Edible flowers’ flavor, safety and their utilization as functional ingredients: a review

Abstract

Edible flowers have been a part of various traditional dishes around the world. The consumption of edible flowers has been rising due to their nutritional properties, minerals, antioxidants, phenolic and bioactive compounds, therapeutic properties, and also aesthetic appeal. Along with the nutrients, some antinutrients and other chemical, biological, microbial hazards may render flowers non-edible. The components responsible for flavor in edible flowers are different from species to species. Bioactive compounds play a major role in sensory attributes of edible flowers. Various functional food products such as bakery items, dairy products, beverages etc. can be developed by incorporating edible flowers. Understanding various properties of edible flowers, their safe consumption, and utilization as functional ingredients in the development of various food products is not only useful but also necessary to popularize edible flowers for novel applications. It is important for food safety experts to recognize and reduce the risks connected with edible flowers.

Graphical abstract

Introduction

Edible flowers are widely consumed due to their potential to cater beneficial health effects. Flowers can also provide sensory attributes to food, for example garnishing, enhance flavor of dishes, liqueurs, vinegar or oils, and serving as ingredients for jam, jellies, salads, soups, desserts, breads, cakes, cheeses, curry, tea, syrups or infusions. Different species of roses (Rosa spp.) were used for cooking puree and omelets in ancient Rome (Mlcek et al., 2011). In Mexico, hibiscus flowers were used in preparing drinks (Nicolau and Gostin 2016). Many countries around the world (China, India, Thailand, Mexico, Central Europe, etc.) have a history of using edible flowers in their traditional cuisines (Newman et al. 2009), typically eating edible flowers fresh or processed (such as in curry, steamed, boiled, or deep-fried, etc.). There are more than 97 families belonging to hundreds of genera and 180 species of edible flowers available worldwide (Lu et al. 2016). Edible flowers are flowers that are non-toxic and innocuous (Guiné et al. 2021). Edible flowers used for consumption must be free from diseases and chemical treatments. Flowers like broccoli, cauliflower, artichoke, and capers, which are commonly used on a day-to-day basis, are often misunderstood as vegetables by most consumers. Traditionally edible flowers were believed to cure various health issues. Edible flowers also exhibit medicinal properties such as antitumor, anti-inflammatory, antimutagenic (Benvenuti et al. 2016), antibacterial, antifungal and antiviral properties.

Nutritional composition of edible flowers is reported to have polyphenols, anthocyanins, flavonoids, anthocyanin, carotenoids, protein, carbohydrates, saturated and unsaturated lipids, sugars, organic acids, minerals (Iron, copper, zinc, potassium etc.) (Zhang et al. 2011) and vitamins (tocopherols, ascorbic acid and phylloquinone) etc. Various phenolic acids reported in edible flower are gallic acid, chlorogenic acid, p-hydroxybenzoic acid, and p-coumaric acid; and flavonoid groups such as anthocyanins, flavanones and flavones (Zheng et al. 2019 and Morais et al. 2019). It is important to note that the nutritional composition of flowers can vary from specie to species. The development of functional food products using edible flowers is currently trending. Edible flowers offer several functional properties that enhance their desirability for culinary use. They provide colors, flavors, exotic aromas, delightful tastes, and texture variations, while also enhancing the nutritional value of dishes. Due to the presence of various health-promoting chemical compounds, flowers have functional properties that promote health protection, such as antioxidant, anti-aging, anti-inflammatory, antimicrobial, anticancer, neuroprotective and antidiabetic effects etc. Recent reviews have extensively discussed the nutritional composition and functional properties of edible flowers, as highlighted by Pires et al. (2019), Prabawati et al. (2021), and others. Flavor is an important quality of edible flowers, though it differs from species to species. The flavor compounds present in the flowers are mostly volatile and are likely to be lost during processing. However, techniques such as steam distillation, supercritical extraction, maceration, simultaneous fermentation, pentane extraction or the enfleurage process can extract flavor compounds from elder flowers (Sambucus nigra L.) extract (Jørgensen et al. 2000).

Although edible flowers are highly nutritious and beneficial to human health but their consumption is mostly confined to traditional dishes. This might be due to the lack of awareness among consumers regarding the identification of edible flowers and their health beneficial properties. This review addresses edible flowers that are not popularly used for consumption, with a special focus on the flavor attributes and the safety of edible flowers and as well as their applications in the development of functional food products.

Flavor of edible flowers

Edible flowers deliver nutritional properties along with flavor and color. Flavor is the outcome of two broad classes of compounds, with one responsible for taste and the other for odor/aroma. Together active compounds from these two classes provide the impression of flavor for food by stimulating senses in the mouth and nose. Taste, delightful fragrance and visual appeal of a flower along with organoleptic properties such as sweetness, spiciness, aroma, and bitterness etc. can attract a consumer (Knudsen et al. 2006). Implementing metabolic engineering can enhance the aroma and flavor of fruits and flowers. A flower usually contains a range of complex chemical substances including compounds like aliphatics, benzenoids, phenylpropanoids, and terpenes (mono- and sesquiterpenes) which provide a particular scent in a flower (Knudsen et al. 2006). When fresh flowers undergo various processing treatments, it affects their color and flavor. Understanding the flavor profile of edible flowers can help in their valorization, application in functional food formulations and also in the aroma industry. Table 1 showed the aroma/odor compounds (fragrance) or flavor found in some common edible flowers.

