Stability and Bioaccessibility of Lignans in Food Products

Lignans are a group of plant phenolic compounds with various technofunctional and health-promoting properties. They can be found in oilseeds (291.7-2513 mg/100 g), nuts, vegetables, fruits, and alcoholic and nonalcoholic drinks. The most common structural representative feature of lignans' backbone is a dimeric phenylpropanoid, which consists of two C6-C3 units joined by a central carbon. Compared to other phenolics, such as flavonoids, the literature on lignan stability and bioaccessibility is limited. This Mini-Review aims to present an overview of recent literature, draw connecting lines to the known regarding polyphenols, and suggest the main knowledge gaps. Processing methods and processing conditions influence the stability of lignans with several thermal treatments explored. Roasting, as a major studied processing step, displayed varying effects as a function of the lignan structure and matrix. The content of specific and even total lignans was shown to increase in some cases even after intense thermal treatment. Lignans were also reported to present a stabilizing effect against oxidation to oils when added externally. Different fermentation methods presented inconclusive outcomes on the content of lignans, likely stemming from the various matrices and microorganisms studied in a relatively limited pool of studies. The bioaccessibility of lignans in in vitro studies was usually low (from less than 1% in fermented flaxseed to 30% for microwaved artichokes). Yet, a clear conclusion regarding the digestive fate of lignans as a function of processing and structure cannot be currently suggested, and significant additional effort in this direction is needed.

The Effect of Storage and Pasteurization (Thermal and High-Pressure) Conditions on the Stability of Phycocyanobilin and Phycobiliproteins

The utilization of natural blue pigments in foods is difficult as they are usually unstable during processing and the commonly applied pH. The current study focuses on natural blue pigment, possessing antioxidant properties, found in Arthrospira platensis (spirulina), and phycobiliproteins (PBP). These pigments are a complex of conjugated protein and non-protein components, known as phycocyanobilin. PBP has low stability during pasteurization (high-pressure or heat treatments), resulting in protein denaturation and color deterioration that limits the application. The phycocyanobilin pigment might also be liable to oxidation during pasteurization and storage, resulting in color deterioration. Yet, the instability of the pigment phycocyanobilin during the pasteurization process and storage conditions was never studied before, limiting the comprehensive understanding of the reasons for PBP instability. In this study, the stability of phycocyanobilin under high-pressure and high-temperature conditions was compared to the stability of phycobiliproteins. We revealed that phycobiliproteins have a higher color deterioration rate at 70–80 °C than at high-pressure (300–600 MPa) whereas phycocyanobilin remained stable during high-pressure and heat processing. During storage at pH 7, phycocyanobilin was oxidized, and the oxidation rate increased with increasing pH, while at lower pH phycocyanobilin had low solubility and resulted in aggregation.

Bovine alpha-lactalbumin assemblies with capsaicin: Formation, interactions, loading and physiochemical characterization

Numerous human conditions can benefit from diets rich in proteins and bioactives, such as capsaicin (CAP), yet their effective delivery is a sensorial, scientific and technological challenge. This study hypothesized that CAP can form various complexes with native bovine alpha-lactalbumin (holo-ALA) and decalcified-ALA (apo-ALA). Calorimetric and spectroscopic techniques reveals ALA-CAP molecular complexation is spontaneous, exothermic and accompanied by various conformational changes. ITC shows the interaction stoichiometry (n) and binding constant (K_b) for holo-ALA to be 0.87 ± 0.03, 1.54 ± 0.23 × 10⁵ M^-1 and for apo-ALA to be 0.64 ± 0.09, 9.41 ± 2.16 × 10⁴ M^-1. Molecular docking further elucidates that hydrogen bonds govern CAP binding to holo-ALA while hydrophobic interactions dominate binding to apo-ALA in a structural cleft. Finally, this work shows these interactions along with controlled aggregation can be utilized to form CAP-loaded colloids with encapsulation efficiency of 47.1 ± 1.0%. Thus, this study shows great promise in the prospective use of ALA as an edible delivery vehicle for CAP.

