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Sunday, 10 June 2018

Antioxidant power, anthocyanin content and organoleptic performance of edible flowers

Scientia Horticulturae Volume 199, 16 February 2016, Pages 170-177 Author links open overlay panelStefanoBenvenutiElisaBortolottiRitaMaggini Department of Agriculture, Food and Environment, Via Del Borghetto, 80, 56124 Pisa, Italy Received 21 September 2015, Revised 24 December 2015, Accepted 26 December 2015, Available online 5 January 2016. crossmark-logo https://doi.org/10.1016/j.scienta.2015.12.052 Get rights and content Highlights • Edible flowers provide an opportunity for food innovation based on the ethnobotanical tradition. • The antioxidant activity of flowers is significantly higher than common leafy vegetables. • Varieties with red and blue flowers have the greatest antioxidant power due to the highest anthocyanin content. • A panel test experiment showed a high biodiversity of sensory profiles. • Some species are likely to be highly popular in a market aimed at taste and health. Abstract The growing need for nutraceutical new foods has generated interest in edible flowers. This flower trait inspired us to conduct experiments aimed at evaluating both the antioxidant activity and anthocyanin content in twelve species commonly used as ornamental plants. The antioxidant power of the edible flowers was very high compared to common vegetables and/or fruits. Except for the low values of Borago officinalis (only 0.5 mmol FeSO4 100 g−1 fresh weight; FW), the antioxidant power in the edible flowers ranged from 3.6 for Calendula officinalis to 70.4 for Tagetes erecta. Part of this high antioxidant activity is often due to their high anthocyanin content at least in the case of the more pigmented flowers (red or blue). For example in the red varieties of Viola × wittrockiana, Dianthus × barbatus, Pelargonium peltatum the high anthocyanin content (12.4, 13.3, 12.5 mg cyn-3-glu eq. 100 g−1 FW, respectively) was associated to a high antioxidant activity. Indeed the best nutraceutical performances (antioxidant and/or anthocyanin values) were shown by more pigmented flowers. A panel test was also carried out in order to evaluate the different degree of the flower’s palatability. This taste evaluation showed a high biodiversity of sensory profiles showing the greatest appreciation for Trapaeolum majus, Ageratum houstonianum and Viola × wittrockiana. Finally, the overlap between nutraceuticals and organoleptic aspects highlighted promising species for a potential market targeting new foods aimed at satisfying both taste and health. Previous article in issue Next article in issue Keywords Antioxidant Anthocyanin Sensory analysis New food Health 1. Introduction The growing interest in nutraceuticals and functional foods has increased research into new foods that are beneficial to health. Thus the studies on fruits (Amagase et al., 2009), herbs (Wojdyło et al., 2007) and seeds (Jayaprakasha et al., 2001) characterized by antioxidant, free radical scavenging and anti-aging activities assume a crucial importance, since these properties are strongly linked to the prevention and care of chronic illnesses such as cardiovascular diseases (Vivekananthan et al., 2003) and cancer (Greenlee et al., 2012). Although flowers were already used as food in ancient Greece and Rome (Melillo, 1994), they have only recently sparked off nutraceutical research (Mlcek and Rop, 2011), focusing on new agronomic and economic horizons (Kelley and Biernbaum, 2000). Their rich pigmentation, which evolved to attract pollinators (Grotewold, 2006), suggests a high antioxidant activity that is of interest for human nutrition. Anthocyanin pigments are primarily involved in this color-mediated attraction strategy and consequently their antioxidant activity (Stintzing and Carle, 2004) makes the flowers an important resource that could be agronomically and nutritionally enhanced. Indeed these pigmented flavonoids are considered a very important category of phytochemicals in plant foods due to their strong antioxidant activity and other beneficial physicochemical and biological properties (De Pascual-Teresa and Sanchez-Ballesta, 2008). Highly pigmented fruits, particularly small berries such as blueberry, blackberry, cherry, raspberry and strawberry fruits, have been studied greatly due to their anthocyanin content and their consequent strong antioxidant activity. The interest in