM Trolox 100 g−1), reducing the wounding stress induced by processing operations for at least ten days.

Pulsed light of near-infrared and visible light wavelengths induces the accumulation of carotenoids in tomato fruits during post-treatment time.

Pulsed light (PL) is proposed as a novel strategy for the food industry to enhance the antioxidant potential of fruits and vegetables for industrial uses. The main aim of this work is to evaluate the impact of postharvest PL treatments of different spectral ranges on the carotenoid concentration as well as quality attributes of tomatoes during post-treatment time. Doses of wide-spectrum light (180-1100 nm), full-spectrum without ultraviolet (UV)-C wavelengths (305-1100 nm), and visible (VIS) + near-infrared light (NIR) (400-1100 nm) were compared. Total carotenoids, lycopene, and chlorophyll contents were spectrophotometrically assessed just after treatments and 1, 5, and 10 days post-treatment. PL treatments accelerated the accumulation of both total carotenoids and lycopene concentrations in tomato fruits. Nevertheless, the efficacy of PL depended on the applied spectral range. Tomato subjected to VIS + NIR treatment exhibited the greatest enhancement in total carotenoids (31 %) and lycopene (35 %) content at day 5 post-treatment and quality attributes were not affected. Conversely, UV-light exposure did not enhance carotenoid concentrations. These results evidenced that VIS + NIR treatments induced a faster accumulation of carotenoids without negatively affecting tomato quality attributes. PRACTICAL APPLICATION: The integration of visible and near-infrared (VIS + NIR) light filters in pulsed light (PL) processing allows enhancing the accumulation of bioactive compounds in tomato tissues in a sustainable way, which can be processed to obtain derived products (e.g., juices, purees) with health-promoting properties. PL technology is characterized by a lack of residual compounds and the absence of applying chemicals potentially harmful to humans. Industries can attract the attention of consumers through their application, which allows offering this added value.

Pomegranate (Punica granatum L.) Peel Extracts as Antimicrobial and Antioxidant Additives Used in Alfalfa Sprouts.

Aqueous and ethanolic pomegranate peel extracts (PPE) were studied as a source of phenolic compounds with antimicrobial, anti-quorum sensing, and antioxidant properties. The aqueous extract showed higher total phenolic and flavonoid content (153.43 mg GAE/g and 45.74, respectively) and antioxidant capacity (DPPH radical inhibition: 86.12%, ABTS radical scavenging capacity: 958.21 mg TE/dw) compared to the ethanolic extract. The main phenolic compounds identified by UPLC-DAD were chlorogenic and gallic acids. The aqueous PPE extract showed antimicrobial activity against Listeria monocytogenes, Salmonella Typhimurium, Candida tropicalis (MICs 19-30 mg/mL), and anti-quorum sensing activity expressed as inhibition of Chromobacterium violaceum violacein production (%). The aqueous PPE extracts at 25 mg/mL applied on alfalfa sprouts reduced psychrophilic bacteria (1.12 Log CFU/100 g) and total coliforms (1.23 Log CFU/100 g) and increased the antioxidant capacity of the treated sprouts (55.13 µmol TE/100 g (DPPH) and 126.56 µmol TE/100 g (ABTS)) compared to untreated alfalfa. This study emphasizes PPE's antioxidant and antimicrobial activities in alfalfa sprouts preservation.

Spectroscopic and Thermal Characterization of Extra Virgin Olive Oil Adulterated with Edible Oils.

The substitution of extra virgin olive oil with other edible oils is the primary method for fraud in the olive-oil industry. Developing inexpensive analytical methods for confirming the quality and authenticity of olive oils is a major strategy towards combatting food fraud. Current methods used to detect such adulterations require complicated time- and resource-intensive preparation steps. In this work, a comparative study incorporating Raman and infrared spectroscopies, photoluminescence, and thermal-conductivity measurements of different sets of adulterated olive oils is presented. The potential of each characterization technique to detect traces of adulteration in extra virgin olive oils is evaluated. Concentrations of adulterant on the order of 5% can be detected in the Raman, infrared, and photoluminescence spectra. Small changes in thermal conductivity were also found for varying amounts of adulterants. While each of these techniques may individually be unable to identify impurity adulterants, the combination of these techniques together provides a holistic approach to validate the purity and authenticity of olive oils.

