Characterization of two prickly pear species flowers growing in Tunisia at four flowering stages

LWT - Food Science and Technology 59 (2014) 448e454

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Characterization of two prickly pear species flowers growing in Tunisia at four flowering stages Imene Ammar a, Monia Ennouri a, b, *, Olfa Bali a, Hamadi Attia a a b

Alimentary Analysis Laboratory, National Engineering School of Sfax, BPW 3038 Sfax, Tunisia Higher Institute of Applied Sciences & Technology of Mahdia, Sidi Messaoud, 5111 Mahdia, Tunisia

a r t i c l e i n f o

a b s t r a c t

Article history: Received 28 October 2012 Received in revised form 20 February 2014 Accepted 1 May 2014 Available online 20 May 2014

Opuntia flowers belonging to two species of prickly pear were evaluated at four flowering stages: vegetative, initial flowering, full flowering and post-flowering stage, for possible use as a potential source in the food enrichment. Chemical composition including moisture, ash, protein, fat, soluble sugars, total fibers, mineral amounts and fatty acid profiles of Opuntia ficus-indica and Opuntia stricta flowers were investigated. Functional properties (swelling capacity (SWC), water holding capacity (WHC), water solubility index (WSI) and oil holding capacity (OHC)) were also studied. Results showed that during the maturation of flowers, there is a decrease in protein contents whereas fat contents increase, for both species. High minerals amounts were noticed in Opuntia flowers and they can be considered as an excellent source of minerals. The fatty acids profiles were dominated by the palmitic acid (38e59%). The techno-functional properties (SWC, WSI, WHC and OHC) were found to be important and they can be modulated according to the temperatures. Owing to its chemical profile and functional properties, Opuntia flowers could be used as an ingredient to improve different physical and nutritional properties of foods. © 2014 Elsevier Ltd. All rights reserved.

Keywords: Opuntia ficus-indica Opuntia stricta Flowering stage Chemical composition Functional properties

1. Introduction About 1500 species of cactus, belonging to the Opuntia genus are native to Mexico and widespread throughout Central and South America, Australia, South Africa, and the whole Mediterranean area (Hegwood, 1990). Opuntia ficus-indica and Opuntia stricta derived from Cactaceae family, and their fruits are the cactus pears. This plant grows wild in arid and semi-arid regions, where the production of more succulent food plants is severely limited. Many uses of different parts of Opuntia are reported (Hoffmann, 1980). The cladodes are consumed as fresh vegetables or added to casseroles (Hamdi, 1997; Saenz, 2000). In addition, they have been investigated as a possible treatment for gastritis, hyperglycemia, arteriosclerosis, diabetes, and prostatic hypertrophy (Frati-Munari, Jimenez, & Ariza, 1990; Hegwood, 1990; Palevitch, Earon, & Levin, 1993). Studies showed also the potential textural properties of cactus cladodes for the food industry (Ayadi, Abdelmaksoud,

* Corresponding author. Alimentary Analysis Laboratory, National Engineering School of Sfax, BPW 3038, Sfax, Tunisia. Tel.: þ216 98 278 684; fax: þ216 74 221 160. E-mail address: [email protected] (M. Ennouri). http://dx.doi.org/10.1016/j.lwt.2014.05.002 0023-6438/© 2014 Elsevier Ltd. All rights reserved.

Ennouri, & Attia, 2009; Sepúlveda, Saenz, Aliaga, & Aceituno, 2007). The fruits are used for the manufacture of food products such as juices (Espinosa, Borrocal, Jara, Zorilla, & Medina, 1973), alcoholic beverages (Bustos, 1981), jams (Sawaya, Khatchadourian, & Almuhammad, 1983), and natural liquid sweeteners (Saenz, Arriagana, Fizsman, & Calvo, 1996). Moreover, nutritional, biological value and rheological characteristics of seed oil were studied (Ennouri, Bourret, Mondolot, & Attia, 2005; Ennouri et al., 2007). Opuntia flowers have been traditionally used for medical purposes for a long time. The dried flowers of prickly pear are usually sold on the popular Tunisian markets, and are traditionally used as an infusion to treat kidney stones. To our knowledge, no data were reported concerning both the nutritional aspect of these flowers and their application in food products. The nutritional and pharmacological benefits of the different parts of the prickly pear, in addition to its increasing importance at the industrial level, have motivated our investigation about the chemical contents of the flowers which are less known. Previous
o, De Abreu, Pawlowska, Cioni, and Braca (2010) study of De Le describes the chemical content of O. ficus-indica flowers methanol extract. Also, a recent study shows the antiulcerogenic activities of Opuntia inermis flowers (Alimi, Hfaiedh, Bouoni, Sakly, & Ben Rhouma, 2011). In addition, the hexane extract and antibacterial

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Table 1 Proximate analysis of Opuntia ficus-indica and Opuntia stricta flowers during four flowering stages. Species

Flowering stage

Moisturea

Opuntia ficus- indica

(A) (B) (C) (D) (A) (B) (C) (D)

81.5 83.8 84.6 20.3 83.6 85.9 88.3 24.3

Opuntia stricta

± ± ± ± ± ± ± ±

0.4ax 0.4bx 0.2cx 0.1dx 0.3ay 0.3by 0.2cy 0.3dy

Ashb 1.6 1.4 1.5 9.0 1.5 1.5 1.2 6.3

± ± ± ± ± ± ± ±

Soluble sugarsb 0.0ax 0.3ax 0.1ax 0.8bx 0.0ax 0.1ax 0.1by 0.4cy

0.5 1.4 9.3 5.9 4.0 3.9 14.9 1.4

± ± ± ± ± ± ± ±

0.0ax 0.2bx 0.7cx 0.5dx 0.6ay 0.3ay 0.4by 0.7cy

Total fiberb 54.1 50.4 41.4 45.7 53.5 49.5 54.1 58.8

± ± ± ± ± ± ± ±

Proteinb

5.2ax 4.6ax 2.4bx 2.6abx 4.9abx 4.5ax 5.0aby 1.8aby

16.7 15.4 13.1 5.7 13.5 9.01 10.1 5.6

± ± ± ± ± ± ± ±

Fatb

0.78ax 0.7bx 0.9cx 0.35dx 0.84ay 0.95by 0.13cy 0.82dy

1.8 3.79 2.27 3.8 1.5 2.16 1.2 3.4

± ± ± ± ± ± ± ±

0.24ax 0.19bx 0.19ax 0.85bx 0.43ax 0.24by 0.32ay 0.27cx

Carbohydratesb

Energyc

26 ± 4.8ax 29.0 ± 4.0ax 41.7 ± 3.1bx 35.9 ± 2.1bx 30.4 ± 5.9abx 37.8 ± 4.7by 33.5 ± 5.1aby 26.1 ± 2.1ay