Table 1.

. Aroma/odor compounds (fragrance) or flavor similarity of some common edible flowers

Sl no	Flowers with scientific name and common name	Aroma/odor compounds (fragrance) or flavor similar to	References
1	Abelmoschus aesculentus Okra, gumbo, gombo	Mild, sweet and slightly mucilaginous	Nicolau and Gostin (2016)
2	Agastache foeniculum Anise hyssop	strong anise, sweet, lico rice
3	Alcea rosea Hollyhock	Slightly bitter
4	Allium schoenoprasum Chive	Onion, strong
5	Allium tuberosum Garlic chive	Onion, strong
6	Anethum graveolens Dill	Stronger than leaves
7	Anthemis nobilis English chamomile	Sweet apple flavor
8	Anthriscus cerefolium Chervil	Parsley-like, hint of citrus, tarragon
9	Begonia x tuberhybrida Tuberous begonia	Citrus
10	Ageratum houstonianum	Carrot	Benvenuti et al. (2016)
11	Antirrhinum majus	Chicory
12	Begonia semperfloren	Lemon
13	Bellis perennis English daisy	Mild to bitter	Nicolau and Gostin (2016)
14	Borago officinalis Borage	Cucumber
15	Brassica spp. Broccoli, cauliflower	Broccoli
16	Brassica spp. Mutards	Mutards, hot
17	Calendula officinalis Calendula, pot marigold	Tangy and peppery
18	Carthamus tinctorius Safflower, American safflower, saffron	Bitter
19	Cercis Canadensis Redbud	Beanlike to tart apple
20	Chrysanthemum coronarium Garden chrysanthemum, shungiku	Tangy, slightly bitter
21	Chrysanthemum leucanthemum Oxeye daisy	Faint peppery to mild cauliflower
22	Cichorium intybus Chicory	Pleasant, mild-bitter similar to endive
23	Citrus limon Lemon	Citrus, slightly bitter/sweet floral
24	Citrus sinensis Orange	Citrus, sweet/ strong
25	Coriandrum sativum Coriander	Like leaf but milder fragrant
26	Cucurbita spp. Squash or pumpkin	Mild, raw squash slightly floral
27	Cynara scolymus Artichoke	Atichoke
28	Dendranthema x grandiflorum Chrysanthemum	Varieties differ, strong to bitter pungent
	Dianthus × barbatus	Cloves	Benvenuti et al. (2016)
29	Dianthus spp. Dianthus or pinks	Spicy, cloves	Nicolau and Gostin (2016)
30	Eruca vesicaria Rocket, arugula	Nutty, smoky, less piquant than leaves
31	Feijoa sellowiana Pineapple guava	Floral flavor; papaya or exotic melon
32	Foeniculum vulgare Fennel	Licorice, milder than leaves, sweet
33	Galium odoratum Sweet woodruff	Sweet, grassy, vanilla
34	Hemerocallis fulva Daylily	Cooked, combination of asparagus/ zucchini
35	Hibiscus rosa-sinensis Hibiscus, China rose, Rose-of-China	Citrus/cranberry flavor
36	Hibiscus syriacus Rose-of-Sharon	Mild, nutty
37	Hyssopuso fficinalis Hyssop	Bitter; similar to tonic
38	Lavandula angustifolia Lavender	Highly perfumed/floral
39	Levisticum officinale Lovage	Mild celery
40	Malus spp. Apple	Slightly floral to sour
41	Melissa officinalis Lemon balm	Lemony, sweet
42	Mentha spp. Mint	Minty; milder than leaves
43	Monarda didyma Bergamot, bee balm, Oswego tea	Tea-like, more aromatic than leaves/sweet, perfumed
44	Muscari atlanticum, M. botryoides, Grape hyacinth	Grapey, slightly sour with bitter aftertaste
45	Nepeta × faassenii	Strong aromatic	Marchioni et al. (2020) Nicolau and Gostin (2016)
46	Ocimum basilicum Basil	Milder than leaves, spicy
47	Ocimum × citriodorum Vis	Lemon peel
48	Origanummajorana Marjoram	Spicy, sweet
49	Origanum spp. Oregano	Spicy, pungent-like leaves	Nicolau and Gostin (2016)
50	Pelargonium odoratissimum (L.)	lemon
51	Pisum sativum Garden pea	Raw peas
52	Poterium sanguisorba Burnet	Cucumber
53	Prunus spp. Plum	Mild, like flower nectar/sweet
54	Raphanus sativus Radish	Spicy
55	Rosa spp. Rose	Highly perfumed; sweet to bitter/rose
56	Rosmarinus officinalis Rosemary	Mild rosemary
57	Salvia discolour Kunth	Black currant and pine nut Floral and fruity	Marchioni et al. (2020)
58	Salvia elegans Pineapple sage	Pineapple/sage overtones	Nicolau and Gostin (2016)
59	Salvia officinalis Garden sage	Flowery sage, slightly musky
60	Satureja hortensis Summer savory	Mildly peppery, spicy
61	Satureja montana Winter savory	Mildly peppery, spicy
62	Syringa vulgaris Lilac	Perfume, slightly bitter
63	Tagetes erecta African marigold	Variable; some cultivars are strong and bitter/strong, pungent
64	Tagetes tenuifolia Signet marigold	Citrus; milder than T. erecta
65	Taraxacum officinale Dandelion	Bitter
66	Thymus spp. Thyme	Milder than leaves
67	Trifoliumpratense Red clover	Hay
68	Tropaeolum majus Nasturtium	Watercress, peppery
69	Tulbaghia violacea Society garlic	Onion flavor
70	Viola odorata Violet	Sweet
71	Viola x wittrockiana Viola tricolor Pansy or Johnny Jump-Up	Stronger than violets
72	Yucca filamentosa Yucca	Hint of artichoke, slightly bitter

