Influence of drying conditions on colour,betacyanin content and antioxidant capacities in dried red-fleshed dragon fruit (Hylocereus polyrhizus)

In this study, drying of red-fleshed dragon fruit at different temperatures (40, 50, 60, 70 and 80 °C) and air velocities (1.0 and 1.5 m s⁻¹) was conducted under the specific humidity of 25 g H₂O kg⁻¹ dry air. The results showed that drying at higher temperatures resulted in shorter drying times. However, temperature and air velocity did not significantly affect the total betacyanin contents and antioxidant capacities in dried products. Seven betacyanins identified by LC-MS were betanin, isobetanin, phyllocactin, isophyllocactin, betanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside, isobetanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside and decarboxylated phyllocactin. In addition, the temperature increased the isomerisation of betacyanins. The most preferable condition for preserving the colour and betacyanin contents of red-fleshed dragon fruit was the drying at a temperature of 80 °C and air velocity of 1.5 m s⁻¹ since it could shorten the drying time and give a bright red colour to the dried product as well as it had no significant impact on the betacyanins.     

Physico-chemical and structural changes of red-fleshed dragon fruit (Hylocereus polyrhizus) during fruit development

BACKGROUND: Determination of physico‐chemical (weight, length, diameter, stomatal density, respiration rate, colour, soluble solids concentration, titratable acidity, chlorophyll and betacyanin content) and structural changes of red‐fleshed dragon fruit (Hylocereus polyrhizus (Weber) Britton & Rose) was carried out from 5 to 35 days after pollination (DAP) in order to explain their growth, development, maturations and ripening stages. RESULTS: Fruit growth of red‐fleshed dragon fruit followed a sigmoid growth pattern. Significant changes in colour were obtained in both peel and pulp as DAP progressed, which were indicated by reductions of L*, C* and h° values as both changed from green to red–violet colour at ripening. Red–violet betacyanin was manifested earlier in pulp at 25 DAP, followed by peel 4–5 days later, and finally both peel and pulp turned full red–violet by 30 DAP. There was a significant increase in soluble solids concentration and titratable acidity with the continuous increase in betacyanin content as DAP progressed. CONCLUSION: The physico‐chemical and betacyanin accumulation of red‐fleshed dragon fruit changed as it developed, matured and ripened which coincided with structural changes. Copyright © 2010 Society of Chemical Industry     

Study on bioaccessibility of betacyanins from red dragon fruit (Hylocereus polyrhizus)

Food Science and Biotechnology - Betacyanins are bioactive dietary phytochemicals which can be found in red dragon fruit (RDF). Therefore, the bioaccessibility of betacyanins that present in...     

Spray drying of red (Hylocereus polyrhizus) and white (Hylocereus undatus) dragon fruit juices: physicochemical and antioxidant properties of the powder

This study aims to investigate physical stability and antioxidant properties of spray‐dried red (Hylocereus polyrhizus) and white (Hylocereus undatus) dragon fruit powder upon storage at various relative humidity (RH). Inlet air temperatures of 120 °C (red dragon fruit) and 110 °C (white dragon fruit) as well as maltodextrin concentration of 30% (w/v) were selected as the spray drying conditions as powder was obtained at these minimum conditions. The powder was ranging from 3 to 7 μm in particle size with spherical morphology. The powder had lower antioxidant content and antioxidant activities compared with the control before spray drying. Storage of powder at 43%, 54% or 75% RH at 25 °C for 25 days resulted in structural changes correlating to the depression of glass transition temperatures (T_g) to below storage temperature. At 33% RH, no visible structural changes were observed. Antioxidant properties of the powder remained unchanged after 25 days' storage at the studied RHs.     

Effects of processing and storage on juice colour and betacyanin stability of purple pitaya (<Emphasis Type="Italic">Hylocereus polyrhizus</Emphasis>) juice

Purple pitaya (Hylocereus polyrhizus) fruits have been recently proposed as a promising source of betalains. In the present study, purple pitaya juice processing at pilot-plant scale is reported for the first time. Each processing step was examined in terms of juice colour and betacyanin retention. Lightness (L ^*) and hue angle (h°) values were strongly influenced by juice filtration, while chroma (C ^*) and betacyanin retention were most strongly altered by pasteurisation. Three systems of juice pasteurisation were evaluated. Betacyanin loss and colour alteration were minimal upon pasteurisation in an HTST system and a standard tubular heat exchanger, respectively. Additionally, storage experiments using mucilage-free purple pitaya juice were conducted. Whereas light exposure of unsupplemented samples resulted in significant pigment degradation, detrimental effects of light exposition were completely prevented by the addition of 1% ascorbic acid prior to storage. After 6 months, about 70% of the initial betacyanin content was retained in the presence of ascorbic acid, irrespective of illumination.     

