Skip to main content
NCBI home page
Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2020 Jul 22;58(4):1401–1410. doi: 10.1007/s13197-020-04651-8

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

Ashwini Gengatharan 1, Gary Dykes 2, Wee Sim Choo 1,✉
PMCID: PMC7925792  PMID: 33746268

Abstract

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.

Keywords: Betalain, E162, Colour, Pigment, Red dragon fruit, Red pitahaya

Introduction

Production of coloured bioactive ingredients from natural sources, such as fruits and vegetables, are not only determined by the availability but also by the subsequent extraction procedure. Homogenization and solvent extraction are conventional recovery methods of natural pigments from plant materials (Hua et al. 2013). Extraction efficiency is influenced by many factors such as solvent composition, extraction time, extraction temperature, solvent to solid ratio and extraction pressure (Wettasinghe and Shahidi 1999; Cacace and Mazza 2002). Betalains are natural pigments that are gaining popularity for use as colorants in the food industry (Gengatharan et al. 2015). There are two main classes of betalains, betacyanins and betaxanthins (Choo 2018). Betacyanins can easily dissolve in common polar solvents including water, ethanol and methanol and their mixtures (Naderi et al. 2012). Ethanol is preferred over methanol for extractions of bioactive compounds from plants in the food industry due to the toxic nature of methanol (Hua et al. 2013).

Pectins are a group of polysaccharides that are rich in galacturonic acids and found in the middle lamella of plant cell wall or intercellular lamellar region (Chan et al. 2017). Pectin can function as a barrier to the diffusion of intracellular compounds during extraction. For this reason solvent-based extraction of bioactives may suffer result in low extraction yields, require longer extraction times and the final product may contain traces of organic solvent, all of which decrease the quality of the bioactives (Yang et al. 2011). The use of hydrolytic enzymes to lyse plant cell walls assists in the release of bioactive compounds from plants and is gaining more attention due to the need for eco-friendly extraction technologies (Puri et al. 2012). Since the degradation of polysaccharides that make up the cell wall is a fundamental step to improve the release of bioactive compounds, enzymes such as pectinases are essential to catalyse the hydrolysis of glycosidic bonds in the plant cell wall (Pinelo et al. 2006). Pectinase is a commercially important enzyme, especially in the food bioprocess industry, where it is a prerequisite to obtain well clarified and stable juices with higher yields (Sandri et al. 2012). Pectinase degrades the long and complex molecules called pectins in the fruit peels or pulp. The addition of pectinases reduces viscosity of fruit juices, improves the press-ability or extraction of juice and enables the production of higher yields of fruit juices of extracts (Tapre and Jain 2014).

Red pitahaya or red dragon fruit (Hylocereus polyrhizus) is rich in betacyanins (Yong et al. 2018) and contains 10–20% pectin (Ismail et al. 2012). Enzymatic treatment using pectinase can be applied during extraction of betacyanins from red pitahaya to effectively increase the extraction efficiency. However, the combination of solvents at different substrate to solvent ratio have not been studied to determine the efficacy of pectinase-assisted extraction of betacyanins from red pitahaya. The present study therefore investigates the effect of pectinase assisted extraction on the yield, betacyanin content and total sugar content of betacyanins from the pulps of red pitahaya extracted using various solvents (water, 50% ethanol and 95% ethanol) at two different substrate to solvent ratios (1:1 and 1:2). As a natural colourant, betacyanin extracted from red pitahaya was applied successfully in milk (Gengatharan et al. 2016) and yogurt (Gengatharan et al. 2017). The present study also investigates the application of the extracted betacyanins as a natural food colourant in ice cream in comparison to a commercial colourant (E-162).

Materials and methods

Materials

Fresh red pitahaya fruits with total soluble solid values of 20°–22° Brix were obtained from a local farm in Selangor, Malaysia. E-162 was obtained from Behn Meyer, Selangor, Malaysia.