these phytochemicals has grown significantly in recent years due to the evidence that they play a crucial role in counteracting the oxidative stress related to chronic diseases (Li et al., 2012). They are water-soluble compounds that impart color in plants (leaves, stems, roots, flowers and fruits) to appear red, purple or blue according to the pH and their structural features (Fossen and Andersen, 2003). Despite the fact that the main gastronomic use of flowers stems from their attractive color (Kelley et al., 2001a, 2002), there is growing evidence of their role as anti-free radical functional-foods, as is well demonstrated in several ornamental species (Barros et al., 2010; Kaisoon et al., 2011; Navarro-González et al., 2014; Shi et al., 2009). As a source of antioxidants (Chanwitheesuk et al., 2005), edible flowers have also been shown to be effective as antitumor (Ukiya et al., 2002), anti-inflammatory (Ukiya et al., 2006) and antimutagenic (Wongwattanasathien et al., 2010) biological agents. Although the beneficial effects of flowers as a new promising source of mineral elements in human nutrition should not be neglected (Rop et al., 2012), care needs to be taken regarding the anti-nutritional substances that are sometimes produced by some species (Sotelo et al., 2007). In any case, there is an increasing number of ornamental (Mlcek and Rop, 2011) and wild species (Kucekova et al., 2013) grown as edible flowers. Unfortunately, despite their agronomic potential, the idea of eating flowers is still viewed with suspicion. Indeed it involves a kind of neophobia (the reluctance to try novel foods) since often a new food generates an innate distrust (Pliner and Hobden, 1992) especially in children (Dovey et al., 2008). Consequently it is necessary, first of all, to develop nutrition education aimed at proposing flowers as a common food. It is also important to verify consumer tastes when selecting flowers for human nutrition. Although there are some encouraging results on the nutraceuticals of edible flowers, there is little information on their organoleptic appreciation by consumers. The aim of this work is twofold: (i) to analyze the content of antioxidants and anthocyanins in some well-known ornamental species, and (ii) test their organoleptic appreciation by free-tasters. 2. Material and methods 2.1. Plant material Twelve species of cultivated edible flowers (Table 1) were studied. The fresh flowers (Fig. 1) were collected during autumn 2011 (October) and spring 2012 (April) from a greenhouse cultivation in Torre del Lago (LU) in north-west Tuscany, near the sea (43° 85′N, 10° 27′E), in an area called Versilia, where flowers have been grown for ornamental purposes for many decades. The plants were kindly provided by a floriculture company (Carmazzi Farm), which for several years has specialized in the cultivation and sale of edible flowers grown with organic agricultural systems. In brief, this cultivation was carried out in unheated greenhouses during autumn and spring (mean temperature about 15–25 °C) in sandy soil using organic fertilizers and without pesticides. In addition, the agronomic management was conducted without pesticides and/or growth regulating substances. Table 1. Botanical and agronomic information on the tested edible flowers. Species Botanic family Biological cycle Origin Colors Cultivar Ageratum houstonianum Asteraceae Annual Central America Blue Tycoon Blue Antirrhinum majus Scrophulariaceae Perennial Europe, Central America, North Africa Red Montego Red Rose Montego rose White Montego white Begonia semperflorens Begoniaceae Perennial South and Central America, Africa, South Asia Red Eureka Borago officinalis Boraginaceae Annual Mediterranean environment Blue Wild germplasm Calendula officinalis Asteraceae Perennial South Europe Orange Alice Orange Dianthus × barbatus Caryophyllaceae Perennial South Europe, Asia Red Diabunda Red Rose Diabunda Rose White Dulce White Fuchsia hybrida Onagraceae Perennial South America Red Coral Pelargonium peltatum Geraniaceae Perennial Southern Africa Red Tornado Petunia × hybrida Solanaceae Annual South America Red Duvet Red Rose Duvet Pink White Duvet White Tagetes erecta Asteraceae Perennial Central America Orange Moonstruck Tropaeolum majus Tropaeolaceae Perennial South America Orange African Queen Viola × wittrockiana Violaceae Annual Europe, Western Asia Red Delta Pure Red Blue Karma True Blue Yellow Mammoth Prima Yellorina White