185.1 212.9 240.8 206.3 184.7 205.6 182.8 157.9

± ± ± ± ± ± ± ±

21.9ax 17.6abx 10.9bx 3.9ax 21.1abx 16.4bx 22.1aby 6.0ay

(A) Vegetative, (B) initial flowering, (C) full flowering and (D) post-flowering stage. Values are expressed as mean ± standard deviation, n ¼ 3. Means followed by the same letter in the same column are not significantly different at P > 0.05, Duncan test. a, b, c, d: are used to compare stages for the same species. x,y: are used to compare the same stage for the two species. a results are expressed in g per 100 g of fresh weight. b results are expressed in g per 100 g of dry weight. c energy is expressed in kcal per 100 g of dry weight.

activity of O. ficus-indica and O. stricta were investigated based on our previous contribution (Ammar, Ennouri, Khemakhem, Yangui, & Attia, 2012). The aims of the present study were firstly to characterize the flowers belonging to two Opuntia species at four flowering stages regarding proximate composition, minerals, dietary fibers and fatty acids in order to explore the nutritional properties during different developmental stages. Secondly, some functional properties (such as water holding capacity, swelling capacity and oil holding capacity) were investigated because of their importance in relation to the functionality and nutritional quality in food applications. The results may contribute to improve the value of these flowers and may also provide an advanced knowledge about their uses in the food products.

are yellowish to orange; stamens are grouped together around the style in the beginning and become separated in the full flowering stage. The flower is in full when its color is bright yellow, it exhibits larger shape than that of the other flowering stages and starts nectar production. In the post-flowering stage, the flower becomes closed and dry (flower senescing). Opuntia flowers are of variable size from 3 up to 10 cm long according to the progression of flowering. Floral development from bud to anthesis requires between 20 and 40 days. Harvesting of O. ficus-indica for vegetative and initial flowering stage is taking place in the period ranging from 20 to 25 May. The flowers at full flowering stage were harvested in the beginning of June. For O. stricta the harvesting period starts in the middle of June for the first three stages. For the post-flowering stage, flowers for both species, were collected in the last week of June.

2. Materials and methods 2.2. Processing of flowers for analysis 2.1. Origin of the flowers O. ficus-indica and O. stricta flowers were collected from wild populations located in the region of Sfax, Tunisia (latitude 34 460 2900 N, longitude 10 390 7300 E; elevation: 41 m), where the climate is semi arid and is characterized by a mean rainfall of 200 mm/year. Samples were gathered during vegetative (A), initial flowering (B), full flowering (C) and post-flowering (D) stages during the period extending from May to June, 2010. The degree of flower maturity was determined on the basis of flower size, opening and coloring. In vegetative stage (bud developing), we have green closed petal flowers. In initial flowering stage, flowers

Whole flowers were collected in one batch in the same sampling area at every developmental stage. Samples were classified and separated according to species and flowering stage. Each collected group was processed separately. The plant authenticity and the selection of the flowering stages were evaluated in the Alimentary Analysis Laboratory of the National Engineering School of Sfax, Tunisia. Flowers were processed immediately after their harvest. The flowers samples were selected, cut into small pieces, and the initial moisture content was analyzed as shown in the Table 1. Then the flowers were stored at 20  C until analysis.

Table 2 Mineral content of Opuntia ficus-indica and Opuntia stricta flowers during four flowering stages (mg/100 g of dry weight basis). Species

Flowering stage

Ca

Opuntia ficus indica

(A) (B) (C) (D) (A) (B) (C) (D)

394.0 400.4 770.1 651.9 777.8 834.9 718.1 854.9

Opuntia stricta

Fe ± ± ± ± ± ± ± ±

15.6ax 10.2bx 32.6cx 21.8dx 61.2ay 43.4bx 51.1cy 73.8by

4.2 9.5 9.5 12.4 3.7 12.8 14.1 13.8

K ± ± ± ± ± ± ± ±

0.7ax 0.3bx 2.1bx 1.1cx 0.1ax 2.6by 0.8by 0.6bx

2238.6 2386.4 2278.7 1255.9 2028.3 1995.8 2077.2 1459.9

Mg ± ± ± ± ± ± ± ±

46.1ax 38.1bx 16.4ax 61.5cx 86.3ay 50.1acy 10.4ady 45.5by

(A) Vegetative, (B) initial flowering, (C) full flowering and (D) post-flowering stage. Values are expressed as mean ± standard deviation, n ¼ 3. Means followed by the same letter in the same column are not significantly different at P > 0.05, Duncan test. a, b, c, d: are used to compare stages for the same species. x,y: are used to compare the same stage for two species.

