Phenolic Stabilizers Research Articles

Stability of Propolis Phenolics during Ultrasound-Assisted Extraction Procedures.

Propolis has gained popularity in recent years as a potential preventive and therapeutic agent due to its numerous health benefits, which include immune system boosting, blood pressure lowering, allergy treatment, and skin disease treatment. The pharmacological activity of propolis is primarily attributed to phenolics and their interactions with other compounds. Given that phenols account for most of propolis's biological activity, various extraction methods are being developed. The resin-wax composition of the propolis matrix necessitates the development of an extraction procedure capable of breaking matrix-phenol bonds while maintaining phenol stability. Therefore, the aim of this study was to assess the stability of two major groups of phenolic compounds, flavonoids and phenolic acids, in propolis methanol/water 50/50 (v/v) extracts obtained after ultrasound-assisted extraction (USE) under different extraction parameters (extraction time and pH) and heat reflux extraction (HRE). The methodology involved varying the USE parameters, including extraction time (5, 10, and 15 min) and pH (2 and 7), followed by analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify phenolic recoveries. Results revealed that benzoic acid and chlorogenic acid derivatives demonstrated excellent stability across all ultrasound extraction procedures. The recoveries of flavonoids were highly diverse, with luteolin, quercitrin, and hesperetin being the most stable. Overall, neutral pH improved flavonoid recovery, whereas phenolic acids remained more stable at pH = 2. The most important optimization parameter was USE time, and it was discovered that 15 min of ultrasound resulted in the best recoveries for most of the phenols tested, implying that phenols bind strongly to the propolis matrix and require ultrasound to break the bond. However, the high variability in phenol extraction and recovery after spiking the propolis sample shows that no single extraction method can produce the highest yield of all phenols tested. As a result, when working with a complex matrix like propolis, the extraction techniques and procedures for each phenol need to be optimized.

Fabrication of phenolic loaded spray-dried nanoliposomes stabilized by chitosan and whey protein: Digestive stability, transepithelial transport and bioactivity retention of phenolics

Low bioavailability of phenolic compounds (phenolics) results in low in vivo bioactivity, thus their co-encapsulation could enhance potential health benefits. In this study, reconstitutable nanoliposomes loaded with phenolics varying in solubility were fabricated using spray drying after stabilized by chitosan (CH) or whey protein (WP). The physicochemical properties, biocompatibility, digestive fate, and bioactivity retention of phenolics in different forms were investigated. The surface charge of nanoliposomes (NL) shifted from −18.7 mV to positive due to conjugation with cationic CH (53.1 mV) and WP (14 mV) after spray drying while it was −26.6 mV for only spray-dried phenolics (SDP). Encapsulation efficiency of the tested phenolics ranged between 64.7 % and 95.1 %. Simulated gastrointestinal digestion/Caco-2 cell model was used to estimate the digestive fate of the phenolics yielding up to 3-fold higher bioaccessibility for encapsulated phenolics compared to their native form, combined or individually. However, the cellular uptake or transepithelial transport of phenolics did not differ significantly among formulations, except trans-resveratrol in WP-NL. On the contrary, the suppressive effect of phenolics on fatty acid induced hepatocellular lipid accumulation was strongly dependent on the encapsulation method, no activity was retained by SDP. These findings suggested that reconstitutable nanoliposomes can improve the absorption of phenolics by facilitating their bioaccessibility and thermal and/or processing stability during spray drying.

Controlling the stability and adhesion performance of cold-setting phenol–resorcinol–formaldehyde resin adhesives through methanol addition