Mariposa White Download full-size image Fig. 1. Morphology of the tested edible flowers: (1) Ageratum houstonianum, (2) Antirrhinum majus, (3) Begonia semperflorens, (4) Borago officinalis, (5) Calendula officinalis, (6) Dianthus × barbatus, (7) Fuchsia hybrid, (8) Pelargonium peltatum, (9) Petunia × hybrid, (10) Tagetes erecta, (11) Tropaeolum majus, (12) Viola × wittrockiana. The fully open flowers were collected between 08.00 and 10.00 AM and placed in special plastic containers (the same as those used for the packets on sale). Absorbent paper was placed at the bottom of these containers to prevent any lymph leakage due to guttation, thus ensuring optimal conservation. The packs were immediately placed in refrigerator bags and stored at −80 °C on the same day (within 12.00 A.M.). The material was then analyzed within 3–4 weeks from collection. 2.2. Laboratory analysis Both the antioxidant activity and the total content of anthocyanins were expressed on a fresh weight (FW) basis. Flower samples (1 g) were extracted with 10 mL methanol 80% (v/v), containing 1% of HCl, for 12 h at 4 °C. Antioxidant activity was determined on the extracts by the FRAP (ferric ion reducing antioxidant power) assay following Pellegrini et al. (2003). A calibration curve was prepared with increasing concentrations of FeSO4 (reagent grade, Sigma–Aldrich), and results were expressed as mmol FeSO4 100 g−1 FW. Total content of anthocyanins was determined spectrophotometrically (UV-1204 Shimadzu, Tokyo, Japan). by measuring the absorbance of the extracts at 535 nm (Hrazdina et al., 1982). Data were expressed as mg cyn-3-glu eq. 100 g−1 FW. For some of the species under examination (Viola × wittrockiana, Petunia × hybrida, Antirrhinum majus and Dianthus × barbatus), three or four cultivars were available which differed only by the color of the flower. Therefore, the relationship between the color and the antioxidant activity or the concentration of anthocyanins could also be investigated. 2.3. Sensory analysis The sensory panel was carried out in April 2012. Eighty-seven free-tasters (37 males and 50 females, mean age 38 years) were recruited by adverts among the university community (students, teachers, other staff, etc.) from the Department of Agriculture, Food and Environment of Pisa University. In order to evaluate only the real sensory profile of the various flowers, it was decided to get the tasters to examine the flowers without any condiments, bread, crackers, etc. After a careful evaluation of the perceived flavors, the tasters were asked to fill out a questionnaire aimed at determining the performances of the edible flowers. These experiments were based on previous experiences of taste evaluation performed on vegetables (Zhao et al., 2007) and/or fruits (Tobin et al., 2013). Five different organoleptic characteristics (spiciness, sweetness, softness, scent, bitterness) were included in the evaluation scheme and were expressed in a scale of 1–100. The data enabled the sensory profile to be highlighted with spider plots (Johansson et al., 1999). A synthetic evaluation (scale 1–10) for each flower was also required in order to establish the effective degree of appreciation of each species. Finally, tasters were also asked to determine which known food each of the flowers resembled. 2.4. Statistical analyses The experiments were replicated three times in each experimental period (autumn and spring). Analysis of variance (ANOVA) in a completely randomized design and the Student–Newman–Keuls test were used to compare any significant differences between samples. The confidence limits used were based on 95% (P < 0.05). The lack of significance between the data of the laboratory analyses in the autumn and spring enabled them to be grouped into a single media. For the synthetic taste evaluation (scale 1–10), values were expressed as means ± standard deviations. For each statistical analysis, commercial software (CoHort software, Minneapolis, MN) was used. 3. Results 3.1. Nutraceutical analysis Table 2 shows the antioxidant activity and the anthocyanin content of the various edible flowers. The antioxidant power of the edible flowers varied within a very wide range, encompassing two orders of magnitude. The strongest antioxidant activity was displayed by Tagetes erecta, which reached 70.4 mol FeSO4 100 g−1 FW. Similarly, Fuchsia hybrida showed a very high value (although significantly lower), which reached almost 50 mmol FeSO4 