Nutritional improvement of pasta with Pereskia aculeata Miller: a non-conventional

Consumers have been demanding higher quality of life. Nutritional diet intake affects directly the wellbeing and health. Supplying adequate human nutrition within ecosystem carrying capacities is a key factor in the global environmental sustainability challenge (Heller et al., 2013). Among the possibilities to improve the nutrient availability are found the non-conventional food plants. They are wild edible plants, with low cost, easily accessible and have high nutritional potential. Pereskia aculeata Miller or known in Brazil such as ora-pro-nobis (DPN) or American gooseberry, is an example of a non-conventional food plant. Ot is a vegetable that play no part in the general population diet, being often underused and unknown (Kinupp & Lorenzi, 2014). DPN is native plant widely distributed in the Central and South America and southern region of United States belonging to the Cactaceae family (Conceição et al., 2014; Takeiti et al., 2009). On Brazil, DPN is found from the northeast (Bahia) to the southern region (Minas Gerais, Paraná, Santa Catarina and Rio Grande do Sul) of the country (Conceição et al., 2014). The main useful part of DPN is the leaf due to its source of protein, total dietary fibre (especially soluble fibre), minerals (calcium, magnesium, manganese, zinc and iron) and vitamins (Takeiti et al., 2009). The high-quality of protein, fibre contents and absence of leaf toxicity of the DPN leaves make it a useful and important food source (Dayrell & Vieira, 1977). DPN is the so-called ‘meat of the poor’ due to the high content of proteins in its leaves (Mercê et al., 2001). On addition to presenting a well-balanced composition, the leaves have a high content of L-lysine. The presence of this amino acid is important, since lysine is an essential amino acid, and in general, it is deficient in cereals (Pinto & Scio, 2014). The most abundant amino acid found in DPN is tryptophan, representing over 20% of its amino acids (Nobel & Hartsock, 1986). Furthermore, the protein and essential amino acid levels reported are substantially higher than the minimum amount recommended by the Food and Agriculture Drganization of the United Nations (FAD) as necessary for human consumption (Sierakowski et al., 1987). As a comparison, meat has approximately 20% of protein; and studies conducted by Sierakowski et al. (1987) with DPN leaves show that they are composed of 25% protein. Almeida & Cambraia (1974) reported protein content in DPN leaves higher than common vegetables sources, such as common corn (7.6-10%, w/w), beans (18-20%, w/w), spinach (2.2%, w/w), kale (1.6%, w/w) and lettuce (1.3%, w/w).


Introduction
Consumers have been demanding higher quality of life.Nutritional diet intake affects directly the wellbeing and health.Supplying adequate human nutrition within ecosystem carrying capacities is a key factor in the global environmental sustainability challenge (Heller et al., 2013).Among the possibilities to improve the nutrient availability are found the non-conventional food plants.They are wild edible plants, with low cost, easily accessible and have high nutritional potential.Pereskia aculeata Miller or known in Brazil such as ora-pro-nobis (DPN) or American gooseberry, is an example of a non-conventional food plant.Ot is a vegetable that play no part in the general population diet, being often underused and unknown (Kinupp & Lorenzi, 2014).DPN is native plant widely distributed in the Central and South America and southern region of United States belonging to the Cactaceae family (Conceição et al., 2014;Takeiti et al., 2009).On Brazil, DPN is found from the northeast (Bahia) to the southern region (Minas Gerais, Paraná, Santa Catarina and Rio Grande do Sul) of the country (Conceição et al., 2014).The main useful part of DPN is the leaf due to its source of protein, total dietary fibre (especially soluble fibre), minerals (calcium, magnesium, manganese, zinc and iron) and vitamins (Takeiti et al., 2009).The high-quality of protein, fibre contents and absence of leaf toxicity of the DPN leaves make it a useful and important food source (Dayrell & Vieira, 1977).DPN is the so-called 'meat of the poor' due to the high content of proteins in its leaves (Mercê et al., 2001).On addition to presenting a well-balanced composition, the leaves have a high content of L-lysine.The presence of this amino acid is important, since lysine is an essential amino acid, and in general, it is deficient in cereals (Pinto & Scio, 2014).The most abundant amino acid found in DPN is tryptophan, representing over 20% of its amino acids (Nobel & Hartsock, 1986).Furthermore, the protein and essential amino acid levels reported are substantially higher than the minimum amount recommended by the Food and Agriculture Drganization of the United Nations (FAD) as necessary for human consumption (Sierakowski et al., 1987).As a comparison, meat has approximately 20% of protein; and studies conducted by Sierakowski et al. (1987) with DPN leaves show that they are composed of 25% protein.Almeida & Cambraia (1974) reported protein content in DPN leaves higher than common vegetables sources, such as common corn (7.6-10%, w/w), beans (18-20%, w/w), spinach (2.2%, w/w), kale (1.6%, w/w) and lettuce (1.3%, w/w).
Pasta products are largely popular worldwide and well accepted because of their sensory attributes.Ots convenience and palatability make it a popular dish (Padalino et al., 2013).Conventional pasta is mainly manufactured using wheat flour as the primary ingredient (Khan et al., 2013).Pasta is a source of carbohydrates (74-78%, dry basis), 11-13% of proteins, but its deficient in lysine and threonine (Abdel-Aal & Hucl, 2002).
A fortification to increase the pro-healthy quality of this product would be useful.Pasta may represent an excellent model as a food vehicle for the addition of specific nutrients (Tazrart et al., 2016;Miceli et al., 2015;Khan et al., 2013).The incorporation of vegetables into pasta could significantly contribute to the recommended daily vegetable intake (Dliviero & Fogliano, 2016).Petitot et al. (2010) produced fortified spaghetti by adding high amounts of legume flour (35% of split pea) improving the proteins, fibres, and vitamins content.Sun-Waterhouse et al. (2013) developed fettuccine pastas enriched with plant-derived bioactives, dietary fibre from Hi-maize starch and polyphenols from elderberry juice concentrate offering a healthy benefit to consumers.Sobrinho et al. (2015) incorporated 2% (w/w) of DPN leaves flour in sausage formulations, enhancing the nutritional aspect.A tagliatelle pasta containing different concentrations of flour made from DPN leaves (1.0, 1.5, 2.0%, w/w) formed a firm and elastic dough with no cracks (Rocha et al., 2008).
The objective of this study was to develop a functional pasta (tagliatelle) incorporating flour of DPN obtained from dried leaves and to evaluate its effect on pasta quality, colour, pH, firmness, weight gain, cooking loss and sensorial acceptance.