Extraction of betacyanins

The pulp of red pitahaya fruit was extracted using either distilled water, 50% ethanol or 95% ethanol at a fresh weight to solvent ratio (w/v) of 1:1 or 1:2. Commercially available pectinase enzyme (Pectinex SP-L) (Sigma-Aldrich, U.S.A.) with an enzyme activity of 10,292 PGU/mL at a concentration of 0, 0.5%, 1.0%, 1.5%, 2.0% or 2.5% in the chosen solvent (w/v) was added to degrade the pectin and the mucilaginous compounds of the pulp. The pulp was homogenized in the solvent for 2 h with occasional stirring before being filtered and centrifuged at 15,000 × g for 15 min. Supernatant containing the betacyanins was poured into a weighed clean beaker and placed in a vacuum oven for 24 h. In this study, the vacuum-dried extracts are described as betacyanins.

Yield of betacyanins

The yield of the vacuum-dried betacyanins was calculated based on the formula below:

Yield (%) = (Weight of vacuum−dried betacyanins/Weight of fresh material)  × 100

Betacyanin content (BC)

The determination of BC was according to the method of Esquivel et al. (2007). Absorbance was carried out using a Lambda 25 UV–Vis spectrophotometer (Perkin Elmer, U.S.A) at a wavelength of 538 nm. The betacyanin content (BC) was calculated as below.

Betacyanin content (BC) (g kg−1) = A538 (MW) × V × (DF) × 1000/(ELW)

where A538 = the absorbance at 538 nm (λmax), L (path length) = 1.0 cm, DF = dilution factor, V = extract volume (mL), W = fresh weight of extracting material (g), E = mean molar absorptivity of betanin which equals to 6.5 × 104 L mol−1 cm−1 in water and MW = 550.

Total sugar content

Betacyanins from red pitahaya were prepared at a standardized absorbance of 0.70 ± 0.02 at a wavelength of 537 nm. The total sugar content in these betacyanin preparations was determined according to the phenol–sulphuric acid method (Dubois 1956). The total sugar content was expressed as mg L−1.

Application of betacyanins in ice-cream

Preparation of ice-cream

Fresh raw cow milk with 20% of 50 mg mL−1 betacyanins from red pitahaya or E-162 added was packed in sterilised Schott bottles. The milk was pasteurised at a temperature of 63 °C for 30 min and was allowed to cool to room temperature followed by refrigeration at 4 °C. After pasteurisation, a commercial powdered ice-cream pre-mix (Haan, Indonesia) was added to the chilled pasteurised milk and mixed thoroughly using a hand-mixer. The commercial ice-cream mix composed of sugar, non-dairy creamer, milk powder, vegetable emulsifier, thickening agent, sodium carboxymethyl cellulose and salt. The total fat content of the ice cream mix was 2%. This mixture was poured into an ice-cream maker (Kenwood, Malaysia), where the mixture was rapidly frozen and blended until the soft serve ice cream was formed. The soft serve ice-cream was packed into plastic sample cups with lids and stored in a freezer at − 18 °C. The determination of betacyanin content and colour measurement was carried out immediately after the soft serve ice cream was formed. The colour measurements betacyanin content and antioxidant activity were determined once every three days over 21-days of frozen storage at − 18 °C.

Colour measurement

Colour measurements were carried out using a colourimeter (HunterLab, U.S.A.). The L*, a* and b* values were measured. L* describes the lightness with L* values from white (L* = 0) to black (L* = 100). The a* value denotes positive values for reddish colours and negative values for greenish ones, whereas b* denotes positive values for yellowish colours and negative value for bluish colours. The total colour changes were calculated from L, a* and b* Cartesian coordinates by means of the following expressions:

ΔE∗=ΔL∗2+Δa∗2+Δb∗21/2

where Δa* = a* − a0*, Δb* = b* − b0*, ΔL* = L* − L0*; a0*, b0* and L0* are the initial colour values of ice cream.

