Impaginato 13 Adv. Hort. Sci., 2020 34(1S): 13­20 DOI: 10.13128/ahsc­7444 Postharvest aptitude of Begonia semperflorens and Viola cornuta edible flowers S. Demasi, N.M. Falla, M. Caser, V. Scariot (*) Department of Agricultural, Forest and Food Sciences, University of Torino, Largo Paolo Braccini, 2, 10095 Grugliasco (TO), Italy. Key words: anthocyanins, antioxidant activity, fresh cut flowers, polyphenols, postproduction, pot plants, shelf­life. Abstract: The edible flowers are sold as pot plants or fresh cut produce and are attracting interest recently thanks not only to their organoleptic characteristics but also to their content in bioactive molecules. However, there is little infor­ mation about the variations that these characteristics undergo during posthar­ vest. In this study, the productivity and longevity of Begonia x semperflorens‐ cultorum Hort. and Viola cornuta L. pot plants were evaluated in an interior environment simulating the house conditions. Besides, the effect of cold stor­ age (4°C) was evaluated on the aesthetic quality and the bioactive compounds content (total polyphenols, total anthocyanins, antioxidant activity through FRAP assay) of B. semperflorens and V. cornuta fresh cut flowers, using two dif­ ferent packaging, modelling a plastic box or a flowpack. The results suggest that V. cornuta could be a better choice for retailers because of its longer shelf life and better maintenance of its content in bioactive compounds, especially in the flowpack packaging. Conversely, B. semperflorens could be more suitable as pot plant, showing more adaptability and flower production in a domestic envi­ ronment. 1. Introduction Numerous flowers have been used in culinary arts since ancient times both in Europe, including Rosa L. spp., Calendula officinalis L., Viola spp., and Taraxacum officinale F.H. Wigg (Mlcek and Rop, 2011; Grzeszczuk et al., 2016; Fernandes et al., 2017; Scariot et al., 2018), and in Asia and South­America, such as Begonia spp. (Laferrière, 1992; Basurto­Peña et al., 2003; Zheng et al., 2018). Nowadays, edible flowers are horticultural niche products, sold as pot plant or as fresh cut flowers, with increasing appeal for the food industry due to their organoleptic and healthy proper­ ties (Kaisoon et al., 2012; Grzeszczuk et al., 2016; Lu et al., 2016). Edible flowers improve the sensorial qualities of food by adding colour, fragrance, flavour and visual appeal to culinary preparations (Kelley et al., 2001a; Mlcek and Rop, 2011; Koike et al., 2015). In the third millennium, several studies revealed the chemical compo­ sition of many wild and cultivated flowers, highlighting the presence of (*) Corresponding author: valentina.scariot@unito.it Citation: DEMASI S., FALLA N.M., CASER M., SCARIOT V., 2020 ­ Postharvest aptitude of Begonia semper‐ florens and Viola cornuta edible flowers ­ Adv. Hort. Sci., 34(1S): 13­20 Copyright: © 2020 Demasi S., Falla N.M., Caser M., Scariot V. This is an open access, peer reviewed article published by Firenze University Press (http://www.fupress.net/index.php/ahs/) and distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Competing Interests: The authors declare no competing interests. Received for publication 13 November 2019 Accepted for publication 4 May 2020 AHS Advances in Horticultural Science http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ http://creativecommons.org/licenses/by/4.0/ Adv. Hort. Sci., 2020 34(1S): 13­20 14 important bioactive compounds, such as carotenoids and phenolics (Lu et al., 2016). These phytochemicals with antioxidant activity are very important for plants, since they inhibit their natural senescence process, mainly caused by the presence of reactive oxygen species (ROS) (Mlcek and Rop, 2011). During metabolism ROS and other free radicals are produced in human body too, normally inactivated by an endogenous antioxidant system (Mlcek and Rop, 2011; Loizzo et al., 2016). However, under stress con­ ditions, in high load situations, because of lifestyle or pathological situations, these free radicals can accu­ mulate, generating oxidative stress (Loizzo et al., 2016) by reacting and damaging all types of biomolecules such as lipids, proteins, carbohydrates, and DNA (Kaisoon et al., 2012). If damaged DNA is left unrepaired, it may become cancerous (Mlcek and Rop, 2011; Kaisoon et al., 2012; Li et al., 2014). Thus, a diet rich in antioxidants, which can scavenge free radicals, can reduce the oxidative stress and may be a strategy to prevent some chronic conditions (Kaisoon et al., 2012; Loizzo et al., 2016; Lu et al., 2016). Epidemiological data showed that dietary pat­ terns were significantly associated with the preven­ tion of these chronic diseases, especially when rich in antioxidants (Kaisoon et al. , 2012), including carotenoids and phenolics (Koike et al., 2015; Grzeszczuk et al., 2016). As a result of the increased knowledge of the edi­ ble flowers’ properties, the consumers’ demand of this kind of product is increasing worldwide (Fernandes et al., 2017; Pires et al., 2019; Falla et al., 2020), thanks to the increased attention to the quali­ ty of foodstuffs and to the content of individual com­ pounds (Rop et al., 2012; Lu et al., 2016). However, edible flowers are highly perishable and have a short shelf life (petal abscission and discol­ oration, flower wilt, dehydration, and tissue brown­ ing start to appear 2­5 days after harvest), which lim­ its their marketability (Koike et al., 2015; Fernandes et al., 2018). Fresh cut edible flowers are typically packaged in small, rigid, plastic boxes, in order to protect them from desiccation and to preserve their frail structure (Kelley et al., 2003; Kou et al., 2012). It is noteworthy that consumers eat with their eyes well before they taste with their mouths, thus it is important to maintain the visual appeal of a flower on market; quality is essential: consumers want more varieties of top quality plants with a longer shelf life (Kelley et al., 2001 b). Nevertheless, edible flower’s postproduction technology still receives less atten­ tion than that of other horticultural products, such as vegetables and fruits, because edible flowers’ pro­ duction is still low and it is a niche market (Fernandes et al., 2018). Temperature is usually the most important envi­ ronmental factor limiting shelf life of horticultural products (Kelley et al., 2003): both respiration and transpiration processes are considered as the major causes of postharvest losses and poor quality in pro­ duce. Thereby, controlling temperature of storage is very important since these factors directly influence the two metabolic processes mentioned above, extending the product’s shelf life (Flores­López et al., 2016). A flower’s short shelf life may cause not only a rapid decrease in visual quality, but also a rapid loss of its nutraceutical compounds, however very few articles reported the effects of storage on quality of edible flowers, and even less investigated these effects on their nutraceutical compounds (Landi et al., 2015). Therefore, it would be interesting to deep­ en the knowledge on whether the loss of nutraceuti­ cal compounds in edible flowers during storage occurs more or less quickly than the loss of visual quality. This information could promote the con­ sumption of edible flowers at visual quality levels less than perfect, with minor flaws (Kelley et al., 2001 b). Thus, the aim of this work was to evaluate two common edible flowers’ species (Begonia x semper‐ florens‐cultorum Hort., commonly referred to as Begonia semperflorens, and Viola cornuta L.) as 1) pot plants, by evaluating the productivity and longevity in an interior environment simulating the domestic conditions; and 2) fresh cut flowers by eval­ uating the shelf life and the content in biologically­ active compounds (total polyphenols, anthocyanins) and antioxidant activity, when stored at 4°C, testing two types of packaging (a plastic box closed with its own lid or closed with a plastic film in a flowpack). 2. Materials and Methods Pot plant postproduction The potted flowering plants of Begonia semperflo‐ rens (10 plants) and Viola cornuta (36 plants) were obtained from the nursery Fratelli Gramaglia (Collegno, Italy; 45°05’22.4’’ N, 7°34’26.4’’ E, 302 m a.s.l.). Plants were kept at room temperature (about 20°C), in a peat­based substrate, hand­watered when needed, throughout the harvest period: 30 days for begonias and 11 days for violas. Every two days Demasi et al. ‐ Edible flowers post‐harvest quality 15 opened flowers were harvested and weighed to eval­ uate the flowering longevity and productivity. For each plant, the number of flowers produced was counted and the weight of flowers suitable to be con­ sumed (opened flowers in good visual conditions) was calculated: namely each plant’s productivity. Fresh cut flower postharvest Fresh flowers harvested when fully open and in good visual conditions were put into plastic packages (Ondipack 250 cc, 123x114x50 mm, polypropylene, Plemet, France), 5 g of flowers for each box (Fig. 1). Two packaging methods were assessed, for both species: ­ Plastic box closed with its own plastic lid (abbr. PP; 8.96 g); ­ Plastic box without its lid, inserted into a bi­orient­ ed polypropylene plastic film (abbr. BOPP; 6.04 g). The plastic films were folded and closed on three sides through heat­sealing (FR400, Ferplast, Cuneo, Italy), modelling a flowpack. Flowers were stored at 4°C, in refrigerators with a glass door [Fiocchetti fridge, Luzzara (RE), Italy], sim­ ulating markets’ shelves conditions, with four repeti­ tions per packaging type. Every two days, each package was weighed, in order to obtain data about the flowers’ weight varia­ tion. The visual appeal of flowers was scored on a 9­ point scale based on visual observation of the degree of decay (Aquino­Bolaños et al., 2013; Landi et al., 2018), where 9 was assigned to flowers without imperfections, 5 was the limit of marketability of the product (the limit of acceptability for the consumer), while 1 was the value of a decomposing flower, at the end of its life cycle. Ultrasound extraction At the beginning of the trial, so that the day of harvest (t0) could be represented, about 5 g of flow­ ers of both B. semperflorens and V. cornuta were col­ lected from pot plants; the same was done after stor­ age, when the flowers reached grade 5 of the visual scale. One of the four packages stored per method was taken and the 5 g of flowers contained in it were stored at ­80°C until analysis. Flower samples were grinded with liquid nitrogen, then 0.5 g of grinded plant material were put into a glass tube, to which 25 ml of a 50% aqueous MeOH (methanol) solution were added. Three repetitions were carried out for each sample. The tubes were put into the ultrasound extractor (23 kHz, Reussarl, Drap, France) for 15 min­ utes at room temperature. The obtained phyto extract was filtered with paper filters (Whatman filter papers No. 1, Whatman, Maidstone, UK) and the obtained solution was stored at ­20°C for further analysis. Total polyphenols The total phenolic content was determined fol­ lowing the Folin­Ciocalteu method (Singleton et al., 1999). The analysis was performed as follows: 750 µl of diluted 1:10 Folin reagent were mixed with 150 µl of phytoextract and 600 µl of Na2CO3 (7.5%) in each plastic tube. Samples were left in the dark at room temperature for 30 minutes. Absorbance was mea­ sured at 765 nm by means of a spectrophotometer (Agilent Technologies, Cary 60 UV­Vis, Santa Clara, CA, United States), and the results were expressed in milligrams of gallic acid equivalents per 100 g of fresh weight (mg GAE/100 g FW). Total anthocyanins The total anthocyanin content in the extracts was determined through the pH­differential method as indicated by Lee et al. (2005) and Giusti and Wrolstad (2005). The analysis was performed as follows: 1 ml of phytoextract was put into a 10 ml flask, and then made up to volume with an aqueous buffer solution at pH 1 (KCl and HCl). The same was made in a sec­ ond flask with an aqueous buffer solution at pH 4.5 (C2H3NaO2and C2H4O2). Samples were put in the dark at room temperature for 20 minutes. Absorbance of both flasks was measured at 515 nm and 700 nm by means of a spectrophotometer (Agilent Technologies, Cary 60 UV­Vis, Santa Clara, CA, United States), and the results were expressed in milligrams of cyanidin­3­O­glucoside per 100 grams of fresh weight (mg C3G/100 g FW). Fig. 1 ­ Flowers of V. cornuta (A) and B. semperflorens (B) freshly harvested and put in the plastic package. Adv. Hort. Sci., 2020 34(1S): 13­20 16 Fig. 2 ­ Flower production of B. semperflorens (red) and V. cor‐ nuta (purple). Data are shown in a cumulative curve. Antioxidant activity ‐ FRAP assay The method used to evaluate the antioxidant activity is the FRAP (Ferric ion Reducing Antioxidant Power) assay as indicated by Benzie and Strain (1996). The antioxidant activity was determined mixing 30 µl of phytoextract with 90 µl of deionised water and 900 µl of FRAP reagent. The samples were then placed at 37°C for 30 minutes. Absorbance was mea­ sured at 595 nm by means of a spectrophotometer (Agilent Technologies, Cary 60 UV­Vis, Santa Clara, CA, United States). Results were expressed as mil­ limoles of ferrous iron equivalents per kilogram of fresh weight (mmol Fe2+/kg FW). Statistical analysis All data were subjected to the statistical analysis for the homogeneity of variance (Levene test). Weight variations were compared using a one­ way ANOVA test. Mean comparisons between data obtained from the two different packages during postharvest were performed using an independent samples t­test, by means of the SPSS 25 software (version 25.0; SPSS Inc., Chicago. Illinois). 