Oligosaccharides of pitaya (dragon fruit) flesh and their prebiotic properties

The major carbohydrates of white and red-flesh pitayas (dragon fruit) were glucose, fructose and some oligosaccharides (total concentrations of 86.2 and 89.6 g/kg, respectively). The molecular weight distribution of the extract was affected by the extraction solvent. The maximum oligosaccharides content (27.40%), which included fractions with molecular weights of 273–275, 448–500 and 787–911 Da, were obtained using 80% ethanol extraction at room temperature (28 ± 2 °C). The low molecular weight fraction, including glucose and fructose, was successfully removed by yeast cultivation. The molecular weights of mixed oligosaccharides (716, 700, 490 and 474 Da) were confirmed by mass spectrometry. The mixed oligosaccharides showed that they were resistant to hydrolysis by artificial human gastric juice and human α-amylase, giving maximum hydrolysis of 4.04% and 34.88%, respectively. The mixed oligosaccharides were also found capable of stimulating the growth of lactobacilli and bifidobacteria.     

Effect of high pressure processing on the stability of anthocyanin,ascorbic acid and color of Chinese bayberry juice during storage

The stability of anthocyanin (Cy3Gl) and ascorbic acid (AA) of pressure treated Chinese bayberry (Myrica rubra Sieb. et Zucc.) juice was investigated during storage at temperature of 4 °C and 25 °C. Samples of Chinese bayberry juice (350 mL each, packed with a polyethylene bag) were processed at 400, 500, 600 MPa in room temperature for 10 min. The retention ratio of Cy3Gl and AA content after pressure treatment was more than 98% and 96%, respectively. Both Cy3Gl and AA of pressure treated juice were more stable during storage as compared to those of the untreated control juice. The degradation of Cy3Gl and AA of samples during storage could be described using first order kinetic model. It was observed that there was a significant (p < 0.01) correlation between changes of Cy3Gl and AA content for all tested samples of Chinese bayberry juice during storage.     

Ascorbic acid degradation kinetics of sonicated orange juice during storage and comparison with thermally pasteurised juice

Ascorbic acid degradation kinetics of sonicated orange juice during storage were determined and compared to thermally pasteurised samples. Acoustic energy densities (AED) ranging from 0.30 to 0.81 W/mL and treatment times of 2-10 min were investigated. The degradation kinetics of sonicated samples followed first-order kinetics (R² ≥ 0.91) during processing. During storage ascorbic acid degradation of sonicated samples followed the Weibull model (R² ≥ 0.97) with β values ranging from 0.662 to 0.697. Comparatively, first-order degradation kinetics were observed during storage for thermally pasteurised (R² = 0.98) and control samples (R² = 0.96). Increased shelf life based on ascorbic acid retention was found for sonicated samples compared to thermally pasteurised samples. Predicted shelf life for sonicated orange juice ranged from 27 to 33 days compared to 19 days for thermally pasteurised juice during storage at 10 °C. These results indicate that sonication results in enhanced retention of ascorbic acid in orange juice during storage compared to thermal processing.     

Stability of betacyanin from red pitahaya (Hylocereus polyrhizus) and its potential application as a natural colourant in milk

The effects of temperature (30, 50, 85 and 100 °C) treatment and 10 weeks of refrigerated storage (4 °C) on the betacyanin content and colour stability of betacyanins from red pitahaya (Hylocereus polyrhizus) were investigated and compared to red beet (Beta vulgaris; E‐162) which was used as a control. Temperature treatment at 50 and 85 °C caused a greater reduction in betacyanin content (BC) in E‐162 compared to red pitahaya by inducing changes in betacyanin profile. The 10 weeks of refrigerated storage at 4 °C induced colour changes in betacyanins from red pitahaya and E‐162. In milk, betacyanins from red pitahaya presented a lower loss of BC and total colour changes (ΔE*) compared to E‐162. The microbial onset in milk containing betacyanins from red pitahaya and E‐162 was delayed up to day 5 of refrigerated storage at 4 °C compared to day 3 in plain milk. Milk containing betacyanins from red pitahaya showed better colour acceptability (3.89 ± 1.89) compared to E‐162 (6.10 ± 1.71). Hence, betacyanins from red pitahaya may be a potential natural functional colourant to simulate strawberry colour in milk.     