Sensory attributes of edible flowers are generally influenced by bioactive and volatile compounds. The best flavor of a flower can be indulged by picking early in the daytime during full bloom season. Different edible flowers comprise a variety of tastes which vary in intensity from species to species (Fernandes et al. 2019). Bioactive compounds have a major role in sensory attributes of edible flowers because phenolic compounds are linked to a flower’s color, bitterness, and astringency (Ferrer et al., 2014). For example, tannin and flavonoids provide astringency and bitterness respectively. Various volatile compounds such as terpenes, esters, alcohols, carbonyls, and alkanes together can provide a distinctive flavor to flowers. Furthermore, the volatility of aroma compounds and taste of edible flowers are also affected by nonvolatile compounds such as phenolic compounds, sugars, and organic acids.

The volatile compounds present in edible flowers vary significantly. Terpenes are the major chemical constituent among flowers of calendula, johnny jump up, pansy, cosmos and borage (Fernandes et al. 2019). However, the types of terpenes present in them vary. Limonene was found in pansy, α-thujene followed by α-pinene is in calendula, in borage and cosmos ρ-cymene was present and johnny jump up contains β-myrecene and limonene. Ethyl benzoate delivers wintergreen or mint like pleasant odor (Yuan et al. 2014). It was the most abundant ester found in flower of borage and johnny jump up where 16 and 9 ester compounds were detected in them respectively. 1-hexanol and (Z)-3-hexen-1-ol were detected under the alcoholic group. A small amount of aldehyde such as nonanal in cosmos and borage, phenylacetaldehyde in johnny jump ups and (E)-2-octenal in pansies was found to be present. In case of ketones, low amount of 6-methyl-5-hepten-2-one was identified in cosmos, johnny jump ups, and pansies. Calendula, Johnny Jump Up, Pansy, Cosmos possesses “dodecane” which is an aliphatic hydrocarbon. Veratrole which is a colorless liquid possess a pleasant odor found in Johnny Jump up and aromatic hydrocarbon such as ρ-xylene detected in Cosmos and Pansies. Different types of sesquiterpenes are present in flowers such as in calendula several sesquiterpenes i.e., β-bourbonene and α-muurolene; α-caryophyllene and oxide in Johnny Jump up; longifolene in Pansies; α-guaiene in cosmos and β-caryophyllene were found abundantly in both flowers of Pansie and Cosmos.

Jasmine flowers contain a higher number of volatile compounds than France Rose buds and Osmanthus as reported by Hussain et al., (2019). Tea infusions of France Rose Buds were found to have 5 volatile compounds, with phenylethyl alcohol comprising 57.12%. This compound has an odor resembling roses, imparting a slightly bitter to sweet flavor reminiscent of peach. Other volatile compounds, such as 1-Iodo-2-methylundecane (15.75%), tridecane (3.22%), cis-2-Methyl-7-octadecene (3.18%), and 1-Iodo-2-methylnonane (2.67%), classified as hydrocarbons, were detected in this tea infusion. Tea infusions of jasmine flower and osmanthus flower showed some common volatile compounds such as Benzyl benzoate (6.81%) and 1,6-Octadien-3-ol,3,7-dimethyl- (3.81%) or linalool. In case of jasmine flowers there were 13 constituents identified linalool (25.01%), benzyl acetate (23.71%) and 3-hexenyl acetate (13.80%). Also, pregna-5, 14-diene-3, 20-diol-18-carboxylic acid, 3-acetate-, lactone were detected. It has been mentioned that the composition of volatile compounds in the flower might vary due to genetics, soil, climate, and agricultural practices, and different parts of flowers contain different volatile compounds.