DPPH free radical scavenging activity assay

Free radical scavenging activity was determined according to the method of Gengatharan et al. (2017). Ice cream (4 mL) was homogenized with with 1 mL of water. One mL of methanol (blank) or homogenized ice cream was added to 2 mL of 0.02 g/L of 2,2-diphenyl-1-picrylhydrazyl (DPPH) solution in methanol and shaken vigorously. The mixture was left to stand in the dark room for 30 min at room temperature. The reduction of DPPH was measured at 517 nm against a blank at 30 min. Antioxidant activity was expressed as free radical scavenging activity (FRSA) using the following equation:

FRSA%=Acontrol-Asample/Acontrol×100

Sensory evaluation

The sensory evaluation of ice-cream was approved by the Monash University Human Research Ethics Committee (Project Approval ID: 5599). A panel consisting of 100 untrained staff members and students of Monash University Malaysia was recruited for the sensory evaluation. The panelists evaluated the colour acceptability based on visual assessment using a 9-point hedonic scale (1 = like extremely; 2 = like very much; 3 = like moderately; 4 = like slightly; 5 = neither like nor dislike; 6 = dislike slightly; 7 = dislike moderately; 8 = dislike very much; 9 = dislike extremely). Samples were presented in 10 mL plastic cups labelled with a 3-digit code to the panelists. A commercial brand of strawberry flavoured and E-162 containing ice-cream was also included for comparison.

Statistical analysis

All experiments were conducted in three independent replicates (n = 3). Data were analysed by one or two-way analysis of variance (ANOVA) using a SPSS software (IBM, U.S.A.). The Tukey test was used to determine the statistical significance at p < 0.05.

Results and discussion

Effect of solvents, substrate to solvent ratio and pectinase treatment on the yield of betacyanins from pulps of red pitahaya

Without the use of pectinase, the yield of betacyanins extracted from the pulp of red pitahaya was the highest using 95% ethanol at a substrate to solvent ratio of 1:1 followed by 50% ethanol and water at a substrate to solvent ratio of 1:1 and 1:2 (Fig. 1), respectively. This indicates that 95% ethanol is more efficient than 50% ethanol and water in yielding up to 10% of betacyanins from red pitahaya without the use of pectinase. No significant difference was observed in the yield of betacyanins extracted using water or 50% ethanol at the two different substrate to solvent ratios (v/v) (1:1 or 1:2). This is possibly due to a saturation effect produced by the increased substrate to solvent ratio of 50% ethanol or water, which does not increase the yield further. However, a significantly lower (p < 0.05) yield of betacyanins was observed using 95% ethanol at substrate to solvent ratio (w/v) at 1:2 compared to 1:1 (Fig. 1). The time taken for vacuum-drying time of betacyanins from red pitahaya was longer at a substrate to solvent ratio (w/v) of 1:2. This may possibly reduce the recovery of betacyanin due to a longer drying time. According to Shang et al. (2017), drying duration significantly affects the physicochemical properties of natural plant bioactives. These results indicate that 95% ethanol at a substrate to solvent ratio of (w/v) 1:1 is suitable for the extraction of betacyanins from pulps of red pitahaya without the use of pectinase enzyme.

Fig. 1.

Fig. 1

Open in a new tab

Yield of betacyanins extracted from the pulps of red pitahaya using water, 50% ethanol or 95% ethanol at two different substrates to solvent ratios (w/v) across various enzyme concentrations. Results are presented as means ± standard deviations (n = 3). Superscript lowercase letters indicate significant difference (p < 0.05) between samples within an enzyme concentration. Asterisk marks indicates significant difference (p < 0.05) between enzyme concentrations within a sample

With the use of pectinase, the yield of betacyanins from the pulp of red pitahaya significantly increased (p < 0.05) from 0.5 to 1.5% using water as solvent at substrate to solvent ratio (w/v) of 1:1 and 1:2 (Fig. 1). This may be due to the properties of water which provides a suitable environment for pectinase to carry out its activity without adversely affecting the enzyme. The results of this study are in accordance with the study of Lavecchia and Zuorro (2008) in which lycopene extraction from tomatoes using pectinase and water as a solvent resulted in a tenfold increase of lycopene as compared to the control without pectinase treatment.

Lower yields of betacyanins from the pulps of red pitahaya were obtained with the application of pectinase at concentrations of 0.5%, 1.0%, 1.5%, 2.0% and 2.5%, extracted with ethanol at substrate to solvent ratio (w/v) of 1:1 and 1:2 (Fig. 1). There were also no significant differences in the yield of betacyanins extracted with ethanol at substrate to solvent ratio (w/v) of 1:1 and 1:2 with pectinase concentrations of 0.5%, 1.0%, 1.5% and 2.5% in comparison to their corresponding controls (without pectinase treatment) (Fig. 1). These results are most likely due to the function of ethanol as a denaturant which altered the physicochemical properties of the pectinase (Bezerra and Dias 2005), disabling its ability to breakdown the glycosyl bonds of pectin (Kunnika and Pranee 2011) which are present in the pulp of red pitahaya.

