Effect of cultivar and storage temperature on identification and stability of polyphenols in strawberry cloudy juices

The effect of strawberry (Fragaria x ananassa Duchesne) cultivars (cvs) and storage temperature on the stability of polyphenols in cloudy juices was determined. Identification of phenolic compounds by ultra performance liquid chromatography-electrospray ionization/mass spectrometry (UPLC–ESI/MS), as well as quantitative analysis by ultra-performance liquid chromatography–photodiode array–fluorescence (UPLC–PDA–FL), were carried out on fresh and stored products (6 months, 4 °C and 20 °C) from 7 different strawberry cvs. A total of 32 polyphenolic compounds were identified: flavan-3-ols (6), anthocyanins (8), flavonols (4) and flavones (3), hydroxycinnamic acids (4), and ellagic acid derivatives (7). Total polyphenol content ranged from 642.08 mg/L in fresh ‘Florence’ cv. juice to 296.72 mg/L in ‘Honeoye’ cv. juice after 6 months of storage at 20 °C. Anthocyanins (max. 161.40 mg/L in ‘Honeoye’ juice) demonstrated the greatest degree of degradation (31–100%, depending on the molecular structure and temperature). Cyanidin-3-malonylglucoside was less labile than 3-glucoside. In the case of pelargonidin glycosides, 3-glucoside was more stable. The degradation process was the least advanced in ‘Kimberly’ cv. juice (58.53% at 4 °C). Storage conditions also influenced the decrease in p-coumaroyl-hexose, and quercetin-glucuronide content. However, low temperatures limited this process. This was especially noticeable in ‘Florence’ and ‘Honeoye’ cvs. In turn, proanthocyanidins showed the most stability and were the main polyphenols identified in juices (212–434 mg/L). Generally, it was observed that the total content of polyphenols and their stability in juices was dependent on the cultivar, and the duration of storage conditions.     

The effect of frying on anthocyanin stability and antioxidant activity of crisps from red- and purple-fleshed potatoes (Solanum tuberosum L.)

Red- and purple-fleshed potatoes (Solanum tuberosum L.) are a good source of polyphenols, mainly anthocyanins as one of the most important components. The chemical composition with reducing sugars and the total polyphenol contents were analyzed in four purple potato varieties (Salad Blue, Vitelotte, Valfi, Blue Congo) and three red-fleshed potato varieties (Rosalinde, Herbie 26, Highland Burgundy Red). The anthocyanin composition of raw potato and potato crisps was characterized by high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) method. Moreover, the antioxidant activity was measured with the radical scavenging assays using 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical as well as ferric reducing ability of plasma assay (FRAP). In addition, colour parameters in prepared potato crisps were evaluated. Both red and purple-fleshed potato varieties contained high levels of total polyphenols (227–845 mg 100 g⁻¹ dry weight) and anthocyanins (21–109 mg 100 g⁻¹ dry weight). The process of frying caused degradation of anthocyanin compounds (38–70%). The HPLC–MS/MS analysis showed that pelargonidin and malvidin derivates were more stable during frying than petunidin derivatives. Although frying process affected the anthocyanin and polyphenol levels, obtained potato crisps exhibited bright intensive colour and good antioxidant activity.     

