Mucilage from Yellow Pitahaya (Selenicereus megalanthus) Fruit Peel: Extraction, Proximal Analysis, and Molecular Characterization.

Mucilage is a hydrophilic biopolymeric material of interest in the food industry due to its high content of dietary fiber, antioxidant activity, and gelling and thickening capacities, which is present in high concentration in agricultural by-products, such as the peel of cacti fruits. In this work, the powdered mucilage extracted from the peel of yellow pitahaya (Selenicereus megalanthus) fruit was characterized using a multi-technical approach that included proximal analysis (proteins, lipids, crude fiber, ash, and carbohydrates), as well as structural (FTIR, NMR, UPLC-QTOF-MS, and X-ray diffraction), colorimetric (CIELab parameters), morphological (SEM), and thermal (DSC/TGA) methods. Likewise, its total content of dietary fiber and polyphenols, as well as its antioxidant activity, were determined. This dried mucilage presented a light pale yellow-reddish color, attributed to the presence of betalains (bioactive pigments with high antioxidant activity). The FTIR spectrum revealed functional groups associated with a low presence of proteins (5.45 ± 0.04%) and a high concentration of oligosaccharides (55.26 ± 0.10%). A zeta potential of -29.90 ± 0.90 mV was determined, denoting an anionic nature that favors the use of this mucilage as a stable colloidal dispersion. UPLC-QTOF-MS analysis revealed a major oligosaccharide composition based on galacturonic acid units in anionic form. SEM micrographs revealed a cracked morphology composed of amorphous and irregular particles. According to the DSC/TGA results, this mucilage can be introduced as a new source of hydrocolloids in food processes since it has high thermal stability that has been manifested up to 373.87 °C. In addition, this biopolymer exhibited a high content of polyphenols (25.00 ± 0.01-g gallic acid equivalent (GAE)/100-g sample), dietary fiber (70.51%), and antioxidant activity (1.57 ± 0.01 mmol Trolox equivalents/kg of sample). It was concluded that this mucilaginous material presents sufficient physicochemical and functional conditions to be used as a nutritional ingredient, thus giving valorization to this agricultural by-product.

Betacyanins from Hylocereus polyrhizus: pectinase-assisted extraction and application as a natural food colourant in ice cream.

The effect of solvent, substrate-to-solvent ratio and concentration of pectinase on the extraction of betacyanins from the pulp of red pitahaya (Hylocereus polyrhizus) was evaluated with respect to yield, betacyanin content (BC) and total sugar content. The application of betacyanins from red pitahaya in ice cream was then evaluated by comparison to a commercial colourant, E-162. Without the use of pectinase, the highest yields (9.11 ± 0.35%) of betacyanins were obtained using 95% ethanol at a substrate-to-solvent ratio of 1:1. With the use of pectinase at a concentration of 1.5%, the highest yield (17.11-17.45%) of betacyanins were obtained using water as a solvent at a substrate-to-solvent ratio of 1:1 and 1:2. Pectinase treatment (1.5-2.5%) using water as a solvent yielded betacyanins with the highest BC (126.47-130.83 g kg-1) and lowest total sugar content (57.85-59.74 g kg-1). The BC and total colour changes were similar in ice cream containing betacyanins from red pitahaya and E-162 throughout the 21-days of frozen storage at -18 °C. Betacyanins from red pitahaya or E-162 enhanced the antioxidant properties of ice cream. The sensory evaluation of ice cream containing betacyanins from red pitahaya showed a better colour acceptability than E-162.

Comparative Study of Betacyanin Profile and Antimicrobial Activity of Red Pitahaya (Hylocereus polyrhizus) and Red Spinach (Amaranthus dubius).

Betacyanins are reddish to violet pigments that can be found in red pitahaya (Hylocereus polyrhizus) and red spinach (Amaranthus dubius). This study investigated the impact of sub-fractionation (solvent partitioning) on betacyanin content in both plants. Characterization of betacyanins and evaluation of their antimicrobial activities were also carried out. Betanin was found in both plants. In addition, isobetanin, phyllocactin and hylocerenin were found in red pitahaya whereas amaranthine and decarboxy-amaranthine were found in red spinach. Sub-fractionated red pitahaya and red spinach had 23.5 and 121.5 % more betacyanin content, respectively, than those without sub-fractionation. Sub-fractionation increased the betanin and decarboxy-amaranthine content in red pitahaya and red spinach, respectively. The betacyanin fraction from red spinach (minimum inhibitory concentration [MIC] values: 0.78-3.13 mg/mL) demonstrated a better antimicrobial activity profile than that of red pitahaya (MIC values: 3.13-6.25 mg/mL) against nine Gram-positive bacterial strains. Similarly, the red spinach fraction (MIC values: 1.56-3.13 mg/mL) was more active than the red pitahaya fraction (MIC values: 3.13-6.25 mg/mL) against five Gram-negative bacterial strains. This could be because of a higher amount of betacyanin, particularly amaranthine in the red spinach.