Addition of Anionic Polysaccharide Stabilizers Modulates In Vitro Digestive Proteolysis of a Chocolate Milk Drink in Adults and Children

There is a need to better understand the possible anti-nutritional effect of food stabilizers on the digestibility of important macronutrients, like proteins. This study hypothesized that the anionic nature of κ-, ι-, λ-, Carrageenan (CGN) and xanthan gum directs their interactions with food proteins leading to their subsequent attenuated digestive proteolysis. Model chocolate milk drinks were tested for their colloidal properties, viscosity and proteolytic breakdown in adults and children using in vitro digestion models coupled with proteomic analyses. SDS-PAGE analyses of gastro-intestinal effluents highlight stabilizers hinder protein breakdown in adults and children. Zeta potential and colloidal particle size were the strongest determinants of stabilizers’ ability to hinder proteolysis. LC-MS proteomic analyses revealed stabilizer addition significantly reduced bioaccessibility of milk-derived bioactive peptides with differences in liberated peptide sequences arising mainly from their location on the outer rim of the protein structures. Further, liberation of bioactive peptides emptying from a child stomach into the intestine were most affected by the presence of ι-CGN. Overall, this study raises the notion that stabilizer charge and other properties of edible proteins are detrimental to the ability of humans to utilize the nutritional potential of such formulations. This could help food professionals and regulatory agencies carefully consider the use of anionic stabilizers in products aiming to serve as protein sources for children and other liable populations.

Comparison of Thermal and High-Pressure Gelation of Potato Protein Isolates

Potato protein isolate (PPI), a commercial by-product of the starch industry, is a promising novel protein for food applications with limited information regarding its techno-functionality. This research focused on the formation of both thermal and high-pressure gels at acidic and neutral pH levels. Our results reveal that physical gels are formed after 30 min by heat at pH 7 and pH 3, while pressure (300-500 MPa) allows the formation of physical gels only at pH 3, and only when the system crosses 30 °C by adiabatic heating during pressurization. Texture profile analysis (TPA) revealed that gel hardness increased with both gelation temperature and pressure, while water-holding capacity was lower for the pressure-induced gels. The proteins released in the water-holding test suggested only partial involvement of patatin in the gel formation. Vitamin C as a model for a thermally liable compound verified the expected better conservation of such compounds in a pressure-induced gel compared to a thermal one of similar textural properties, presenting a possible advantage for pressure-induced gelation.

The Link between Polyphenol Structure, Antioxidant Capacity and Shelf-Life Stability in the Presence of Fructose and Ascorbic Acid

Polyphenols play an important role in the sensorial and health-promoting properties of fruits and vegetables and display varying structure-dependent stability during processing and shelf-life. The current work aimed to increase the fundamental understanding of the link between the stability of polyphenols as a function of their structure, presence of ascorbic acid and fructose and total antioxidant capacity (TAC), using a multi-component model system. Polyphenol extract, used as the multi-component model system, was obtained from freeze-dried, high polyphenol content strawberry (Fragaria × ananassa ‘Nerina’) and twenty-one compounds were identified using high-performance liquid chromatography-mass spectrometry (HPLC-MS). The TAC and the first-order degradation kinetics were obtained, linking the polyphenol stability to its chemical structure, with and without the presence of fructose and ascorbic acid. The TAC (measured by oxygen radical absorption capacity (ORAC) and ferric reducing antioxidant potential (FRAP) assays) was not dramatically affected by storage temperatures and formulation, while polyphenol stability was significantly and structure dependently affected by temperature and the presence of ascorbic acid and fructose. Anthocyanins and phenolic acids were more unstable in the presence of ascorbic acid, while flavonol stability was enhanced by its presence. Shelf life study performed at 37 °C revealed significantly higher stability of purified polyphenols vs. the stability of the same polyphenols in the strawberry extract (multi-component system).

