Quantification of soluble solids in reconstituted açaí (Euterpe oleracea Mart.) pulp using near‐infrared spectroscopy

Açaí consumption is increasing worldwide because of the growing recognition of its nutritional and therapeutic properties. This product is classified based on its soluble solids content (SS), but the determination of SS in pulp is time consuming, tedious and not suitable for modern food processing plants. As near‐infrared (NIR) systems have been implemented to measure various quality attributes of food products, the objective of this study was to evaluate the feasibility of NIR diffuse reflectance spectroscopy to quantify the SS content of açaí pulp. Partial least squares (PLS) regression models were constructed to predict the SS. An optimum PLS model required one latent variable [principal component (PC)1 = 97%] with a root‐mean‐square error of calibration (RMSEC) of 1.06% for the calibration data set and the root‐mean‐square error of prediction (RMSEP) of 1.03% for internal cross‐validation. External validation using an independent data set showed good performance (RMSEP = 1.33% and Rp² = 0.82). NIR spectroscopy is a reliable method with which to determine SS in açaí pulp and thereby to classify açaí pulp according to established minimum quality standards.     

Consumer Liking of Fruit Juices with Different Açaí (Euterpe oleracea Mart.) Concentrations

ABSTRACT:  Overall liking, flavor, and perceived healthiness of one newly developed fruit juice with high açaí content (40% açaí) and 5 commercially available fruit juices with lower (4% to 20%) açaí concentrations were evaluated by consumers in Belgium. General trends for the overall sample were examined by means of analysis of variance, whereas individual consumer preferences were evaluated using internal preference mapping and hierarchical cluster analysis. The relative contribution of flavor and perceived health benefits as predictors of consumers' overall liking of the 6 açaí-based fruit juices was estimated through linear regression analysis. The results showed a negative relationship between the juices' overall liking and their açaí concentrations. Although the vast majority of consumers preferred the juices having a low açaí content (4% to 5% açaí), a small consumer segment liked the juice with 40% açaí. Flavor or taste experience superseded consumers' perceived health benefits as the primary determinant of the fruit juices' overall liking. The impact of perceived health benefits on the overall liking of the açaí juices decreased with higher taste dissatisfaction.     

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.     

Physicochemical and morphological characterisation of açai (Euterpe oleraceae Mart.) powder produced with different carrier agents

Physicochemical and morphological properties of açai powder produced with different carrier agents were evaluated in this work. Powders were produced by spray drying, using maltodextrin 10DE, maltodextrin 20DE, gum arabic and tapioca starch as carrier agents. Powder characterisation included analysis of moisture content, water activity, solubility, hygroscopicity, particle size distribution, morphology, total polyphenolics and antioxidant activity. Results showed that the samples produced with maltodextrin 20DE and gum arabic presented the smallest size and highest hygroscopicity. The powder produced with tapioca starch exhibited the lowest hygroscopity and solubility, and the highest mean diameter. With regard to morphology, all particles exhibited spherical and shrivelled surfaces, except those produced with tapioca starch, which exhibited rounded and smooth surfaces. Powders produced with maltodextrins and gum arabic showed high polyphenolic retention and antioxidant activity preservation after storage at 40 °C for 15 days, while for the particles produced with tapioca starch, this protective effect was less pronounced.     

Water sorption and glass transition temperature of spray dried açai (Euterpe oleracea Mart.) juice

Sorption isotherms and glass transition temperature (T_g) of powdered açai juice were evaluated in this work. Powders were produced by spray drying using different materials as carrier agents: maltodextrin 10DE, maltodextrin 20DE, gum Arabic and tapioca starch. The sorption isotherms were determined by the gravimetric method, while the T_g of powders conditioned at various water activities were determined by differential scanning calorimetry. As results, experimental data of water adsorption were well fitted to both BET and GAB models. Powders produced with maltodextrin 20DE and gum Arabic showed the highest water adsorption, followed by those produced with maltodextrin 10DE and with tapioca starch, respectively. With respect to the glass transition temperature, Gordon–Taylor model was able to predict the strong plasticizing effect of water on this property. Both a_w and T_g were used to determine the critical conditions for food storage, at which powders are not susceptible to deteriorative changes such as collapse, stickiness and caking.     