Red Dragon Fruit Peels: Effect of Two Species Ratio and Particle Size on Fibre Quality and Its Application in Reduced-Fat Alpaca-Based Sausages.

This research aimed to assess the influence of red dragon fruit peels ratio (RDF-PR) from two species, Hylocereus hybridum (HH) and Hylocereus undatus (HU), and particle size (PS) on quality parameters of red dragon fruit peel powder (RDF-PP) and its further application in emulsified alpaca-based sausages as partial substitutes of pork-back fat. A three-level full factorial design (nine treatments) was employed to evaluate the effect of RDF-PR (HH(0%):HU(100%), HH(50%):HU(50%), and HH(100%):HU(0%)) and PS (499-297, 296-177, and <177 µm) on the dependent variables: L*, a*, b*, C, h°, water-holding capacity, oil-holding capacity, swelling capacity, pectin yield, degree of esterification (analysed through FT-IR), and crude fibre content. The data analysed through a response surface methodology showed that treatment one (T1) is the best with the optimised conditions at 100% HU RDF-PR and PS of <177 µm. The statistical validation of T1 exhibited the highest water-holding capacity (32.1 g/g peel), oil-holding capacity (2.20 g oil/g peel), and pectin yield (27.1%). A completely randomised design (four formulations) was then used to assess the effect of partial replacement of pork-back fat by T1 in emulsified alpaca-based sausages on the colourimetric, physicochemical, and texture properties (hardness, chewiness, cohesiveness, springiness, adhesiveness, and adhesive force). Likewise, a sensory hedonic scale was employed to evaluate the appearance, colour, odour, flavour, texture, and overall acceptability of sausages. The results revealed that 65.7% of pork-back fat content was successfully replaced compared with a control formulation. Additionally, F3 showed significantly (p < 0.05) better colourimetric, physicochemical, and textural characteristics, such as lower hardness (34.8 N) and chewiness (21.7 N) and higher redness (a* = 19.3) and C (22.9), compared to a control formulation. This research presents RDF-PP as a promising fat substitute for developing healthier, reduced-fat meat products using fibre-rich agroindustry by-products.

Microencapsulation of Betaxanthin Pigments from Pitahaya (Hylocereus megalanthus) By-Products: Characterization, Food Application, Stability, and In Vitro Gastrointestinal Digestion.

The yellow pitahaya peels generated as by-products during the consumption and processing of the fresh fruit are a rich and underutilized source of betaxanthins (natural yellow-orange pigment with antioxidant activity) and mucilage (structuring material used in the spray-drying process), molecules of high interest for the food industry. In this work, the betaxanthin-rich extract (BRE) obtained from this by-product was microencapsulated by spray drying (SD) using pitahaya peel mucilage (MPP) and maltodextrin (MD) as wall materials. Both types of microencapsulates (i.e., SD-MPP and SD-MD) retained high betaxanthin content (as measured by UV-vis) and antioxidant activity (ORAC). These microencapsulates were characterized structurally (FTIR and zeta potential), morphologically (SEM and particle size/polydispersity index), and thermally (DSC/TGA). The powdered microencapsulates were incorporated into the formulation of candy gummies as a food model, which were subjected to an in vitro gastrointestinal digestion process. The characterization study (FTIR and antioxidant activity) of the microcapsules showed that the fruit peel mucilage favors the retention of betaxanthins, while the SEM analysis revealed a particle size of multimodal distribution and heterogeneous morphology. The addition of SD-MPP microcapsules in the candy gummy formulation favored the total dietary fiber content as well as the gumminess and chewiness of the food matrix; however, the inhibition of AAPH• (%) was affected. The stability of the yellow color in the gummies after 30 days of storage indicates its suitability for storage. Consequently, the microencapsulation of betaxanthins with pitahaya peel mucilage can be used as a food additive colorant in the food industry, replacing synthetic colorants, to develop products with beneficial qualities for health that can satisfy the growing demand of consumers.

Optimization of Ultrasound-Assisted Extraction of Dietary Fiber from Yellow Dragon Fruit Peels and Its Application in Low-Fat Alpaca-Based Sausages.