Partially Acetylated Cellulose Dissolved in Aqueous Solution: Physical Properties and Enzymatic Hydrolysis

Cellulose acetate is one of the most important cellulose derivatives. The use of ionic liquids in cellulose processing was recently found to act both as a solvent and also as a reagent. A recent study showed that cellulose dissolution in the ionic liquid 1-ethyl-3-methylimidazoliumacetate (EMIMAc) mixed with dichloromethane (DCM) resulted in controlled homogenous cellulose acetylation; yielding water-soluble cellulose acetate (WSCA). This research investigated the properties of cellulose acetate prepared in this manner, in an aqueous solution. The results revealed that WSCA fully dissolves in water, with no significant sign of molecular aggregation. Its conformation in aqueous solution exhibited a very large persistence length, estimated as over 10 nm. The WSCA exhibited surface activity, significantly reducing the surface tension of water. Because of the molecular dissolution of WSCA in water, augmented by its amphiphilicity, aqueous solutions of WSCA exhibited an overwhelmingly high rate of enzymatic hydrolysis.

The Influence of Chemical Structure and the Presence of Ascorbic Acid on Anthocyanins Stability and Spectral Properties in Purified Model Systems

The loss of color pigment is an important quality factor of food products. This work aimed to systematically study, in purified model systems, the influence of anthocyanins' structure (by increasing the size of the conjugated sugar) and the presence of ascorbic acid on their stability and spectral properties during storage at two pH levels relevant to medium and high acid foods (6.5 and 4.5, respectively). Anthocyanins (cyanidin (Cy), cyanidin 3-O-β-glucoside (Cy3G) and cyanidin 3-O-β-rutinoside (Cy3R)) displayed first-order degradation rates, presenting higher stability in acidic medium and enhanced stability with increasing size of conjugated sugar. The addition of ascorbic acid resulted in significantly enhanced degradation. Changes in ultra violet visible (UV-VIS) spectral properties presented a decrease in typical color intensity and pointed towards formation of degradation products. Identification and kinetics of formation for cyanidin degradation products were obtained by high performance liquid chromatography system-mass spectrometry (HPLC-MS).

Reply to the Comment on “Revisiting the carrageenan controversy: do we really understand the digestive fate and safety of carrageenan in our foods?” by M. Weiner and J. McKim, Food Funct., 2019, 10: DOI: 10.1039/C8FO01282B

Diversity of food-grade carrageenan and rising levels of exposure to carrageenan mandate re-evaluation of its safety for the entire population.

Revisiting the carrageenan controversy: do we really understand the digestive fate and safety of carrageenan in our foods?

An overview of evidence on Carrageenan (CGN), a family of marine polysaccharides, their characteristics and digestive fate that highlight various gaps in our understanding.

Berries extracts as natural antioxidants in meat products: A review

The aim was to evaluate antioxidants from berries as replacement food additives for inhibition of lipid and protein oxidation in meat and meat products, since meats are highly susceptible to oxidation. Oxidation can be delayed/retarded by synthetic antioxidants with phenolic structures (e.g. butylated hydroxytoluene). However, new natural alternatives are needed for synthetic antioxidants due to the controversy regarding their possible negative health effects and consumers' demand for more 'natural' food additives. Berries are a good source of phenolic compounds, especially anthocyanins, which can be used as the potential alternative. Reviewed berries included bearberry (Arctostaphylos sp.), blueberry (Vaccinium sp.), blackberry (Rubus sp.), blackcurrant (Ribes nigrum), cranberry (Vaccinium sp.), cloudberry (Rubus chamaemorus), strawberry (Fragaria ananassa), and grape berries (Vitis sp.). Data implied that blueberries, blackberries, cranberries, and grapes can be useful for replacing/decreasing synthetic antioxidants in meat products. Their extracts have antioxidant polyphenols with health benefits that are useful for stabilizing meat products.