Recent Advances toward the Application of Non-Thermal Technologies in Food Processing: An Insight on the Bioaccessibility of Health-Related Constituents in Plant-Based Products.

Fruits and vegetables are rich sources of bioactive compounds and micronutrients. Some of the most abundant are phenols and carotenoids, whose consumption contributes to preventing the occurrence of degenerative diseases. Recent research has shown the potential of non-thermal processing technologies, especially pulsed electric fields (PEF), ultrasounds (US), and high pressure processing (HPP), to trigger the accumulation of bioactive compounds through the induction of a plant stress response. Furthermore, these technologies together with high pressure homogenization (HPH) also cause microstructural changes in both vegetable tissues and plant-based beverages. These modifications could enhance carotenoids, phenolic compounds, vitamins and minerals extractability, and/or bioaccessibility, which is essential to exert their positive effects on health. Nevertheless, information explaining bioaccessibility changes after non-thermal technologies is limited. Therefore, further research on food processing strategies using non-thermal technologies offers prospects to develop plant-based products with enhanced bioaccessibility of their bioactive compounds and micronutrients. In this review, we attempt to provide updated information regarding the main effects of PEF, HPP, HPH, and US on health-related compounds bioaccessibility from different vegetable matrices and the causes underlying these changes. Additionally, we propose future research on the relationship between the bioaccessibility of bioactive compounds and micronutrients, matrix structure, and non-thermal processing.

Applying Pulsed Electric Fields to Whole Carrots Enhances the Bioaccessibility of Carotenoid and Phenolic Compounds in Derived Products.

We propose the application of pulsed electric fields (PEF) to carrots to obtain derived products with increased phenolic and carotenoid bioaccessibility. For this purpose, juices, purees, and oil-added purees were obtained from whole PEF-treated carrots (five pulses of 3.5 kV cm-1; 0.61 kJ kg-1). In order to obtain shelf-stable products, the effect of a thermal treatment (70 °C for 10 min) was also studied. Carrot juices exhibited the highest carotenoid (43.4 mg/100 g fresh weight) and phenolic (322 mg kg-1 dry weight) contents. However, caffeic and coumaric acid derivatives were highly sensitive to PEF. The phenolic bioaccessibility reached 100% in purees obtained from the PEF-treated carrots, whereas the further thermally treated oil-added purees exhibited the greatest carotenoid bioaccessibility (7.8%). The increase in carotenoid bioaccessibility could be related to their better release and solubilization into micelles. The results suggest that food matrix aspects apart from particle size (e.g., pectin characteristics) are involved in phenolic bioaccessibility.

Pulsed electric field treatment strategies to increase bioaccessibility of phenolic and carotenoid compounds in oil-added carrot purees.

The impact of pulsed electric fields (PEF) and their combination with a thermal treatment on the bioaccessibility of phenolic and carotenoid compounds in oil-added carrot puree (5 %) was investigated. Fractions of such puree were differently treated: subjected to PEF (5 pulses of 3.5 kV cm-1) (PEF); thermally treated (70 °C for 10 min) (T) or first PEF treated and then thermally treated (PEF/T). Purees were in vitro digested, carotenoid and phenolic content and bioaccessibility were determined. Likewise, quality attributes and microstructure were analyzed. Generally, treatments did not affect carotenoid content and quality attributes, whereas phenolic content dramatically decreased after PEF. Nevertheless, all treatments enhanced both compounds bioaccessibilities, which were trebled in PEF-treated purees. Particle size reduction may suggest that microstructural changes could be responsible of bioaccessibility increases. Therefore, PEF could be a feasible treatment to enhance phenolic and carotenoid bioaccessibility without altering quality attributes of carrot-based puree.

Effect of pulsed electric fields on carotenoid and phenolic bioaccessibility and their relationship with carrot structure.

