Chemical stability of açai fruit (Euterpe oleracea Mart.) anthocyanins as influenced by naturally occurring and externally added polyphenolic cofactors in model systems

The influence of different classes of naturally occurring and externally added polyphenolic cofactors on the phytochemical and colour stability of anthocyanins in açai fruit (Euterpe oleracea) was investigated. Model systems were based on anthocyanin isolates from açai fruit, rich in cyanidin-3-rutinoside (311 ± 27 mg/l) and cyanidin-3-glucoside (208 ± 18 mg/l), and isolated groups of naturally occurring polyphenolic cofactors in açai fruit (phenolic acids, procyanidins, and flavone-C-glycosides, each adjusted to ∼50 mg/l). Anthocyanin degradation kinetics were assessed as a function of pH (3.0, 3.5, and 4.0) and storage temperature (5, 20 and 30 °C). During storage, anthocyanins experienced pH and temperature-dependent losses, and the half life cyanidin-3-rutinoside (t_1/2 = 2.67–210 days) was consistently longer than cyanidin-3-glucoside (t_1/2 = 1.13–144 days). The presence of flavone-C-glycosides induced significant hyperchromic shifts and enhanced anthocyanin stability at all pH and temperature combinations, while no significant effects were attributed to the presence of phenolic acids or procyanidins. Additional models using externally added cofactors from rooibos tea, also rich in flavone-C-glycosides, resulted in up to 45.5% higher anthocyanin colour and up to 40.7% increased anthocyanin stability compared to uncopigmented anthocyanin isolates and had similar copigmentation effects to a commercial rosemary-based colour enhancer. Results suggest flavone-C-glycosides offer potential for their use as colour enhancers and stabilizing agents in products rich in cyanidin glycosides, particularly açai fruit-containing foods, juice blends, and beverages.     

In vitro absorption and antiproliferative activities of monomeric and polymeric anthocyanin fractions from açai fruit (Euterpe oleracea Mart.)

Anthocyanins are among the most important and widely consumed natural pigments in foods, and have attracted increased attention as natural food colourants and potent bioactive agents. However, anthocyanins are generally unstable and may undergo chemical changes that include oxidative and polymerisation reactions during processing and storage. The role of anthocyanin polymerisation reactions on in vitro intestinal absorption and anti-cancer properties has not been assessed. This study investigated the chemical composition, antioxidant properties, antiproliferative activity, and in vitro absorption of monomeric and polymeric anthocyanin fractions from açai fruit (Euterpe oleracea Mart.). Cyanidin-3-rutinoside (58.5 ± 4.6%) and cyanidin-3-glucoside (41.5 ± 1.1%) were the predominant compounds found in monomeric fractions, while a mixture of anthocyanin adducts were found in polymeric fractions and characterised using HPLC–ESI-MSⁿ analyses. Monomeric fractions (0.5–100 μg cyanidin-3-glucoside equivalents/ml) inhibited HT-29 colon cancer cell proliferation by up to 95.2% while polymeric anthocyanin fractions (0.5–100 μg cyanidin-3-glucoside equivalents/ml) induced up to 92.3% inhibition. In vitro absorption trials using Caco-2 intestinal cell monolayers demonstrated that cyanidin-3-glucoside and cyanidin-3-rutinoside were similarly transported from the apical to the basolateral side of the cell monolayers (0.5–4.9% efficiency), while no polymeric anthocyanins were transported following incubation for up to 2 h. The addition of polymeric anthocyanin fractions also decreased monomeric anthocyanin transport by up to 40.3 ± 2.8%. Results from this study provide novel information regarding the relative size, absorption, and bioactive properties of anthocyanin monomers and polymer adducts.     