3. Results Pot plant productivity Begonia semperflorens and V. cornuta pot plants showed differences in the number of flowers pro­ duced over time. On average, from the day of arrival at the laboratory, plants of B. semperflorens pro­ duced flowers for 30 days (with an initial production of about 38 flowers per plant, and a final production of 1­2 flowers per plant) (Fig. 2), with an average total productivity of 11 flowers per plant per day. Pot plants of V. cornuta bloomed for 11 days (starting with an average of 21 flowers per plant up to 3­4 flowers per plant) (Fig. 2), with an average total pro­ ductivity of 9 flowers per plant per day. Cut flower shelf life As shown in figure 3, the shelf life of B. semperflo‐ rens and V. cornuta assessed at 4°C is quite different: the first species reached the limit of marketability (grade 5) after 9 days (both in PP and in BOPP) (Fig. 3, red lines), while the viola flowers remained accept­ able for the consumer up to two weeks (both for PP and for BOPP) (Fig. 3, purple lines). During storage up to grade 5, the flowers did not show significant weight variations in both packaging type (Table 1). Bioactive compounds The total polyphenol and anthocyanin content, and the antioxidant activity (FRAP) of B. semperflo‐ rens and V. cornuta’s flowers are reported in Table 2. Values are referred to flowers freshly picked, corre­ sponding to grade 9 (t0), and after storage at 4°C, when they reached grade 5 of the visual scale (i.e. limit of marketability), that corresponded to 9 days for begonias and 16 days for violas (Fig. 3). Comparisons aimed to highlight flower differences between the two species and along time within the same packaging and between the two types of pack­ aging (Table 2). Variations are visualized in figure 4. Concerning the pot plants, V. cornuta flowers at t0 showed higher values of both polyphenols (p<0.001) and antioxidant activity (p<0.001) than B. semperflo‐ rens, while this latter showed a higher content in anthocyanins (p<0.05) than V. cornuta. Fig. 3 ­ Trend of visual quality during storage for B. semperflo‐ rens (red) and V. cornuta (purple). Data are shown as mean values. The intersection of the curves with the dot­ ted horizontal line corresponds to the marketability limit (grade 5). PP= plastic box + lid; BOPP= Plastic box without its lid, inserted into a bi­oriented polypropylene plastic film. Demasi et al. ‐ Edible flowers post‐harvest quality 17 Regarding the bioactive compound’s evaluation during the post­harvest, begonia flowers kept in PP encountered a decrease of all parameters (polyphe­ nols: ­45.78%; anthocyanins: ­85.33%; antioxidant activity: ­52.35%) while in BOPP only the antho­ cyanins decreased (­99.44%). Viola flowers kept in PP encountered an increase in anthocyanins (+202.5%) and a decrease of antioxidant activity (­34.21%) while total polyphenols were constant (Table 2). In BOPP all the parameters decreased (phenolic content ­ 76.51%, antioxidant activity ­88.05%, anthocyanins ­ 32.52%). Table 1 ­ Flower weight variation during cold storage (4°C) up to the grade of marketability Table 2 ­ Total polyphenols, total anthocyanins, and antioxidant activity (FRAP) at grade 9 (day of harvest) and grade 5 (i.e. limit of marketability, corresponding to 9 days for begonias and 14 days for violas) of visual quality scale of B. semperflorens and V. cornuta flowers stored at 4°C in two different packaging PP= plastic box + lid; BOPP= Plastic box without its lid, inserted into a bi­oriented polypropylene plastic film). Data are shown as mean values. Comparisons between data were performed using a one­way ANOVA analysis. PP= plastic box with its own lid; BOPP= flowpack. Data are shown as mean values. * p≤0.05. ** p≤0.01. *** p≤0.001. Mean comparisons between data were performed using an independent samples T­test. Flower species Day Weight (g) PP Weight (g) BOPP Begonia semperflorens 0 5.25 5.04 2 5.25 5.04 4 5.25 5.03 7 5.24 5.18 9 5.23 5.01 p NS NS Viola cornuta 0 5.18 5.43 2 5.18 5.43 4 5.14 5.44 7 5.16 5.47 9 5.12 5.41 11 5.10 5.40 14 5.17 5.38 16 5.17 5.37 p NS NS Flower species Packaging Total polyphenols (mg GAE/100 g FW) Total anthocyanins (mg C3G/100 g FW) Antioxidant activity FRAP (mmol Fe²⁺/kg FW) Grade 9 Grade 5 p Grade 9 Grade 5 p Grade 9 Grade 5 p Begonia semperflorens PP 246.71 133.75 ** 378.67 55.57 *** 95.23 45.38 ** BOPP 246.71 264.77 NS 378.67 2.12 *** 95.23 83.49 NS p ‐ *** ­ *** ­ *** Viola cornuta PP 767.26 877.01 NS 27.76 83.99 ** 391.89 257.84 * BOPP 767.26 180.26 *** 27.76 18.74 * 391.89 46.83 * p ‐ * ­ ** ­ * Fig. 4 ­ Percentage variation of the content of A) total anthocya­ nins, B) total polyphenols, C) antioxidant activity (FRAP) in B. semperflorens (red) and V. cornuta (purple), up to grade 5 of visual quality scale, depending