Phenol–resorcinol–formaldehyde (PRF) resin adhesives are commonly used in the manufacture of laminated timber products, and they are cold-set at room temperature rather than hot-pressed to generate a three-dimensional polymer structure in the products. However, their excellent reactivity often leads to poor storage stability and a short pot life. This study examines the influence of methanol addition on the stability and adhesion performance of PRF resins. These resins were synthesized by various levels of methanol addition (5 %, 10 %, and 15 %), and their structures were investigated using Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies. Furthermore, differential scanning calorimetry (DSC) was used to analyze their thermal behavior, and their cure kinetics were analyzed with two isoconversional analyses: Kissinger–Akahira–Sunose (KAS) and Vyazovkin (VYZ) method. The adhesion performances of PRF resins were evaluated for glue-laminated timber (GLT). The results demonstrated that the viscosity and solids content of PRF resins decreased while their gelation time increased as the methanol addition level increased. Methanol addition has also improved the resin stability over time. The chemical structure of PRF resins did not change considerably with an increase in the methanol level. However, methanol interaction with formalin in a hardener presumably hindered the reactivity of PRF resins. This was supported with an increase in the apparent activation energy of the curing process of PRF resins as the methanol level increased. In addition, decreasing the methanol levels from 15 % to 5 % enhanced the adhesion performance of GLT bonded with PRF resins. The results indicated that adding methanol to PRF resins improved its stability while simultaneously weakened its performance. However, 5 % methanol level is recommended for PRF resins.

Degradation processes in polyolefins with phenolic stabilizers subjected to ionizing or non-ionizing radiation

We investigated degradation processes in polymer plaques made of polyolefin (HDPE or UHMWPE or COC) prepared by melt-mixing with or without phenolic stabilizer (natural α-tocopherol or synthetic Irganox®1010) and spin trapping agent (TTBNB; 2,4,6-Tri‑tert-butylnitrosobenzene). The degradation was initiated either by low-energy, non-ionizing radiation (wavelengths corresponding to terrestrial range of solar UV radiation) or high-energy, ionizing radiation (electrons accelerated at 1.5 MeV). The motivation for the study was our recent finding that some phenolic stabilizers exhibited a surprising pro-oxidant activity in polyolefins subjected to non-ionizing radiation. Consequently, we asked if the phenolic stabilizers in polyolefins behave in the same way during long-term, low-energy, non-ionizing UV irradiation and after short-term, high-energy, ionizing e-beam irradiation. All samples were characterized thoroughly by means of electron spin resonance (ESR; the information about radiation-induced radicals), infrared microspectroscopy (IR; the detection of oxidation products and structural changes), instrumented microindentation (MHI; local mechanical properties) and light and electron microscopy (LM and SEM; surface morphology). The results proved that (i) the degradation processes in polyolefins subjected to non-ionizing or ionizing radiation were different, (ii) the phenolic stabilizers exhibited mostly their expected antioxidant activity, while pro-oxidant activity was detected only for specific conditions and/or systems subjected to non-ionizing radiation, and (iii) the selected spin trapping agent, TTBNB, was stable enough to survive standard sample preparation by melt-mixing and catch short-living unstable radicals.

Effect of Spray Drying on Physicochemical Stability and Antioxidant Capacity of Rosa pimpinellifolia Fruit Extract-Loaded Liposomes Conjugated with Chitosan or Whey Protein During In Vitro Digestion

Spray drying is a well-established, energy efficient, and scalable process widely used in the food industry, however it may lead to thermal degradation of susceptible compounds, such as (poly)phenols, resulting in biological activity loss to some extent. In this study, we aimed to improve the physicochemical stability and bioaccessibility of (poly)phenols from Rosa pimpinellifolia fruit extract (Rosa extract) loaded in liposomes by generating solid particles via spray drying. Liposomes were conjugated with chitosan (Ch) and whey protein (Wp) to optimize the biopolymer concentrations by monitoring mean particle diameter, polydispersity index, and surface charge. The mean diameter of liposomes ranged between 135 and 210 nm upon optimal addition of Ch (0.4%, w/v) and Wp (4.0%, w/v) which also increased the entrapment efficiency of (poly)phenols from 74.2 to 77.8% and 79.1%, respectively. After spray drying, about 65–76% of the antioxidant capacity were retained in biopolymer-conjugated liposomes (Ch or Wp) while the retention rate was 48% in only spray-dried extract (Rosa extract powder). Compared to unencapsulated Rosa extract, spray drying (Rosa extract powder) and conjugation with Ch (Ch-Lip powder) or Wp (Wp-Lip powder) significantly increased the bioaccessibility of (poly)phenols and preserved their antioxidant capacity. Based on the findings of this study, Ch- or Wp-conjugation of liposomes prior to spray drying could improve physicochemical stability and protect (poly)phenols loaded in liposomes against processing stress and passage through the digestive tract. Further in vitro and in vivo investigations on a variety of bioactive compounds may draw more attention to their potential as functional foods.