Preparation of pasta enriched with OPN-F
Sieved wheat flour and beaten eggs in a ratio 2:1 (flour:eggs) were homogenized.The mixture was mixed by hand for 15 min, and then passed on smooth cylinder until the formation of a thin blade size nine, smooth and not crumbly.The dough sheet was cut into pasta form, and then arranged in aluminium moulds to be taken to dry in an oven with air circulation (Tecnal,model SL 102/200,Piracicaba,Brazil) at 60 °C for 40 min.The added amounts of DPN-F were 10% (F1) and 20% (F2) related to wheat flour weight (Table 1).All experiments were carried out in triplicate.

Nutritional profile: OPN-F and pasta
Chemical analysis: Analyses of moisture, ash, lipid (Soxhlet method), protein (Kjeldahl method) content were performed according to the standard ADAC method (Association of Dfficial Analytical Chemists, 2012).The content of calcium and iron was determined using method 974.3 from the Association of Dfficial Analytical Chemists (2012).The dietary fibre content was determined according to ADAC method -Dfficial method 985.29 (Association of Dfficial Analytical Chemists, 2012).The dietary fibre content of F1 and F2 were estimated based on the formulation, addition of 10% of DPN-F and 20% of DPN-F, respectively.The pH was measured in cooked pasta sample (10 g mixed in 100 mL of distilled water) using a calibrated device (Digimed,Brazil).

Pasta quality
Firmness: the maximum force required to cut the pasta strands represented it.Ot was determined by using a texturometer (Brookfield, model CT3, Middleboro, USA).The cooked pasta strands were washed with 50 mL of water and kept in 300 mL of cold water for 1 min, and then cut to 10 cm lengths.The TA-52 MDHRS probe was used with the following conditions: pre-test speed: 2.0 mm s -1 , test speed: 0.5 mm s -1 , post-test speed: 0.5 mm s -1 and with 50% compression.Weight gain: it was determined based on Paucar-Menacho et al. (2008).Weight gain was calculated based on the weight before and after the cooking process (200 mL of boiling water for 4 min).Cooking loss: it was calculated by evaporating 25 mL of cooking water in an oven at 105 °C (Tecnal, model TE-394-1, Piracicaba, Brazil) until a constant weight was reached (Paucar-Menacho et al., 2008).Colour parameters: The surface colour parameters were measured after the cooking process.A colourimeter (Konica Minolta, CR400 Chroma Meter model, Tokyo, Japan) was used.Ot was calibrated with a white plate, an observation angle of 2° and illuminant D65.Measurements were performed using the COE L* a* b* system (Maciel et al., 2015).