Phenolic compounds and antioxidant activity of Spanish commercial grape juices

Evaluation of the antioxidant activity of components of the diet is important in order to establish healthy consumption patterns. Data are reported here on the antioxidant activity (FRAP and ABTS), of 20 commercial grape juices and 10 typical Spanish wines and on their content of total phenolic compounds, anthocyanins, flavonoids and 10 individual phenolic compounds (flavanols, benzoic acids and cinnamic acids, measured by HPLC-UV). Red grape juices had a significantly higher (p < 0.05) concentration of total phenols (1177 vs. 744 mg gallic acid/L), flavonoids (98 vs. 63 mg catechin/L) and a higher antioxidant activity (9.16 vs. 2.83 meq Trolox/L) in comparison to white grape juices. In comparison to the white wines, white grape juices contained more total phenols (744 vs. 286 mg gallic acid/L) and flavonoids (63 vs. 29 mg catechin/L) and evidenced higher antioxidant activity (p < 0.05). In comparison to the red wines, a lower content of total phenols (286 vs. 2358 mg gallic acid/L) and flavonoids (228 vs. 29 mg catechin/L) and an absence of anthocyanins were observed in the white wines, which are therefore less antioxidant. Although a two-fold higher concentration of antioxidant compounds was found in red wines than in red grape juices, the latter may be a good option for all age groups because of the absence of alcohol and the potentially beneficial health effects of their phenolic composition and elevated antioxidant activity.     

Ancient apple varieties from Croatia as a source of bioactive polyphenolic compounds

Several ancient apple varieties and a wild apple variety grown in Croatia were analysed for the polyphenol content and compared to two varieties grown in USA. In the flesh, flavanols, dihydrochalcones and phenolic acids (24 to 137, 23 to 109, 3 to 238 mg kg⁻¹ of fresh weight (FW), respectively) were found. Peel contained flavanols, dihydrochalcones, phenolic acids, flavonols and anthocyanins (65 to 690, 21 to 141, 0 to 107, 205 to 1223, 0 to 213 mg kg⁻¹ FW, respectively). The wild apple was characterized by much higher flavanol and phenolic acid content in the flesh (301 and 734 mg kg⁻¹ FW, respectively) while the peel was similar to other apples. The polyphenol profile was similar to apples from USA. The varieties Zimnjara, Lještarka and Adamova zvijezda could be highlighted as sources of polyphenols. Varieties are categorized by the content of dihydrochalcones and flavanols in the flesh (whether that content is high or low), and by the relative portion of phenolic acids and flavanols in the flesh (high phenolic acid proportion, lower flavanol proportion and vice versa). There was not observed to be as strong a pattern for categorizing differences in the peel.     

Bioactive compound composition of pomegranate fruits removed during thinning

Thinning consists of reducing fruit load at immature stage and thus allowing remaining fruits to develop to their maximum size and quality. The waste material produced during this farming practice was characterised in 9 pomegranate cultivars, by evaluating: weight, size, maturity index, pH, organic acids and sugars profiles, contents of minerals, punicalagin, and ellagic acid, total polyphenols and antioxidant activity. Citric and quinic were the main organic acids. Potassium was the predominant mineral, reaching up to 11 g kg⁻¹ dry weight (dw). Total polyphenol content ranged from 777 to 1660 g GAE kg⁻¹ dw, α-punicalagin from 101 to 195 and β-punicalagin from 80.1 to 111 g kg⁻¹ dw. The antioxidant activity was assessed by three methods and its values varied from 2923 to 4486 for ABTS, from 3153 to 4685 for FRAP, and from 2075 to 2934 mmol Trolox kg⁻¹ dw for DPPH. Pomegranate thinning fruits, especially sour-sweet cultivars, are rich in bioactive compounds, with a potential use in the food, chemical and pharmaceutical industries.     

Cold storage of blueberry (Vaccinium spp.) fruits and juice: Anthocyanin stability and antioxidant activity

Blueberries (Vaccinium spp.) may be considered one of the best potential sources of antioxidants in the diet. This characteristic results from the presence of flavonoids (especially anthocyanins), tannins and phenolic acids in the fruits. The objective of this work was to analyze the anthocyanin stability and antioxidant activity of refrigerated whole blueberry juice stored at 4 °C for 10 d, and of fruits stored frozen (−18 °C) for 6 months, in order to determine the changes occurring during storage. The frozen fruits showed a significant increase (p < 0.05) in antioxidant activity during the 3rd month of frozen storage, followed by a decrease up to the end of the 6-month period. The juice was analyzed every other day, and the antioxidant activity changed on the 8th d of refrigerated storage, remaining stable up to the 10th d. There were significant losses of anthocyanins both in the frozen fruits (59%) and refrigerated juice (83%). The antioxidant capacity was shown to be stable during cold storage both in the case of the fruits and whole juice, whereas the anthocyanins were degraded, possibly due to oxidations and/or condensation reactions with other phenolic compounds. More studies are required to optimize the storage time and temperature of these products with respect to nutrient stability.     