The main objective of this study was to optimize the extraction of dietary fiber (insoluble dietary fiber and soluble dietary fiber) and degree of esterification from yellow dragon fruit peels using ultrasound-assisted extraction. Additionally, the study aimed to investigate the potential application of this fiber as a fat replacement in alpaca-based sausages. The optimization process for extracting dietary fiber and degree of esterification involved considering various factors, including the liquid-to-solid ratio, pause time, and total ultrasound application time. A Box-Behnken design consisting of 15 treatments was employed to determine the optimal levels for ultrasound-assisted extraction. The optimized conditions were found to be a liquid-to-solid ratio = 30 mL/g, pause time = 1 s, and total ultrasound application time = 60 min, which resulted in the highest values of insoluble dietary fiber (61.3%), soluble dietary fiber (10.8%), and the lowest value of degree of esterification (39.7%). The predicted values were validated against experimental data and showed no significant differences (p > 0.05). Furthermore, a completely randomized design was utilized to assess the effect of dietary fiber on replacing fat content during the production of alpaca-based sausages. The findings revealed that up to 78% of the fat content could be successfully replaced by soluble dietary fiber obtained from yellow dragon fruit peels when compared to high-fat sausages. Additionally, experimental sausages using soluble dietary fiber showed similar (p > 0.05) quality characteristics, such as hardness (24.2 N), chewiness (11.8 N), springiness (0.900), cohesiveness (0.543), redness (a* = 17.4), and chroma values (20.0), as low-fat commercial sausages.

Ultrasound-alkaline combined extraction improves the release of bound polyphenols from pitahaya (Hylocereus undatus 'Foo-Lon') peel: Composition, antioxidant activities and enzyme inhibitory activity.

In this study, ultrasound-assisted alkaline hydrolysis was used to extract polyphenols from pitahaya peel. The effects of sonication time, ultrasonic density, NaOH concentration and the liquid-material ratio on the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of the extracts were studied. The composition and content difference of the extracts were analyzed and the inhibitory effect of α-amylase and α-glucosidase was measured. The results of single-factor analysis showed that when the sonication time was 45 min, the ultrasonic density was 32 W/L, the NaOH solution concentration was 6 M and the liquid-material ratio was 30 mL/g, the release of phenolic compounds was the largest and the antioxidant activity was the strongest. An UPLC-QTOF-MS/MS method was used to analyze the components and contents of the extracts. We found that there was a great difference in the component content of the free polyphenol extract and the bound polyphenol extract. From the results, we concluded that there was a strong correlation between the type and content of phenolic compounds and antioxidant activities, indicating that phenolic compounds were the main compounds of these biological activities. Moreover, the bound polyphenol extracts showed a significant inhibitory effect on α-amylase and α-glucosidase was stronger than that of the free polyphenol extracts. In addition, scanning electron microscopy showed that ultrasound-assisted extraction is crucial to the destruction of the cell wall and the release of bound polyphenols. Therefore, the pitahaya peel has the potential for therapeutic, nutritional, and functional food applications, and ultrasound-assisted alkaline hydrolysis is an effective means to release phenolic compounds.

Phenolic Compounds Profile and Antioxidant Capacity of Pitahaya Fruit Peel from Two Red-Skinned Species (Hylocereus polyrhizus and Hylocereus undatus).

Pitahaya peel is a good source of bioactive polyphenols. However, the bound phenolics and their antioxidant activity remain unclear. The bound phenolics of pitahaya peel from two red-skinned species with red pulp (RP) and white pulp (WP) were released with different methods (acid, base, and composite enzymes hydrolysis). The results revealed that base hydrolysis was the most efficient method for releasing the bound phenolics from RP (11.6 mg GAE/g DW) and WP (10.5 mg GAE/g DW), which was 13.04-fold and 8.18-fold for RP and 75.07-fold and 10.94-fold for WP compared with acid hydrolysis and enzymatic hydrolysis, respectively. A total of 37 phenolic compounds were identified by UPLC-TOF/MS with most chlorogenic acid, caffeic acid, ferulic acid and p-coumaric acid in RP, whereas chlorogenic acid, caffeic acid, ferulic acid, rutin and isoquercitrin were the main compounds in WP. Regardless of the hydrolysis method, the extracts having the highest phenolic content showed the strongest antioxidant activities. The work shows that hydrolysis methods have a significant effect on the release of phenolics, and the contents of major characteristic bound phenolic compounds are related to the ecological type of pitahaya.

Occurrence and characterisation of calcium oxalate crystals in stems and fruits of Hylocereus costaricensis and Selenicereus megalanthus (Cactaceae: Hylocereeae).

