Molecular motifs encoding self-assembly of peptide fibers into molecular gels.

Peptides are a promising class of gelators, due to their structural simplicity, biocompatibility and versatility. Peptides were synthesized based on four amino acids: leucine, phenylalanine, tyrosine and tryptophan. These peptide gelators, with systematic structural variances in side chain structure and chain length, were investigated using Hansen solubility parameters to clarify molecular features that promote gelation in a wide array of solvents. It is of utmost importance to combine both changes to structural motifs and solvent in simultaneous studies to obtain a global perspective of molecular gelation. It was found that cyclization of symmetric dipeptides, into 2,5-diketopiperazines, drastically altered the gelation ability of the dipeptides. C-l-LL and C-l-YY, which are among the smallest peptide LMOGs reported to date, are robust gelators with a large radius of gelation (13.44 MPa1/2 and 13.90 MPa1/2, respectively), and even outperformed l-FF (5.61 MPa1/2). Interestingly, both linear dipeptides (l-FF and l-LL) gelled similar solvents, yet when cyclized only cyclo-dityrosine was a robust gelator, while cyclo-diphenylalanine was not. Changes in the side chains drastically affected the crystal morphology of the resultant gels. Symmetric cyclo dipeptides of leucine and tyrosine were capable of forming extremely high aspect ratio fibers in numerous solvents, which represent new molecular motifs capable of driving self-assembly.

Oleosome interfacial engineering to enhance their functionality in foods.

This study aimed to increase the physical stability of native sunflower oleosomes to expand their range of applications in food. The first objective was to increase the stability and functionality of oleosomes to lower pH since most food products require a pH of 5.5 or lower for microbial stability. Native sunflower oleosomes had a pI of 6.2. One particularly effective strategy for long-term stabilization, both physical and microbial, was the addition of 40% (w/w) glycerol to the oleosomes plus homogenization, which decreased the pI to 5.3 as well as decreasing oleosome size, narrowing the size distribution and increasing colloidal stability. Interfacial engineering of oleosomes by coating them with lecithin and the polysaccharides xanthan and gellan, effectively increased stability, and lowered their pI to 3.0 for lecithin and lower than 3.0 for xanthan. Coating oleosomes also caused a greater absolute value of the ζ-potential; for example, this amount was shifted to -20 mV at pH 4.0 for xanthan and to -28 mV at pH 4.0 for lecithin, which provides electrostatic stabilization. Polysaccharides also provide steric stabilization, which is superior. A significant increase in the diameter of coated oleosomes was observed with lecithin, xanthan and gellan. The oleosome sample with 40% glycerol showed high storage stability at 4 °C (over three months). The addition of glycerol also decreased the water activity of the oleosome suspension to 0.85, which could prevent microbial growth.

Enzymatic glycerolysis for the conversion of plant oils into animal fat mimetics.

Substituting animal-based fats with plant-based fats of similar stability and functionality has always posed a significant challenge for the food industry. Enzymatic glycerolysis products are systems formed by converting native triacylglycerols in liquid oils into monoacylglycerols and diacylglycerols, mainly studied in the last few years for their unique structural ability. This study aims to modify and scale up the glycerolysis process of different plant oils, e.g., shea olein, palm olein, tigernut, peanut, cottonseed, and rice bran oils, with the goal of producing animal fat mimetics. The reactions were conducted at 65 °C, with a plant oil:glycerol molar ratio of 1:1, and without the addition of water, using a lab-scale reactor to convert up to 2 kg of oil into solid fat. Product characteristics were comparable at both laboratory and pilot plant scales, supporting the commercial viability of the process. Oil systems containing higher levels of both saturated and monounsaturated fatty acids, such as shea olein and palm olein, displayed higher solid fat content at elevated temperatures and broader melting profiles with significantly higher melting points. Comparison of the thermal softening behavior and mechanical properties of these systems with those of pork, beef, and lamb fat showed their high potential to replace adipose fat in the new generation of plant-based meat analogs.

Oleosome interfacial engineering to enhance their functionality in foods.