The influence of nitrogen and potassium fertilisation on the content of polyphenolic compounds and antioxidant capacity of coloured potato

The effect of fertilisation rates of nitrogen: 0 (control treatment—no soil fertilisation), 40, 80 and 120 kg/ha and potassium: 0 (control treatment), 120, 150 and 180 kg/ha on the content of anthocyanins, phenolic acids and antioxidant capacity in purple–blue potato cv. ‘Blue Congo’ was examined. Anthocyanins and phenolic acids were identified and quantified by LC–MS and UPLC–PDA. Nitrogen was more effective in increasing the anthocyanin content—their quantity in tubers after nitrogen application was twice as much as that found after potassium application. Among phenolic acids, the dominant one was chlorogenic acid, the content of which significantly increased after nitrogen fertilisation at 120 kg/ha, in line with the increase in total concentration of phenolic acids and antioxidant capacity. The adjustment of nitrogen and potassium fertilisation levels during the growth of purple–blue potatoes seems to be an effective way to increase the expression of polyphenolic compounds in these cultivars. Therefore, fertilisation with N at 120 kg/ha and K at 120 and 150 kg/ha is recommended as a way to improve the content of biologically active compounds and antioxidant properties, and consequently, to enhance the nutritional value and the functionality of purple–blue potatoes.     

Seasonal and cultivar variations in antioxidant and sensory quality of pomegranate (Punica granatum L.) fruit

Fruits of diverse pomegranate (Punica granatum L.) cultivars were analyzed for soluble phenolics content, antioxidant activity, soluble solid concentration, acidity and internal red color intensity. Analysis was carried out at various dates throughout the harvest season, corresponding to different climatic conditions during fruit ripening. Values obtained varied with cultivar and ripening date. In three cultivars of different sensory properties and harvest season, comparison between late- and early-ripening fruit revealed that arils of fruit ripening later in the season contained more soluble phenolics (1.21–1.71 compared to 0.22–0.88 pyrogallol equivalents, g L^?1) and exhibited a higher antioxidant activity, as measured by the ferric reducing ability (FRAP) assay (1.22–2.37 compared to 0.86–1.95 vitamin C equivalents, g L^?1). The red color intensity of the arils inversely related (R² = 0.89–0.94) to the sum of heat units accumulated during fruit ripening. Multiple linear regression analysis on fruit characteristics in 11 diverse cultivars indicated that juice antioxidative capacity linearly correlated with soluble phenolics content (R² = 0.98), but not with the red color intensity of the arils (R² = 0.38). Also, no significant correlation was established between aril color and either juice pH or total soluble phenolics content. The results imply that pomegranate fruit antioxidant and sensory quality traits can be enhanced by the choice of cultivar and controlled-climate cultivation management.     

An efficient,rapid and microwave-accelerated dispersive liquid–liquid microextraction method for extraction and pre-concentration of some organophosphorus pesticide residues from aqueous samples

In this paper, microwave-accelerated dispersive liquid–liquid microextraction has been developed for the extraction/preconcentration of some organophosphorus pesticides from aqueous samples prior to their analysis by gas chromatography–flame ionization detection. In this method, temperature of a high volume of aqueous sample is elevated by a microwave oven and then a mixture of extraction and disperser solvents is rapidly injected into the aqueous phase. After cooling to room temperature, the phase separation is accelerated by centrifuging. The main experimental factors affecting performance of the method including type and volume of the extraction and disperser solvents, temperature, pH, and salt addition were investigated and optimized. Under the optimum extraction conditions, the method resulted in low limits of detection and quantification within the ranges of 0.65–1.3 and 2.2–4.5 μg L⁻¹, respectively. Relative standard deviations were in the range of 2–7% (C = 40 or 100 μg L⁻¹) for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method was successfully applied to analysis of the target analytes in surface water and well water and fruit juice samples; diazinon was determined at μg L⁻¹ level in apple juice.     