An Integrated Approach to Mandarin Processing: Food Safety and Nutritional Quality, Consumer Preference, and Nutrient Bioaccessibility

Mandarins are a member of the Citrus genus and are the focus of growing commercial interest, with satsuma mandarins (Citrus unshiu) and the common mandarin (Citrus reticulata Blanco) being the most important mandarin varieties. The possible health benefits and functional properties of those fruits are often associated with the antioxidative function of vitamin C, carotenoids, and phenolic compounds. While most mandarins are consumed fresh, many are processed into juices (mostly cloudy), usually via thermal processing which can lead to the creation of off-flavors and may diminish nutritional quality. The aim of this review is to summarize the most significant and recent information on the safety, sensorial properties, and nutritional benefits of mandarins and their processing into juice. The article also discusses recent information regarding the bioaccessibility of valuable, mandarin specific, compounds.

Innovative "Green" and Novel Strategies for the Extraction of Bioactive Added Value Compounds from Citrus Wastes-A Review

Citrus is a major processed crop that results in large quantities of wastes and by-products rich in various bioactive compounds such as pectins, water soluble and insoluble antioxidants and essential oils. While some of those wastes are currently valorised by various technologies (yet most are discarded or used for feed), effective, non-toxic and profitable extraction strategies could further significantly promote the valorisation and provide both increased profits and high quality bioactives. The present review will describe and summarize the latest works concerning novel and greener methods for valorisation of citrus by-products. The outcomes and effectiveness of those technologies such as microwaves, ultrasound, pulsed electric fields and high pressure is compared both to conventional valorisation technologies and between the novel technologies themselves in order to highlight the advantages and potential scalability of these so-called "enabling technologies". In many cases the reported novel technologies can enable a valorisation extraction process that is "greener" compared to the conventional technique due to a lower energy consumption and reduced utilization of toxic solvents.

Direct and indirect measurements of enhanced phenolic bioavailability from litchi pericarp procyanidins by Lactobacillus casei-01

Litchi pericarp procyanidins (LPP) are dietary supplements with high antioxidant activity, but poor oral bioavailability and efficacy, that can be enhanced by probiotics addition.

FT-IR spectroscopy, a reliable method for routine analysis of the degree of methylesterification of pectin in different fruit- and vegetable-based matrices

The use of Fourier transform infrared (FT-IR) spectroscopy as a method for routine analysis of the degree of methylesterification (DM) of pectin was validated. The relationship between the ratio of the intensity of the peak at around 1740cm(-1) (due to ester carbonyl group stretching) to the sum of the intensities of the peaks at around 1740 and 1630-1600cm(-1) (due to carboxylate group stretching) and the DM of pectin in model and real systems was investigated. In model systems of low to medium DM with low added protein (⩽20%), accurate DM determinations were obtained without spectra deconvolution whilst for medium to high DM pectin with high added protein (⩾30%), peak deconvolution was vital. In real systems, good DM determinations were obtained without peak deconvolution except for broccoli-derived samples. Considering that broccoli is a protein-rich vegetable, better determinations of the DM were obtained using deconvoluted FT-IR spectra.

Study of mango endogenous pectinases as a tool to engineer mango purée consistency

The objective of this work was to evaluate the possibility of using mango endogenous pectinases to change the viscosity of mango purée. Hereto, the structure of pectic polysaccharide and the presence of sufficiently active endogenous enzymes of ripe mango were determined. Pectin of mango flesh had a high molecular weight and was highly methoxylated. Pectin methylesterase showed a negligible activity which is related to the confirmed presence of a pectin methylesterase inhibitor. Pectin contained relatively high amounts of galactose and considerable β-galactosidase (β-Gal) activity was observed. The possibility of stimulating β-Gal activity during processing (temperature/pressure, time) was investigated. β-Gal of mango was rather temperature labile but pressure stable relatively to the temperature and pressure levels used to inactivate destructive enzymes in industry. Creating processing conditions allowing endogenous β-Gal activity did not substantially change the consistency of mango purée.