397.3 329.8 429.4 280.7 400.7 513.5 465.9 464.2

Na ± ± ± ± ± ± ± ±

10.6ax 21.7bx 10.2cx 73.1bx 26.5axy 33.3by 7.8cy 11.3cy

76.7 83.5 137.2 117.9 75.8 134.4 95.1 139.7

Zn ± ± ± ± ± ± ± ±

4.6ax 3.9ax 4.3bx 5.7cx 10.7ax 8.7by 1.3cy 11.1by

3.5 3.8 3.6 2.4 2.5 3.4 2.9 1.5

± ± ± ± ± ± ± ±

0.9ax 0.2abx 0.8abx 0.9acx 0.4ay 0.6bx 0.4abx 0.2cy

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2.3. Characterization of plant nutrients 2.3.1. Crude composition The samples were analyzed for their chemical composition (moisture, protein, fat, soluble sugars, dietary fibers, carbohydrates and ash) using the AOAC procedures (1995). The crude protein content (N  6.25) was estimated by the macro-Kjeldahl method; the crude fat was determined by extracting a known weight of powdered sample with hexane, using Soxhlet apparatus for 6 h. The ash content was determined by incineration at 600 ± 15  C; soluble sugars were determined by the phenol sulphuric acid method (Dubois, Gilles, Hamilton, Rebers, & Smith, 1956). The total dietary fibers content was determined using the enzymatic-gravimetric method of Prosky, Asp, Schweizer, De Vries, and Furda (1988). Total carbohydrates were calculated by difference: Total carbohydrates ¼ 100  (g protein þ g fat þ g ash). Total energy was calculated according to the following equation: Energy (kcal) ¼ 4  (g protein þ g carbohydrate) þ 9  (g lipid). 2.3.2. Mineral composition To remove carbon, samples were ignited and incinerated in a muffle furnace at 550  C for 8 h (AOAC, 1995). The ashes were dissolved in HNO3 (AFNOR, 1996) and the mineral constituents (Ca, Fe, K, Mg, Na and Zn) were determined using an atomic absorption spectrophotometer (Hitachi Z-6100, Japan). 2.3.3. Fatty acid analysis Fatty acids were determined by gaseliquid chromatography with flame ionization detection (GCeFID)/capillary column after trans-esterification. Fatty acid methyl esters were prepared in the presence of potassium hydroxide (2 mol equi/l) in methanol and analyzed on a HewlettePackard model 5890 series II gas chromatograph (Agilent Technology, California, USA) equipped with a flame ionization detector and a polar capillary column: HP Innowax cross-linked PEG, Carbowax 20 M (0.32 mm internal diameter, 30 m length and 0.25 mm film thickness). The operational conditions were: injector temperature 220  C; detector temperature 275  C; column temperature 50  C for 5 min then a gradient of 10  C/min to 240  C; carrier gas was nitrogen at a 1.47 ml/min flow. 2.4. Functional properties of powdered flowers 2.4.1. Swelling capacity (SWC) Samples were accurately weighed (200 mg), transferred into a calibrated cylinder (1.5 cm diameter), and 10 ml of distilled water were added. After thoroughly mixing, cylinders were let to stand for 18 h at room temperature. The swelling volume was measured and expressed as cm3 of swollen sample per gram of sample. Then, the bed volume was recorded and swelling was calculated as volume occupied by sample (ml) per gram of dry sample (Robertson et al., 2000). 2.4.2. Water solubility index (WSI) Water solubility index (WSI) of the flowers powder was determined by slightly modifying the method of Anderson, Conway, Pfeifer, and Griffin (1969). Powder samples (2.5 g) were dispersed in 30 ml of distilled water, using a glass rod, and cooked at 90  C for 15 min in a water bath. The cooked paste was cooled at room temperature and centrifuged at 3000 g for 10 min. The supernatant was decanted for determination of its solid content into a tarred evaporating dish. The weight of dry solids was recovered by evaporating the supernatant overnight at 110  C. WSI was calculated by the following equation:

WSIðg=100 g of solidsÞ ¼ ðWS =WDS Þ  100 where Ws: weight of dissolved solids in supernatant and WDS: weight of dry solids. 2.4.3. Water holding capacity (WHC) The water absorption of the flowers powder samples was measured by the modified centrifugation method described by Sosulski (1962). The samples (1 g) were dispersed in 25 ml of distilled water and placed in pre-weighted centrifuge tubes. Then, the dispersions were stirred and left at 25, 40, 60 or 80  C for 1 h, followed by centrifugation for 25 min at 3000 g. The supernatants were discarded and the tubes were kept inverted for 25 min at 50  C. The water absorption capacity was expressed as grams of water bound per gram of the sample on a dry basis. 2.4.4. Oil holding capacity (OHC) OHC of the flowers powder samples was determined by the method of Lin, Humbert, and Sosulski (1974) with slight modifications. Samples (0.5 g) were mixed with 6 ml of corn oil in preweighted centrifuge tubes. Then, the dispersions were stirred and left at 25, 40, 60 or 80  C for 1 h, followed by centrifugation for 25 min at 3000 g. The oil supernatant was then removed and the tubes were inverted for 25 min to drain the oil prior to reweighting. The OHC of flowers powder samples were expressed as g of oil hold per g of sample on dry weight basis. 2.5. Statistical analysis The results were statistically analyzed and treated by a Duncan test using SPSS (version 11) to determine any significant differences between the average values obtained at the different temperatures, at 95% confidence. The data obtained for the comparison of both species were analyzed statistically by Student's t-test to establish significance of difference between the samples at the level of P < 0.05. 3. Results and discussion 3.1. Moisture The initial moisture values of the samples expressed on fresh weight were higher than 81.5 g/100 g, at the first three flowering stages, before decreasing significantly at the post-flowering stage to reach 20.3 and 24.3 g/100 g for O. ficus-indica and O. stricta, respectively, due to the natural drying process occurring during the flower maturity. O. stricta flowers had significantly (P < 0.05) higher moisture content than O. ficus-indica during the four flowering stages (Table 1). Opuntia flowers could only be consumed fresh in the days of their harvest, due to their high moisture content which can result in deterioration by microorganism and chemical reactions. Nevertheless, the water content could be controlled by drying in order to increase the shelf life of flowers. 3.2. Ash and mineral composition It must be noted that the first three flowering stages show relatively low ash contents for both Opuntia species (1.2e1.6 g/ 100 g dry weight) (Table 1). During the post-flowering stage, this amount increased to reach 6.3 and 9 g/100 g for O. stricta and O. ficus-indica, respectively. These contents were conform to those reported by Maisuthisakul, Pasuk, and Ritthiruangdej (2008) for the flowers of Cassia siamea Brit, Azadirachta indeca and Allium