Phytochemical composition and thermal stability of two commercial açai species, Euterpe oleracea and Euterpe precatoria

Açai fruit are native to the Amazon region of South America and two predominant species are commercially exported as fruit pulps for use in food and beverage applications. Detailed characterisation of the polyphenolic compounds present in the de-seeded fruits of Euterpe oleracea and Euterpe precatoria species were conducted by HPLC–ESI–MSⁿ analyses and their thermal stability and overall influence on antioxidant capacity were determined. Anthocyanins were the predominant polyphenolics in both E. oleracea (2247 ± 23 mg/kg) and E. precatoria (3,458 ± 16 mg/kg) species, and accounted for nearly 90% of the trolox equivalent antioxidant capacity in both E. oleracea (87.4 ± 4.4 μmol TE/g) and E. precatoria (114 ± 6.9 μmol TE/g) fruits. Various flavones, including homoorientin, orientin, taxifolin deoxyhexose and isovitexin; various flavanol derivatives, including (+)-catechin, (−)-epicatechin, procyanidin dimers and trimers, and phenolic acids, including protocatechuic, p-hydroxybenzoic, vanillic, syringic and ferulic acids, were also present in both species. Thermal stability of these compounds was evaluated, following a thermal holding cycle (80 °C for up to 60 min) in the presence and absence of oxygen. Both species experienced only minor changes (<5%) in non-anthocyanin polyphenolic contents during all thermal processes whereas 34 ± 2.3% of anthocyanins in E. oleracea and 10.3 ± 1.1% of anthocyanins in E. precatoria were lost under these conditions, regardless of the presence of oxygen. Proportional decreases (10–25%) in antioxidant capacity accompanied the anthocyanin changes. Results suggest that both açai species are characterised by similar polyphenolic profiles, comparable antioxidant capacities, yet only moderate phytochemical stability during heating.     

Bioactivities of açaí (Euterpe precatoria Mart.) fruit pulp,superior antioxidant and anti-inflammatory properties to Euterpe oleracea Mart.

There are two predominant palm tree species producing edible fruit known as “açaí” found widely dispersed through the Amazon: Euterpe oleracea Mart. and Euterpe precatoria Mart. They differ from each other in terms of how the plants grow and their phytochemical composition. E. oleracea (EO) has received considerable attention as a “super fruit” because of its high antioxidant capacity, while studies on E. precatoria (EP) remain rare. In this study, the antioxidant and anti-inflammatory activities of EP fruit pulps were evaluated by different assays including a series of oxygen radical absorbance capacity (ORAC) based assays, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the cell-based antioxidant protection in erythrocyte (CAP-e) assay, as well as the nuclear factor-kappa B (NF-κB) secreted embryonic alkaline phosphatase (SEAP) assay. Total phenolics were also measured as an indication of the total phenol content. For comparative purposes, the EO fruit pulp was included. The antioxidant capacity of the EP fruit pulp was determined to be superior to the EO fruit pulp in every chemical based assay. In the cell-based CAP-e assay, the EP fruit pulp showed a dose-dependent inhibition against oxidative damage with an IC₅₀ of 0.167 g/l. In the SEAP reporter assay, the EP fruit pulp polyphenol-rich extracts inhibited lipopolysaccharide (LPS)-induced NF-κB activation by 23% (p < 0.05) at 20 μg/ml, whereas the extract of the EO fruit pulp did not show a significant inhibitory effect at comparable doses. In addition, carotenoids were quantified for the first time in EP, since EP has high scavenging capacity against singlet oxygen.     

The high ascorbic acid content is the main cause of the low stability of anthocyanin extracts from acerola

Acerola is considered to be one of the best natural sources of ascorbic acid (AA) and, for this reason, the influence of this component on the stability of anthocyanins from acerola extracts was determined and compared to those from açai, which have no detectable AA. The addition of three different levels of AA to the solution of açai anthocyanins resulted in a 110-fold increase in the degradation rate (k_obs) at the highest fortification level (276 mg/ml). The fact that the flavonoid concentration of the açai anthocyanin extract was 10 times higher than that of the acerola was probably responsible for the three times higher stability of the AA-fortified açai system compared to the acerola system, both at the same AA concentration and similar total polyphenol levels. The higher the level of AA addition to açai anthocyanin solutions, the greater was the colour fading, indicated by increase of L^∗ and decrease of a^∗ and C^∗ values.     