Effect of solvents, substrate to solvent ratio and pectinase treatment on the betacyanin content (BC)

When comparing the BC without the use of pectinase, betacyanins extracted from the pulp of red pitahaya with water showed the lowest BC compared to those extracted with 50% or 95% ethanol irrespective of the substrate to solvent ratio (w/v) (Fig. 2). This possibly indicates that the use of water alone (without the aid of pectinase) is not sufficient to extract the betacyanin pigments from red pitahaya.

Fig. 2.

Fig. 2

Open in a new tab

Betacyanin content of betacyanins extracted from the pulps of red pitahaya using water, 50% ethanol or 95% ethanol at two different substrate to solvent ratios (w/v) across various enzyme concentrations. Results are presented as means ± standard deviations (n = 3). Superscript lowercase letters indicate significant difference (p < 0.05) between samples within an enzyme concentration. Asterisk marks indicates significant difference (p < 0.05) between enzyme concentrations within a sample

A significant increase (p < 0.05) was observed in BC of betacyanins extracted from the pulp of red pitahaya using water and pectinase treatment (0.5–1.5%) irrespective of the substrate to solvent ratio (w/v) (1:1 and 1:2) used (Fig. 2). The highest BC was observed in the betacyanins extracted from the pulp of red pitahaya with water at a substrate to solvent ratio (w/v) of 1:1 or 1:2 and a pectinase treatment of 1.5%, 2.0% or 2.5% (Fig. 2). Pardo et al. (1999) evaluated the effect of commercial pectinase on the extraction of anthocyanins and total polyphenol content from grapes, showing that pectinase increases the content of polyphenols and anthocyanins as compared to non-enzymatic control. Chang et al. (1994) also reported an average of 30% increase of total anthocyanin content in pectinase treated Stanley plum juice.

With the use of pectinase (0.5%, 1.0%, 1.5%, 2.0% or 2.5%), the lowest BC was observed in betacyanins from the pulp of red pitahaya extracted using 95% ethanol (Fig. 2). There were no significant differences in the BC of betacyanins from the pulp red pitahaya that were extracted using 95% ethanol at a substrate to solvent ratio (w/v) of 1:1 and 1:2 irrespective of pectinase treatment (Fig. 2). Naderi et al. (2012) reported that betacyanins such as phylocactin and hylocerenin showed a steady decline when extracted using ethanol. In addition, Herbach et al. (2006) indicated that the use of high concentrations of organic solvents such as ethanol would increase the susceptibility of betacyanins to deacylation and thus decrease the betacyanin equivalent values of the extracts of betalains. Narkprasom et al. (2012) reported that the betacyanin degradation index of Djulis (Chenopodium formosanum Koidz.) extracts increased with ethanol concentrations. Pure water was reported to be more efficient than ethanol at extracting pigments from Opuntia stricta fruits (Castellar et al. 2006). This indicated that ethanol may not be able to preserve the pigment concentration in terms of BC when compared to water during the pectinase-assisted extraction of betacyanins from the pulp of red pitahaya. This data shows that not only is water essential to solubilise desirable plant pigments, but also preserves the plant pigments by preventing degradation (Bezerra and Dias 2005).

Effect of solvents, substrate to solvent ratio and pectinase treatment on the total sugar content

Wichienchot et al. (2010) reported that glucose, fructose and sucrose are the major soluble sugars in the flesh of the red pitahaya fruits. The co-presence of high amounts of sugars in betacyanins may be undesirable in the food processing industry as it may cause spontaneous fermentation of betacyanin extracts and caramelization during food processing (Koubaier et al. 2013). The extraction method which results in the least amount of sugars in betacyanin extracts from red pitahaya are therefore very desirable to facilitate the use of betacyanins in food processing.

