Materials and methods
Fruit materialGuapeva fruit (Pouteria cf. gardneriana Radlk) were collected during the 2017-2018 season (between June and September) from plants that naturally occurred in the city of Palmas, Tocantins, Brazil. The fruits were harvested ripe and free from any uniformity or physical injuries. After sanitizing, pulps were extracted manually and kept at -20 °C until jam preparation.
Jam preparation proceduresThe jams were processed in an open stainless-steel pan in an electric gas cooker. When the soluble solids content reached 65 °Brix, citric acid was incorporated, and the cooking was finished. The hot jams were packed into sterile 250 mL polyethylene flasks and weighed to obtain the yield of the final product, and after that, stored at 4 °C. The passion fruit albedo used as a source of pectin was produced as described by Silva et al. (2012).
Jam formulation -experimental planningA response surface with a complete factorial design 2 3 was used to optimize the guapeva jams (Pouteria cf. gardneriana Radlk), according to the methodology described by Box & Draper (1987) (Table 1). The experimental design aimed to evaluate the influence of the independent variables (citric acid concentration, pulp/sugar ratio, and albedo concentration as a source of