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ascalonicum which represent 5.6, 6.3 and 7.5 g/100 g ash content, respectively. Table 2 shows the results regarding some nutritionally important minerals (Ca, Fe, K, Mg, Na and Zn) for O. ficus-indica and O. stricta during flowering stages. The content of mineral elements is one of the most essential aspects that influence the use of edible flowers in human nutrition. The mineral composition shows that K was the predominant component followed by Ca, Mg, Na, Fe and Zn. It can be observed that there was a significant variation in the mineral amounts during the flowering stages, which is probably due to the modifications related to the flowers maturity. The full and post-flowering stages were characterized by a high Ca and Fe concentration for both species. Whereas, the first three flowering stages showed minimal changes and accumulated abundant amounts in K which decreased slightly at the post-flowering stage. The study of the K content is very important because the consumption of crops which are rich in K is recommended for the prevention of cardiovascular or oncogenic diseases (Kader, 2008). Indeed, in the traditional Italian medicine (Sicily), the infusion of prickly pear flowers is particularly used for its diuretic and relaxing action for the renal system. Furthermore, it is stipulated that Opuntia flower infusion can help persons with renal problems. Battaglini (1939) showed a correlation between the diuretic activity of the Opuntia flowers infusion and their high K content, whereas Galati, Tripodo, Trovato, Miceli, and Monforte (2002) demonstrated the diuretic effect in rats, not only in flowers, but also in all the Opuntia plant tissues: cladodes, fruits and flowers. The Ca concentration increased at the full and post-flowering stages for O. ficus-indica, while for O. stricta, it revealed high levels mainly at the post-flowering stage (854 mg/100 g dry weight). These results were in the same range with those reported by Maisuthisakul et al. (2008) for flowers of Musa spiantum Linn. (fully opened flower), except for the Ca content which was lower. The Fe content at full flowering stage reaches 9.5 and 14 mg/ 100 g for O. ficus-indica and O. stricta, respectively. We should notice that Opuntia flowers constitute a good source of Zn (1.5e3.8 mg/ 100 g), which is recognized as being an essential element against prostate pain (Palevitch et al., 1993). Taking into account the high levels of these minerals, Opuntia flowers may have potential applications as supplements in meals and drinks. Moreover, the study of the minerals composition provides information not only for the benefits of human health, but can also be very useful for predicting the fruit quality variables such as: fresh fruit mass and maturation index for the following year. For example, Mg, Ca and Zn concentrations measured in flowers were related to fruit fresh mass estimations, and Na, K and Fe concentrations were related to the fruit maturation index (Pestana, Beja, Correia, De Varennes, & Faria, 2005). 3.3. Soluble sugars Soluble sugars were found in low levels for vegetative and initial flowering stages in O. ficus-indica flowers while, for O. stricta flowers, they are more important in the same stages (Table 1). This significant variation (P < 0.05) could be attributed to species differences. The full flowering stage shows the highest proportion of soluble sugars. Moreover, in this stage, O. stricta flowers revealed a higher amount of soluble sugars (14.9 g/100 g) than that for O. ficusindica (9.3 g/100 g) (P < 0.05). These results were relatively similar to those reported by Barros, Carvalho, and Ferreira (2010), for Malva sylvestris flowers (13.95 g/100 g). However, at post-flowering stage, there is an important decrease in the levels of soluble sugars for both species, which could be explained by the migration of sugar amounts from flowers towards fruits or other parts of the plant.

451

3.4. Total dietary fibers This study is the first one dealing with the total dietary fibers content of Opuntia flowers. In fact, total fibers were the main component in Opuntia flowers (about 50 g/100 g of dry weight), suggesting that they constituted good sources of fiber which include polysaccharides and substances of plant tissue such as lignin and cellulose (Salisbury & Ross, 1992). The high amount of dietary fibers for both Opuntia flowers species is noticeable when it is compared to the cereal total dietary fibers (Grigelmo-Miguel, Gorinstein, & Martin-Belloso, 1999). The present data may support the use of these flowers in food applications as good sources of dietary fibers. 3.5. Protein content Nitrogen content results were illustrated in Table 1. Opuntia flowers had relatively considerable amounts of protein which varied significantly according to the flowering stage. Indeed, the vegetative stage revealed the most important rates 16.5 and 13.1 g/100 g for O. ficus-indica and O. stricta, respectively. However, at full flowering stage, the protein content decreased and reached 13.1 and 9.73 g/100 g for O. ficus-indica and O. stricta, respectively. These values are more important than those reported by Barros et al. (2010) for the flowers of M. sylvestris (8.5 g/100 g of dry weight). We should notice that protein contents decreased with the flowers maturity for both species; the post-flowering stage exhibiting the lowest protein content (5.4e8.9 g/100 g). This low protein content could be attributed to the dehiscence produced at post-flowering stage and to the stamens that didn't contain pollen since Opuntia flowers were picked up when they were closed, knowing that pollen is very important as a source of proteins (mainly in apiculture) (Barth, 1989). Opuntia flowers could be considered as a good source of protein, mainly at full flowering stage since they provide similar contents to those of other vegetables (Lee, Pyo, Ahn, & Kim, 2005). 3.6. Fat content Fat contents were the least abundant component among examined nutrients, this fact being similar to other commonly consumed flowers (Rop, Mlcek, Jurikova, & Neugebauerova, Vabkova, 2012). Both Opuntia flowers species have a similar fat content at the different flowering stages (Table 1). This fat content increased with the flower maturity to reach 3.3 g/100 g of dry weight at post-flowering stage. This result agreed with the one obtained by Barros et al. (2010) for the flowers of M. sylvestris (2.84 g/100 g of dry weight). During the flowers development, it was interesting to note a decrease in fat content at the full flowering stage for both species which is probably due to the morphology and the physiology changes of the flower, or to the differences in environmental factors, such as changes in weather conditions (Bravo, 1978; Reyes-Agüero, Aguirre, & Valiente-Banuet, 2006). 3.7. Energy The energy contribution of 100 g of flowers was low (Table 1), ranging from 157 to 240 kcal. The highest energetic value was guaranteed by full flowering stage in O. ficus-indica flowers (240 kcal/100 g of dry weight) and initial flowering stage in O. stricta flowers (205 kcal/100 g of dry weight), while the vegetative stage for O. ficus-indica and post-flowering stage for O. stricta had the lowest energetic contribution. The energy provided by a