Irrespective of pectinase treatment, betacyanins obtained from the the pulp of red pitahaya using water at substrate to solvent ratio (w/v) of 1:1 and 1:2 and 50% ethanol at substrate to solvent ratio (w/v) of 1:2 was found to contain the least sugar content when compared to betacyanins extracted with 95% ethanol (Fig. 3). Betacyanins extracted from the the pulp of red pitahaya with 95% ethanol with or without pectinase treatment showed the highest total sugar content (Fig. 3). This indicates that ethanol extracts more sugars from red pitahaya.

Fig. 3.

Fig. 3

Open in a new tab

Total sugar content of betacyanins extracted from the pulps of red pitahaya using water, 50% ethanol or 95% ethanol at two different substrates to solvent ratios (w/v) across various enzyme concentrations. Results are presented as means ± standard deviations (n = 3). Superscript lowercase letters indicate significant difference (p < 0.05) between samples within an enzyme concentration. Asterisk marks indicates significant difference (p < 0.05) between enzyme concentrations within a sample

Application of betacyanins from red pitahaya and E-162 in ice cream

Ice cream is a valuable dairy product due to its high level of nutritional (protein) and caloric density. The effect of betacyanins from red pitahaya or E-162 on the shelf-life of ice cream was assessed based on betacyanin content (BC), total colour changes, antioxidant activity and sensory evaluation.

Betacyanin content (BC)

Overall, the BC was similar in ice cream containing betacyanins from red pitahaya or E-162 throughout the 21-days of frozen storage at −18 °C (Fig. 4). However, a significant increase (p < 0.05) of BC was observed in ice creams containing betacyanins from red pitahaya or E-162 from day-3 to day-9 and day-9 to day-15, respectively (Fig. 4). This indicates that freezing may play a role in the possible regeneration of natural pigments such as betacyanins. For instance, 22–108% of increase in natural pigments such as anthocyanins was observed in cherries, nectarines, peaches, and plums over six months of frozen storage at −20 °C (Sablani 2014). Application of betacyanins from red pitahaya or E-162 in yoghurt (Gengatharan et al. 2017) and milk (Gengatharan et al. 2016), however, showed loss of betacyanin content during refrigerated storage at 4 °C. The results in this study suggest that application of betacyanins in ice cream coupled with frozen storage is a better food application of betacyanin.

Fig. 4.

Fig. 4

Open in a new tab

Increase of betacyanin content (BC) in ice creams containing betacyanins from red pitahaya or E-162 during 21-days of frozen storage at −18 °C. Results are presented as means ± standard deviations (n = 3)

Total colour changes

The total colour changes (ΔE*) in ice cream containing betacyanins from red pitahaya or E-162 was between 0.10 and 0.12 (Fig. 5). These values indicate a small difference in total colour change (ΔE * < 1.5) as the total colour change can be methodically categorised as ΔE* > 3 (very distinct), less than 1.5 < ΔE* < 3 (distinct) and ΔE* < 1.5 (small difference) (Francis and Clydesdale, 1975). This is in accordance with the studies on milk (Gengatharan et al. 2016) and yoghurt (Gengatharan et al. 2017) containing betacyanins from red pitahaya and E-162 during refrigerated storage at 4 °C. Overall, the total colour changes of all ice creams containing betacyanins from red pitahaya or E-162 were similar (Fig. 5). In addition, no significant difference was observed in the total colour change of ice cream containing betacyanins from red pitahaya or E-162 over the 21-days of storage at −18 °C (Fig. 5). Kaur et al. (2011) also showed that there were insignificant changes in the L∗, a∗, and b∗ values of ice cream containing tomato lycopene stored at −25 °C causing an indistinct total colour changes over a 4-months of storage. These suggest that the total colour changes of food products may be minimally affected during a short period of frozen storage.

Fig. 5.