Phenolic composition and antioxidant capacity of bacaba-de-leque (Oenocarpus distichus Mart.) genotypes

Phenolic compound composition and antioxidant capacity of four Oenocarpus distichus Mart. (bacaba-de-leque) genotypes were determined. In order to set the parameters for phenolic compound extraction, the effect of methanol concentration and extraction time on the reducing power of the extracts was evaluated using the surface response methodology. The optimal conditions were: a 60:40 methanol:water (v/v) solution and 11 min of extraction. Extracts were analyzed by ultra-high performance liquid chromatography with diode array detection and by ultra-high performance liquid chromatography coupled to mass spectrometry. Eleven substances were identified, of which six were quantified. Rutin was the major compound in bacaba-de-leque genotypes (15.2–56.8 μg.g⁻¹) followed by epicatechin (15.5–21.2 μg.g⁻¹). The Black-03 genotype had the highest amounts of all phenolic compounds and the highest antioxidant capacity by DPPH and ORAC assays, indicating that this genotype may be selected in breeding programs to obtain cultivars with higher phenolic compound contents and antioxidant capacity. Moreover, the results indicated that bacaba-de-leque has great potential as a novel supplier of phenolic acids and flavonoids to human diet, with levels comparable to or higher than other fruits belonging to the same family, such as açaí.     

Anthocyanin composition in fig (Ficus carica L.)

The anthocyanin composition was analysed in fig fruit (Ficus carica L.) from five different varieties (Colar, Cuello de Dama (green), Cuello de Dama (dark purple), Granilla and Bursa Siyahi). Fifteen anthocyanin pigments were detected, most of them containing cyanidin (Cy) as aglycone; some pelargonidin (Pg) derivatives were also found. Rutinose and glucose were present as substituting sugars, as well as acylation with malonic acid. Minor levels of peonidin 3-rutinose (Pn 3-rutinoside) in the pulp were also detected. Other noticeable aspects in the pigment composition of the fig were the detection of anthocyanidin-derived pigments, namely 5-carboxypyranocyanidin-3-rutinoside, a cyanidin 3-rutinose dimer and five condensed pigments containing C–C linked anthocyanins (Cy and Pg) and flavanol (catechin and epicatechin) residues. Total anthocyanin content in the skin ranged between 32 and 97 μg g⁻¹ and between 1.5 and 15 μg g⁻¹ in the pulp. The main anthocyanin in both parts of the fruit was Cy 3-rutinoside (48–81% in skin and 68–79% in pulp) usually followed by Cy 3-glucoside (5–18% in skin and 10–15% in pulp). Malonyl derivatives were more abundant in the skin (1.2–6.5%) than in the pulp (1.0–2.6%).     

Genetic diversity of nutritionally important carotenoids in 94 pea and 121 chickpea accessions

Biofortification of staple crops via breeding is an attractive strategy for reducing human micronutrient deficiencies. The objective of this research was to examine the concentration of carotenoids in diverse pea and chickpea accessions grown in Saskatchewan (Canada) using high performance liquid chromatography. In pea accessions mean concentration of lutein was highest (11.2 μg g⁻¹) followed by β-carotene (0.5 μg g⁻¹), zeaxanthin (0.3 μg g⁻¹), and violaxanthin (0.3 μg g⁻¹). Green cotyledon pea accessions were richer in β-carotene and total carotenoids compared to yellow cotyledon accessions. In chickpea accessions mean concentration of lutein (8.2 μg g⁻¹) was highest followed by zeaxanthin (6.2 μg g⁻¹), β-carotene (0.5 μg g⁻¹), β-cryptoxanthin (0.1 μg g⁻¹), and violaxanthin (0.1 μg g⁻¹). Desi chickpea accessions had higher carotenoid concentration than kabuli accessions. This research identified pea and chickpea accessions that can be utilized in breeding for the improvement of carotenoid concentration through biofortification.     