100 g−1 FW. Other rather high values were also shown by the red-flowered cultivars of D. barbatus, V. wittrockiana and Pelargonium peltatum, with antioxidant powers of 38.6, 36.5 and 34.7 mmol FeSO4 100 g−1 FW, respectively. Table 2. Antioxidant activity (mmol FeSO4 100 g−1 FW) and anthocyanin content (mg cyn-3-glu eq. 100 g−1 FW) of the edible flowers. The ±standard deviation of the means are shown. Means followed by different letters in the same row are not statistically different for p < 0.05. Species Flower color Antioxidant activity (mmol FeSO4 100 g−1 FW) Anthocyanin content (mg cyn-3-glu eq. 100 g−1 FW) Ageratum houstonianum Blue 27.85 ± 3.3 d 2.99 ± 0.2 d Antirrhinum majus Red 21.18 ± 2.6 d 7.37 ± 0.5 b Rose 9.85 ± 1.1 e 9.73 ± 0.5 b White 4.71 ± 0.6 f 0.70 ± 0.1 f Begonia semperflorens Red 13.24 ± 1.7 e 5.09 ± 0.4 c Borago officinalis Blue 0.55 ± 0.1 g 1.43 ± 0.1 e Calendula officinalis Orange 3.68 ± 0.3 f 0.47 ± 0.1 f Dianthus × barbatus Red 38.67 ± 3.0 c 13.35 ± 1.2 a Rose 29.12 ± 2.3 d 10.61 ± 1.0 a White 4.36 ± 0.8 f 0.73 ± 0.1 f Fuchsia hybrida Red 47.52 ± 3.2 b 7.58 ± 0.6 b Pelargonium peltatum Red 34.78 ± 2.9 c 12.52 ± 1.1 a Petunia × hybrida Red 10.22 ± 0.8 e 14.44 ± 1.2 a Rose 9.45 ± 0.6 e 12.85 ± 1.1 a White 5.40 ± 1.3 f 2.5 ± 1.1 d Tagetes erecta Orange 70.42 ± 4.1 a 0.75 ± 0.1 f Tropaeolum majus Orange 10.05 ± 0.8 e 8.27 ± 0.7 b Viola × wittrockiana Red 36.55 ± 3.0 c 12.4 ± 1.1 a Blue 29.12 ± 2.1 d 13.6 ± 1.2 a Yellow 3.31 ± 0.3 g 2.93 ± 0.2 d White 0.82 ± 0.1 g 0.35 ± 0.1 f Values of the antioxidant power in the range 20–30 mmol FeSO4 100 g−1 FW were found in the pink cultivar of D. barbatus (29.1), in blue flowered V. wittrockiana (29.1) and Ageratum houstonianum (27.8), and in the red variety of A. majus (21.2). Fairly lower results, in descending order, were obtained for red-flowered Begonia semperflorens (13.2) and P. hybrida (10.2), for orange-flowered Trapaeolum majus (10.0), for pink-flowered A. majus (9.8) and P. hybrida (9.4). A weaker antioxidant power was displayed by three white cultivars (P. hybrida, 5.4; A. majus, 4.7; D. barbatus, 4.4), along with Calendula officinalis (orange, 3.7). Finally, the antioxidant activity values of yellow (3.3) and white (0.8) V.wittrockiana, and especially Borago officinalis (blue, 0.5) were the lowest ones among the samples under examination. Similarly to the antioxidant power, the anthocyanin amount showed great diversity depending on the species considered (Table 2). Nevertheless, one third of the flowers had statistically similar high concentrations of anthocyanins, exceeding 10 mg cyn-3-glu eq. 100 g−1 FW. These included the red and pink cultivars of D. barbatus (13.3 and 10.6, respectively) and P. hybrida (14.4 and 12.8, respectively), along with P. peltatum (red, 12.5) and the blue cultivar of V. wittrockiana (13.6). Concentrations ranging from 5 to 10 mg cyn-3-glu eq. 100 g−1 FW were found in the red and pink cultivars of A. majus (7.4 and 9.7, respectively) and in T. majus (orange, 8.3), followed by B. semperflorens (red, 5.1). The range 1–5 mg cyn-3-glu eq. 100 g−1 FW included the similar concentrations of blue A. houstonianum, yellow V. wittrockiana and white P. hybrida (3.0), 2.9 and 2.5, respectively and that of blue B. officinalis (1.4). Extremely low values, below 1 mg cyn-3-glu eq. 100 g−1 FW, were displayed by three white varieties (D. barbatus, 0,7; A. majus, 0,7; V. vittrockiana, 0.3) and two orange cultivars (T. erecta, 0.7; C. officinalis, 0.5). 3.2. Organoleptic performances Fig. 2 shows the sensory profiles of the various edible flowers following the panel test. The same graphic processing of a similar investigation was adopted (Johansson et al., 1999). First of all it should be noted that the color of flowers did not determine any different perception (data not shown) and consequently the data were reported only in relation to the studied species. Download full-size image Fig. 2. Sensory profile (spicy, sweet, soft, scent, bitter expressed as percentage) of the twelve flower species. For this organoleptic test, the flower colors shown in Table 1 were selected. In terms of spiciness, T. majus showed the highest values followed by A. houstorianum, C. officinalis, B. semperflorens and P. peltatum. In contrast, low values were reached by B. officinalis, P. hybrida and V. vittrockiana. As regards the flowers’ sweetness, the species with the best performances were T. majus and B. officinalis and, to a lesser