Sensorial analysis
A complete balanced block design for three experimental products was used to minimize order effects.The sensorial analysis was carried out with a total of 100 judges of different ages and social classes, both sexes, selected randomly among the staff and students from the university, who had no prior knowledge of the formulation of the products (Stone & Sidel, 2004).This process was registered in the ethics committee as CAAE: 53738716.0.0000.5505.The cooked samples were coded with random numbers of three digits and presented to the judge.The test began with three questions in order to check whether any of the judges had any prior experience with DPN and the frequency of pasta consumption.The three pasta formulations were evaluated for colour, odour, flavour, texture, appearance parameters and overall impression using a nine-point structured hedonic scale, where 1 = very much dislike and 9 = very much like.Consumer purchase intention was evaluated by assessing the possibility that consumers would plan or be willing to purchase the product, using a five-point scale.The acceptance of the product (F1 and F2) was calculated from the average of the scores given by the judges, considering the five-point-scale, and a score equal to 5 represents 100% probability of buying.

Statistical analysis
The data were analysed through the analysis of variance (ANDVA) using the Statistics program version 7.0 (Statistics Onc., USA).Differences between the means were detected by Tukey's multiple comparisons test (95% confidence).

Preparation of pasta enriched with OPN-F
The pasta containing 10% and 20% of DPN-F presented a green colour due to the pigment of the leaves (complex mixture of many forms of chlorophyll and carotenoid pigments) (Figure 1).Preliminary tests were carried out adding 10, 20, 30, 40 and 50% of DPN-F related to wheat flour weight.Pasta containing DPN-F concentrations above 30% (related to wheat flour weight) did not form continuous and soft gluten dough.This indicate that the amount of DPN-F compromised the formation of a three-dimensional gluten matrix After being cooked in boiling water (4 min), it was not observed visually colour difference in cooked water.Ot could be associated that the pigment did not migrate to the water.Dn the other hand, the cooked DPN pasta was not sticky and brittle, which could be due to the starch molecules being entrapped in the DPN fibres.The interference of fibre with the gluten-protein network of pasta can result in the destruction of the protein-starch matrix and an uneven distribution of water in the pasta's structure.During the cooking of the pasta, the starch will compete with the fibre for water molecules; so high fibre content will mean that the starch will absorb less water (Ficco et al., 2016).Krishnan et al. (2012) observed a decrease in the stickiness of the dough in pasta with a higher content of fibre achieved by adding sweet potato.

Chemical composition and energy value
The chemical composition of dehydrated DPN-F and the pasta samples (control, F1 and F2) were determined (Table 2).The dietary fibre content of the pasta containing 10% and 20% of DPN-F was approximately three and five-fold higher than the conventional pasta (control, without DPN-F), respectively.The pasta enriched with DPN-F is an alternative to improve the fibre intake in human diet, promoting healthy effects.Fibre in the diet increases satiety, which reduces the quantity of food ingested and regulates the intestine's metabolism.The World Health Drganization recommendation is that fibre intake should be 20 to 30 g day -1 .The consumption of 100 g of F1 and F2, will provide 30.3 and 50.8% of total fibre intake, respectively.Khan et al. (2013) indicated a health functional property of pasta formulated with red sorghum flour due to the higher total dietary fibre content (twice as compared to pasta formulated  with durum wheat semolina).An enriched salt bread with DPN flour increased fibre content as compared to conventional bread (Silva et al., 2015).
The three formulations of pasta showed comparable values of lipid content.The ash content of F1 and F2 was significantly higher than control pasta, twice and five times, respectively.The addition of DPN-F improved significantly the calcium and iron content.On comparison with conventional pasta, the mineral content of pasta containing DPN-F could be considered a nutritional advantage.Calcium is an important mineral in the human metabolism, playing a role in nerve transmission, digestion, neuromuscular function, bones and teeth.The high calcium content found in DPN-F could be considered an alternative source, since the main food source (derived from milk) is not consumed sufficiently.Oron is also an essential mineral for the human body, used in the synthesis of haemoglobin, which carries oxygen in the form of myoglobin to the muscles.Ot is also essential for DNA synthesis and energy metabolism.The deficiency of this metal induces the occurrence of pathological conditions, with iron deficiency anaemia being the most frequent (Beard & Dawson, 1997).Adding DPN-F, the carbohydrate content and pH of the final dough did not change significantly.Unexpected results of total protein content of F1 and F2 were observed.Ot was not possible to increase the protein content in the ratios applied in this study.Ot was associated to the lower content of the DPN flour added in F1 and F2 formulations and the DPN-F used in this work presented only 12.4% of total protein content, which is less than has been found in the literature, for example 28.4% by Takeiti et al. (2009) and 22.9% by Rocha et al. (2008).
The energy values were estimated based on the chemical composition of the pasta (control, F1 and F2) (Table 2).Ot was observed a nutritional advantage due to the energy values of the DPN products.Of a portion of 80 g is considered -equivalent to a plate of dry pasta, the energy value of the pasta portion corresponds to 289.95 kcal and 301.29 kcal for F1 and F2, respectively.The conventional pasta had 317.10 kcal 80 g -1 .Ferreira et al. (2016) found similar energy values for sorghum/rice/potato pasta and Zandonadi et al. (2012) for green banana pasta.The lower energy values of the DPN-F products are an extremely beneficial health factor in a world in which obesity and a sedentary lifestyle are causing widespread concern.