Kinetic Modeling of Anthocyanin Degradation and Microorganism Growth during Postharvest Storage of Açai Fruits (Euterpe oleracea)

Abstract: The unavoidable damage of açai (Euterpe oleracea) fruits (AF) during picking leads to microbial contamination and anthocyanin degradation, which prejudice the consumed fruit drink. Thirteen lots of AF (24 kg) from different municipal districts of the Pará State (Brazil) were monitored during a 75‐h‐long storage in the dark at 30 °C for microbial growth, and 7 lots for anthocyanin degradation. On arrival at the laboratory, anthocyanins presented a mean concentration of 828 mg kg⁻¹ fruits with a standard deviation of 323 mg kg⁻¹ fruits whereas mean microbial contamination was 2.64 10⁶ CFU g⁻¹ of dry matter for total mesophilic bacteria, 1.98 10³ MPN g⁻¹ DM for fecal coliforms, and 1.11 10⁵ CFU g⁻¹ DM for moulds and yeasts. Kinetic growth of the microbes could be fitted to a quadratic equation with an unusual rapid growth during the 1st 24 h. The kinetics of anthocyanin degradation fitted a 1st‐order equation. The mean velocity constant of the reaction (k₁) was of 0.0137 h⁻¹ and the mean half‐life (t_½) of the anthocyanins was 50 h. These results indicate that the AF simultaneously suffer extensive anthocyanin degradation and explosive microbial growth during the postharvest period needing a special care. Practical Application: The data presented in this article help the industrial sector of açai (Euterpe oleracea) juice to understand: (1) the rapid kinetics of anthocyanin oxidation and (2) the uncommon kinetics of microorganism growth during a postharvest storage of açai fruits for up to 75 h. Our results allow to predict the global deterioration of açai fruits and pointed out the necessity of blanching the fruits or pasteurizing the juice.     

Effects of gastrointestinal digestion models in vitro on phenolic compounds and antioxidant activity of juçara (Euterpe edulis)

This study evaluated the effects of different gastrointestinal digestion models in vitro on the bioaccessibility of phenolics and antioxidant activity in juçara frozen pulp. In the sequence, method 3 was applied to juçara fruit in three different stages of maturation (vitrin – reddish fruits, mature – purple fruits, tuíra – deep purple fruits). In the method applied, the final pH adopted was 5.0, in order to avoid interference in the assay used to determine the antioxidant activity, and BHT was used to prevent excessive oxidation in the system. In this method, higher values for antioxidant activity were obtained (3574.95–3719.10 μmol L^?1 Trolox 100 g^?1 pulp) compared with the other two methods tested (1969.14–3034.74 μmol L^?1 Trolox 100 g^?1 pulp). In relation to juçara fruit, the mature stage was found to be ideal for processing, showing generally higher values of the bioaccessibility for phenolics and antioxidant activity compared to other maturation stages.     

Optimizing the Enzymatic Maceration of Foliole Purée from Hard Pieces of Hearts of Palm (Euterpe edulis Mart.) using Response Surface Analysis

Response surface analysis was applied to investigate modifications in viscosity of foliole purée treated with commercial enzyme preparations high in cellulase and endopolygalacturonase (pectinase) with changes in enzyme concentration (0.3–1.2%), incubation time (3.3–6.7 hr) and temperature (40–50°C). Foliole purée was obtained by trituration of hard pieces of hearts of palm (Euterpe edulis) and incubated in a rotating agitator. After treatment with 0.81% cellulase for ～5 hr at 50°C, a fourfold reduction in viscosity was found relative to a control sample. The minimum viscosity for this treatment was within the experimental range investigated. Optimized experimental conditions for treatment with pectinase however were outside the experimental range. The application of the cellulase preparation to the purée resulted in a 10% increase in yield of edible palm.     

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.     

Heat inactivation and kinetics of polyphenoloxidase from palmito (Euterpe edulis)

Polyphenoloxidase (PPO, EC 1.14.18.1)was extracted from palmito (Euterpe edulis Mart) using 0.1 M phosphate buffer, pH 7.5. Partial purification of the enzyme was achieved by a combination of (NH₄)₂SO₄precipitation (35–90% saturation) and Sephadex G-25 and DEAE-cellulose chromatography. The purified preparation gave five protein bands on polyacrylamide gel electrophoresis, three of them with PPO activity. The K_mvalues for chlorogenic acid, caffeic acid, catechol, 4-methylcatechol and catechin were 0.57, 0.59, 1.1, 2.0 and 6.25 mM , respectively. PPO has a molecular weight of 51 000 Da, maximum activity at pH 5.6 with chlorogenic acid as substrate, and was stable between pH 5.0 and 8.0. The enzyme was heat stable at 50–60°C and inactivated at 75°C. The heat stability of palmito PPO was found to be pH dependent; at 50°C and pH 4.0 the enzyme was fully inactivated after 30 min. The pH/activity studies showed two groups with pK values c 4.6 and 6.7 involved in PPO catalysis.     