extent, also V. vittrockiana. All other species, except C. officinalis, were not perceived as sweet in the taste test. Flower softness was judged as excellent for T. majus, V. vittrockiana and P. hybrida with almost maximum range values. Satisfactory organoleptic evaluations of softness were also detected in A. majus and P. peltatum. On the other hand, the flowers of A. houstorianum, F. hybrida, D. barbatus, T. erecta and C. officinalis were described as tough. In terms of the flowers’ scent, V. vittrockiana, T. majus and P. hybrida showed an excellent performance since they reached the approximate maximum values. Suboptimal, but however satisfactory results, were found in terms of the scent of A. houstorianum, D. barbatus and B. semperflorens. In contrast A. majus, T. erecta, P. peltatum B. officinalis, F. hybrida and C. officinalis were reported as not being very fragrant. The majority of the species such as B. semperflorens (above all), A. houstonianum, D. barbatus, P. peltatum, F. hybrida, C. officinalis and T. erecta were reported as being notably bitter. Intermediate values of bitterness were reported for P. hybrida, A. majus and V. vittrockiana. B. officinalis and T. majus flowers were considered to be unpleasantly bitter. A comprehensive assessment (0–10 scale) was included in the questionnaire regarding the sensory attractiveness of the different flowers. Table 3 shows these assessments followed by the prevailing reference flavor perceived as similar to a known food. T. majus was regarded the most attractive, since overall it scored 8.3, with a taste that was judged to be similar to radish. This was the highest value among the twelve species tested,and was followed by those of A. haustorianum and V. wittrockiana (7.3 and 7.8, respectively). The flowers of A. haustorianum were associated with the taste of carrot, but V. wittrockiana did not remind tasters of any known food. The flowers of B. semperflorens and B. officinalis were also judged to have a good taste since they achieved ratings of 7.1 and 7.2, respectively. For B. semperflorens, the flower’s flavor was associated with lemon, and B. officinalis with cucumber. D. barbatus, P. hybrida, A. majus, P. peltatum and T. erecta were scored 6.4, 6.3, 62, 6.1 and 6.0, respectively. For P. peltatum, the flavor was defined as unknown. The others (in order of citation respectively) were found to be similar, or at least comparable, to the following: cloves, grass, grapefruit, and pomegranate. Table 3. Synthetic overall evaluation (scale 1–10) and prevailing reference flavor of a known food. The ±standard deviation of the means are shown. Species Tasting evaluation (1–10 scale) Flavor similarity to known food Ageratum houstonianum 7.8 ± 0.4 Carrot Antirrhinum majus 6.2 ± 0.3 Chicory Begonia semperflorens 7.1 ± 0.3 Lemon Borago officinalis 7.0 ± 0.3 Cucumber Calendula officinalis 5.5 ± 0.4 Saffron Dianthus × barbatus 6.4 ± 0.2 Cloves Fuchsia hybrida 5.2 ± 0.3 Unknown Pelargonium peltatum 6.1 ± 0.3 Grapefruit Petunia × hybrida 6.3 ± 0.3 Unknown Tagetes erecta 6.0 ± 0.2 Pomegranate Tropaeolum majus 8.2 ± 0.4 Radish Viola × wittrockiana 7.3 ± 0.3 Unknown Despite C. officinalis was associated with the delicate taste of saffron, it only scored 5.5. Finally, the flowers of F. hybrida were considered to be rather tough and with no known flavor, and thus only scored 5.0. 4. Discussion 4.1. Nutraceutical analysis The antioxidant power of the edible flowers was very high compared with literature data on vegetables and fruits obtained by means of the FRAP assay. For example, a range of 0.02–2.44 mmol FeSO4 100 g−1 FW was reported for a screening of common vegetables (Llorach et al., 2008; Wold et al., 2006). Fruits have often higher antioxidant capacities compared with vegetables. For example, the tissues (peel or pulp) of five different apple cultivars showed values of the antioxidant power in the range from 1.6 to 21.0 mmol FeSO4 100 g−1 FW (Henrìquez et al., 2010). Guo et al. (2003) tested the antioxidant power of 28 fruits commonly consumed in China, distinct for peel, pulp and seed tissues. With the exception of the peel tissue of white pomegranate, which showed an antioxidant power of 82 mmol FeSO4 100 g−1 FW, all the other fruit tissues displayed values of this parameter similar or lower than those that we observed in our samples, ranging from 0.16 (watermelon pulp) to 55.5 (red rose grape seeds). Goji, a fruit originating from Asia whose market has