Phenolic profile of micro- and nano-encapsulated olive leaf extract in biscuits during in vitro gastrointestinal digestion.

Olive leaf was characterized by a high content of phenols and flavonoids (oleuropein, luteolin, and their derivatives), presenting functional and health-related properties. The chemical instability of phenolics through technological processes and their degradation in the digestive system may negatively impact them, leading to lower absorption. This study evaluates the phenolic profile of micro- and nano-encapsulated olive leaf extract in biscuits during the INFOGEST static in vitro digestion, aiming to enhance stability and sensorial properties. Ultrasound-assisted extraction and chromatography characterized the extract, while spray drying (maltodextrin-glucose) and nano-encapsulation (maltodextrin, whey protein isolate, and arabic gum) techniques were used with specific solutions. Encapsulated formulations underwent microscopy (TEM, SEM) and encapsulation efficiency analysis. Micro- and nano-encapsulation improved biscuit functionality by enhancing phenolic stability during digestion. However, the highest concentration adversely affected sensory and textural parameters. These findings contribute to developing functional food products enriched with bioactive compounds, providing improved health benefits while maintaining sensory attributes.

The Extraction and Impact of Essential Oils on Bioactive Films and Food Preservation, with Emphasis on Antioxidant and Antibacterial Activities-A Review.

Essential oils, consisting of volatile compounds, are derived from various plant parts and possess antibacterial and antioxidant properties. Certain essential oils are utilized for medicinal purposes and can serve as natural preservatives in food products, replacing synthetic ones. This review describes how essential oils can promote the performance of bioactive films and preserve food through their antioxidant and antibacterial properties. Further, this article emphasizes the antibacterial efficacy of essential oil composite films for food preservation and analyzes their manufacturing processes. These films could be an attractive delivery strategy for improving phenolic stability in foods and the shelf-life of consumable food items. Moreover, this article presents an overview of current knowledge of the extraction of essential oils, their effects on bioactive films and food preservation, as well as the benefits and drawbacks of using them to preserve food products.

Effect of milling on in vitro Digestion-Induced release and bioaccessibility of active compounds in rice

To investigate the impact of milling on the active components in rice, this study examined the stability of phenols, vitamin B1 (VB1), and alpha-aminobutyric acid (α-GABA) during cooking and digestion of rice and their distribution in digestive juices and residue by adjusting the degree of milling (DOM). The findings revealed that milling exacerbated the instability of γ-GABA during cooking and VB1 during digestion. Their total losses peaked at 19.76% and 39.53% as DOM respectively reached 6.07% and 8.06%. In vitro digestion combined with release mathematical models demonstrated the impact of milling on their bioaccessibility. This effect increased the small intestinal bioaccessibility of phenols and γ-GABA, whilst reducing that of VB1. This was attributed to milling-induced pre-gastric full release of VB1, which amplifies its intestinal susceptibility and induces its re-entry into digestive residues. In conclusion, this study recommends keeping DOM below 6.07% to optimize the bioaccessibility of these active compounds.

Impact of aging on the physical-chemical and phenolic stability of tropical red wines from Brazil produced with grapes harvested in the summer season

The São Francisco Valley in the Brazilian Northeast is characterized by the production of tropical wines from grapes obtained from at least two annual harvests. Previous studies showed that wines made with grapes harvested from the second semester (summer season, with high temperatures and solar radiation, as well as low rainfall) presented a shorter shelf-life than those made from grapes harvested in the first semester (winter season). This study aimed to characterize the changes in the chemical composition of three red wines from the summer season, during aging. Wines elaborated with grapes harvested between November and December 2014, with the main red varieties commercially used, were analyzed 12, 24 and 36 months after bottling. Decreases occurred in the concentrations of anthocyanins, flavonols, organic acids, potassium, and condensed tannins, as well as increases in polymerized pigments, hue, turbidity, and calcium. Flavanols and flavonols were associated with Syrah and Touriga Nacional wines, while myricetin was the metabolite considered to be the main indicator of the aging of ‘Alicante Bouschet’ wines. Rootstock vigor was affected by variety. This study showed that the choice of rootstock and variety combination could increase the wine stability after bottling, using grapes harvested from the second semester.