Phytochemical,antioxidant and pigment stability of açai (Euterpe oleracea Mart.) as affected by clarification,ascorbic acid fortification and storage

Açai juice at two clarity stages (semi-clarified and clarified) was compared to 100% açai pulp following ascorbic acid fortification to evaluate phytochemical and antioxidant changes during storage at 4 and 20 °C. Cyanidin-3-rutinoside (202 ± 5.8 mg/L) and cyanidin-3-glucoside (75 ± 4.8 mg/L) were the predominant anthocyanins in açai while 11 non-anthocyanin polyphenolics were detected in concentrations from 1.1 to 55 mg/L of açai pulp. Clarification of açai pulp resulted in a 27% loss in total polyphenolics (197 ± 6.9 mg gallic acid/100 mL) and in a 20% reduction in both total anthocyanins (729 ± 3.4 mg/L) and antioxidant capacity (54 ± 1.7 μmol Trolox equivalents/mL). Anthocyanin degradation followed first order kinetics, with half-lives ranging from 9.4 to 43 days for cyanidin-3-glucoside and from 18 to 82 days for cyanidin-3-rutinoside. Fortification with ascorbic acid accelerated anthocyanin degradation in clarified juice at both storage temperatures, likely due to the loss of polymeric anthocyanin forms (21%) during clarification. Although clarification enhanced the amount of monomeric anthocyanins present in açai juice which relates positively to the aesthetic quality, processing and handling regimes must be optimized to achieve maximum retention of their functional properties during storage.     

Flavonoids from acai (Euterpe oleracea Mart.) pulp and their antioxidant and anti-inflammatory activities

Five flavonoids, (2S,3S)-dihyrokaempferol 3-O-β-d-glucoside (1) and its isomer (2R,3R)-dihydrokaempferol 3-O-β-d-glucoside (2) , isovitexin (3), velutin (4) and 5,4′-dihydroxy-7,3′,5′-trimethoxyflavone (5), were isolated from acai (Euterpe oleracea Mart.) pulp. The structures of these compounds were elucidated based upon spectroscopic and chemical analyses. To our knowledge, compounds 1, 2, 4 and 5 were identified from acai pulp for the first time. The in vitro antioxidant activities of these compounds were evaluated by the oxygen radial absorbance capacity (ORAC) assay. The ORAC values varied distinctly (4458.0–22404.5 μmol Trolox equivalent (TE)/g) from 5,4′-dihydroxy-7,3′,5′-trimethoxyflavone (5) to isovitexin (3) and were affected by the numbers/positions of hydroxyl groups, substitute groups, as well as stereo configuration. The anti-inflammatory effects of these compounds were screened by the secreted embryonic alkaline phosphatase (SEAP) reporter assay, which is designed to measure NF-κB activation. Velutin (4) was found to dose-dependently inhibit SEAP secretion in RAW-blue cells induced by LPS, with an IC₅₀ value of 2.0 μM. Velutin (4) also inhibited SEAP secretion induced by oxidised LDL, indicating potential athero-protective effects.     

Chemical characterization and evaluation of antioxidant properties of Açaí fruits (Euterpe oleraceae Mart.) during ripening

Consumption of açaí fruits has been linked to positive health effects due to its phenolic content and nutritive value. The objective of this study was to characterize açaí fruits chemically and to determine the antioxidant capacity at three different maturity stages. With the exception of fat, amounts of macronutrients, minerals and titratable acids decreased during the ripening process. The same trend was observed for most of the phenolic constituents identified by HPLC–ESI-MS/MS. A consistent decline was shown for flavones and hydroxycinnamic acids. The concentration of the anthocyanins increased in the course of ripening. In accordance with the total amount of the identified phenolic compounds, the antioxidant capacity, measured by TEAC and TOSC, also decreased. However, the contribution of the main phenolic compounds to the overall antioxidant capacity evaluated by TOSC was estimated to be low.     