been expanding worldwide during the last decade, was recently found to have an average antioxidant power of 1.9 mmol FeSO4 100 g−1 FW, comparable with those of traditional fruits (Donno et al., 2015). Similarly to goji, non-traditional food that is introduced on the market is often recommended for its nutraceutical properties, such as the antioxidant capacity. Hence, according to our results, edible flowers could be considered as a non-traditional food capable to satisfy this requirement, with an antioxidant capacity that is often similar or higher than those of fruit tissues. For this reason, the agronomic perspective of edible flowers could be similar to that of exotic fruits, like Pitahaya (Le Bellec et al., 2006). In addition, flowers usually display very intense colors that could contribute to increase their appeal toward the consumer (Kelley et al., 2001b). Table 2 shows that the flower’s color plays a role not only on the content of antocyanins, but also on the antioxidant power. Except for B. officinalis, the intense colors of the flowers (especially red and blue) are good indicators for both parameters in the tested flowers. Specifically, red color is generally associated to high values of the antioxidant power and white color to the lowest ones. Indeed the higher values of the red-flowered cultivars, compared to the others, were statistically significant in V. vittrockiana, A. majus and D. barbatus. On the other hand, in P. hybrida both red and pink cultivars displayed a much higher antioxidant power than the white cultivars. The blue color of V. vittrockiana also showed higher values than the lighter colors (yellow and white). These results suggest that the antioxidant activity is partly due to anthocyanins. However, some species with a high antioxidant activity are not characterized by a high anthocyanin content, and consequently this antioxidant power is derived from other phytochemicals. One example is T. erecta, which showed a very low anthocyanin content, in spite of a strong antioxidant power. This imbalance between antioxidant power and antocyanin content indicates, at least in this species, that the high antioxidant activity is primarily due to phytochemicals such as flavonoids, especially quercetin and rutin (Kaisoon et al., 2011). Similarly, V. vittrockiana and T. majus contain antioxidants having a different chemical nature from anthocyanin, such as vitamin C (Proteggente et al., 2002), polyphenols (Paganga et al., 1999; Kaisoon et al., 2012), carotenoids (Rao and Agarwal, 1999), chlorogenic acid (Shi et al., 2009). For example the xanthophyll (lutein) content was found to be high in T. majus flowers (Niizu and Rodriguez-Amaya, 2005), and capable to confer a high antioxidant power to this species (Garzón and Wrolstad, 2009). Moreover, the variety of V. vittrockiana with blue flowers had lower antioxidant power than the red-flowered variety, although both were characterized by a similar concentration of anthocyanins. This suggests the presence of additional antioxidant phytochemicals in the red cultivar, probably carotenoids. In fact in this species, the cultivars with red flowers were found to be rich in carotenoids, as shown by spectroscopy studies (Gamsjaeger et al., 2011). However, in spite of these generally species-dependent phytochemicals, most of the nutraceutical features are also due to color of the flower cultivars, which is strongly linked to pigment content. This fully confirms experiments conducted in flowers of Althaea officinalis, in which a higher antioxidant activity was found in the red flower varieties than in other cultivars with lighter colors. This activity slightly decreases in the pink colored variety and then fell in white flowers (Sadighara et al., 2012). The antocyanin content followed the same trend as a function of the color, decreasing in the order red–pink–white. The results reported in Table 2 also evidence the importance of flower color in terms of anthocyanin content within the same species. As expected, a higher antocyanin concentration in the red or pink cultivars than in the white ones was confirmed in the species under examination: V. vittrockiana (where the blue variety had a similar antocyanin content to the red one), P. hybrida, D. barbatus and A. majus. In any case, as with the antioxidant power, the white color was associated with the lowest values of anthocyanin concentration. In particular, in V. vittrockiana and D. barbatus the