This study aimed to increase the physical stability of native sunflower oleosomes to expand their range of applications in food. The first objective was to increase the stability and functionality of oleosomes to lower pH since most food products require a pH of 5.5 or lower for microbial stability. Native sunflower oleosomes had a pI of 6.2. One particularly effective strategy for long-term stabilization, both physical and microbial, was the addition of 40% (w/w) glycerol to the oleosomes plus homogenization, which decreased the pI to 5.3 as well as decreasing oleosome size, narrowing the size distribution and increasing colloidal stability. Interfacial engineering of oleosomes by coating them with lecithin and the polysaccharides xanthan and gellan, effectively increased stability, and lowered their pI to 3.0 for lecithin and lower than 3.0 for xanthan. Coating oleosomes also caused a greater absolute value of the ζ-potential; for example, this amount was shifted to -20 mV at pH 4.0 for xanthan and to -28 mV at pH 4.0 for lecithin, which provides electrostatic stabilization. Polysaccharides also provide steric stabilization, which is superior. A significant increase in the diameter of coated oleosomes was observed with lecithin, xanthan and gellan. The oleosome sample with 40% glycerol showed high storage stability at 4 °C (over three months). The addition of glycerol also decreased the water activity of the oleosome suspension to 0.85, which could prevent microbial growth.

Erratum: Removal notice to "Oleosome interfacial engineering to enhance their functionality in foods" [Curr. Res. Food Sci. 6 (2023) 100465].

[This corrects the article DOI: 10.1016/j.crfs.2023.100465.].

Hardness, plasticity, and oil binding capacity of binary mixtures of natural waxes in oliveoil.

In this study, olive oil oleogels structured with less than 4% binary blends of sunflower wax (SFW), rice bran wax (RBW), candelilla wax (CDW), and beeswax (BW) were characterized. Among the different binary wax oleogels, samples structured with 3% (w/w) of binary mixtures of SFW and RBW, as well as binary mixtures of CDW and BW, displayed a high oil binding capacity relative to any other mixtures. Moreover, in some binary wax oleogels, back extrusion hardness and elastic constant were significantly higher than that of oleogels prepared using the individual waxes. This was interpreted as a synergism between these waxes. Image analysis of oleogel brightfield micrographs indicated that the samples with a higher elastic constant had a lower box-counting fractal dimension and larger crystals, suggesting that this increase in the elastic constant was a consequence of the lower fractal dimension of the wax crystal network, in agreement with established fractal structural-mechanical models for van der Waals colloidal networks. The crystal structure of the individual waxes and their blends showed orthorhombic perpendicular subcell packing arrangements, which did not change upon mixing, suggesting this length scale did not play a role in the observed synergism. The melting point of binary mixtures of waxes in olive oil was in the range of 43.2 °C to 67.4 °C and pseudo-ideal mixing behavior was observed. The hardness and plasticity (brittleness) of the 2% and 3% binary wax mixtures in olive oil characterized using back extrusion, were similar to those of a commercial soft margarine, suggesting a potential use of the wax oleogels as margarine or spread replacers.

Higher palmitic acid and dipalmitoyloleate levels are correlated to increased firmness in commercial butter.

The physical properties of butter are impacted by the fatty acid and triacylglycerol composition of the milkfat. Increased butter hardness and melting temperature results in decreased consumer satisfaction since these affect the culinary performance and spreadability. During the winter of 2021, consumers reported anecdotal evidence of an increase in butter hardness, leading to news reports blaming the increased hardness on palm oil-based supplementation of cows' feed. Commercial butter samples were collected from across Canada to test the correlation between fatty acid and triacylglycerol composition, and hardness. We determined that palmitic acid (r = 0.74) and dipalmitoyloleate (r = 0.72) were significantly and positively correlated to commercial butter hardness (P < 0.01). However, due to restricted access to existing historical data on the chemical composition of milk fat and hardness of butter, it was not possible to compare the firmness of butter in 2021 with butter produced in the past.

Molecular Origins of Polymorphism in Cocoa Butter.