Benvenuti et al. (2016) revealed in their study that edible flowers contribute to taste biodiversity, each having a peculiar taste. For example, Petunia × hybrida, Antirrhinum majus, and Viola × wittrockiana are moderately bitter, whereas Borago officinalis and Tropaeolum majus flowers have a higher concentration of bitterness that is displeasing in taste. It was reported that elderberry species’ flowers could possess high levels of sugars such as fructose and glucose. Also, Sambucus nigra and the hybrid ((Sambucus javanica × Sambucus nigra) × Sambucus cerulean) contained high levels of total sugars, making them a natural source of sweet-tasting infusions (Mikulic-Petkovsek et al. 2016). Borage has a higher concentration of esters, which confer fruity fragrances, but floral and green fragrances can also be found, possibly due to the presence of ethyl octanoate and 1-hexanol (Fernandes et al. 2019).

After harvesting, the retention of aroma compounds and other nutritional compounds of flowers differs from species to species. Different post-harvest treatments affect the properties of volatile compounds in flowers differently. Drying flowers might result in low retention of bioactive compounds. A study (Xu et al. 2022a) conducted on blanching pretreatments, such as steam blanching, high-humidity hot air impingement blanching, and vacuum-steam pulsed blanching before drying on Peony (Paeonia lactiflora Pall.) flowers, found retention of volatile compounds after 1 min of blanching. Abbas et al. 2021 conducted an experiment to examine the influence of various drying methods such as shade for 1 week; sunlight for 72 h; oven at 40 °C for 72 h; solar dryer for 72 h; and microwave for 5 min on the essential oil of chamomile (Matricaria chamomilla L.) and its chemical composition. It was reported that the highest amount of oil was observed after solar drying, and the lowest amount was found after microwave drying. Due to volatilization the loss of essential oil was occurred in microwave drying and shade drying stood to be the best among these drying methods in terms of preserving color, appearance, and chemical oil composition.

Xu et al. (2022b) revealed that drying methods adopted to enhance the storability of flowers could influence the aroma profile of dried flowers. It is better to adopt a suitable drying method for the optimal retention of aroma components. A study conducted on effect of different drying techniques such as hot air drying (HAD), combined infrared and hot air drying (IR-HAD), and sequential IR- HAD and HAD (IR-HAD + HAD) were performed on Chrysanthemum (Chrysanthemum morifolium Ramat.) cakes and found that among all the techniques IR-HAD showed the highest concentration of volatile compounds. A study (Shi et al. 2021) found that application of combined drying technique i.e., microwave-assisted drying and air drying (MAD-AD) while processing of fresh tea flowers (Camellia sinensis L.) could preserved a more floral fragrance and improved the color of tea flowers. Tea flowers processed by this drying technique showed higher content of catechins, flavonol glycosides, and triterpenoid saponins, and high antioxidant activities compared to other drying techniques such as air drying and freeze drying. In another study on Hemp flower drying, it was found that applying 240 W during vacuum–microwave drying and maintaining 50 °C during convection drying resulted in higher content of aroma compounds, along with color changes, compared to different drying techniques such as convection drying, vacuum–microwave drying, and combined drying consisting of convective pre-drying followed by vacuum–microwave finishing drying (Kwaśnica et al. 2020). Highest essential oil recovery of True lavender flowers (Lavandula angustifolia Mill.) were found in convective drying at 50 °C. But focusing on odour quality the sensory panel indicated that, vacuum-microwave drying (power 360 W), and also convective pre-drying followed by vacuum-microwave finish-drying (50 °C) were delivered the strongest aroma compared to fresh True Lavender flowers (Łyczko et al. 2019). Storage conditions, such as packaging, also play an important role in preserving the quality of volatile compounds in flowers. A study claimed that plastic or aluminium packaging materials for storing of tea processed by gentle air-drying of flowers from the black elder cultivars from Sampo and Sambu resulted in good retention of flavor and aroma compounds upto 3 months (Kaack and Christensen et al., 2008).

Research has claimed that adding flowers to develop a product not only enhances its nutritional properties but also its flavor. It was found that dealcoholization of wine could significantly impact the original quality of rose wine specifically the wine’s phenolic composition, volatile aroma compounds, and sensory characteristics (Ma et al. 2022). Improved sensory properties (fruity and floral, red fruits, aroma intensity, and overall acceptability) were investigated when aqueous extracts of rose, peach and lily flowers had used in the reconstitution of dealcoholized Pinot Noir rose wines.

Antinutritional components and safety issues of consuming edible flowers

Edible flowers have been consumed traditionally since time immemorial and the edible and nonedible flowers were selected by our ancestors based on the presence of alkaloid content and chemicals responsible for the plants’ defence system. According to our ancestors’ view, edible flowers are those, which have alkaloids and also confer pharmacological activities and mostly belong to medicinal plants. However, flowers containing alkaloids that deliver toxic effects, as well as psychotropic and stimulant activities, are considered non-edible flowers (Nicolau and Gostin 2016). For example presence of phytate in our body can inhibit the absorption of minerals in our body’s system. Also, nutrients can be degraded by antinutrients as well. It is known that toxicity is generally dose dependent. Saponin though regarded as antinutritional factor but it is also claimed to provide effect of hypocholesterolemia, immunostimulatory, and anticarcinogenic properties. Likewise at lower or moderate doses tannin also deliver positive effects in our body by improving mood and alertness etc. (Morton 1992). Traditionally to eliminate toxic compounds from some specific edible flowers, various pretreatments were adopted, such as cooking edible flowers and then discarding the broth (Sotelo et al. 2007). Except flowers physicochemical properties, other factors such as introduction of chemical hazards (pesticides such as diethyl-meta-toluamide (insect repellent), dimethoate (insecticide), and sulfites), microbiological hazards (pathogenic bacteria eg: Salmonella spp.) and biological hazards (insects) into edible flowers can make flowers non edible (Nicolau and Gostin 2016, Matyjaszczyk and Śmiechowska et al., 2019). Table 2 showed some antinutritional compounds with their amount found in some edible flowers.