anthocyanin contents of the white flowers were well below 10% compared with the related values found in the red ones. 4.2. Organoleptic performances The studied flowers showed a high taste biodiversity. Although the prevailing gastronomic role of flowers is to make the chromatic dishes attractive, they are also able to confer a peculiar taste and improve their palatability. In our screening, C. officinalis and F. hybrida were the only species whose flowers were quite difficult to masticate. This seems the main reason for which the flowers were not greatly appreciated (at least as raw and undressed food, as in the sensory analysis). In all the other species, the preference resulted generally from the overall combination of softness, taste and flavor, although some flowers, such as A. majus, P. hybrida, A. houstorianum and B. officinalis were mainly characterized by only one parameter. On the other hand, T. majus, which had the highest score in the sensory analysis (Table 3), showed a strong spiciness together with sweetness, softness and scent. Its flavor was associated with radish, therefore the taste of this vegetable could be surprisingly perceived in a soft and unusual version. Similarly, both V. vittrockiana and D. barbatus were appreciated for the combination of two features (softness/scent or bitterness/scent, respectively). The appreciation levels of B. semperflorens, P. peltatum and T. erecta, which were strongly dependent on personal taste, were probably due to the unusual taste defined as “acidic”, since their flavors were associated with lemon, grapefruit and pomegranate, respectively. Thus, an additional variety of tastes and aromas provided by edible flowers could increase the biodiversity of sensory profiles that are required to food (Martin et al., 2014; Lease et al., 2015). The combination of flowers with common vegetables or other food could generate new and appreciated tastes (Chambers and Koppel, 2013). Within this frame, possible taste affinities or contrasts with wine could also promote an interest on edible flowers as sensory “elicitors”. For example, recent studies have been published concerning the consumer perception on food-beverage pairings (Paulsen et al., 2015), or the taste interaction between vegetables and wine (Koone et al., 2014). Anyway, the consumption of edible flowers is strongly linked to food education, as taste preference is developed early in childhood (Mennella, 2014). Finally, it is important to underline that the flowers used in this study had been obtained by means of organic cropping. This aspect could play a critical role in order to attract possible consumers toward edible flowers as new food (Kelley and Biernbaum, 2000), since organic cropping can properly preserve and ensure both nutraceutical properties and food safety. 5. Conclusions It is difficult to consider both nutraceutical and organoleptic quality of edible flowers in predicting which species could be the most promising ones in a hypothetical market dedicated to this new food. Organoleptic aspects are subjective and therefore susceptible to change depending on the tastes of the consumers (and on the geographical areas of the world) and also on how the flowers are cooked and seasoned. Nevertheless, there is no doubt that A. houstorianum, B. semperflorens, V. vittrockiana and T. majus are very attractive, and satisfy at the same time health requirements due to their high antioxidant levels. The flowers of T. majushave already been investigated for the postharvest physiology (Friedman et al., 2005) and for the thermal requirements for their storage (Kelley et al., 2003). The cultivars with the most intensely colored flowers (such as red and blue) appear to be the most suited to a gastronomic and nutraceutical evolution in terms of the discovery of new food and new dishes. Moreover they could have an interesting application as natural colorants, representing an alternative to the use of synthetic dyes in foods (Giusti and Wrolstad, 2003). Their organic production appears to be an additional agronomic opportunity that fully meets the future needs of food aimed at improving the quality of human nutrition. Further research will be required to improve other nutraceutical parameters (carotenoids, micronutrients, vitamins, etc.) and to offer them as an additional source of vegetable biodiversity for the future scenario of growing health needs. 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