Anthocyanin profile and antioxidant capacity of black carrots (Daucus carota L. ssp. sativus var. atrorubens Alef.) from Cuevas Bajas,Spain

The present work deals with the study of the anthocyanin profile of two different black carrots (Daucus carota L. ssp. sativus var. atrorubens Alef.) cultivars, associated with Antonina and Purple Haze varieties, from Cuevas Bajas (Málaga, Spain) and some of their antioxidant features. The main anthocyanins detected by LC–MS were found to correspond to five cyanidin-based anthocyanins: cyanidin 3-xylosylglucosylgalactoside, cyanidin 3-xylosylgalactoside and the sinapic, ferulic and coumaric acids derivative of cyanidin 3-xylosylglucosylgalactoside. The anthocyanins present in the black carrots were essentially acylated and their levels were found to correspond to 25% and 50% of the total phenolic content for the Purple Haze and Antonina varieties, respectively. Moreover, the reducing capacity of the two black carrots extracts (86.4 ± 8.0 and 182.0 ± 27 μM TE/100 g fw) and the radical scavenging ability (17.6 ± 9.0 and 240.0 ± 54.0 μM TE/100 g fw) expressed in Trolox equivalents units were determined. The antioxidant features of the black carrot extracts were shown to be significantly higher than those of orange carrots used herein for comparison. Overall, this work highlights the Cuevas Bajas black carrots as rich sources of anthocyanins with significant antioxidant capacities and good nutritional value.     

Optimization of cheese sample preparation methodology for free amino acid analysis by capillary isotachophoresis

The objective of this work was the evaluation of different conditions for the selected free amino acids extraction from cheese samples, followed by capillary isotachophoresis analysis. Parameters of the extraction: concentration and type of extraction reagents (solvents: methanol, ethanol and mineral acids: perchloric acid, trichloroacetic acid, sulphuric acid and hydrochloric acid), time and temperature, and isotachophoretic separation conditions (voltage, time) were studied. Repeatability, reproducibility and stability of this method at different conditions are discussed. The best yield of free amino acids was obtained after triple extraction (30 min each process) with 0.1 M hydrochloric acid at 50 °C. Histidine, lysine, arginine, ornithine, tyrosine, and phenylalanine were determined using calibration curves and the standard additions method in different types of cheeses. The highest level of amino acids was determined in semi-hard cheese (2626.3 mg 100 g⁻¹ – calibration curve, and 2679.2 mg 100 g⁻¹ – standard additions method), whereas the lowest were found in sheep cheese (426.3 mg 100 g⁻¹ and 455.7 mg 100 g⁻¹, respectively), and Gouda type cheese samples (441.5 mg 100 g⁻¹ and 472.8 mg 100 g⁻¹, respectively).     

Fast method for the determination of copper,manganese and iron in seafood samples