on the type of packaging (stored at 4°C). The statistical analyses were made separately on B. semperflorens and V. cornuta values. Mean comparisons between data were perfor­ med using an independent samples T­test. * p≤0.05. ** p≤0.01. ***p≤0.001. Axis 0 uses the t0 value as a refe­ rence. PP= plastic box + lid; BOPP= Plastic box without its lid, inserted into a bi­oriented polypropylene plastic film. 18 Adv. Hort. Sci., 2020 34(1S): 13­20 4. Discussion and Conclusions This study aimed to evaluate the aptitude of two common edible flower species, i.e. B. semperflorens and V. cornuta, to be sold as pot plants or fresh cut flowers. The growing conditions adopted in this study (i.e. 18­20°C and low lighting) were useful to simulate the maintenance of pot plants in a domestic environ­ ment, so to give information on productivity to the final consumer. These conditions are unlikely to be fully appropriate, especially for violas. Indeed, V. cor‐ nuta plants are more productive at temperatures from 4 to 10°C (Ball, 1991; Nau, 1998). Cooper and Watson (1952) noticed that flowers sizes are also big­ ger when plants grow at night­time temperatures of 10°C. A frequent harvest could concur to cause a gen­ eral reduction in productivity and in flowers size too. In this study, where flowers were picked every 2­3 days, a change in flowers weight was observed. Begonia flowers weighted 0.5­0.6 g at the beginning of the experiment and 0.3­0.4 g at the end, while viola flower varied from 0.2 g to 0.1 g. Begonias flow­ ers, moreover, showed petals discoloration during the last days of harvest. Few data are available in literature about B. sem‐ perflorens and V. cornuta so that comparisons with results of other studies are difficult. Some informa­ tion could be found in other congener species. Low temperature (4°C) and natural lighting during storage mimed the retailer conditions. Data about B. semper‐ florens agreed with those assessed by Friedman et al. (2007) in flowers of Begonia elatior and B. semperflo‐ rens that were stored in plastic trays for about ten days at 2­5°C. Viola cornuta shelf life was in accor­ dance with the data found by Kelley et al. (2003) in Viola wittrockiana, that was considered marketable after two weeks of storage at 5°C. Regarding the phy­ tochemical content, results were partially discordant with those found by Benvenuti et al. (2016) in V. wit‐ trockiana that showed a higher antioxidant activity but also a higher anthocyanins content than B. sem‐ perflorens. Results of works that evaluated the content of edible flower phytochemicals during cold storage are sometimes conflicting. Aquino­Bolaños et al. (2013) observed a reduction in the nutraceutical values of squash (Cucurbita pepo L.) edible flowers, conversely Friedman et al. (2007) found no differences in antho­ cyanins content in B. semperflorens flowers. Landi et al. (2018) analysed B. semperflorens flowers too, finding a general constancy in the nutraceutical val­ ues during storage. Data obtained in this study showed that the phytochemical content of B. sem‐ perflorens decreased during storage in the plastic box closed with its own lid, while in the flow pack the total phenolic content, and the antioxidant activity, remained constant. The best way to store flowers of B. semperflorens could be therefore the flowpack, preferably a perforated one to prevent condensation of vapours on their inner surface (Mlcek and Rop, 2011). Conversely, V. cornuta flowers seemed to bet­ ter preserve its characteristics in the plastic box closed with its own lid, showing a certain constancy in polyphenols and antioxidant activity, and a signifi­ cantly increased level of anthocyanins, while in the flow­pack showed a significant reduction in all three parameters. In conclusion, our data confirm that B. semperflo‐ rens and V. cornuta are suitable for edible flower pro­ duction both in term of shelf life and phytochemical characteristics. Begonia semperflorens seems prefer­ ably marketable as pot plants, thanks to its better adaptability to grow in the domestic environment and longer flowering. Conversely, V. cornuta flowers resulted more suitable as fresh cut produce, showing a longer shelf life and preserving better the phyto­ chemical characteristics during storage at 4°C. New technological approaches (ethylene inhibitors, modified atmosphere packaging, edible film coatings, high hydrostatic pressure, irradiation, etc.) could further improve the distribution and mar­ keting efficiency of edible flowers, contributing to their success in the market (Fernandes et al., 2018). 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