Effect of grape seed extract on oxidative, color and sensory stability of a pre-cooked, frozen, re-heated beef sausage model system

To compare grape seed extract (GSE) to common antioxidants in a pre-cooked, frozen, stored meat model system sausage was manufactured from lean beef (70%), pork fat (28%), and salt (2%). Antioxidants added for comparison with control included grapeseed extract (100, 300, and 500 ppm), ascorbic acid (AA, 100 ppm of fat) and propyl gallate (PG, 100 ppm of fat). Product was formed into rolls, frozen, sliced into patties, cooked on a flat griddle to 70 °C, overwrapped in PVC, then frozen at - 18 °C for 4 months. GSE- and PG-containing samples retained their fresh cooked beef odor and flavor longer (p < 0.05) than controls during storage. Rancid odor and flavor scores of GSE-containing samples were lower (p < 0.05) than those of controls after 4months of storage. The L* value of all samples increased (p<0.05) during storage. Thiobarbituric acid reactive substances (TBARS) of the control and AA-containing samples increased (p < 0.05); those of GSE-containing samples did not change significantly (p > 0.05) over the storage period.     

Effect of storage time on sensory and instrumental properties of skim‐milk yoghurt obtained with microbial transglutaminase

Not many studies have examined changes in microbial transglutaminase (MTG) yoghurts during storage. In this work, yoghurts manufactured with skimmed milk and treated with MTG were evaluated in refrigerated storage for 35 days. Instrumental measurements showed that firmness, consistency and pH values in MTG yoghurt experienced a significant increase with the storage time. However, sensory measurements showed that MTG yoghurts were not affected significantly by storage time. Acid taste scores only increased significantly with storage time in the control samples. Microbial transglutaminase treatment showed a positive effect on textural properties and allowed syneresis to be prevented completely during storage.     

Studies on the storage stability of fermented red dragon fruit (<Emphasis Type="Italic">Hylocereus polyrhizus</Emphasis>) drink

The objective of this work was to study the effect of storage temperatures and duration on the stability of fermented red dragon fruit drink (FRDFD) on its betacyanins content, physicochemical and microbiological qualities (BPM) and determining sensory acceptability. Results showed that both storage temperatures and duration have a significant effect on betacyanins content and physicochemical properties of FRDFD. Aerobic mesophilic and yeast and mold counts were lower than 1?×?10³ CFU/mL for FRDFD stored at both temperatures. The loss of betanin (16.53–13.93 g/L) at 4 °C was 15.73% with no significant changes in physicochemical properties from week two onwards compared to 56.32% (16.53–7.22 g/L) of betanin loss at 25 °C. At week eight, FRDFD stored at 4 °C still contained 13.93 g/L betanin with a pH value of 3.46, suggested its potential as a functional drink which is sensory acceptable (mean score?>?80% using hedonic test) among consumers.     

Thermal degradation kinetics of anthocyanins and visual colour of Urmu mulberry (Morus nigra L.)

Urmu mulberry (Morus nigra L.) juice was concentrated from 15.02 to 45.20 °Brix by rotary vacuum evaporator at 40 °C. The objectives of this study were to determine the titratable acidity, soluble solid content, antioxidant capacity, total monomeric anthocyanins and total phenolic matter in prepared concentrate, to investigate the thermal degradation kinetics of anthocyanins and Hunter colour parameters (L^∗, a^∗, b^∗) and total colour difference (TCD^∗) and to develop a relationship between visual colour and anthocyanin during thermal processing at 60, 70 and 80 °C. Monomeric anthocyanin degradation showed a first order reaction kinetics. The zero order, first order and a combined kinetics model were applied to the changes in Hunter colour parameters (L^∗, a^∗ and b^∗) and total colour difference (TCD^∗). All colour parameters followed an apparent combined kinetics model. The degradation of anthocyanins showed positive correlation with a^∗, b^∗ and L^∗ and negative correlation with TCD^∗.     