Whey-pectin microcapsules improve the stability of grape marc phenolics during digestion.

Grape marc (GM) is an agri-food residue from the wine industry valuable for its high content of phenolic compounds. This study aimed to develop an encapsulation system for GM extract (GME) using food-grade biopolymers resistant to gastric conditions for its potential use as a nutraceutical. For this purpose, a hydroalcoholic GME was prepared with a total phenolics content of 219.62±11.50mg gallic acid equivalents (GAE)/g dry extract and 1389.71±97.33µmol Trolox equivalents/g dry extract antioxidant capacity, assessed through ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) assay. Moreover, the extract effectively neutralized reactive oxygen species in Caco-2 cells, demonstrating an intracellular antioxidant capacity comparable to Trolox. The GME was encapsulated using whey protein isolate and pectin through nano spray drying (73% yield), resulting in spherical microparticles with an average size of 1±0.5µm and a polydispersity of 0.717. The encapsulation system protected the microcapsules from simulated gastrointestinal digestion (GID), where at the end of the intestinal phase, 82% of the initial phenolics were bioaccessible compared to 54% in the free GME. Besides, the encapsulated GME displayed a higher antioxidant activity by the ferric reducing antioxidant power assay than the free extract after GID. These results show the potential of this encapsulation system for applying GME as a nutraceutical with a high antioxidant capacity and protective effect against cellular oxidation.

Effects of Thyme Essential Oil Microcapsules on the Antioxidant and Quality Characteristics of Mutton Patties.

This study aimed to assess the stability of thyme essential oil microcapsules (TEOMs) and their impacts on the antioxidant properties and quality of lamb patties. The results demonstrated that gum Arabic effectively enhanced the stability of phenols within the thyme essential oil (TEO), with an optimal core/wall ratio of 1:8. Substituting TEO with TEOMs in lamb patties led to reductions in the thiobarbituric acid content, carbonyl content, sulfhydryl loss, and protein cross-linking. Additionally, the TEOMs positively influenced the mutton patties' color, texture, microbiological stability, and sensory attributes. These findings substantiate the idea that TEOMs exhibit significant potential as a natural preservative to enhance the quality of mutton patties.

Food-grade phytosome vesicles for nanoencapsulation of labile C-glucosylated xanthones and dihydrochalcones present in a plant extract matrix-Effect of process conditions and stability assessment.

Phytosomes consist of a phytochemical bound to the hydrophilic choline head of a phospholipid. Their use in food products is gaining interest. However, literature on the use of food-grade solvents, crude plant extracts as opposed to pure compounds, and unrefined phospholipids to prepare phytosomes is limited. Furthermore, studies on compound stability are lacking. This study aimed to develop nano-phytosome vesicles prepared from inexpensive food-grade ingredients to improve the stability of polyphenolic compounds. Cyclopia subternata extract (CSE) was selected as a source of phenolic compounds. It contains substantial quantities of C-glucosyl xanthones, benzophenones, and dihydrochalcones, compounds largely neglected to date. The effect of process conditions on the complexation of CSE polyphenols with minimally refined food-grade fat-free soybean lecithin (PC) was studied. The PC:CSE ratio, sonication time, and reaction temperature were varied. This resulted in phytosomes ranging in vesicle size (113.7-312.7 nm), polydispersity index (0.31-0.48), and zeta potential (-55.0 to -38.9 mV). Variation was also observed in the yield (93.5%-96.0%), encapsulation efficiency (3.7%-79.0%), and loading capacity (LC, 1.3%-14.7%). Vesicle size and LC could be tailored by adjusting the sonication time and PC:CSE ratio, respectively. Chemical interaction between the lipid and the phenolic compounds was confirmed with nuclear magnetic resonance. Phytosomal formulation protected the compounds against degradation when freeze-dried samples were stored at 25 and 40°C for 6 months at low relative humidity. The study provided valuable information on the importance of specific process parameters in producing food-grade phytosomes with improved phenolic stability.

