Project Year 2013
Hunting for the perfect berry
About 100 varieties of strawberry and raspberry have been tested to find those best suited for making jam. Only a few made the grade.
The most promising varieties include the raspberries ‘Glen Fyne’ and ‘Cascade Delight’ and the strawberry ‘Saga’.
As well as thriving in Norwegian weather conditions, the varieties must provide good crops, maintain high quality and be suitable for processing.
The most important qualities of jams are colour, taste, aroma and nutrient content. Making jams from 100 varieties of berries, and then analysing them for both sensory qualities and chemical composition, is a
large and demanding job. All the jam producers used the same recipe, stored the jams for up to six months and assessed taste and colour of the jams.
Research Scientists Kjersti Aaby and Berit Karoline Martinsen and PhD student Sebastian Mazur (Bioforsk) analyzed the jams for compounds that contribute to colour and healthiness. In this context, the anthocyanins
play a very important role, providing both the red colour and promising health-beneficial properties.
SOURCE OF PURPLE: The scientists analysed how the anthocyanins, and thereby colour, managed when the berries were homogenized and heated and the jam was stored. They also investigated how the anthocyanins
were affected by other constituents in the berries.
“For raspberries, there appears to be a correlation between the amount of anthocyanins in the berries and the colour stability of the jam. The more anthocyanins in the berries, the more stable the colour was. For strawberries,
finding correlations is harder, but it appears that jams made from strawberries containing high concentrations of vitamin C have less stable colour,” says Kjersti Aaby.
The scientists have also studied the consequence of making jams from berries at various stages of ripeness.
It was found that the colour changed most during storage of jams made from the least ripe berries.
“So, make jam from well-ripened berries,” advises Aaby.