Ensuring the best storage temperature of Egyptian pastrami based on microbiological,physico-chemical and sensory evaluation

Egyptian pastrami is among the most important and widely consumed meat products in Egypt and due to the great defects in its storage as a ready-to-eat products by retailers, distributers or even consumers, the aim of the current research is to assess the effect of storage temperatures on physico-chemical, microbiological, and sensory properties of Egyptian pastrami using autoclaved non-meat ingredients to ensure the best storage temperature of such important food. Four storage temperatures were applied including room temperature during summer (25 °C), room temperature during winter (15 °C), in fridge at 4 °C and in freezer at −18 °C for a period of 60 days using whole unsliced produced pastrami arms. The findings showed that there was no significant effect (P > 0.05) of storage temperatures on the physico-chemical and sensory properties of tested Egyptian pastrami as the four types were highly accepted based on the physico-chemical and sensory evaluation. Meanwhile, there was noticeable effect of storage temperatures on the microbiological properties of the four manufactured types of pastrami, as the samples stored at −18 °C or at 4 °C for 60 days had the lowest microbial loads and was the best from microbiological aspect.     

Effect of gamma irradiation on fungal load, chemical and sensory characteristics of walnuts (Juglans regia L.)

Walnuts of the Baladi variety were treated with 0, 0.5, 1.0, 1.5 and 2.0 kGy of gamma irradiation. The irradiated and unirradiated nuts were stored at room temperature (15-18°C) and 50-70% r.h. Fungal load, proximate composition (moisture, protein, fat and ash contents), chemical changes and sensory properties of nuts were evaluated immediately after irradiation and after 12 months of storage. The results indicated that gamma irradiation reduced fungal load. The doses applied did not cause any significant change in proximate composition of walnuts. Gamma irradiation increased total acidity and decreased iodide value and volatile basic nitrogen (VBN) immediately after treatment. After 12 months of storage, gamma irradiation decreased total acidity and peroxide value and increased iodide value and VBN. No significant differences were observed between irradiated and nonirradiated samples in flavor and aroma immediately after irradiation. After 12 months of storage, higher doses (1.5 and 2.0 kGy) had a negative effect on sensory characteristics.     

Structural and chromatic stability of purple pitaya (Hylocereus polyrhizus [Weber] Britton & Rose) betacyanins as affected by the juice matrix and selected additives

Ascorbic, isoascorbic, and citric acids were applied for stabilisation of betacyanins during thermal treatment of purple pitaya juice at pH 4 and 6, respectively. In addition, to exclude matrix effects of juice constituents, selected food ingredients were added to a pigment preparation comprising the entire betacyanin pattern of purple pitaya, but being devoid of sugars, acids and pectic substances. After thermal treatment at pH 4, pigment retention, overall colour changes, betanin isomerisation, and phyllocactin deacylation were determined. As supported by statistical analyses, pigment stability and colour depended on type and concentration of the respective additive as well as on the pH conditions. Unexpectedly, the stabilising effects of the additives under investigation were more pronounced in purple pitaya juice than in the pigment preparation. After heating at 85 °C for 1 h, optimal pigment retention amounting to 91% was obtained in the juice supplemented with 1% ascorbic acid and adjusted to pH 4. For the first time, formation of indicaxanthin and isoindicaxanthin upon thermal treatment of purple pitaya juice is reported.     

Effect of the type of fat on rheology,functional properties and sensory acceptance of spreadable cheese analogue

The objective of this work was to evaluate the effect of different types of fat (butter oil, partially hydrogenated soybean fat and soybean oil) on the functionality, rheology and sensory acceptance of spreadable cheese analogues. Analogues made with partially hydrogenated soybean fat or soybean oil in substitution to butter oil presented lower fat globule size. As a consequence, these analogues showed lower melting, lower spreadability, higher hardness and higher values for the elastic and viscous moduli than cheese made with butter oil. Despite not managing to imitate the flavour of the traditional cheese, the analogue made with partially hydrogenated soybean fat showed good sensory acceptance.