A slurry sampling flame atomic absorption spectrometric method is proposed for the determination of copper, manganese and iron in oysters (Crassostrea rhizophora), clams (Anomalocardia brasiliana) and mussels (Mytella guiyanensis; Perna perna). Optimization was carried out using univariate methodology involving the following variables: nature and concentration of the acid solution for slurry preparation, sonication time and sample mass. The optimized conditions were 80 mg of sample ground in a cryogenic mil, dilution using 1.0 mol L⁻¹ nitric /hydrochloric acid solution, sonication time of 30 min and a slurry volume of 10 mL. The calibration curves had been prepared using standards of copper, manganese and iron also in 1.0 mol L⁻¹ nitric/hydrochloric acid solution. This method allowed the determination of copper, manganese and iron by FAAS, with detection limits of 0.17, 0.09 and 0.46 μg g⁻¹, respectively. The precision, expressed as relative standard deviation (RSD), are 3.0%, 2.9% and 3.8% (n=10), for concentrations of copper, manganese and iron of 17, 22 and 719 μg g⁻¹, respectively. The accuracy of the method was confirmed by analysis of the certified oyster tissue (NIST 1566b). The proposed method was applied for the determination of copper, manganese and iron in samples of oyster, clams and mussels, collected in Ubatuba and Todos os Santos Bay, Brazil. The obtained concentrations varied between 17.1 and 143.9 μg g⁻¹, 17.9 and 29.7 μg g⁻¹ and 364 and 1388 μg g⁻¹, respectively, for copper, manganese and iron. These values agree well with other data reported in the literature. The results showed no significant differences (P>0.005) using the proposed method with those obtained after complete digestion and determination by inductively coupled plasma-optical emission spectroscopy (ICP-OES).     

Determination of free quinic acid in food matrices by Hydrophilic Interaction Liquid Chromatography with UV detection

A new method using Hydrophilic Interaction Liquid Chromatography and UV detection was developed for the determination of free quinic acid in fourteen commercial beverages (fruit juices, red wine, coffee, vinegar, and edible mushroom extract). Samples were directly injected into the HPLC system after dilution and centrifugation. All separations were carried out by gradient elution on a ZIC^®-cHILIC column, using an eluent consisting of acetonitrile and aqueous phosphate buffer at pH 6. Quinic acid eluted in 12 min as a symmetric peak well separated from all other peaks in the chromatograms. The total turnaround time per sample was 60 min. The method was validated using cranberry juice as model beverage matrix. Linearity was demonstrated on spiked juice between 200 and 600 μg/mL (r² = 0.999), and precision and accuracy were satisfactory (RSD ≤ 10% and recovery 100 ± 1%, respectively).The method was proven to be suitable for its purpose. Quinic acid levels ranged from undetectable (<15 μg/mL in red grape juice, elderberry juice, and in red wine vinegar) to 740 ± 30 μg/mL (in mushroom extract). The results were discussed in comparison with the previous reports on similar matrices using different HPLC separation modes.     

Proximate composition and lipid profile of red mullet (Mullus barbatus) from two sites of the Tyrrhenian and Adriatic seas (Italy): a seasonal differentiation

Proximate composition, unsaponifiable lipid components (cholesterol, squalene, tocopherols, all-trans retinol, total carotenoids) and fatty acid profile were evaluated on red mullet (Mullus barbatus) caught in the Central Tyrrhenian and Central Adriatic seas (Italy). The study was conducted in spring, the reproduction period, and in autumn, the period of maximum recruitment and market demand for this species. Results showed that, in fish from both sites, protein (18.1–18.8 g 100 g⁻¹), nonprotein nitrogen (0.32–0.35 g 100 g⁻¹), ash (1.27–1.42 g 100 g⁻¹) and cholesterol (56.8–73.7 mg 100 g⁻¹) contents were almost stable. Total lipid levels were highly variable, with very low levels in spring (0.96–1.48 g 100 g⁻¹) and high levels in autumn (7.28–8.72 g 100 g⁻¹). On a total fatty acids basis, polyunsaturated fatty acids (PUFA) were significantly higher in spring (30–40% of total fatty acids), when fish was lean, than in autumn (20%), while monounsaturated fatty acids were significantly higher in autumn (35–38%) than in spring (18–29%). Saturated fatty acids were almost stable throughout the year (34–39% of total fatty acids). Red mullet from the two sites showed a good nutritional value; in particular they proved to be a good source of n-3 PUFA, which accounted for 75–80% of total PUFA, regardless of the fishing season. However, it was in autumn that red mullet exhibited the highest content of n-3 PUFA (>1000 mg 100 g⁻¹ wet fillet). The comparison of samples by geographical origin showed no difference in autumn, while slight differences were observed in spring.     