Table 2.

Antinutrients present in some edible flowers

Sl no	Flower name	Antinutrients	Reference
1	Musa balbisiana	Tannin (14.3 mgTAE/100 g), phytate (46.90 mg Phytic acid/100 g), cyanogenic glycoside (0.0001%)and alkaloids (2.78 mg/100 g)	Muchahary and Deka (2021)
2	Allium cepa (onion)	Tannin (1.72 mg/100 g), phytates (3.06 mg/100 g), oxalates(1.51 mg/100 g), alkaloids (0.88 mg/100 g), saponin (850 mg/100 g)	Halder and Khaled (2021)
3	Carica papaya (papaya)	Tannin (0.44 mg/100 g), phytates (6.58 mg/100 g), oxalates(3.18 mg/100 g), alkaloids (0.18 mg/100 g), saponin (230 mg/100 g)
4	Cucurbita maxima (pumpkin)	Tannin (2.16 mg/100 g), phytates (5.07 mg/100 g), oxalates(0.2 mg/100 g), alkaloids (0.35 mg/100 g), saponin (50 mg/100 g)
5	Blue water lily	Phytate (304 mg/100)	Aunget al. (2020)
6	White water lily	Phytate (456 mg/100)
7	Chinese water lily	Phytate (304 mg/100)
8	Moringa oleifera	Phytate (12.6 mg/100 g), oxalate (2.9 mg/100 g), tannin (0.150 mg/100 g)	Athira et al. (2021)
9	Sennaalata Linn	Alkaloids (8.50%), saponin(5.16%), oxalte (3.50 mg/100 g)	Abdulwaliyu et al. (2013)
10	Gynandropsis gynandra	Phytate (1.34 mg), Oxalate (0.12 mg), hydrocyanic acid (0.03 mg), nitrate (0.04 mg)	Abubakar et al. (2014)
11	Parkia biglobosa	Phytate (1.41 mg/100 g), oxalate (0.03 mg/100 g), hydrocyanic acid (0.17 mg/100 g), nitrate (1.32 mg/100 g)	Hassan et al. (2011)
12	Agave salmiana	Trypsin inhibitors (1.11TUI/mg sample), Hemagglutinating activity (6 titre), Hemolytic activity (3 titer)	Soteloet al. (2007)
	Aloe vera	Trypsin inhibitors (2.54 (TUI/mg sample), Hemagglutinating activity (8 titre),
13	Arbutus xalapensis	Trypsin inhibitors (1.60TUI/mg sample, Hemagglutinating activity (10 titre), alkaloids (0.16 g kg − 1 sample)
14	Cucurbita pepo	Trypsin inhibitors 1.40(TUI/mg sample),
15	Erythrina americana,	Trypsin inhibitors (4.88TUI/mg sample), Alkaloids (0.37 g kg − 1 sample)
16	Erythrina caribaea	Trypsin inhibitors (6.32TUI/mg sample), Hemagglutinating activity (4 titre), alkaloids (0.24 g kg − 1 sample)
17	Euphorbia radian benth	Trypsin inhibitors (1.56 TUI/mg sample), Hemagglutinating activity (5 titre),
18	Yucca filifera	Trypsin inhibitors (3.57TUI/mg sample), Hemagglutinating activity (3 titre), Hemolytic activity (4 titer)