Fig. 5

Open in a new tab

Total colour changes (ΔE*) of ice creams containing betacyanins from red pitahaya or E-162 during 21-days of frozen storage at −18 °C. Results are presented as means ± standard deviations (n = 3). Superscript uppercase letters indicate significant differences at p < 0.05 between storage days

Antioxidant activity

Ice cream containing betacyanins from red pitahaya or E-162 was found to have significantly greater (p < 0.05) antioxidant activity in terms of free radical scavenging compared to plain ice cream (Fig. 6). This may be due to the antioxidant property of the betacyanins compounds itself (Wu et al. 2006) and this was also demonstrated in yoghurt containing betacyanins from red pitahaya and E-162 (Gengatharan et al. 2017). However, the significantly lower (p < 0.05) free radical scavenging activity in ice cream containing E-162 compared to those containing betacyanins from red pitahaya may be due to the difference in the composition of betacyanins. The presence of phyllocactin and hylocerenin in betacyanins from red pitahaya may have conferred an enhanced antioxidant property compared to E-162 which lack these betacyanins (Gengatharan et al. 2016).

Fig. 6.

Fig. 6

Open in a new tab

Percentage of free radical scavenging activity of ice cream containing betacyanins from red pitahaya or E-162 during 21-days of frozen storage at −18 °C. Results are presented as means ± standard deviations (n = 3). Superscript uppercase letters indicate significant difference at p < 0.05 between storage days for ice cream samples. Asterisk marks indicate significant differences at p < 0.05 between ice cream samples on a particular day of storage

The free radical scavenging activity of ice cream with or without betacyanins remained constant throughout the 21-days of frozen storage at −18 °C (Fig. 6). Similarly, the antioxidant capacity of red raspberry fruits was not affected by freezing (Mullen et al. 2002). However, the free radical scavenging activity of yoghurt containing betacyanins from red pitahaya and E-162 decreased at day 6 during refrigerated storage at 4 °C (Gengatharan et al. 2017). It can be suggested that the ice cream in this study may have a enhanced antioxidant status due to frozen storage.

Sensory evaluation

The ice cream containing betacyanins from red pitahaya was found to have similar liking (3.65 ± 1.71) to that (3.50 ± 1.90) of the commercial strawberry flavoured ice cream. On the other hand, the ice cream containing E-162 (6.07 ± 2.07) was found to have the least colour acceptability. This is most likely due to the ice cream containing betacyanins from red pitahaya may have had a colour closer to that of commercial strawberry flavoured ice cream initiating a better liking among panelists. On the other hand, the colour of ice cream containing E-162 varied from that of the commercial strawberry flavoured ice cream due to the different betacyanin composition. The colour acceptability results in this study are similar to those of milk containing betacyanins from red pitahaya and E-162 (Gengatharan et al. 2016).

Conclusion

This study revealed that the use of water as a solvent with pectinase at a concentration of 1.5% and a substrate to solvent ratio (w/v) at 1:1 was able to produce a two to four-fold of increase in the yield of betacyanins from the the pulp of red pitahaya as compared to water without pectinase treatment. The addition of betacyanins from red pitahaya or E-162 to ice cream provided antioxidant activity to the ice creams as measured using DPPH radical scavenging activity. An increasing betacyanin content was observed in the ice creams containing betacyanins from red pitahaya or E-162 during 21-days of frozen storage at −18 °C. Total colour changes (ΔE*) in ice creams containing betacyanins from red pitahaya or E-162 were categorized as small differences when compared to initial ice cream during frozen storage. In sensory evaluation, the ice cream containing betacyanins gave better colour acceptability than that of E-162. Betacyanins from red pitahaya haves the potential to be developed as a functional natural colourant in the food industry.

Acknowledgement

This work was funded by School of Science, Monash University Malaysia.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