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.     

Chemical characterization and antioxidant capacity of berries from Clidemia rubra (Aubl.) Mart. (Melastomataceae)

The flora of Latin America attracts gaining interest as it provides a plethora of still unexplored or under-utilized fruits that can contribute to human well-being due to their nutritional value and their content of bioactive compounds. Clidemia rubra (Aubl.) Mart. is a shrub belonging to the family of the Melastomataceae that grows preferably in a tropical climate. This paper comprises a nutritional characterization of the berries from Clidemia rubra and provides data on the phenolic compounds as well as the antioxidant capacity of the fruit. Findings in macronutrients like protein, carbohydrates, and fat were comparable to that of common berry fruits. Clidemia rubra berries seemed to be a good source for dietary fibers and some minerals (Ca, Mn, and Zn). In contrast, contents of titratable acids and ascorbic acid were low. The polyphenolic profile was determined by using HPLC-MS/MS in comparison to standard compounds. Noteworthy amounts of cyanidin 3-O-rutinoside (39.43 ± 1.66 mg/100 g fresh weight (FW)), delphinidin 3-O-rutinoside (23.74 ± 1.18 mg/100 g FW), cyanidin 3-O-glucoside (11.68 ± 0.56 mg/100 g FW), and delphinidin 3-O-glucoside (6.08 ± 0.35 mg/100 g FW) were found. Non-anthocyanin phenolic constituents were phenolic acids (gallic, protocatechuic, p-hydroxy-benzoic, vanillic, and caffeic acid), flavan-3-ols (epigallocatechin, epigallocatechin gallate, and epicatechin gallate), and 11 different myricetin and quercetin derivatives of which quercetin 3-O-arabinoside (5.26 ± 0.16 mg/100 g FW) and quercetin 3-O-rhamnoside (5.06 ± 0.08 mg/100 g FW) were dominating. Anthocyanins and ascorbic acid were mainly responsible for the antioxidant capacity of Clidemia rubra berries assessed with the total oxidant scavenging capacity (TOSC) assay.     

Biological evaluation and quantitative analysis of antioxidant compounds in pulps of the Amazonian fruits bacuri (Platonia insignis Mart.), ingá (Inga edulis Mart.), and uchi (Sacoglottis uchi Huber) by UHPLC‐ESI‐MS/MS

Bacuri, ingá, and uchi are Amazon fruits consumed specially in the North region of Brazil. Due to their large consumption and the lack of knowledge regarding its chemical composition, these fruits were studied in relation to their Antioxidant chemical constitution. The total phenolic content ranged from 3.86 ± 0.47 to 33.38 ± 1.51 mg GAE/100 g, and the total flavonoid content ranged from 1.75 ± 0.22 to 19.44 ± 0.87 mg QUERE/100 g, where the contents showed a significant correlation with DPPH and ABTS antioxidant assays. Thus, UHPLC‐MS/MS was applied do quantify selected compounds, been citric acid the most abundant for all fruits. Furthermore, samples were screened for their α‐glycosidase and lipase inhibitory effects, in addition to their antimicrobial potentials. Bacuri showed the highest antioxidant and α‐glycosidase inhibitory capacity (IC₅₀ 15.20 μg/mL), whereas uchi and its main metabolite bergenin displayed moderate antimicrobial activities. The results shed light into the potentials of Amazonian fruit sources.

Practical applications

Plant phenolics are essential components of functional foods, due to their antioxidant and enzyme inhibition activities, which are directly linked to several diseases prevention. This is the first study about the quantification of antioxidant compounds in the Amazonian fruits: bacuri, ingá, and uchi. Although they are quite consumed in the North region of Brazil, there are no bio‐products made from them. This study aimed to elucidate the knowledge about the chemical composition and potentialities within these fruits with the practical purpose of highlighting them to future commercial applications. In addition, once we indicate their capabilities, we contribute with local populations in respect to the production of such fruits, which still is a family activity.