TAE- Tannic Acid Equivalent, TUI- Trypsin Inhibitor Units

Though some antinutrients are present in edible flowers, based on their concentration and permissible limits for the human body, we can still consume these flowers. A dose upto 6000 mg/kg on oral administration of aqueous extract of B. monosperma was regarded as safe by Khan et al., (2017). Muchahary and Deka (2021) found tannin, phytate, cyanogenic glycoside and alkaloids in conventional extract of whole bhimkol blossome were 14.3 mg TAE /100 g, 46.90 mg phytic acid/100 g, 0.0001%, 2.78 mg/100 g respectively. Halder and Khaled (2021) quantify the some anti-nutritional compounds (per 100 gfresh flowers) such as tannin, phytate, oxalate, alkaloids and saponin present in flowers of Allium cepa (onion), Carica papaya (papaya) and Cucurbita maxima (pumpkin). It was observed that tannin present in Allium cepa (onion), Carica papaya (papaya) and Cucurbita maxima (pumpkin) were 1.72, 0.44 and 2.16 mg/100 g respectively. Also, phytate, oxalate, alkaloids and saponin found in Allium cepa (onion) were 3.06, 1.52, 0.88 and 850 mg/100 g; in Carica papaya (papaya) 6.58, 3.18, 0.18 and 230 mg/100 g; and finally in Cucurbita maxima (pumpkin) were 5.07, 0.2, 0.35 and 50 mg/100 g respectively. Aung et al.,(2020) claimed that flowers of blue water lily, white water lily and Chinese water lily were found to have phytate (mg/100 g) content of 304, 456 and 304 respectively; and this higher content is due to the presence of higher fiber content in them. Antinutrients such as phytate, oxalate and tannin reported to present in Moringa oleifera flower were 12.6, 2.9 and 0.150 (mg/100 g) respectively (Athira et al. 2021). Senna alata Linn is traditionally believed to cure syphilis and diabetes. It was found that antinutrients such as alkaloids, saponin, and oxalate found in them were 8.50%, 5.16%, and 3.50 mg/100 g, respectively (Abdulwaliyu et al. 2013). Antinutrients such as phytate, oxalate, hydrocyanic acid and nitrate presented in Gynandropsis gynandra flowers were 1.34 mg, 0.12 mg, 0.03 mg and 0.04 mg respectively which were below the recommended antinutritional toxic level (Abubakar et al. 2014). The antinutrients may be present in the edible flowers. Therefore, the information about the concentration of antinutrients in edible flowers, along with their dietary intake, is crucial for safely incorporating edible flowers into our diets while maximizing their nutritional benefits and avoiding potential hazards.

Lachumy et al. (2010) tested the toxicity of Etlingera elatior (torch ginger) flower extract by brine shrimp bioassay (against Artemia salina) and found LD50 value of 2.52 mg/ml, considered safe LD50 is a toxicological metric that signifies the quantity of a substance which causes mortality in 50% of a test group of animals within a defined timeframe. Kunhachan et al. (2012) revealed that the flower of Jasmine sambac is safe to use in the food industry. They found no significant effects on male ICR mice when a dose of 15 mg/mouse of Jasminum sambac flower extract was injected. Additionally, in cases of acute toxicity, the LD50 was found to be greater than 5,000 mg/kg in both male and female Wistar rats. The LD50 value of the methanolic extract of neem flowers was found to be more than 12 g/kg body weight. Doses of methanolic extract of neem flowers exceeding 150 mg/kg/day caused slight toxicity to rats (Kupradinun et al. 2010). A lower amount of antinutrients found in Parkia biglobosa flower were phytate (1.41 mg/100 g), oxalate (0.03 mg/100 g), hydrocyanic acid (0.17 mg/100 g) and nitrate (1.32 mg/100 g) which was below the toxic level or daily intake (Hassan et al. 2011). There were no cyanogenic glycosides found in flowers of Agave salmiana, Aloe vera, Arbutus xalapensis, Cucurbita pepo (cultivated), Erythrina americana, Erythrina caribaea, Euphorbia radianbenth and Yucca filifera and trypsin inhibitors found in them were 1.11(TUI/mg sample), 2.54 (TUI/mg sample, 1.60(TUI/mg sample), 1.40 (TUI/mg sample), 4.88(TUI/mg sample), 6.32(TUI/mg sample), 1.56(TUI/mg sample) and 3.57(TUI/mg sample) respectively. Among all these flowers, A. xalapensis contains the highest lectins content. Saponins were detected in both A. salmiana and Y. filifera plants. It was found that flowers of A. xalapensis, E. Americana and E. caribaea contained alkaloids (Sotelo et al. 2007).

Flower infused tea is common beverage worldwide. Based on some research, it has been found that due to external factors such as spraying pesticides on flowers, there is a health risk when these pesticides transfer into tea solutions. Jiang et al. (2020) found that based on different infusion conditions such as water temperature, infusion duration, repetitions, and physicochemical properties of the pesticides, the water solubility of pesticides, and pesticide concentrations in dry chrysanthemum flowers, pesticides transfer into the tea solution, etc. The amount of pesticides transferred into tea solution typically rises with increasing pesticide water solubility, infusion duration, temperature of water, and pesticide concentrations in dry chrysanthemum flowers. Conversely, the transfer decreased with higher octanol–water partition coefficients and when the infusion process was repeated many times. It can be said that although there are varying levels of antinutritional compounds present in flowers, they can be made safe for consumption through proper processing to eliminate these compounds and consumption should also adhere to permissible limits. We need to concern for food allergy also. This brief discussion on the safety of consuming edible flowers indicates that more research is needed to explore their toxicological properties and develop processes for their removal.

Applicability in food products

Edible flowers are a rich source of nutrients and phytochemicals, offering numerous health benefits. When edible flowers are used as food ingredients, they deliver their impact, making a significant contribution to the food industry by utilizing these easily available natural resources to develop functional food products. Flowers not only provide fragrance and appealing appearance, but they also offer good textural and other sensory properties when incorporated with other food ingredients. There is a booming trend in using edible flowers on food product development although the research behind it is scanty. In this review, some research studies on producing new food products using edible flowers were included to understand their beneficial contributions. Edible flowers add value to dishes by enhancing color, nutrients, textural properties etc. Various product developments such as meat products, beverages, bakery items etc. could be fortified by incorporation of edible flowers too. The addition of edible flowers as an ingredient also changes the characteristic of the final product also. Here are some food products prepared using edible flowers, and their impact was briefly discussed.

