Physicochemical and Sensorial Properties of Grapefruit Jams as Affected by Processing

Jam is an effective and tasty way of preserving fruit. Jam processing procedures as well as storage conditions and duration are important factors for jam quality. Traditional jam processing involves the application of severe thermal treatments that imply undesirable changes in the product quality characteristics such as colour, texture, flavour and nutritional and functional value. In this work, osmotic dehydration (OD) and/or microwave energy (MW) was proven as adequate to obtain jam with the typical characteristics of water content, degree Brix, pH and water activity of jam obtained by conventional thermal heating. The sensory evaluation carried out to compare the product showed that samples submitted to more intense heating treatments (conventional or MW) had significantly higher scores in colour saturation, brightness, grapefruit taste and extensibility than OD or OD+MW ones. As deduced from the obtained results, OD treatment prevents grapefruit colour changes, and mild MW heating contributes to increase the consistency and decrease the extensibility of the obtained jam. In this way, OD+MW jam was preferred by assessors mainly due to its higher consistency. The sample obtained by this procedure was stable during storage.