Liquid chromatography/mass spectrometry based fingerprinting analysis and mass profiling of Euterpe oleracea (açaí) dietary supplement raw materials

Chemical fingerprinting and mass profiling methods to identify biologically active compounds in botanical dietary supplements is gaining much attention in recent years. Euterpe oleracea (açaí) has been reported to be rich in health-beneficial chemical constituents. We have developed LC/MS based fingerprinting and mass profiling methods to identify fatty acids, anthocyanins and non-anthocyanin polyphenols in three processed raw materials; non-organic açaí powder (ADSR-1), raw-organic açaí powder (ADSR-2) and freeze-dried açaí powder (ADSR-3) that are used in the preparation of botanical dietary supplements. For LC/MS analysis of fatty acids and non-anthocyanin polyphenols, the açaí samples were extracted sequentially with dichloromethane followed by methanol. To study fingerprinting analysis of anthocyanins, açaí samples were extracted with acidic methanol–water. The LC separation of fatty acids, non-anthocyanin polyphenols and anthocyanins in açaí raw materials was achieved using a C18 column with a gradient mobile phase consisting of solvents A (0.1% formic acid in water), and B (0.1% formic acid in methanol). MS experiments were carried out with negative and positive mode electrospray ionization. LC/MS analysis of dichloromethane extracts of (ADSR-1), (ADSR-2) and (ADSR-3) açaí powders have shown to contain fatty acids, γ-linolenic acid, linoleic acid, palmitic acid, and oleic acid. Whereas, the fingerprinting analysis of methanol extracts of ADSR-1, ADSR-2 and ADSR-3 led to the identification of phenolic acids, anthocyanin and non-anthocyanin polyphenols. The results from our study may be useful for the authentication and quality assessment of açaí dietary supplement raw materials.     

Effect of differently processed açai (Euterpe oleracea Mart.) on the retention of phenolics and anthocyanins in chewy candies

This study investigated the effects of processing and storage on the physicochemical properties and retention of antioxidant compounds of no‐added sucrose chewy candies (NASC) incorporated with differently processed açai (frozen pulp, spray‐dried and freeze‐dried powders). NASC containing freeze‐dried açai had the highest softness and recoveries of total phenolic (TP) and total anthocyanin (TA) immediately after production. Colour parameters and antioxidant capacity by ABTS and ORAC assays had no significant differences after 6 months of NASC storage, except for ORAC in NASC containing spray‐dried açai, whereas DPPH^? in all samples significantly increased. Water activity and hardness also increased after storage, whereas TP and TA contents decreased, despite presenting good retentions (approx. 72–78% TP and 84–99% TA). This study suggests that açai has a great potential to be used as a natural pigment and antioxidant source in candy manufacturing, meeting consumption trends towards healthier products.     

Effect of high pressure processing on the stability of anthocyanin,ascorbic acid and color of Chinese bayberry juice during storage

The stability of anthocyanin (Cy3Gl) and ascorbic acid (AA) of pressure treated Chinese bayberry (Myrica rubra Sieb. et Zucc.) juice was investigated during storage at temperature of 4 °C and 25 °C. Samples of Chinese bayberry juice (350 mL each, packed with a polyethylene bag) were processed at 400, 500, 600 MPa in room temperature for 10 min. The retention ratio of Cy3Gl and AA content after pressure treatment was more than 98% and 96%, respectively. Both Cy3Gl and AA of pressure treated juice were more stable during storage as compared to those of the untreated control juice. The degradation of Cy3Gl and AA of samples during storage could be described using first order kinetic model. It was observed that there was a significant (p < 0.01) correlation between changes of Cy3Gl and AA content for all tested samples of Chinese bayberry juice during storage.     

Influence of germination techniques on sprout yield,biosynthesis of ascorbic acid and cooking ability,in chickpea (Cicer arietinum L.)

Effects of germination time and illuminations on sprout yield, biosynthesis of ascorbic acid, cooking ability and moisture accumulation in chickpeas were significant (p ? 0.01). Green light had the highest promoting effect on the ascorbic acid level (40.59 mg/100 g) as compared to other illuminations but significantly reduced the sprout yield (188.6 g) as compared to dark, fluorescence and γ-rays illuminations with significantly high sprout yield (196 g) and imbibing moisture (51%). Cooking time was reduced by 43% due to γ-rays in un-soaked seed. Cooking time increased in all treated chickpea samples after 24 h germination and thereafter decreased significantly. Red light significantly increased the cooking time (68.44 min) followed by fluorescent (64.5 min), yellow (61.8 min) and green light (60.9 min). The results indicated that germination of chickpea under green light was an effective process in enhancing ascorbic acid content while dark, fluorescence and γ-rays were effective in promoting sprout growth and to some extent biosynthesis of ascorbic acid.     