Rice

Using flowers while cooking can change the characteristics of rice. Clitoria ternatea (butterfly pea) flower extracts (1.25% and 2.5%) lower the starch digestibility in cooked rice (cooked using an electric rice cooker) and decrease stickiness while increasing cohesiveness. Additionally, rice cooked in a microwave showed retention of reducing sugar release when incorporated with 2.5% Clitoria ternatea extract, without significant changes in textural properties (Chusak et al. 2019).

Infant food formulations

Infant food prepared from cereal blend such as fermented yellow maize and millet blend (Ogi) can be a great source of nutrition by incorporation of Moringa oleifera flower powder. Arise et al. (2014) stated that a blend ratio of 70:10:20 for maize, millet, and Moringa oleifera flower powder, respectively, is the best formulation based on sensory evaluation and the requirements for protein, carbohydrates, and fat in infant food. Increasing the amount of Moringa oleifera flower powder could augment the content of crude protein, crude fibre, ash and fat while lowering the content of carbohydrate and moisture content.

Meat products

Madane et al., (2019) said that cooked chicken nuggets incorporated with Moringa oleifera flower extract (1% & 2%) showed improved cooking yield, emulsion stability, higher content of dietary fiber, protein, ash and total phenolic content. Acceptability was maintained untill the 15th day of refrigeration storage. Dietary fiber has an impact on emulsion stability, cooking yield and also fiber increases water holding capacity in meat. In terms of sensory characteristics 2% Moringa oleifera flower extract incorporated nuggets were showed the lightest color along with lower hardness in texture compared to others. Lipid oxidation was also lowered down by addition of the flower extract during storage. The content of dangerous heterocyclic amines (HCAs) in cooked goat meat patties could be decreased when Chrysanthemum morifolium flower extract is incorporated during patty preparation. This is because the phenolic compounds such as Quercetin 3-O-rutinoside & glucuronide, Morin, 3-Caffeoylquinic acid, Melanettin, Luteolin 7-O-glucuronide, Apigenin 7-O-glucoside, Glycitin, Cyanidin 3-O-galactoside and 2,3-Dihydroxybenzoic acid are present in the Chrysanthemum morifolium flower extract and act as antioxidants. But, the effect is dependent on cooking methods and temperatures used (Khan et al. 2019). It was found that among cooking methods such as pan fried, deep fat fried, charcoal barbecue and oven roasted the impact of Chrysanthemum morifolium flower extract was most leading in case of deep fat frying and pan frying cooking methods. Indeed, in both cooking methods temperature increment resulted increase in potency of flower extract in reducing HCAs content. Among temperature levels 175 °C, 195 °C & 225 °C, the inhibition of HCAs formation was highest in pan fried and deep fat fried methods. In that 225 °C temperature 52%, 47% and 32% HCAs were lessened in deep fat fried, pan fried and oven roasted patties respectively. The flowers extract reduced HCAs content to 36% in barbecue patties (Khan et al. 2019). Santos et al., (2022) investigated the antioxidant effect of pumpkin flower powder in chicken patties. It was observed that incorporation of pumpkin flower in chicken patties offered improvement of the antioxidant and sensorial properties. The antioxidant property of pumpkin flower helped the reduction of the oxidation processes which was occurring during the cooking and storage of patties. Three drying methods such as foam-mat drying, freeze drying, and oven drying was employed to obtain the pumpkin flower powder. It was noticed that these drying methods had an effect on retention of bioactive compounds in pumpkin flower powder. Indeed, it was seen that powders obtained from foam-mat and freeze-drying processes had better antioxidant and sensorial effects. Finally, it was observed that powder obtained from foam-mat drying of fresh pumpkin flowers stood best to be incorporated in chicken patties and showed better antioxidative properties even after 7 days of storage.

Bakery products

The addition of apple flower’s powder impeded the formation of methylglyoxal and fluorescent AGEs in cookies (Gao et al. 2020). This could be beneficial for diabetic patients as it showed impact on thermal-treated foods i.e., cookies. Hnin et al. (2021) found that incorporation of rose flower powder for the development of cookies could enhance the color, bioactive compounds and antioxidant activities of the cookies etc. In this study various percentage of rose flower powder (3%, 5%, 7%, and 10%) were used to prepare flour in cookies and revealed that bulk density and hardness of cookies increased with increasing level flower powder and cookies prepared by using 5% rose flower powder stood up for higher color score and suitable to prepare from sensory score. During 0, 2, 4, 6, and 8 weeks of storage, it was found that the total phenolic content, anthocyanin content, and antioxidant activity of cookies incorporated with flower powder were higher and retained compared to the control cookies made only with wheat flour, throughout the storage period. Their findings concluded that the addition of edible rose flower powder could enhance the nutritional properties of cookies along with enhancing its shelf life. Flower extracts can be used as a natural coloring agent. Lyophilized or spray-dried, ultrasound-assisted extract of Gomphrena globosa L. flowers could deliver a pink color to cookies due to the presence of betacyanins in the flower without significantly altering the chemical composition of the final product. Indeed, results showed that cookies prepared by using spray-dried extract had the most intense pink color and the pink color intensity of cookies made from lyophilized color extract was less degraded with respect to time (Roriz et al. 2020).

