Freeze-dried pulp and peel from pitahaya (Selenicereus undatus): physicochemical properties and potential source of fructooligosaccharides

The pitahaya Selenicereus undatus is a fruit widely consumed in the Yucatan Peninsula in Mexico, and its cultivation is promising due to its adaptability to adverse climatic conditions, its nutritional quality, and its bioactive compounds. The objective of this work was to determine the physical parameters of the fresh fruit (weights and diameters) and chemical parameters of the pulp (stored at -18 ºC) of pitahaya grown in two locations in the state of Yucatán, as well as to estimate the yield of fructooligosaccharides (FOS) present in freeze-dried pulp and peel flour, using the solid/liquid extraction method. Six physicochemical and six proximal descriptors (in freeze-dried pulp and peel), which were statistically compared using the t-student test, were quantified. The fruits had an average weight of 534.81 and 520.36 g for the pitahaya grown in Kinchil and Yobain, respectively. The peel weight of the fruit from Kinchil was significantly (p < 0.05) higher. The pulp represented between 67 – 72 % of the weight of the fruits. The physicochemical analysis of the fruit pulp indicated that the average total soluble solids/titratable acidity (TSS/TA) ratio was 20.5, and the pH was 3.29. The proximal analysis expressed on a dry basis (% d.b.) showed average values for the pulp of 4.80 % ash, 0.47 % crude fat, 10.42 % crude fiber, and 6.92 % protein; while for the peel 14.20 % ash, 1.39 % crude fat, 22.22 % crude fiber, and 5.31 % protein. The values of crude fiber and total carbohydrates in the peel, as well as the crude fat content in the pulp, were different (p < 0.05) between the locations. The estimated extraction yield of FOS with water was 86.49 g/kg for the freeze-dried pulp and 17.64 g/kg for the freeze-dried peel flour. This fruit exhibited good nutritional properties, and the freeze-dried flour from its peel could be used as supplement rich in dietary fiber and, together with the freeze-dried pulp, could be added to products such as juices, yogurt, and jams, among others, with a potential prebiotic effect due to its fructooligosaccharides content.