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Table 3 Fatty acids composition of Opuntia ficus-indica and Opuntia stricta flowers during four flowering stages (g/100 g of total fatty acid). Fatty acid

C12:0 C14:0 C14:1 C15:0 C16:0 C16:1 C17:0 C17:1 C18:0 C18 :1 C18:2 C18:3 C20:0 C20:1 C20:2 C21:0 C24:0 SAFA MUFA PUFA

Opuntia ficus-indica

Opuntia stricta

A

B

C

D

A

B

C

D

2.1 0.53 0.48 1.22 38.25 0.97 0.45 3.08 7.47 9.17 5.66 3.69 12.73 2.92 4.42 3.23 3.62 69.62 16.6 13.8

2.08 0.41 0.35 0.2 38.52 4.77 0.22 3.68 5.23 13.80 8.18 9.88 7.45 1.57 1.64 1.75 0.28 56.14 24.2 19.7

1.87 0.6 0.34 0.15 43.03 2.74 0.36 3.55 4.47 11.91 5.43 6.17 8.22 2.86 4.39 1.33 2.6 62.62 21 16

0.28 2.41 0.05 0.18 37.15 0.22 0.17 3.6 3.96 14.42 9.42 11.84 6.87 2.57 4.48 1.05 1.31 53.39 21 26

0.52 2.02 0.18 1.75 48.91 2.72 0.89 0.66 4.33 16.09 0.52 8.8 3.81 0.57 2.91 3.99 1.33 67.55 20.22 12.23

1.34 2.08 0.68 1 57.64 1.15 0.43 0.23 1.85 19.12 0.94 1.5 4.05 0.47 0.48 4.63 2.4 75.43 21.65 2.92

0.21 3.51 0.17 1.71 59.52 1.31 0.62 0.31 2.43 17.08 0.6 2.6 3.19 0.45 0.34 4.15 1.79 77.13 19.32 3.55

0.12 2.36 0.35 0.67 48.3 0.48 0.23 0.16 1.68 17.14 0.95 8.12 8.58 0.28 0.64 8.58 1.33 71. 87 18. 42 9.71

(A) Vegetative, (B) initial flowering, (C) full flowering and (D) post-flowering stage. Data are the means of two replicates. SAFA: Saturated fatty acids. MUFA: Monounsaturated fatty acids. PUFA: Polyunsaturated fatty acids.

portion of 100 g of the flowers was significantly different for both species at the full flowering and post-flowering stages. 3.8. Available carbohydrate content Carbohydrates, showed similar contents and they were higher than 26 g/100 g. They didn't show a direct relationship pertaining to flowering stage. 3.9. Fatty acid composition of Opuntia flowers The fatty acid composition for both Opuntia species was dominated by saturated fatty acids (SAFA) throughout the four flowering stages. The SAFA content, varied from 67 to 87 g/100 g of total fatty acids for O. stricta and from 53 to 70 g/100 g of total fatty acids for O. ficus-indica, during all flowering stages (Table 3). Monounsaturated fatty acids (MUFA) represent approximately 20 g/100 g of total fatty acids. The post-flowering stage contained the highest level of polyunsaturated fatty acids (PUFA) for O. ficus-indica which are mainly linoleic (C18:2) and linolenic acids (C18:3) (Table 3), whereas for O. stricta the content of PUFA for the same stage was only about 10 g/100 g of total fatty acids. However, the vegetative stage contained the highest level of PUFA. Our results differed from those of other plant flowers, for example for the flowers of Malva sylvestris, the composition of fatty acids were: 36 g/100 g SAFA, 7 g/ 100 g MUFA and 56 g/100 g PUFA (Barros et al., 2010) and for fertilized flowers of Rosa canina these amounts were about 29 g/ 100 g SAFA, 7 g/100 g MUFA and 63 g/100 g PUFA (Barros, Carvalho, & Ferreira, 2011). 3.10. Functional properties of powdered flowers 3.10.1. Hydration properties The hydration properties of Opuntia flowers were investigated because of their importance in relation to the functionality in food products.

