title: Impact of pH and temperature on the colour and betalain content of Colombian yellow pitaya peel (Selenicereus megalanthus).
abstract: The effects of different pHs (4, 5 and 6), temperatures (4, 20 and 80 °C) and storage (up to 12 days) on differential tristimulus colorimetry and betalain content related to the colour of yellow pitaya (Selenicereus megalanthus) have been investigated. The peel of the yellow pitaya was extracted with different solvents to see its colorant capacity. Highly-acidic extracts (pH 4) showed the lowest betalain content, chroma (C* ab = 60 against 70) and the yellow component of the colour (b*). Storage temperature manifested a great influence on CIELAB parameters when yellow pitaya peel was added to highly-acidic foodstuffs, with a tendency towards red hues (h ab , from 100° to 85°) and remarkable changes on lightness (L*, from 90 to 75) as temperature increased. However, low-acidic extracts (pH 5 and 6) were superior from a colour stability standpoint, not being influential the temperature of storage. All colour changes according to pH and temperature were visually appreciable by human eyes (∆E* ab  > 3). New opportunities for diversification of colorant market could be possible by employing yellow pitaya peel as natural resource.
authors.affiliation: Food Colour and Quality Laboratory, Department Nutrition and Food Science, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain.
authors.forename: María Jesús
authors.initials: MJ
authors.lastname: Cejudo-Bastante
authors.affiliation: Departamento de Química, Universidad de Nariño, A.A. 1175 Pasto, Colombia.
authors.forename: Nelson
authors.initials: N
authors.lastname: Hurtado
authors.affiliation: Departamento de Química, Universidad de Nariño, A.A. 1175 Pasto, Colombia.
authors.forename: Angélica
authors.initials: A
authors.lastname: Delgado
authors.affiliation: Food Colour and Quality Laboratory, Department Nutrition and Food Science, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain.
authors.forename: Francisco J
authors.identifier: 0000-0002-3849-8284
authors.initials: FJ
authors.lastname: Heredia
keywords: Betalains; Differential tristimulus colorimetry; Stability; Yellow pitaya (Selenicereus megalanthus)