Phenolic compounds (PC) and carotenoids from carrots are bound to dietary fibre or stored in vacuoles and chromoplasts, respectively. To exert their antioxidant effects these compounds must be released during digestion, which is hindered by such barriers. Pulsed electric fields (PEF) modify cell membrane permeability, thus enhancing their bioaccessibility. The effect of PEF on the carrot carotenoid and PC content and bioaccessibility was investigated. With this purpose, PEF-treated carrots (5 pulses of 3.5 kV cm-1) were stored for 24 h at 4 °C and microstructure was evaluated before subjecting them to in vitro digestion. PEF did not affect carotenoid content, whereas their bioaccessibility improved (11.9%). Likewise, PEF increased the content of some PC, e.g. coumaric acid (163.2%), probably caused by their better extractability. Conversely, caffeic acid derivatives decreased, which may be associated to greater contact with oxidative enzymes. Total PC bioaccessibility (20.8%) and some derivatives increased, e.g. caffeoylshikimic (68.9%), whereas some decreased (e.g. ferulic acid). Structural changes caused by PEF may improve bioaccessibility of carotenoids and PC by favouring their release and easy access to digestive enzymes. However, other antioxidants may be further degraded or entrapped during digestion. Therefore, PEF is an effective technology for obtaining carrots with enhanced carotenoids and phenolic bioaccessibility.

Volatile compounds and changes in flavour-related enzymes during cold storage of high-intensity pulsed electric field- and heat-processed tomato juices.

BACKGROUND: The effects of high-intensity pulsed electric field (HIPEF) processing (35 kV cm(-1) for 1500 micros, using 4 micros bipolar pulses at 100 Hz) on the production of volatile compounds and flavour-related enzymes in tomato juice were investigated and compared with those of thermal processing (90 degrees C for 30 or 60 s). RESULTS: Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 degrees C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 degrees C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 degrees C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION: HIPEF-treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat-treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments.

Formation of patulin-glutathione conjugates induced by pulsed light: A tentative strategy for patulin degradation in apple juices.

Patulin is a toxic mycotoxin usually associated with apple products. Due to its unhealthy effects for humans, its content is regulated by the food safety authorities. The removal or degradation of this mycotoxin in contaminated apple juices has been studied with different approaches with uneven effectiveness. However, a strategy based on the chemical reaction between patulin and glutathione (GSH), in order to generate the conjugates that are formed during cell detoxification process, is an innovative approach yet to be evaluated. In this work, the formation of patulin-GSH conjugates activated by the application of pulsed light treatments and catalyzed by Fe2+ ions was evaluated. The study of patulin degradation and effect of the GSH/Fe2+ molar ratio showed that a molar ratio of 5 allows an adequate catalytic effect of the metal ions. In addition, mono-substituted patulin-glutathione adducts were identified as the main type of generated conjugates.

Control of Pathogenic and Spoilage Microorganisms in Fresh-cut Fruits and Fruit Juices by Traditional and Alternative Natural Antimicrobials.

Traditional antimicrobials have been extensively used for many years. However, consumers are currently demanding wholesome, fresh-like, and safe foods without addition of chemically synthesized preservatives. The application of novel natural antimicrobials to assure safety of fresh-cut fruits and unpasteurized juices while preventing quality loss is a promising alternative. The effectiveness of these natural substances added to fruit derivatives has been studied by different researchers. Antimicrobials of animal (lactoperoxidase, lysozyme, and chitosan), plant (essential oils, aldehydes, esters, herbs, and spices), and microbial origin (nisin) can be used to effectively reduce pathogenic and spoilage microorganisms in fresh-cut fruits and fruit juices. Nevertheless, the use of these compounds at a commercial level is still limited due to several factors such as impact on sensory attributes or, in some cases, regulatory issues concerning their use. Therefore, extensive research on the effects of each antimicrobial on food sensory characteristics is still needed so that antimicrobial substances of natural origin can be regarded as feasible alternatives to synthetic ones.