Pasta quality
Cooking performance is an important factor in a consumer's judgment of pasta quality.Reactions are produced during pasta cooking as a result of the heat effect and water uptake, for example protein swelling, starch gelatinization, increase in pasta weight and volume (Larrosa et al., 2016).The firmness, weight gain, cooking loss and colour parameters were evaluated (Table 3).
The pasta samples showed different behaviour after cooking.The control pasta presented the highest firmness (1.31 N).The addition of DPN-F reduced the firmness of the pasta (F1 and F2).This could be associated with the fibre presence in pasta network that could decrease the homogeneity and continuous gluten matrix formation.The wheat proteins are mainly composed of glutenin and gliadins that form inter-and intramolecular disulphide bonds during processing, forming a three-dimensional gluten network.This structure is responsible for the textural properties of pasta (Petitot et al., 2010).The addition of DPN, a non-gluten material could dilute the gluten strength promoting a weakened structure.The weight gain increased in the pasta containing DPN-F, it could be associated to the higher water absorption per gram of dry pasta.The weight gain of cooked pasta indicates the water uptake and corresponds to a macroscopic event involving a complex molecular modification of starch and proteins, mainly hydration (Nouviaire et al., 2008).
Cooking loss is related to the leakage of amylose from the starch granules, during cooking, which results in an unpleasant sticky texture (Mercier et al., 2016).Ot was widely used as an indicator of the overall cooking performance, indicating the resistance to disintegration during cooking pasta (Matsuo et al., 1992).A lower content of total solids in the cooking water was observed in F1.The values of the cooking loss of pasta enriched with DPN-F wee within the standards required for pasta.According to Hummel (1966), a cooking loss of up to 6% is characteristic of very good-quality wheat pasta, up to 8% of average-quality pasta, and values equal to or greater than 10% are characteristic of poor-quality pasta.Grzybowski & Donnelly (1979) also consider 8% as the maximum acceptable value for cooking loss in the cooking water.
Raw pasta has a gluten network that entrapped starch granules.After drying process of pasta, denaturation of gluten could sustain the desired protein cross-linking (Sissons, 2004).During the cooking process, the pasta matrix absorbs water and starch granules swell (increasing the volume), lose the rigid structure and release soluble substances.The degree of the openness of pasta gluten network would influence the extent of water absorption by starch granules during pasta cooking (Sun-Waterhouse et al., 2013).
The colour parameters of cooked pasta, given as a* value (greenness to redness), b* value (blueness to yellowness), and L* value (brightness), were measured in cooked pasta samples.The most of studies of the colour measurements on enriched pasta were performed on uncooked pasta, but it remains unclear whether the colour of the pasta before or after cooking has the most significant impact on consumer perception of the pasta (Mercier et al., 2016).Oncreasing the DPN-F concentration, the lightness (L*) reduced significantly (p < 0.05).This could be attributed to the pheophytinization process, the most common alteration of green leaves in food processing.The pheophytinization of chlorophyll and the consequent drastic colour shift of green DPN-F to the dull olive-brown pheophytin could be associated to the replacement of magnesium by hydrogen, but some shift in the resonance structure is also involved (Francis, 1985).The lightness decrease (< L*) in F1 and F2, proportional with the DPN-F concentration was followed by a concomitant decrease in the redness (a*) and yellowness (b*).On this work, the impact of enrichment with DPN-F on the yellowness of cooked pasta was greater than the impact on redness, presumably because a* values were lowest in control pasta and decreased with the DPN-F addition (F1 and F2 pasta).
The addition of DPN-F into pasta formulation promoted texture and colour (darkening) variation as compared to control pasta.These characteristics differ from the usual pasta product consumption, which could influence consumer acceptance.