Morus alba L. Leaves (WML) Modulate Sweet (TAS1R) and Bitter (TAS2R) Taste in the Studies on Human Receptors – A New Perspective on the Utilization of White Mulberry Leaves in Food Production?

From the nutritional perspective, the main direction of the utilization of white mulberry (Morus alba L.) parts so far has been to produce dietary supplements or functional foods for individuals with diabetes or over-weight. Its leaves are widely known as a valuable source of bioactive compounds responsible for its antioxidant and antidiabetic effects, both in animals and humans. The authors found that processed leaves can also be investigated as potential bitter and/or sweet taste modulators—an important property of new functional foods. The study aimed to validate the inhibitory effect of Morus alba L. on the TAS2R3 and TAS2R13 bitter taste and TSA1R2/TSA1R3 receptors and determine the changes that the conditioning process caused in such receptors. The effect on the receptors was evaluated in specially transfected HEK293T cells, and the inhibition ratio was measured using the calcium release test. Moreover, the stability of phenolics in the simulated intestinal in vitro digestion process was determined. Results showed that the Morus alba leaf extracts were rich in gallic, chlorogenic and caffeic acids together with rutin and quercetin 3-(6-malonyl)-glucoside, while the conditioning process positively affected their amount. Most identified phenolics were reduced during in vitro digestion. In the taste receptors test, it was found that the phytochemicals from conditioned Morus alba leaf extract enhanced sweet taste, together with a reduction of bitter taste receptor activity in some cases. To conclude, the study has found that Morus alba, especially when conditioned for 4 h, seems to be a valuable modulator of taste, which should be considered in future research as a crucial reason for its new utilization.

Stability of Phenols, Antioxidant Capacity and Grain Yield of Six Rice Genotypes.

The environment is the main factor affecting variations in phytochemicals and antioxidant activity in rice. The objective of this study was to evaluate the stability of grain yield, phytochemicals and antioxidant capacity of six rice genotypes. Six rice genotypes were evaluated in a randomized complete block design with three replicates at three locations in Trat, Bangkok and Sakon Nakhon provinces in July-October 2019. Data on grain yield, yield components, total phenolic content, ferulic acid and antioxidant capacity were recorded. Grain yield was highest for crops grown in Bangkok, whereas antioxidant activity was highest for crops grown in Bangkok and Sakon Nakhon. Hom Nang Nual 1 and Mali Nil Boran had the highest grain yield. Riceberry had the highest grain yield in Trat; it also had high levels of total phenolic compounds, ferulic acid and antioxidant activity. Mali Nil Boran, Mali Nil Surin and Riceberry had the most stable total phenolic content, ferulic acid and antioxidant activity, respectively. Information on the levels and variability of phytochemicals in rice enables the selection of genotypes with high and stabile phytochemicals for production and rice breeding.

Cheminformatics identification of phenolics as modulators of key penicillin−binding proteins of Escherichia coli towards interventive antibacterial therapy

ABSTRACT Data implicating the mutation in penicillin-binding protein (PBP) 3 and occasionally PBP5 in the resistance of Escherichia coli to beta−lactams is intriguing. Thus, the identification of an improved class of inhibitors of PBP3 and PBP5 is imperative, and in this study, phenolics due to their promising antibacterial activities were screened using structure−based pharmacophore and molecular docking approaches against PBP3, and the ability of the lead phenolics to modulate PBP3 and PBP5 was studied using molecular dynamics simulation. The results demonstrated various inhibitory capacities of the lead phenolics, with lysidicichin (−41.66 kcal/mol) and silicristin (−31.11 kcal/mol) being the most potent against PBP3, while epicatechin 3-O-(3-O-methylgallate) (−38.97 kcal/mol) and epigallocatechin-4-benzyl thioether (−37.01 kcal/mol) had higher affinities towards PBP5. Overall, epicatechin gallate had the best broad-spectrum of activity, as the compound was able to bind favourably to both targets. Additionally, the thermodynamic information confirmed the stability of the lead phenolics with both targets. Conclusively, while these observations are suggestive of the modulatory role of the lead phenolics on the growth of E. coli, further in vitro and in vivo validation of the activity elicited by the phenolics in this study is imperative, and efforts are underway in this direction.