For a suitable description of the hydration properties for O. ficusindica and O. stricta flowers at post-flowering stage, three methods were applied, namely swelling capacity (SWC), water solubility index (WSI), and water holding capacity (WHC). As can be observed in Table 4, O. ficus-indica flowers show a significantly higher WSI index (15.5 g/100 g) than that for O. stricta flowers (14.8 g/100 g) (P < 0.05). WSI were related to the presence of soluble molecules (Ayadi et al., 2009). Indeed, O. ficus-indica flowers had higher soluble sugars content than O. strcita flowers which could be responsible for this difference in WSI values between both species. Table 4 also shows that O. ficus-indica and O. strcita flowers' powders exhibited SWC of 7.3 and 8.2 cm3 of water/g of dry weight, respectively. This activity is attributed to its content in polysaccharides. In fact, these results were similar to those of flours obtained from spiny and spineless Opuntia cladodes (z7.5 cm3/g dry weight) (Ayadi et al., 2009) and other vegetable sources such as wheat and carrot (Thebaudin, Lefebvre, Harrington, & Bourgeois, 1997). However, Femenia, Lefebvre, Thebaudin, Robertson, and Bourgeois (1997) reported higher SWC values for cauliflowers (16.9e17.5 cm3/g dry weight). Moreover, the WHC evolution of O. ficus-indica and O. stricta flowers' powders at different temperatures (25, 40, 60 and 80  C) was illustrated in Fig. 1a and b. WHC is the ability of a moist material to retain water when subjected to an external centrifugal gravity force or compression. It's the sum of bound water, hydrodynamic water and, mainly, physically trapped water
zquez-Ovando, Rosado-Rubio, Chel-Guerrero, & Betancur(Va Ancona, 2009). The WHC values show that they were related to the flowers species. In fact, O. ficus-indica flowers exhibited significantly higher WHC values (p < 0.05) as compared to O. stricta flowers. The difference in hydrophilic constituents' content could explain this variation. A slight increase in the WHC for O. stricta flowers' powders at high temperatures should also be observed (Fig. 1). So, WHC for O. stricta increased from 5.2 at 25  C to 5.9 g of water/g of dry matter at 80  C. This increase was probably due to the increase in the solubility of fibers and proteins because of the rise in temperature (Fleury & Lahaye, 1991). In this study, no significant differences (p > 0.05) were observed at 25, 40 and 60  C while WHC found at 60 and 80  C did show significant differences (p < 0.05). Concerning O. ficus-indica flowers, there is no progressive increase according to the temperatures. Nevertheless, the highest WHC values were marked by a significant increase at 40  C from 5.7 to 8.4 g of water/g of dry matter. This result found at 40  C was in the same range of some agricultural by-products (dietary fiber concentrates) at 25  C (6.30e13.2 g of water/g dry weight) reported previously by Grigelmo-Miguel and Martin-Belloso (1999). Furthermore, the WHC values of O. ficus-indica samples were also comparable to the WHC values (6.60e9.00 g of water/g dry weight) of some ~ i & Martincommercial dietary fiber rich supplements (Gon ~n, 1998). Following the peak noted at 40  C for O. ficusCarro indica flowers, there was a decrease at 60 and 80  C reaching 7.7

Table 4 Hydration properties (swelling capacity and water solubility index) for Opuntia ficus-indica and Opuntia stricta flowers at post-flowering stage. Hydration properties

Opuntia-ficus indica

Opuntia stricta

swelling capacity (ml/g) water solubility index (g/100 g)

7.3 ± 0.2a 15.5 ± 0.58a

8.2 ± 0.4a 14.8 ± 0.34b

Results are expressed as mean ± standard deviation (n ¼ 3). Data were analyzed statistically by Student's t-test. Differences between groups were considered significant at least at P  0.05.

I. Ammar et al. / LWT - Food Science and Technology 59 (2014) 448e454

Fig. 1. Evolution of the water holding capacity (WHC) of Opuntia ficus-indica and Opuntia stricta flowers powder at different temperatures (25, 40, 60 and 80  C) (mean ± SD in g water/g of dry weight; n ¼ 3). For each temperature different letters (aebec) mean significant differences (p < 0.05, Duncan test). : Opuntia ficus-indica and : Opuntia stricta.

and 7.1 g of water/g of dry matter (Fig. 1). This evolution was similar to that founded by Femenia et al. (1997) which showed that WHC of cauliflower florets was reduced from 12 at 40  C to 5.7 g of water/g dried samples at 75  C. Significant differences (p < 0.05) in the WHC were observed at 25, 40 and 60  C, while WHC founded at 60 and 80  C did not show any significant differences (p > 0.05). Femenia et al. (1997) reported that the WHC of fiber is mainly dependent on its particle size, its source, temperature, pH and ionic strength. To conclude, the observed influence of temperature calls for the use of 40  C in order to get the maximum WHC for O. ficus-indica, while for O. stricta, WHC showed minimal changes in relation to the variation of temperature. Since Opuntia flowers at post-flowering stage were rich in dietary fiber (Table 1), they may play a major role in the hydration properties. Furthermore, these properties can be modulated according to our needs. 3.10.2. Oil holding capacity Oil holding capacity (OHC) is also a technological property related to the chemical structure of the plant polysaccharides. The evolution of OHC of the Opuntia flowers' powder at different temperatures (25, 40, 60 and 80  C) is shown in Fig. 2. In general, a similar trend could be observed for both tested samples. A considerably high level of OHC of Opuntia flowers at 25  C ranging from 1.4 to 1.7 g oil/g dry sample for O. stricta and O. ficus-indica, respectively. These values were similar to those of flours obtained from spiny and spineless Opuntia cladodes (1.3 g oil/g dry weight) (Ayadi et al., 2009). They were similar to fibers from other fruits, vegetables, and seaweeds (2 g/g) (Femenia
vez, Chiffelle, & Asenjo, et al., 1997; Figuerola, Hurtado, Este 2005; Lopez et al., 1996; Yaich et al., 2011), but lower than for cereal fibers (2e4 g/g) (Femenia et al., 1997). The OHC for O. ficusindica and O. strcita flowers were similar at 25 and 40  C (1.2e1.8 g oil/g dry sample). Hence, there is a gradual increase in OHC due to the temperature's increases, for both species (Fig. 2). In fact, the OHC reached the highest values at 80  C for O. ficusindica and O. strcita flowers. Therefore, the increases in the temperature led to a clear rise in the OHC values. For O. ficus-

453

Fig. 2. Evolution of the oil holding capacity (OHC) of Opuntia ficus-indica and Opuntia stricta flowers powder at different temperatures (25, 40, 60 and 80  C) (mean ± SD in g of oil/g of dry weight; n ¼ 3). For each temperature different letters (aebec) mean significant differences (p < 0.05, Duncan test). : Opuntia ficus-indica and : Opuntia stricta.