  1. Bezerra RMF, Dias AA. Enzymatic kinetic of cellulose hydrolysis inhibition by ethanol and cellobiose. Appl Biochem Biotechnol. 2005;126:49–59. doi: 10.1007/s12010-005-0005-5. [DOI] [PubMed] [Google Scholar]
  2. Cacace JE, Mazza G. Extraction of anthocyanins and other phenolics from black currants with sulfured water. J Agric Food Chem. 2002;50:5939–5946. doi: 10.1021/jf025614x. [DOI] [PubMed] [Google Scholar]
  3. Castellar MR, Obόn JM, Fernández-López JA. The isolation and properties of a concentrated red-purple betacyanin food colourant from Opuntia stricta fruits. J Sci Food Agric. 2006;86:122–128. doi: 10.1002/jsfa.2285. [DOI] [Google Scholar]
  4. Chan SY, Choo WS, Young DJ, Loh XJ. Pectin as a rheology modifier: origin, structure, commercial production and rheology. Carbohydr Polym. 2017;161:118–139. doi: 10.1016/j.carbpol.2016.12.033. [DOI] [PubMed] [Google Scholar]
  5. Chang TS, Siddiq M, Sinha NK, Cash JN. Plum juice quality affected by enzyme treatment and fining. J Food Sci. 1994;59:1065–1069. doi: 10.1111/j.1365-2621.1994.tb08191.x. [DOI] [Google Scholar]
  6. Choo WS. Betalains: application in functional foods. In: Merillon JMK, Ramawat G, editors. Bioactive molecules in food. Cham: Springer; 2018. pp. 1–28. [Google Scholar]
  7. Dubois M, Gilles KA, Hamilton JK, Rebers PA, Smith F. Colorimetric method for determination of sugars and related substances. Anal Chem. 1956;28:350–356. doi: 10.1021/ac60111a017. [DOI] [Google Scholar]
  8. Esquivel P, Stintzing FC, Carle R. Pigment pattern and expression of colour in fruits from different Hylocereus sp. genotypes. Innov Food Sci Emerg Technol. 2007;8:451–457. doi: 10.1016/j.ifset.2007.03.022. [DOI] [Google Scholar]
  9. Francis FJ, Clydesdale FM. Food colourimetry: theory and application. Westport: AVI Publishing Company; 1975. [Google Scholar]
  10. Gengatharan A, Dykes G, Choo WS. Betalains: natural plant pigments with potential application in functional foods. LWT Food Sci Technol. 2015;64:645–649. doi: 10.1016/j.lwt.2015.06.052. [DOI] [Google Scholar]
  11. Gengatharan A, Dykes G, Choo WS. Stability of betacyanin from red pitahaya (Hylocereus polyrhizus) and its potential application as a natural colourant in milk. Int J Food Sci Technol. 2016;51:427–434. doi: 10.1111/ijfs.12999. [DOI] [Google Scholar]
  12. Gengatharan A, Dykes G, Choo WS. The effect of pH treatment and refrigerated storage on natural colourant preparations (betacyanins) from red pitahaya and their potential application in yoghurt. LWT Food Sci Technol. 2017;80:437–445. doi: 10.1016/j.lwt.2017.03.014. [DOI] [Google Scholar]
  13. Herbach KM, Stintzing FC, Carle R. Betalain stability and degradation- structural and chromatic aspects. J Food Sci. 2006;71:R41–R50. doi: 10.1111/j.1750-3841.2006.00022.x. [DOI] [Google Scholar]
  14. Hua Z, Yuesheng D, Ge X, et al. Extraction and purification of anthocyanins from the fruit residues of Vaccinium uliginosum linn. J Chromatogr Sep Tech. 2013;4:167. doi: 10.4172/2157-7064.1000167. [DOI] [Google Scholar]
  15. Ismail NSM, Ramli N, Hani NM, Meon Z. Extraction and characterization of pectin from dragon fruit (Hylocereus polyrhizus) using various extraction conditions. Sains Malaysiana. 2012;41:41–45. [Google Scholar]
  16. Kaur D, Wani AA, Singh DP, Sogi DS. Shelf life enhancement of butter, ice cream, and mayonnaise by addition of lycopene. Int J Food Prop. 2011;14:1217–1231. doi: 10.1080/10942911003637335. [DOI] [Google Scholar]
  17. Koubaier HBH, Essaidi I, Snoussi A, et al. Effect of Saccharomyces cerevisiae fermentation on the colorants of heated red beet root extracts. Afr J Biotechnol. 2013;12:728–734. [Google Scholar]
  18. Kunnika S, Pranee A. Influence of enzyme treatment on bioactive compounds and colour stability of betacyanin in flesh and peel of red dragon fruit Hylocereus polyrhizus (Weber) Britton and Rose. Int Food Res J. 2011;18:1437–1448. [Google Scholar]