Influence of process conditions on the physicochemical properties of açai (Euterpe oleraceae Mart.) powder produced by spray drying

The objective of this work was to study the influence of spray drying conditions on the physicochemical properties of açai powder. The process was carried out on a mini spray dryer and maltodextrin 10DE was used as carrier agent. Seventeen tests were made, according to a central composite design. Independent variables were: inlet air temperature (138–202 °C), feed flow rate (5–25 g/min) and maltodextrin concentration (10–30%). Moisture content, hygroscopicity, process yield and anthocyanin retention were analysed as responses. Powder moisture content and process yield were positively affected by inlet air temperature and negatively affected by feed flow rate, which are directly related to heat and mass transfer. Process yield was also negatively influenced by maltodextrin concentration, due to the increase on mixture viscosity. Powders hygroscopicity decreased with increasing maltodextrin concentration, decreasing temperature and increasing feed flow rate. Powders with lower moisture content were more hygroscopic, which is related to the greater water concentration gradient between the product and the surrounding air. Anthocyanin retention was only affected by temperature, due to its high sensitivity. In respect to morphology, the particles produced at higher temperature were larger and a great number of them showed smooth surface.     

Enhanced chemical stability,chromatic properties and regeneration of betalains in Rivina humilis L. berry juice

Betalains are hydrophilic colorants containing chromophore betalamic acid. Owing to poor stability, its usage is limited to low acidic short shelf-life, and frozen foods. In this report, effect of metals (inorganic Se⁴⁺, Zn²⁺, and Cu²⁺) on stability of betalains in Rivina humilis L. berry juice (RBJ) was studied in presence of 10 and 40 μg metal/mL with/without ascorbic acid (AA; 0.25 and 0.5 g/100 mL). Se bleached RBJ betacyanins mildly, whereas Zn, and Cu bleached the pigments significantly. AA protected the pigments from metal-induced bleaching, and stabilizing effect of 0.25 g AA/100 mL was higher (P < 0.05) than 0.5 g AA/100 mL. AA (0.25 g/100 mL) + Se (40 μg/mL) enhanced (five-fold) the half-life time of betacyanins. RBJ betacyanins degraded up to 95% and 96% on treatment for 36 min at 90 °C and storage for 48 days at 25 °C, respectively, whereas only 15% pigment was lost on storage (5 °C, 90 days). AA (0.25 g/100 mL) + Se (40 μg/mL) regenerated the pigments on storage at 5 °C after thermal degradation. Color values of AA (0.25 g/100 mL) + Se (40 μg/mL) containing samples indicated an orange tinge, whereas other samples turned brown yellow after thermal treatment.     

Effect of endogenous ascorbic acid oxidase activity and stability on vitamin C in carrots (Daucus carota subsp. sativus) during thermal treatment

The purpose of this research was to study the effect of endogenous ascorbic acid oxidase (AAO) on vitamin C in carrots (Daucus carota subsp. sativus), namely Nantes, Egmont Gold and baby carrots during thermal treatment. Enzyme-substrate reaction kinetics of AAO were described using Michaelis–Menten equation. The estimated K_m and V_max values of AAO ranged from 50.34 to 63.54 μM and 23.70 to 26.82 μmol/min, respectively. Nantes carrots had the lowest AAO activity. On the other hand, Egmont Gold had the highest V_max. AAO activity in all carrot cultivars was stable up to 50 °C and inactivated above 50 °C. Irreversible thermal inactivation of AAO followed first order kinetics (55–70 °C) and the estimated activation energy of the three carrot cultivars situated between 114.33 and 191.45 kJ/mol. Regarding vitamin C stability, thermal treatment at 60–70 °C has resulted in total conversion of l-AA to DHAA due to residual AAO activity; a complete AAO inactivation was found in 80 °C-treated carrots with high vitamin C retention predominantly in l-AA form, up to 90%. On average, the carrots had a total vitamin C content amounting from 368.24 to 379.87 μg/g dry matter and the Nantes carrots had the highest vitamin C content. The effectiveness of rapid inactivation of endogenous AAO via heating (>80 °C, 10 min) prior to matrix disruption gave protection to l-AA towards enzymatic oxidation, thus resulted in a higher vitamin C content and stability in carrots.     