Extraction and characterization of pectic polysaccharides from easy- and hard-to-cook common beans (Phaseolus vulgaris)

The occurrence of the hard-to-cook (HTC) defect in legumes is characterized by the inability of cotyledons to soften during the cooking process. This phenomenon may be influenced by pectin properties. The objective of this study was to characterize the pectic polysaccharides comprised in the alcohol insoluble residue (AIR) extracted from easy-to-cook (Rose coco) and hard-to-cook (Pinto) common beans. This would provide an insight in the relationship between the pectin properties and HTC defect. The AIR was extracted from raw, half-cooked hard, half-cooked soft and fully-cooked bean samples. Subsequently, it was fractionated into water-, chelator- and Na₂CO₃-soluble pectin fractions and a hemicellulose fraction. For the AIR and the pectin fractions, determination of the galacturonic acid content, neutral sugars, degree of methylesterfication (DM), degree of acetylation (DAc) and molar mass (MM) distribution was performed. Results on the pectin fractions, MM distribution and pectin content profile, revealed that Rose coco pectin generally showed higher pectin solubility than Pinto. Neutral sugar profiles indicated that Pinto contained higher amounts of branched pectin (i.e. arabinans) than Rose coco. There was no difference between the DM of Pinto and Rose coco, however, the DAc was higher in Rose coco. In conclusion, the differences in pectin structure and solubility properties between easy- and hard-to-cook common beans might contribute to the differences in their cooking behavior.

Pectin modifications and the role of pectin-degrading enzymes during postharvest softening of Jonagold apples

This study aimed at understanding softening in Jonagold apple (Malus×domestica Borkh.) fruits, by investigating pectin modifications and the evolution of pectin-modifying enzymes during postharvest storage and ripening. Jonagold apples were harvested at commercial maturity and stored at different temperatures and controlled atmosphere conditions for 6 months, followed by exposure to ambient shelf life conditions (20 °C under air) for 2 weeks. The composition of the pectic material was analysed. Furthermore, the firmness and the ethylene production of the apples were assessed. Generally, the main changes in pectin composition associated with the loss of firmness during ripening in Jonagold apples were a loss of side chains neutral sugars, increased water solubility and decreased molar mass. Also, the activities of four important enzymes possibly involved in apple softening, β-galactosidase, α-arabinofuranosidase, polygalacturonase and pectin methylesterase, were measured. Pectin-related enzyme activities highly correlated with ethylene production, but not always with pectin modifications.

Intermolecular chiral assemblies in R(-) and S(+) 2-butanol detected by microcalorimetry measurements

Supramolecular chiral assemblies of R(-) and S(+) 2-butanol, in their neat form or when dissolved in their nonchiral isomer isobutanol, were evaluated by isothermal titration calorimetry (ITC) ensuing mixing. Dilution of 0.5 M solution of R(-) 2-butanol in isobutanol into the latter liberated heat of several calories per mole, which was approximately double than that obtained in parallel dilutions of S(+) 2-butanol in isobutanol. The ITC dilution profiles indicated an estimate of about 100 isobutanol solvent molecules surrounding each of the 2-butanol enantiomers, presumably arranged in chiral configurations, with different adopted order between the isomers. Mixings of neat R and S 2-butanol were followed by endothermic ITC profiles, indicating that, in racemic 2-butanol, both the supramolecular order and the intermolecular binding energies are lower than in each of the neat chiral isomers. The diversion from symmetrical ITC patterns in these mixings indicated again a subtle difference in molecular organization between the neat enantiomers. It should be noted that the presence of impurities, α-pinene and teterhydrofuran, at a level totaling 0.5%, did not influence the ITC heat flow profiles. The findings of this study demonstrate for the first time that chiral solutes in organic solvents are expected to acquire asymmetric solvent envelopes that may be different between the enantiomers, thus broadening this phenomenon beyond the previously demonstrated cases in aqueous solutions.