  19. Lavecchia R, Zuorro A. Improved lycopene extraction from tomato peels using cell-wall degrading enzymes. Eur Food Res Technol. 2008;228:153–158. doi: 10.1007/s00217-008-0897-8. [DOI] [Google Scholar]
  20. Mullen W, McGinn J, Lean EJM, et al. Ellagitannins, flavonoids, and other phenolics in red raspberries and their contribution to antioxidant capacity and vasorelaxation properties. J Agric Food Chem. 2002;50:5191–5196. doi: 10.1021/jf020140n. [DOI] [PubMed] [Google Scholar]
  21. Naderi N, Ghazali HM, Hussin ASM, et al. Characterization and quantification of dragon fruit (Hylocereus polyrhizus) betacyanin pigments extracted by two procedures. Pertanika J Trop Agric Sci. 2012;35:33–40. [Google Scholar]
  22. Narkprasom K, Su WL, Cheng MY, et al. Relative effects of alcohol and pH on betacyanin stability in aqueous Djulis extracts and their color qualities after organic acid addition. J Food Qual. 2012;35(283):291. [Google Scholar]
  23. Pardo F, Salinas MR, Alonso GL, et al. Effect of diverse enzyme preparations on the extraction and evolution of phenolic compounds in red wines. Food Chem. 1999;67:135–142. doi: 10.1016/S0308-8146(99)00080-1. [DOI] [Google Scholar]
  24. Pinelo M, Arnous A, Meyer AS. Upgrading of grape skins: significance of plant cell-wall structural components and extraction techniques for phenol release. Trends Food Sci Technol. 2006;17:579–590. doi: 10.1016/j.tifs.2006.05.003. [DOI] [Google Scholar]
  25. Puri M, Sharma D, Barrow CJ. Enzyme-assisted extraction of bioactives from plants. Trends Biotechnol. 2012;30:37–44. doi: 10.1016/j.tibtech.2011.06.014. [DOI] [PubMed] [Google Scholar]
  26. Sablani SS. Freezing of fruits and impact on anthocyanins. Processing and impact on active components in food. UK: Academic Press; 2014. [Google Scholar]
  27. Sandri IG, Fontana RC, Barfknecht DM, da Silveira MM. Clarification of fruit juices by fungal pectinases. Food Sci Technol. 2012;44:2217–2222. [Google Scholar]
  28. Shang HM, Zhou HZ, Li R, et al. Extraction optimization and influences of drying methods on antioxidant activities of polysaccharide from cup plant (Silphium perfoliatum L.) PLoS ONE. 2017;12:e0183001. doi: 10.1371/journal.pone.0183001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Tapre AR, Jain RK. Pectinases: enzymes for fruit processing industry. Int Food Res J. 2014;21:447–453. [Google Scholar]
  30. Wettasinghe M, Shahidi F. Antioxidant and free radical-scavenging properties of ethanolic extracts of defatted borage (Borago officinalis L.) seeds. Food Chem. 1999;67:399–414. doi: 10.1016/S0308-8146(99)00137-5. [DOI] [Google Scholar]
  31. Wichienchot S, Jatupornpipat M, Rastall RA. Oligosaccharides of pitaya (dragon fruit) flesh and their prebiotic properties. Food Chem. 2010;120:850–857. doi: 10.1016/j.foodchem.2009.11.026. [DOI] [Google Scholar]
  32. Wu L, Hsu H, Chen Y, et al. Antioxidant and antiproliferative activities of red pitaya. Food Chem. 2006;2:319–327. doi: 10.1016/j.foodchem.2005.01.002. [DOI] [Google Scholar]
  33. Yang B, Jiang Y, Shi J, Chen F, Ashraf M. Extraction and pharmacological properties of bioactive compounds from longan (Dimocarpus longan Lour.) fruit–a review. Food Res Int. 2011;44:1836–1842. [Google Scholar]
  34. Yong YY, Dykes G, Lee SM, Choo WS. Effect of refrigerated storage on betacyanin composition, antibacterial activity of red pitahaya (Hylocereus polyrhizus) and cytotoxicity evaluation of betacyanin rich extract on normal human cell lines. LWT Food Sci Technol. 2018;91:491–497. doi: 10.1016/j.lwt.2018.01.078. [DOI] [Google Scholar]

Articles from Journal of Food Science and Technology are provided here courtesy of Springer

RESOURCES