Beverages

AL Tamimi et al. (2020) reported that addition of roselle flowers with date palm spathes’ beverage enhanced the vitamin contents and antioxidant activities. Additionally protein, fat and carbohydrate content, and some trace minerals could be achieved in the beverage by adding mixture of 1% date palm pollen grains and 1% roselle flowers but that combination negatively impacted the sensory attributes of the beverage. Dealcoholization of wine could reduce its aroma. One could reintroduce aroma to dealcoholized wine is by reconstituting it with extracts from edible flowers. For example, when extracts of peach, rose, and lily flowers were incorporated into the development of reconstituted dealcoholized Merlot red wine, it was observed that the aroma was improved, and there was no significant effect on the chemical parameters of the wine compared to the original wine (Sam et al. 2023). A nutritionally enriched spiced beverage (appetizer) developed by incorporating rhododendron (Rhododendron arboreum Sm.) flowers could be stored in glass and PET bottles for 6 months under ambient (15–25 °C) and refrigerated temperature conditions (4–7 °C). The beverage with the highest sensory score was found to be made up of 35% extract, 40°B TSS, 1.20% acidity, and with a spice extract (10%) consisting of cardamom (1 g), cumin (2.5 g), black pepper (2.5 g), common salt (5 g), mint juice (1%), and ginger juice (1.5%).

Dairy products

Bragueto Escher et al. (2019) suggested that addition of different concentrations of lyophilized marigold extracts were improved the level of total phenolic content and antioxidant activity in organic yogurt. Vioque et al., (2000) said that when extracts of flowers such as Cynara cardunculus and Cynara humilis used as coagulants in ewes’ Milk Cheese then both coagulants didn’t show any impact based on the moisture, fat, protein, water activity, flavor, and aroma and NaCl contents of the cheese. In comparison of both coagulants, C. humilis lowered down the level of lactic acid content (p < 0.001) and made higher pH values. 2 days of ripened cheese resulted higher microbial counts in both coagulants. C. humilis showed higher enterobacteria, mold, and yeast counts. Proteolytic activity in terms of soluble nitrogen and nonprotein nitrogen was higher in cheeses made with C. cardunculus. Pires et al., (2018) suggested that among the hydrophilic extracts from rose, cornflower and dahlia; rose extract stood out as the best choice for use as a coloring agent in yogurt instead of artificial E163 (anthocyanin extract). It was found that there was no significant difference of nutritional composition, free sugars and fatty acids composition in both rose extract and E163. Qiu et al. (2021) stated that the development of yogurt by incorporating Rosa rugosa cv. Plena extract provided improvements, including increased pH, water holding capacity, a* and b* values, total phenolic content, antioxidant capacity, α-amylase and α-glucosidase inhibitions, and proteolytic activity of yogurts. Additionally, there were decrease in lightness, titratable acidity, and syneresis of yogurts during storage. In their study, they suggested that 0.1% of the flower extract showed the highest sensory scores along with the best viscoelastic properties and flavor attributes, making it a suitable concentration as a food additive for fermented milk product development.

Extruded products

Kowalczewski et al. (2019) stated that phenolics and antioxidant activity of thermally processed pasta could be increased by incorporating black locust flower. Additionally, it was found that thermal processing increased the antioxidant properties (in vitro). This phenomenon might be attributed to the liberation of higher amounts of phenolic acids during the thermal treatment of pasta preparation.

This brief discussion highlights that the addition of edible flowers could provide great benefits. Since they are a natural source of nutrition, they could be utilized by food technologists, the food industry, and pharmacologists.

Conclusions

Consumer’s attention is growing towards naturally abundant edible flowers due to their nutritional and other health beneficial properties. Flavor and nutritional properties of flowers are varies among species to species and also different processing treatment could alter these characteristics of a flower. The development of functional food products using edible flowers can improve the quality such as color, flavour, texture and nutrition etc. of the final food product. It can be understood that the consumption of edible flowers is going to increase in the near future. More scientific studies are needed to address concerns regarding the toxicity of various edible flowers, thereby mitigating potential health hazards. Additionally, research on the utilization of various species of edible flowers as functional food ingredients is essential to understand their effects on the development of various functional food products.

Author contributions

All the authors contributed to the conceptualization of the manuscript. The first draft of the manuscript was written by Indrani Chetia. The manuscript was further written and checked by Akhila Vijayakumar. The manuscript was edited, improved and proofread by Laxmikant S. Badwaik. All the authors read and approved the final version of the manuscript.

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The authors declare that there is no conflict of interest.

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