Researchers from Universiti Sains Malaysia – in a country where the fruit is commonly grown – looked at the potential use of dragon fruit puree as a functional ingredient in providing antioxidant activity, as well as the desired texture and natural red colour.
“There is great potential in the ultilization of red pitaya fruit puree in gummy confection preparation to provide the enhanced functionality besides the natural vibrant red color," they conclude, in their study published in the International Journal of Food Science and Technology.
Dragon fruit: a rich source of antioxidants
Red pitaya fruit – more commonly known as dragon fruit or pittaberry – is a member of the cactus family. It has a red skin and delicate, juicy pulp.
The researchers say that – to the best of their knowledge – there has been no data on the effect of adding its puree to gelatin and pectin-based gummy confections.
Consequently, the study investigated the effects of red pitaya fruit puree with gelling agents, on the physico-mechanical properties and quality of confectionery. The team also investigated its functional use in providing antioxidant activity.
“Recent consumer trends have shifted towards procuring food products that provide phytonutrients to promote good health and well-being without sacrificing taste, texture or convenience,” wrote Norziah Hani, one of the study authors.
“The pitaya fruit is rich in vitamin C, water soluble fibres, minerals, phytoalbumins, polyphenols and antioxidants. It contains different pigments called betalains, which consists of red-violet betacyanins and yellow betaxanthins," she added.
“These pigments are water soluble, heat stable and exhibit antioxidant activities (76.10%) over a wide range of pH (3–7) making it suitable for application in low-acid and neutral food.”
In the study, two types of gummy confections were prepared. One used fish gelatin as a gelling agent, and the other used high-methoxyl pectin. Red pitaya fruit puree was added to the gelling solution. Sucrose, glucose syrup, ascorbic acid, pineapple juice (as a gel stabiliser and flavour enhancer), and citric acid were used in the mixture. The finished gummy confections were stored at room temperature.
No adverse effects on texture and color
A sensory analysis concluded the addition of red pitaya fruit puree had no adverse effect on the texture and overall impact.
“It was noted that gelatin and pectin with 25% pitaya fruit puree showed high scores for all sensory attributes,” said Hani. “The incorporation of puree in both types of gummy confections had a positive impact on all sensory properties, especially color, hardness, gumminess, and overall acceptability.”
The red color of the samples was due to the puree’s pigments. Gelatin samples retained more redness than pectin ones, suggesting the pigments were stable in the gelatin samples.
Red pitaya fruit puree has been noted as an ‘excellent source’ of antioxidants, and increased puree content in both samples produced higher antioxidant activities.
A previous study by the researchers found different gelling agents contained different antioxidants, which were able to scavenge radicals at varying degrees. Furthermore, various anti-oxidative compounds could interact with the gelling matrix in a different fashion, in which free antioxidative compounds in red pitaya fruit puree could be released differently.
“In the present study, antioxidative activities of pectin samples were lower than those of gelatin, regardless of amount of puree used,” said Hani. “This was most likely due to the interaction between pectin and antioxidative compounds in the puree, thus lowering the release of those compounds. As a consequence, the lower antioxidant activity was found in the resulting pectin samples.”
Structural effects of adding fruit puree
The incorporation of fruit puree modified the structure of both samples, mainly in the presence of high water content, making the gel structure more heterogeneous.
It also reduced hardness and rigidity.
“Generally, for each set of gelatin and pectin samples, hardness and gumminess decreased with increasing water and dragon fruit puree content,” said Hani.
“The results indicated that softening of texture occurred after addition of higher water content in the gummy confections. Water is well known as a plasticiser and promotes rupture of hydrogen bonds and formation of new hydrogen bonds between water molecules and associated cross-linking chains of gelatin or pectin.”
Title: ‘Influences of red pitaya fruit puree and gelling agents on the physico-mechanical properties and quality changes of gummy confections’
Authors: Hani, N.M., Romli, S.R., Ahmad, M.
Source: International Journal of Food Science and Technology, 2015, 50, pp.331-339. doi:10.1111/ijfs.12638