Influence of Storage Conditions on Stability of Phenolic Compounds and Antioxidant Activity Values in Nutraceutical Mixtures with Edible Flowers as New Dietary Supplements.

This paper investigates the effects of storage conditions on the stability of phenolics and their antioxidant activities in unique nutraceutical supplements containing non-traditional cereal flakes, edible flowers, fruits, nuts, and seeds. Significant total phenolic content (TPC) of 1170-2430 mg GAE/kg and total anthocyanin content (TAC) with the values of 322-663 mg C3G/kg were determined with the highest TPC content established in free phenolic fractions. The most notable declines in TPC (by 53%), TAC (by 62%), phenolics (e.g., glycosylated anthocyanins by 35-67%), and antioxidant activity (by 25% using DPPH) were established in the presence of sunlight at 23 °C followed by the storage at 40 °C. Quercetin, rutin, peonidin, pelargonidin, p-coumaric, ellagic, and p-hydroxybenzoic acids were identified as the least stable phenolics when exposed to sunlight. Furthermore, glycosylated forms of anthocyanins demonstrated a greater stability when compared with anthocyanidins. The mixtures considerably eliminated ABTS and DPPH radicals. In all samples, water-soluble substances showed a higher antioxidant activity than lipid-soluble substances with the main contributors in the following order: delphinidin-3-glucoside (r = +0.9839) > p-coumaric > gallic > sinapic > p-hydroxybenzoic acids > delphinidin > peonidin and malvidin (r = +0.6538). Gluten-free nutraceutical mixtures M3 (containing red rice and black quinoa flakes, red and blue cornflowers, blueberries, and barberries) and M4 (containing red and black rice flakes, rose, blue cornflower, blueberries, raspberries, and barberries) were evaluated as the least stable under all storage conditions although they showed considerable phenolic concentrations. Phenolic contents and antioxidant activity of the nutraceutical mixtures were the highest at 23 °C without the presence of sunlight with the most stable M1 nutraceutical mixture (containing oat and red wheat flakes, hibiscus, lavender, blueberries, raspberries, and barberries).

Temperature dependent degradation of phenolic stabilizers and ageing behaviour of PP-R micro-specimen

This paper deals with the hot air ageing behaviour of a polypropylene random copolymer (PP-R) model material in a wide temperature range from 65 to 135°C. The PP-R grade was stabilized with a blend of the phenolic antioxidants Irganox 1330 and 1010. To avoid diffusion-limited oxidation effects, micro-specimen with a thickness of 100 µm were investigated. As main ageing indicator the phenol index was evaluated from FTIR-spectra in transmittance mode. The oxidation of the functional phenolic groups was associated with a shift of the absorption peak by 18 and 35 cm-1 of the single- and dual-oxidized phenolic antioxidant Irganox 1330. The implemented FTIR evaluation approach was validated by high-pressure liquid chromatography hyphenated with mass spectroscopy and ultraviolet detection. Gaussian fitting of the triple IR-peak confirmed temperature dependent differences in the degradation pathways of the phenolic antioxidants. The decay of phenol index and the obtained endurance time exhibited a bilinear Arrhenius like behaviour with a transition temperature at 110°C, which was in agreement with the onset of melting of small crystal lamellae. The activation energy values were 94 and 32 kJ mol-1 above and below the transition temperature, respectively.