indica flowers a statistically significant difference (p < 0.05) in OHC was observed at different temperatures 25, 60 and 80  C, while the OHC at 25 and 40  C did not show any significant differences (p > 0.05). For O. stricta flowers significant differences (p < 0.05) in the OHC were observed at 25, 40, 60 and 80  C.
ndez-Lo
pez et al. According to Figuerola et al. (2005) and Ferna (2009), OHC is basically dependent on fiber composition, overall charge density, surface properties and hydrophobic nature of the fiber particles. In addition, the OHC is of great importance from an industrial point of view, since it reflects the emulsifying capacity which represents a highly desirable characteristic in products. 4. Conclusion As far as we know, it's the first report about Opuntia flowers analysis throughout their development for their nutrient and fatty acid compositions, as well as their functional properties. The main conclusion consists in the fact that the nutritional and mineral compositions were associated with the flowering stages. O. ficus-indica and O. stricta flowers represent a rich nutrient composition in proteins at the beginning of flowering. The fat and minerals contents were at their optimum at the postflowering stage when the flower was completely dried. Nineteen fatty acids were identified, putting in evidence the high amount of saturated fatty acids in these flowers. This research has also revealed that Opuntia flowers were a rich source of dietary fiber. Hence, they have important functional properties such as WHC, SWC, WSI and especially the OHC. The combination of the functional properties and the rich nutritional composition of the studied flowers support the benefits of these species. These characteristics may encourage the use of Opuntia flowers for human consumption as an alternative source of dietary fiber and as functional ingredients in order to avoid syneresis, to modify the viscosity and texture of formulated food, or to stabilize food emulsions. Acknowledgments The authors thank Mr. Hammami Mohamed responsible for U.S.C.R. spectrometry (faculty of medicine of Monastir) for chromatographic analyses.

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References1 AFNOR. (1996). Dosage des min
eraux e m
ethodes par spectrom
etrie d’
emission de flamme. NF-T-90e019, AFNOR (Ed.). Paris: Association Française de Normalisation. Alimi, H., Hfaiedh, N., Bouoni, Z., Sakly, M., & Ben Rhouma, K. (2011). Evaluation of antioxidant and antiulcerogenic activities of Opuntia ficus indica f. inermis flowers extract in rats. Environmental Toxicology and Pharmacology, 32, 406e416. *Ammar, I., Ennouri, M., Khemakhem, B., Yangui, T., & Attia, H. (2012). Variation in chemical composition and biological activities of two species of Opuntia flowers at four stages of flowering. Industrial Crops and Products, 37, 34e40. Anderson, R. A., Conway, H. F., Pfeifer, V. F., & Griffin, E. (1969). Gelatinization of corn grits by roll and extrusion cooking. Cereal Science Today, 14, 11e12. AOAC. (1995). Official methods of analyses. Washington, DC: Association of Official Analytical Chemist. *Ayadi, M. A., Abdelmaksoud, W., Ennouri, M., & Attia, H. (2009). Cladodes from Opuntia ficus-indica as a source of dietary fiber: effect on dough characteristics and cake making. Industrial Crops and Products, 30, 40e47. *Barros, L., Carvalho, A. M., & Ferreira, I. C. F. R. (2010). Leaves, flowers, immature fruits and leafy flowered stems of Malva sylvestris: a comparative study of the nutraceutical potential and composition. Food and Chemical Toxicology, 48, 1466e1472. Barros, L., Carvalho, A. M., & Ferreira, I. C. F. R. (2011). Exotic fruits as a source of important phytochemicals: Improving the traditional use of Rosa canina fruits in Portugal. Food Research International, 44, 2233e2236.
len no mel brasileiro. Rio de Janeiro, Brazil: Luxor, 151 P. Barth, O. M. (1989). O po Battaglini, C. (1939). Qualitative and quantitative analysis of the organic constituents of the flowers of Opuntia ficus-indica and the decoction of the flowers. Annali di Chimica Farmaceutica, 70e73.
ceas de M
Bravo, H. H. (1978). Las Cacta exico (Tomo 1. ed.). Universidad Nacional
noma de Me
xico. Auto Bustos, E. O. (1981). Alcoholic beverage from Chilean Opuntia ficus indica. American Journal of Enology and Viticulture, 32, 228e229.
o, M., De Abreu, M. B., Pawlowska, A. M., Cioni, P. L., & Braca, A. (2010). De Le Profiling the chemical content of Opuntia ficus-indica flowers by HPLCePDAESI-MS and GC/EIMS analyses. Phytochemistry Letters, 3, 48e52. Dubois, M., Gilles, K. A., Hamilton, J. K., Rebers, P. A., & Smith, F. (1956). Colorimetric method for determination of sugars and related substances. Analytical Chemistry, 28, 350e356. Ennouri, M., Bourret, E., Mondolot, L., & Attia, H. (2005). Fatty acid composition and rheological behaviour of prickly pear seed oils. Food Chemistry, 93, 431e437. Ennouri, M., Fetoui, H., Hammami, M., Bourret, E., Attia, H., & Zeghal, N. (2007). Effects of diet supplementation with cactus pear seeds and oil on serum and liver lipid parameters in rats. Food Chemistry, 101, 248e253. Espinosa, J., Borrocal, R., Jara, M., Zorilla, C., & Medina, J. (1973). Some properties and preliminary tries of preservation of fruits and juice of prickly pear (Opuntia ficus indica). Fruits, 28, 285e289. *Femenia, A., Lefebvre, A. C., Thebaudin, J. Y., Robertson, J. A., & Bourgeois, C. M. (1997). Physical and sensory properties of model foods supplemented with cauliflower fiber. Journal of Food Science, 62, 635e639.
ndez-Lo
pez, J., Sendra-Nadal, E., Navarro, C., Sayas, E., Viuda-Martos, M., & Ferna
rez-Alvarez, J. A. (2009). Storage stability of a high dietary fiber powder from Pe orange by-products. International Journal of Food Science and Technology, 44, 748e756.
vez, A. M., Chiffelle, I., & Asenjo, F. (2005). Fiber Figuerola, F., Hurtado, M. L., Este concentrates from apple pomace and citrus peel as potential fiber sources for food enrichment. Food Chemistry, 91, 395e401. Fleury, N., & Lahaye, M. (1991). Chemical and physicochemical characterization of fibers from Laminaria digitata (Kombu Breton): a physiological approach. Journal of Science and Food Agriculture, 55, 389e400. Frati-Munari, A. C., Jimenez, E., & Ariza, C. R. (1990). Hypoglycemic effect of Opuntia ficus-indica in non insulin-dependent diabetes mellitus patients. Phytotherapy Research, 4, 195e197. Galati, E. M., Tripodo, M. M., Trovato, A., Miceli, N., & Monforte, M. T. (2002). Biological effect of Opuntia ficus-indica (L.) Mill. (Cactaceae) waste matter: NOTE I: diuretic activity. Journal of Ethnopharmacology, 79, 17e21. ~ i, I., & Martin-Carro ~n, N. (1998). In vitro fermentation and hydration properties Gon of commercial dietary fiber-rich supplements. Nutrition Research, 18, 1077e1089.