Cocoa butter displays complex crystallization behavior and six crystal polymorphic forms. Although the crystal structure of cocoa butter has been studied extensively, the molecular interactions between cocoa butter triacylglycerols in relation to polymorphic transformations from metastable forms (forms III and IV) to stable crystal forms (forms V and VI) remain largely unknown. In this review, the triclinic polymorphism and melting profiles of the major triacylglycerols in cocoa butter-POP, POS, and SOS-are reviewed, and their binary and ternary phase behaviors in metastable (pseudoß') and stable (ß2) crystal forms are discussed. We also attempt to clarify how the transformation of cocoa butter from form IV to V, as a critical step in the tempering of chocolate, is controlled by POS interactions with both POP and SOS. Moreover, we show how the crystal forms V and VI of cocoa butter are templated by crystal forms ß3 and ß1 of POS, respectively.

Tempering of cocoa butter and chocolate using minor lipidic components.

Chocolate manufacture includes a complex tempering procedure to direct the crystallization of cocoa butter towards the formation of fat crystal networks with specific polymorphism, nano- and microstructure, melting behavior, surface gloss and mechanical properties. Here we investigate the effects of adding various minor non-triglyceride lipidic components to refined cocoa butter and chocolate on their physical properties. We discover that addition of saturated phosphatidylcholine and phosphatidylethanolamine to neutralized and bleached cocoa butter or molten and recrystallized commercial chocolate at 0.1% (w/w) levels, followed by rapid cooling to 20 °C in the absence of shear, accelerates crystallization, stabilizes the desirable Form V polymorph and induces the formation of chocolate with an optimal microstructure, surface gloss and mechanical strength. Final chocolate structure and properties are comparable to those of a commercial tempered chocolate. Minor lipidic component addition represents an effective way to engineer chocolate material properties at different length scales, thus simplifying the entire tempering process.

Avocado-derived polyols for use as novel co-surfactants in low energy self-emulsifying microemulsions.

Avocado (Persea americana Mill.; Lauraceae) seed-derived polyhydroxylated fatty alcohols (PFAs) or polyols (i.e., avocadene and avocadyne) are metabolic modulators that selectively induce apoptosis of leukemia stem cells and reverse pathologies associated with diet-induced obesity. Delivery systems containing avocado polyols have not been described. Herein, natural surface active properties of these polyols are characterized and incorporated into self-emulsifying drug delivery systems (SEDDS) that rely on molecular self-assembly to form fine, transparent, oil-in-water (O/W) microemulsions as small as 20 nanometers in diameter. Mechanistically, a 1:1 molar ratio of avocadene and avocadyne (i.e., avocatin B or AVO was shown to be a eutectic mixture which can be employed as a novel, bioactive, co-surfactant that significantly reduces droplet size of medium-chain triglyceride O/W emulsions stabilized with polysorbate 80. In vitro cytotoxicity of avocado polyol-SEDDS in acute myeloid leukemia cell lines indicated significant increases in potency and bioactivity compared to conventional cell culture delivery systems. A pilot pharmacokinetic evaluation of AVO SEDDS in C57BL/6J mice revealed appreciable accumulation in whole blood and biodistribution in key target tissues. Lastly, incorporation of AVO in SEDDS significantly improved encapsulation of the poorly water-soluble drugs naproxen and curcumin.

Heterogeneous Nucleation of 1,3-Distearoyl-2-oleoylglycerol on Tristearin Surfaces.

The following work investigates the heterogeneous nucleation of 2-oleodistearin (SOS) triglycerides on surfaces formed by crystals of tristearin triglyceride (SSS). This work shows, through computer simulations and nucleation kinetics, that SOS may heterogeneously nucleate on SSS surfaces. Atomic-scale molecular dynamics showed that SOS molecules exhibited an affinity to a simulated SSS surface. Nucleation kinetics using differential scanning calorimetry showed that the inclusion of minor amounts of SSS (from 1 to 4%) in an SOS melt resulted in an increase in the isothermal nucleation rate of crystallizing SOS. Using a model based on the Fisher-Turnbull approach, estimates of the surface free energy, activation free energy, and the critical radius were calculated from the nucleation rates. The estimated parameters demonstrate the heterogeneous nucleation of SOS on SSS surfaces: reduced surface free energies, activation free energies, and critical radii with the inclusion of SSS in an SOS melt. This may point to strategies to enhance the nucleation of one of the three major triglycerides present in cocoa butter and the one that crystallizes first from the melt for better control of the chocolate tempering process.

