. Materials and methods
2.1. Raw materials
Grapefruits (Citrus paradise var. Star Ruby) from the city of Murcia (Spain) were purchased from a local supermarket. Fruit pieces were peeled and cut perpendicularly to the fruit axis into 10 mm thick half-slices. Food grade commercial sucrose was used to prepare conventional and microwave (MW) jams. In the case of the jam obtained by osmotic dehydration, an osmotic solution (OS) was prepared by mixing sucrose with distilled water until it was completely dissolved, forming a 65 °Brix syrup. In this case, citrus peel pectin (60% degree of esterification, Fluka Biochemika, Switzerland) was used as a gelling agent.