Study of 2,6-di(propan-2-yl)phenol stability in biomaterial

The aim of this study is to research the stability of 2.6-di(propan-2-yl)phenol in biomaterial. GC-MS (column DB-5MS EVIDEX (25 m×0.2 mm); stationary liquid phase of 5%-phenyl-95% dimethylpolysiloxane), TLC (Sorbfil plates, mobile phase of hexane-diethyl ether (9:1) and spectrophotometry (solvent medium - 95% ethanol) were used as methods of analysis. 2.6-di(propan-2-yl)phenol was isolated from the biomatrix (liver tissue) by infusion with a mixture of ethyl acetate-acetone (7:3). The analyte was purified by combining extraction (water-ethyl acetate system) and semi-preparative chromatography on a column of silica gel L 40/100 µm, eluent - hexane-acetone (7:3). It was found that at -22 °C, 0 °C, 12 °C, 20 °C and 30 °C 2.6-di(propan-2-yl)phenol can be present in the liver tissue for 119, 98, 70, 56 and 42 days, respectively. The possibility of mathematical description of analyte decomposition dynamics in biomaterial (liver tissue) at the considered temperatures on the basis of hyperbola equation has been studied. The experimentally calculated coefficients in the hyperbola equation (km) for temperatures -22 °C, 0 °C, 12 °C, 20 °C and 30 °C are equal to 1823, 1130, 697, 510, and 255, respectively. The dependence km on the conserving temperature (tо) was educed. The equation for the description of dependence is offered: km=30.61∙(50-to)-402.39. It is shown that this equation can be the basis for prediction of 2.6-di(propan-2-yl)phenol stability in biomaterial (liver tissue) in the temperature range from -22 °C to 30 °C.

Impact of cooking methods of red-skinned onion on metabolic transformation of phenolic compounds and gut microbiota changes.

Herein, we investigated the stability and bioaccessibility of phenolics in differently cooked red-skinned onion (RSO) and consequently their impact on the gut microbiota and metabolism of phenolics. In fact, the different processes used to cook vegetables can modify and re-arrange the molecular profiles of bioactive compounds, such as phenolics in phenolic-rich vegetables, such as RSO. Fried and grilled RSO were compared to raw RSO and a blank control and subjected to oro-gastro-intestinal digestion and subsequent colonic fermentation. For upper gut digestion, the INFOGEST protocol was used, and for lower gut fermentation, a short-term batch model, namely, MICODE (multi-unit in vitro colon gut model), was employed. During the process, phenolic compound profile (through high-resolution mass spectrometry) and colon microbiomics (qPCR of 14 core taxa) analyses were performed. According to the results, the degradation driven by the colon microbiota of RSO flavonols resulted in the accumulation of three main metabolites, i.e., 3-(3'-hydroxyphenyl)propanoic acid, 3-(3'-hydroxyphenyl)acetic acid and 3-(3',4'-dihydroxyphenyl)acetic acid. Also, colonic fermentation of raw onions resulted in a substantial increase in beneficial taxa, which was larger compared to the heat-treated onions, particularly Lactobacillales and beneficial clostridia. Also, a higher level of inhibition of opportunistic bacteria was seen for the raw onion samples, namely, Clostridium perfringens group and Escherichia coli. Thus, our results showed that RSO, and especially the raw one, is an excellent dietary source of flavonols that are strongly metabolized by gut bacteria and can positively modulate the gut microbiota. Although additional in vivo studies are necessary, this work is one of the first to explore how RSO processed with different cooking methods can differently impact the phenolic metabolism and microbiota composition in the large intestine of humans, fine-tuning the antioxidant nature of foods.

Encapsulation of Formosa Papaya (Carica papaya L.) Seed Extract: Physicochemical Characteristics of Particles, and Study of Stability and Release of Encapsulated Phenolic Compounds

Papaya seeds are a promising source of phenolic compounds, but these are unstable, and the papaya extract has a bitter taste. This study aimed to encapsulate papaya seed extracts at different maturation levels, and to characterize the obtained microparticles for their physicochemical properties, chemical stability and release of bioactives. Extracts of papaya (unripe and ripe) seeds were spray-dried using concentrations of 0, 15 and 30% of maltodextrin and inlet air temperatures of 130 and 150 °C. The powders were analyzed for yield, moisture, Aw, hygroscopicity, dispersibility, color parameters, morphology, mean diameter, total phenolics, antioxidant activity, stability during storage and release of phenolics in simulated gastrointestinal fluids. Powders produced with maltodextrin showed better results regarding particle diameter, hygroscopicity, dispersibility, and phenolic stability during storage. All powders showed antioxidant action and significant values of total phenolic compounds. Samples without maltodextrin underwent caking. Drying temperatures had little influence on the characteristics of the powders. Encapsulated phenolic compounds were released in large amounts in the intestinal phase (86.6–100%). Powders produced with unripe seeds, 15% of maltodextrin and an inlet air temperature of 130 °C showed the best results. Thus, encapsulation was efficient, and encapsulated papaya seed extract has potential for food application as a natural additive.