Total phenolics,ascorbic acid,and antioxidant capacity of noni (Morinda citrifolia L.) juice and powder as affected by illumination during storage

Total phenolics, ascorbic acid, and antioxidant capacity of noni (Morinda citrifolia L.) juice and powder were determined during storage at 24 °C. After 2 weeks of storage, illuminated noni juice lost 32% of total phenolics, 89% of ascorbic acid, and 46–65% of antioxidant capacity—about 8%, 22%, and 9–15% more than unilluminated juice. Both illuminated and unilluminated juice lost 97% of ascorbic acid by 4 weeks. The difference in antioxidant characteristics between illuminated and unilluminated juice became insignificant at 12 weeks. After 12 weeks, illuminated noni powder lost 21% of total phenolics, 17% of ascorbic acid, and 23–36% of antioxidant capacity—about 13%, 4%, and 7–19% more than the unilluminated powder. Noni powder in brown bottles retained antioxidant characteristics significantly greater than that in clear bottles. Protection from light effectively reduced degradation of antioxidant characteristics of noni juice for only 2 weeks but those of noni powder for at least 3 months.     

Quantification of gallic acid and ellagic acid from longan (Dimocarpus longan Lour.) seed and mango (Mangifera indica L.) kernel and their effects on antioxidant activity

Gallic acid (GA) and ellagic acid (EA) have been identified in longan seed and mango kernel by the use of reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with photodiode array detection (DAD). The ethanolic extract of longan seed contained 23.3 and 156 mg/100 seeds of GA and EA, respectively. The ethanolic extracts of mango kernel contained approximately 87% more GA than the longan seed ethanolic extracts but about 32% less EA. After heat treatment and acid hydrolysis, mango kernel had higher concentrations of GA and EA, contributing to more potent antioxidant activity. The results demonstrated rich sources of GA and EA in longan seed and mango kernel which might provide a novel source of these natural antioxidants.     

Antioxidant action of ganghwayakssuk (Artemisia princeps Pamp.) in combination with ascorbic acid to increase the shelf life in raw and deep fried chicken nuggets

Raw and deep fried chicken nuggets containing various levels of ganghwayakssuk ethanolic extract (GE) in combination with ascorbic acid (Aa) were evaluated for shelf-life during refrigerated storage (4 °C). The pH and color (lightness, redness, and yellowness) values of raw and deep fried samples were significantly affected by the addition of GE (P < 0.05). All antioxidant combinations except for Aa + GE 0.01 were effective at delaying lipid oxidation (CD, POV, and TBARS) when compared to the control or Aa. Raw samples with GE 0.2 and Aa + GE 0.1 exhibited lower bacterial populations during storage. The sensory characteristics (color, juiciness, flavor, tenderness, and overall acceptability) did not differ significantly in all deep fried chicken nugget samples, except color, whereas storage time had a significant effect (P < 0.05). The results suggest the possibility of utilizing raw and deep fried chicken nuggets with a mixture of ganghwayakssuk and ascorbic acid for the increase of shelf-life and quality.     

Effect of microwave pretreatment on the kinetics of ascorbic acid degradation and peroxidase inactivation in different parts of green asparagus (Asparagus officinalis L.) during water blanching

In this study, the effects of two blanching conditions on ascorbic acid (AA) and peroxidase (POD) in different segments of asparagus (bud, upper, middle, and butt) were investigated. The blanching treatments were: blanching in water at 70, 80 and 90 °C (WB); microwave heating (900 W, 30 s) followed by water blanching (MW + WB). AA degradation and POD inactivation in all segments of asparagus for both treatments are well described by first-order models. The degradation rate of AA and POD is gradually increased from butt to bud segment of asparagus. In addition, MW pre-treatment could increase the E_a of AA degradation and decrease the E_a of POD inactivation during water blanching of asparagus. Therefore, it is recommended that the different segments of asparagus should be subjected to different blanching times, and MW pre-treatment could be applied for alleviating AA degradation and accelerating POD inactivation during blanching, cooking and pasteurisation in water.