Lipid digestion of oil-in-water emulsions stabilized with low molecular weight surfactants.

Altering sn-fatty acid position of glycerol mono-oleate (GMO) from sn-1 to sn-2 decreases fatty acid bioaccessibility by 25.9% providing possible strategies to tailor lipemic responses of food emulsions. Lipid digestion kinetics and fatty acid bioaccessibility of monomodal O/W emulsions stabilized at their minimum surfactant concentration (0.5 < MSC > 0.7 (w/w)) were studied in the TNO Intestinal Model (TIM-1) gastrointestinal (GI) tract. No significant differences were observed between induction times nor rate constants when using 1-GMO and 1-GMS, Span 60, Tween 60 and Tween 80 as surfactants in O/W emulsions, as determined by fitting a three-parameter shifted logistic model to the cumulative bioaccessibility. Comparable trends were observed between area under the curve (AUC) of the absolute bioaccessibility and total overall bioaccessibility.

Facile lipase-catalyzed synthesis of a chocolate fat mimetic.

A cocoa butter equivalent (CBE) was synthesized enzymatically from readily available edible fats with fatty acid and triacylglycerol compositions that closely resemble the fat present in chocolate, cocoa butter. A commercially available immobilized fungal lipase, Lipozyme RM IM, was used as the reaction catalyst. Reaction parameters were a temperature of 65 °C, water activity of 0.11, a 4 h reaction time, and a substrate mass ratio of a commercial enzymatically synthesized shea stearin (SS) to palm mid-fraction (PMF) of 6:4 (w/w). Fractionation was also used after reaction completion to further approach the triacylglycerol composition of cocoa butter by removing trisaturated and unsaturated triacylglycerols. The yield of the triglyceride 1-palmitoyl-2-oleoyl, 3-stearoyl-glycerol (POS) produced was 57.7% (w/w). The amounts of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), (POS) and 1,3-stearoyl-2-oleoyl-glycerol (SOS) in the final CBE were 11.2%, 36.3%, and 34.8%, respectively. In comparison, the amounts of POP, POS and SOS in the cocoa butter used in this study were 15.2%, 38.2%, and 27.8%, respectively. No significant differences (P > 0.05) in melting point and enthalpy of fusion between CB and the CBE were observed. In comparison, a non-interesterified blend of SS and PMF (60:40 w/w) showed significantly (P < 0.05) higher melting point and lower enthalpy of fusion compared to CB. The crystal polymorphic form V of CB (ß2-3L) was similar to that of CBE and SS/PMF (60:40 w/w). The solid fat content (SFC) vs. temperature profile of the CBE generally resembled that of CB, except that the CBE had significantly (P < 0.05) higher SFCs at 5, 10, 15, 20 and 25 °C compared to both CB and SS/PMF (60:40 w/w). Addition of 15% (w/w) CBE to CB did not cause any changes in physical properties (melting point, SFC and crystal polymorphic forms) of the CB. This study demonstrates the potential for synthesizing a CB-like CBE using a green, rapid, straightforward one step enzymatic conversion followed by fractionation from widely available edible fats.

Quality and safety of frying oils used in restaurants.

Fresh, in-use and discarded frying oils were collected from randomly selected restaurants in downtown Toronto, Canada, in order to assess the oxidative and hydrolytic state of oil used in commercial practice and consumed regularly by the local population. All in-use and discarded samples showed extremely high levels of oxidation products based on the p-anisidine value (p-AV) (7.610meq/kg) and free fatty acid (FFA) levels (FFA>1%) suggested that 30-35% of in-use frying oils and 45-55% of discarded oils were not acceptable. However, total polar compounds (TPCs), the most widely used measure of frying oil quality in Europe, suggested that the oils were of acceptable quality (15.5>TPC). The TPC test was found to greatly underestimate oil degradation. We recommend that National Public Health authorities include frying oil inspections in their monitoring programs.