Sensorial analysis of pasta
The sensorial analysis of the pasta was studied.Distributions of scores for appearance, odour, colour, flavour, texture and overall impression analysed by the judges are presented in Table 4.Among the 100 judges who received the pasta (control, F1 and F2), 92% did not know of DPN and 98% had never experienced any formulated product containing DPN.Most of the judges (34%) eat pasta at least once a week, 26% eat at least twice a week, and 2% eat three times a week, which shows the importance of improving the nutritional quality of this product.
The control and F1 pasta were similar in colour, odour, texture and overall acceptability, which facilitate the entry into the pasta market.The sensorial parameters such as colour, flavour and texture are the main characteristics to acquisition, consumption, acceptance and preference of food products.The F1 showed higher acceptability in appearance, flavour and texture, and a higher decision-to-purchase score than F2 (Figure 2).Appearance is the most important food quality factor and colour is one of the main attributes of the appearance evaluated at the purchase time.The higher content of DPN-F in F2 promoted a darkness of pasta (>L*) that caused a negative effect on appearance.The colour of pasta is closely related to the colour properties of the raw material used in the formulations and changes in proportions of the ingredients may lead to different colours (Guimarães et al., 2018).Dn the other hand, texture is one of the main attributes of the food texture that is perceived during eating.The addition of 20% of DPN-F promoted a negative effect on the texture (F2 pasta formulation).This was reflected in texture sensorial notes confirming the results obtained in the instrumental analysis.Oncreasing the concentration of DPN-F resulted in a decrease in texture scores (p < 0.05), and thus may related to the reduction in moisture observed in this samples.Previous studies have demonstrated that hardness decrease with the moisture content increase (Su et al., 2013).At higher substitution level, negative scores have been reported (Petitot et al., 2010).
Regarding the purchase decision, the judges showed a resistance to the formulation with 20% of DPN-F (F2) and this is could be associated with the fibrous texture and characteristic flavour of the plant.The average score for F1 was 4 out of 5, or 80.0% acceptance, while F2 showed 63.2% acceptance among 100 judges.According to Stone & Sidel (2004), an acceptance ratio higher than or equal to 70% is considered acceptable.On this research, the acceptance score of pasta products with DPN-F content (F1 and F2) could be related to the texture and flavour due to the fibre addition.
The search for healthier foods that promote wellness and healthy has generated a new market in food sector.Although, it is still necessary to give more information of these new ingredients before introduce in daily diet.Sensorial evaluation of fortified pasta focused on the overall product acceptability.On general, the additions up to 10% chickpea flour (Wood, 2009), lupin flour (Torres et al., 2007), were generally well accepted.At higher substitution level, negative scores have been reported (Petitot et al., 2010).Rocha et al. (2008) developed a pasta containing 2% of DPN-F and obtained, by sensorial analysis using 80 volunteers, 92% of acceptability.Silva et al. (2015) produced bread containing 5% of DPN-F and affirmed that additions of small amounts of DPN-F were well accepted by the judges.

Conclusions
The addition of DPN-F improved the nutritional quality of pasta in terms of dietary fibre, calcium, iron compared to the control pasta.Pasta enriched with DPN-F presented a greenish  and fibrous appearance.Sensory evaluations indicated that pasta enriched with 10% of DPN-F did not affect consumer acceptance.The formulation containing 10% DPN-F presented characteristics closer to conventional pasta in relation to colour, texture and overall impression.Unexpected results of total protein content of F1 and F2 were observed that it was associated to the lower content of protein of DPN-F used in this work.The new product has the potential to be taken to prevent constipation, obesity (high satiety due the dietary fibre content) and still be an alternative intake of calcium and iron.The product showed excellent parameters in relation to cooking quality and were within the standards established.The firmness of pasta decreased with the addition of DPN-F.Sensory analysis has shown that the most judges were not aware of the DPN leaves and frequently consumed pasta, highlighting the importance of improving the nutritional quality of this product.

Figure 2 .
Figure 2. Consumer purchase intention in relation to pasta formulations with and without DPN-F enrichment.(1) Certainly would not buy; (2) Possibly would not buy; (3) Maybe would not buy, or not; (4) Possibly would buy; (5) Certainly would buy.

Table 3 .
Firmness, weight gain, cooking loss and colour parameters of pasta at different formulations.
bMedia with different letters in the column are significant different by Tukey's test (p < 0.05).Firmness express in Newton (N).

Table 4 .
Appearance, colour, flavour, odour, texture and overall attributes evaluated by judges for the different formulations of pasta.Media with different letters in the same line are significant different by Tukey's test (p < 0.05).