1 These references (*) are key references because Barros et al. (2010) studied the nutraceutical composition of flowers from another genus. Ammar et al. (2012) used the same raw material “Opuntia flowers”. However, functionnal properties were not studied. Furthermore Ayadi et al. (2009) studied the functional properties of cladodes from Opuntia ficus-indica. Yaich et al. (2011) studied the Chemical composition of seaweed and their functional properties in different temperatures. Femenia et al. (1997) studied properties of model foods supplemented with cauliflower by- product.

Grigelmo-Miguel, N., Gorinstein, S., & Martin-Belloso, O. (1999a). Characterization of peach dietary fibre concentrate as a food ingredient. Food Chemistry, 65, 175e181. Grigelmo-Miguel, N., & Martin-Belloso, O. (1999b). Characterization of dietary from orange juice extraction. Food Research International, 31, 355e361. Hamdi, M. (1997). Prickly pear cladodes and fruits as a potential raw material for the bioindustries. Bioprocess Engineering, 17, 387e391. Hegwood, D. A. (1990). Human health discoveries with Opuntia sp. (Prickly pear). HortScience, 25, 1515e1516. Hoffmann, W. (1980). The many uses of prickly pears (Opuntia Mill.) in Peru and Mexico. Plant Resources and Development, 12, 58e68. Kader, A. A. (2008). Flavor quality of fruits and vegetables. Journal of the Science of Food and Agriculture, 88, 1863e1868. Lee, Y. C., Pyo, Y. H., Ahn, C. K., & Kim, S. H. (2005). Food functionality of Opuntia ficus-indica var. Cultivated in Jeju Island. Journal of Food Sciences and Nutrition, 10, 103e110. Lin, M. J. Y., Humbert, E. S., & Sosulski, F. W. (1974). Certain functional properties of sunflower meal products. Journal of Food Science, 39, 368.
n, F., Periago, M. J., Martinez, M. C., & Ortun ~ o, J. (1996). Lopez, G., Ros, G., Rinco Relationship between physical and hydration properties of soluble and insoluble fiber of artichoke. Journal of Agricultural and Food Chemistry, 44, 2773e2778. Maisuthisakul, P., Pasuk, S., & Ritthiruangdej, P. (2008). Relationship between antioxidant properties and chemical composition of some Thai plants. Journal of Food Composition and Analysis, 21, 229e240. Palevitch, D., Earon, G., & Levin, I. (1993). Treatment of benign prostatic hypertrophy with Opuntia ficus-indica (L.) Miller. Journal of Herbs, Spices & Medicinal Plants, 2, 45e49. Pestana, M., Beja, P., Correia, P. J., De Varennes, A., & Faria, E. A. (2005). Relationships between nutrient composition of flowers and fruit quality in orange trees grown in calcareous soil. Tree Physiology, 25, 761e767. Prosky, L., Asp, N. G., Schweizer, T. F., De Vries, J. W., & Furda, L. (1988). Determination of insoluble, soluble and total dietary fiber in foods and food products: Collaboration study. Journal of the Association of Official Analytical Chemists, 71, 1017e1023. Reyes-Agüero, J. A., Aguirre R., J. R., & Valiente-Banuet, A. (2006). Reproductive biology of Opuntia: a review. Journal of Arid Environments, 64, 549e585. Robertson, J. A., de Monredon, F. D., Dysseler, P., Guillon, F., Amado, R., & Thibault, J. F. (2000). Hydration properties of dietary fiber and resistant starch: a European collaborative study. Lebensmittel-Wissenschaftund Technologie, 33, 72e79. Rop, O., Mlcek, J., Jurikova, T., Neugebauerova, J., & Vabkova, J. (2012). Edible flowers e a new promising source of mineral elements in human nutrition. Molecules, 31, 6672e6683. Saenz, C. (2000). Processing technologies: an alternative for cactus pear (Opuntia spp.) fruits and cladodes. Journal of Arid Environments, 46, 209e225. Saenz, C., Arriagana, S., Fizsman, S., & Calvo, C. (1996). Influence of pH and contents of carrageenan during the storage of cactus pear gels. Acta Horticulturae, 438, 131e134. Salisbury, F. B., & Ross, C. W. (1992). Plant physiology (4th ed.). California: Wadsworth. Sawaya, W. N., Khatchadourian, H. A., Safi, W. M., & Al-Muhamad, H. M. (1983). Chemical characterization of prickly pear pulp, Opuntia ficus indica, and the manufacturing of prickly pear jam. International Journal of Food Science and Technology, 18, 183e193. Sepúlveda, E., Saenz, C., Aliaga, E., & Aceituno, C. (2007). Extraction and characterization of mucilage in Opuntia spp. Journal of Arid Environments, 68, 534e545. Sosulski, F. W. (1962). The centrifuge method for determining flour absorption in hard red spring wheats. Cereal Chemistry, 39, 344e350. Thebaudin, J. Y., Lefebvre, A. C., Harrington, M., & Bourgeois, C. M. (1997). Dietary fibers: nutritional and technological interest. Trends in Food Science & Technology, 81, 41e48.
zquez-Ovando, A., Rosado-Rubio, G., Chel-Guerrero, L., & Betancur-Ancona, D. Va (2009). Physicochemical properties of a fibrous fraction from chia (Salvia hispanica L.). Food Science and Technology, 42, 168e173. *Yaich, H., Garna, H., Besbes, S., Paquot, M., Blecker, C., & Attia, H. (2011). Chemical composition and functional properties of Ulva lactuca seaweed collected in Tunisia. Food Chemistry, 128, 895e901.