Detailed description about occurrence of calcium oxalate (CaOx) crystals in the edible vine cactus species Hylocereus costaricensis and Selenicereus megalanthus is scarce. Therefore, we evaluated and characterized the presence, morphology and composition of CaOx crystals in both species. Crystals were isolated from greenhouse and in vitro vegetative stems, and from ripe fruit peels and pulp by enzymatic digestion and density centrifugation and quantified with a haemocytometer. Morphologies were studied using scanning electron microscopy, elemental composition with energy-dispersive X-ray spectroscopy and salt composition with X-ray powder diffraction. Analyses conducted confirmed that isolated crystals were exclusively composed by CaOx, both mono- and dihydrated. Highest crystal contents were measured in greenhouse stems, followed by the fruit peels. While very few crystals were quantified in in vitro plants, they were not detected in the fruit pulp at all, which is of advantage for its human consumption and could be linked to mechanisms of seed dispersal through animals. Different crystal morphologies were observed, sometimes varying between genotypes and tissues analysed. This is the first work known to the authors with a detailed characterization of CaOx crystals in vine cacti.

Estimation of glycaemic index of peach palm (Bactris gasipaes) cooked fruits and chips, and pitahaya (Hylocereus spp.) pulp

The glycaemic index (GI) is a physiological measure of a food’s potential to increase postprandial blood glucose, as compared to the effect produced by food taken as reference, such as glucose or white bread. Currently researchers and consumers are interested in low GI foods, since their consumption is associated with better weight control and reduced risk of incidence of chronic diseases, like diabetes. In the present study, the GI value for peach palm cooked fruit, peach palm chips and pitahaya pulp was estimated. The methodology established by the FAO / WHO for determining the GI of food was used. A total of 12 healthy, non-smoking volunteers were selected and they ingested the fore mentioned foods on different occasions, in 25 g portions of available carbohydrates, after 12-14h overnight fast. Blood glucose levels were measured in 30 min intervals up to 120 min after ingestion. Average GI value was 48 ± 11 for the pitahaya pulp and 35 ± 6 for the peach palm cooked fruit, which may be classified as low glyceamic index foods. The GI of peach palm chips was 60 ± 7, corresponding to a food with a moderate GI. The processing for producing the chips caused an increase in the GI value when compared to the cooked fruit, probably because the stages of milling, moulding and baking promote availability of starch during hydrolysis by the digestive enzymes.

Estimación del índice glicémico del fruto cocido y de chips de pejibaye (Bactris gasipaes) y de la pulpa de pitahaya (Hylocereus spp.). El índice glicémico (GI) es una medida fisiológica del potencial de un alimento para incrementar la glucosa sanguínea, en comparación con el efecto producido por un alimento de referencia, tal como la glucosa o el pan blanco. Los investigadores y consumidores tienen interés en los alimentos de bajo GI, dado que su consumo está asociado con un mejor control del peso corporal y una reducción del riesgo de enfermedades crónicas como la diabetes. En el presente estudio se determinó el valor de GI del fruto cocido de pejibaye, de los chips horneados de pejibaye y de la pulpa de pitahaya. Se seleccionaron 12 voluntarios, aparentemente sanos, no fumadores, los cuales consumieron los alimentos evaluados y el alimento de referencia (pan blanco), en una porción que contuviera 25 g de carbohidratos disponibles, después de un período de ayuno de 12-14 h. Los niveles de glucosa en sangre fueron medidos en intervalos de 30 min hasta 120 min después de la ingesta. Se obtuvo un valor promedio de GI de 48 ± 11 para la pitahaya y de 35 ± 6 para el pejibaye cocido, los cuales pueden ser clasificados como alimentos de bajo índice glicémico. El valor de GI de los chips de pejibaye fue de 60 ± 7, lo que corresponde a un alimento de GI moderado. Se encontró que el procesamiento para la obtención de los chips produjo un aumento en el valor del GI, en comparación con el obtenido para la fruta cocida, probablemente debido a que las etapas de molienda, moldeo y horneo favorecen la disponibilidad del almidón para su hidrólisis por parte de las enzimas digestivas.

