The right berry for jam
Korona is the most frequently eaten strawberry in Norway and Glen Ample is the type of raspberry you find in the shops. But neither of these varieties is good for making jam. There are great differences between berries that are suitable for consumption fresh and those that are suitable for industrial production.
The industrial berry project is supported by The Research Council of Norway. Lerum, Findus, Stabburet, Røra, Tine, Valdal Grønt, Graminor, Bioforsk and Nofima Mat are all taking part in the project.
Senga Sengana is a variety of strawberry that has been used to make jam in Norway for more than 50 years. Because of problems relating to growing conditions, this variety is now on its way out. Veten has been the dominant raspberry variety used in the production of jam, but this too is on its way out because of poor cultivation properties. The researchers are therefore searching for goof replacements.
Colour, air and seeds
Most of the research into new varieties of strawberry and raspberry has been concerned with cultivation and volume of crop. A lot of research has been done on soil, climate, pests and diseases. Another aspect of the research concerns the content of antioxidants in the berries and how these are affected by processing.
In a research project that began in 2009, the researchers are investigating the properties and substances contained by various kinds of strawberries and raspberries. When the researchers are out after the perfect industrial berry, colour is a very important quality parameter for both strawberry and raspberry jams. Another significant factor is the berry’s density, that is to say the amount of air it contains. Air causes oxidation, which quickly causes the jam to take on an unpleasant colour and flavour.
The content of substances with possible health properties, such as polyphenols and vitamin C, in berries and berry products is also important when different types of berry are being assessed. For strawberries it is also important to find varieties that are easy to hull. With raspberries, the size of the seeds is important.
The research project is intended to result in a whole new set of criteria for properties that are important for the industry. These requirements will be important for the plant breeders and growers who produce for the industry.
Research scientist Kjersti Aaby and senior engineer Berit Karoline Martinsen have been making jam out of many different varieties. An important goal is to increase our knowledge of berry handling and processing throughout the value chain and to find how to retain sensory quality and health promoting substances in the fruit.
“Varieties may contain the same kinds of antioxidants, but in different quantities. Irregularities in the antioxidant and vitamin C content can cause colour to be destabilised. And this is something you don’t usually find out until after processing. We must therefore find varieties with consistent colour,” explain Kjersti Aaby and Berit Karoline Martinsen, who are both taking part in the project. They are also looking into the significance of different freezing techniques and storage conditions.
“The industry is sensitive about the taste, aroma, colour and sheen of its jam. They know exactly what they want and even though they are sharing a lot of information with competitors in this project, they are also keeping their commercial secrets,” says Kjersti Aaby.