Determination of anthocyanins from acerola (Malpighia emarginata DC.) and açai (Euterpe oleracea Mart.) by HPLC–PDA–MS/MS

The anthocyanins from acerola and açai, two tropical fruits known for their bioactive compounds, were studied. Two varieties of acerola in natura and one brand of frozen pulp of açai were analyzed by high-performance liquid chromatography connected to photodiode array and mass spectrometry detectors (HPLC–PDA–MS/MS). The açai pulp presented 282–303 mg/100 g of total anthocyanin, with predominance of cyanidin 3-glucoside and cyanidin 3-rutinoside, in average proportions of 13% and 87%, respectively. The composition of the two acerola varieties (Waldy Cati 30 and Olivier) were similar, being cyanidin 3-rhamnoside (76–78%) the major anthocyanin, followed by pelargonidin 3-rhamnoside (12–15%). The acerola Waldy variety showed total anthocyanin content of 6.5–7.6 mg/100 g, while 7.9–8.4 mg/100 g were found in the Olivier variety, for fruits harvested in 2003 and 2004. No statistical differences were found between varieties and harvests for the total anthocyanin content in acerola fruits.     

Physicochemical profiles,minerals and bioactive compounds of stingless bee honey (Meliponinae)

This study investigates the physicochemical properties, majority minerals, total phenolic compounds and antioxidant activity of stingless bee honey. Thirty-three samples from ten species were analyzed. The results show moisture as 23.1–43.5% (w/w), the electrical conductivity as 0.150–1.34 mS cm⁻¹, the free acid as 16.2–139 mEq kg⁻¹, the pH as 3.33–6.56, the diastase activity as 4.34–49.6 in Göthe units, the insoluble solids as 55.2–76.1°Brix, the carbohydrates as 48.6–70.5% (w/w) sucrose and the 5-hydroxymethylfurfural (5-HMF) was below the limit of quantitation (LOQ). The most abundant element in the samples was potassium followed by calcium sodium, magnesium and manganese. Stingless bee honeys possess relevant amounts of phenolic compounds and antioxidant activity, suggesting a source of natural antioxidants. The results show that there is great variability in the composition of honey from stingless bees of different species, predominantly flowering and geographical origin. However, it was not possible to identify the real factor influencing its features.     

Flavonols in fresh and processed Brazilian fruits

Flavonols (myricetin, quercetin and kaempferol) and flavones (luteolin and apigenin) were determined in Brazilian fruits, using a previously optimized and validated HPLC method. The flavonoids investigated were not detected in three cultivars each of mango and papaya. Quercetin was found in all the other fruits, the mean values varying from 0.3 mg/100 g in orange cultivar Pêra to 7.5 mg/100 g in apple cultivar Fuji. Kaempferol was encountered in strawberry (0.7–0.9 mg/100 g), acerola (0.9–1.2 mg/100 g), pitanga (0.4 mg/100 g) and cashew-apple (<LQ–0.3 mg/100 g). Myricetin was detected only in pitanga (3.1–3.7 mg/100 g) and cashew-apple (2.0 mg/100 g). The best sources of flavonols among the fruits investigated were pitanga, cashew-apple, acerola and apple, the first three being analyzed for the first time. Luteolin and apigenin were not detected in any of the fruits. The processed products (ready-to-drink juice, concentrated juice, frozen pulp) of acerola, cashew-apple and pitanga had appreciably lower flavonol levels than the unprocessed fruit, indicating losses during processing. Comparison with published data on apple, orange, strawberry and fig shows the need for interlaboratory evaluation of the analytical methodology and more analyses to obtain cultivar-specific data.