Fenologia reprodutiva de pitaia vermelha no município de Lavras, MG / Reproductive phenology of red pitaya in Lavras, MG, Brazil

O estudo do comportamento fenológico pode contribuir para melhorar a produtividade das culturas e a qualidade dos frutos. O trabalho foi realizado com o objetivo de avaliar a fenologia reprodutiva da pitaia vermelha em Lavras, MG, Brasil. Foram avaliados em cem plantas de pitaia vermelha (Hylocereus undatus (Haw.) Britton & Rose) os períodos das subfases desde a emissão das gemas até a maturação dos frutos de 2008 a 2010. O botão floral se desenvolve no período de 19 a 21 dias. A antese é noturna que dura aproximadamente 15 horas. A maturação do fruto ocorre de 30 a 40 dias após a abertura da flor, quando o fruto adquire a coloração rosa a vermelho intenso e a textura firme. Em Lavras, MG o período reprodutivo da pitaia ocorre de novembro a maio e tempo do aparecimento do botão floral até a colheita do fruto é de 50 a 60 dias.

The study of phenology can contribute to improve the productivity of crops and fruit quality. The study was conducted to evaluate the reproductive phenology of red pitaya in Lavras, MG, Brazil. It was evaluated in one hundred plants of pitaya (Hylocereus undatus (Haw.) Britton & Rose) the subphase's periods from the issuance of buds to fruit ripening from 2008 to 2010. The bud develops from 19 to 21 days. The anthesis is nocturnal which lasts about 15 hours. The maturation occurs from 30 to 40 days after flower opening, when the fruit acquires color pink to deep red and firm texture. In Lavras, MG the reproductive period of red pitaya occurs from November to May and the time of appearance of flower buds to fruit harvest is from 50 to 60 days.

Efecto de la agitación sobre la deshidratación osmótica de pitahaya amarilla (selenicereus megalanthus s.) Empleando soluciones de sacarosa / Effect of stirring on osmotic dehydration of yellow pitahaya (selenicereus megalanthus s.) Using sucrose solutions / Efeito da agitação sobre a desidratação osmótica de pitaya amarela (selenicereus megalanthus s.) Empregando soluções de sacarose

Se estudió el efecto de la agitación (180, 220, y 240rpm) sobre la pérdida de agua y la ganancia de azúcar en rodajas de pitahaya deshidratas osmóticamente, empleando soluciones osmóticas de sacarosa con dos niveles de concentración, 45 y 55°Brix. Adicionalmente, se determinó la porosidad de la pitahaya en estado fresco y deshidratado osmóticamente, y se relacionó con los niveles de agitación. Los resultados mostraron que los niveles de agitación inciden significativamente sobre la pérdida de agua, presentando mayor variación relativa para los tratamientos a 45ºBrix. La ganancia de azúcar no presentó diferencias significativas por efecto de los niveles de agitación. Lo anterior se explica por la baja porosidad de la pitahaya en estado fresco (2,78 ±0,35%), que dificulta la entrada de la molécula de sacarosa en la fruta. Los resultados sugieren que la deshidratación osmótica se perfila como una técnica de pretratamiento apropiada para la pitahaya amarilla debido a la baja ganancia de sólidos durante el proceso.

The effect of the stirring (180, 220, y 240rpm) on water loss and sugar gain in the process of osmotic dehydration of pitahaya slices was studied, using osmotic solutions of sucrose with two concentration levels, 45 and 55°Brix. Additionally, the porosity of the pitahaya in fresh and osmotically dehydrated states was determined and related to the stirring speed. The results showed that stirring level has a significant effect on water loss, with a greater relative variation for the treatments at 45°Brix. Sugar gain did not show significant differences as an effect of agitation speed. This is explained by the low porosity of the pitahaya in fresh state (2.78 ±0.35%), which hinders the entry of the sucrose molecules into the fruit. The results suggest that osmotic dehydration is emerging as an appropriate pretreatment technique for the yellow pitahaya due to the low gain in solids during the process.

Estudou-se o efeito da agitação (180, 220, e 240rpm) sobre a perda de água e o ganho de açúcar en rodelas de pitaya desidratas osmoticamente, empregando soluções osmóticas de sacarose com dois níveis de concentração, 45 e 55°Brix. Adicionalmente, se determinou a porosidade da pitaya em estado fresco e desidratado osmoticamente, e se relacionou com os níveis de agitação. Os resultados mostraram que os níveis de agitação incidem significativamente sobre a perda de água, apresentando maior variação relativa para os tratamentos a 45ºBrix. O ganho de açúcar não apresentou diferenças significativas por efeito dos níveis de agitação. O anterior se explica pela baixa porosidade da pitaya em estado fresco (2,78 ±0,35%), que dificulta a entrada da molécula de sacarose na fruta. Os resultados sugerem que a desidratação osmótica se perfila como uma técnica de pre-tratamento apropriada para a pitaya amarela devido ao baixo ganho de sólidos durante o processo.