This article was produced and financed by Nofima The Norwegian Institute of Food, Fisheries and Aquaculture Research

Berit Karoline Martinsen has produced jam from many different varieties of strawberry and raspberry. (Photo: Kjell Merok/Nofima)

How to make the perfect jam

Which types of strawberry and raspberry are best suited for making jam? Researchers, plant breeders and berry and jam producers are working together to find the answer.

Denne artikkelen er over ti år gammel og kan inneholde utdatert informasjon.

Nofima The Norwegian Institute of Food, Fisheries and Aquaculture Research

Nofima is a business oriented research institute working in research and development for the aquaculture, fisheries and food industry in Norway.

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 a good yield, maintain high quality and of course be suitable for processing, so that they maintain their good flavour, aroma and useful constituents in the jam.

"From breeding and research, there is still a long way to go before consumers can buy jams made with the new varieties. If further testing of these varieties gives positive results, the earliest that products made from them can be available is in two or three years," explains Merete Lunde, research and development manager of Lerum and leader of this project.

Source of purple

The most important qualities of good jams are taste, aroma, colour and nutrient content. The taste is closely linked with the sugar and acid content and the relationship between them.

The berries get their characteristic aroma from a mixture of volatile compounds such as esters, alcohols and aldehydes, while water soluble pigments called anthocyanins give raspberries and strawberries their red colour.

The word anthocyanin, which comes from the Greek and means flower purple (anthos = flower, kyaneos = purple), says it all. Anthocyanins are only found in plants and give the plants they are found in their colour. Anthocyanins can also have health-promoting qualities.

There are different types of anthocyanins, and these are among the things that researchers Kjersti Aaby and Berit Karoline Martinsen of the food research institute Nofima have been investigating. They have made analyses and measurements to find out how the anthocyanins, and thereby their colour, stand up when the berries are pulped and heated and when the jam is stored. They have also investigated how the anthocyanins and the colour are affected by the 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. In other words, with a larger quantity of anthocyanins in the berries, they become more stable. It is more difficult to find connections with strawberries, but there appears to be a tendency for jam made with strawberries that contain a high volume of vitamin C to have a less stable colour," says Kjersti Aaby.

Taste colour and health

Making jam out of 100 different varieties of berries, and then analysing them for both sensory properties and constituent substances, is a large and demanding job. All the jam producers taking part in the project have used the same recipes and stored the jam for up to six months. The Nofima researchers have assessed the jams on the basis of taste, colour and health-promoting properties.

"During the project, we have also investigated what differences it might make to store jam made from berries at various stages of ripeness. We found that the colour changed most during storage with jam made from the least ripe berries. So, make jam from good, ripe berries," is the advice of Kjersti Aaby of Nofima.

Both the jam manufacturers and the other project participants, such as researchers from Nofima and Bioforsk, plant breeders, agricultural advisers, berry producers and freezer plants, can see the benefit of working together and exchanging results.

"Growing properties, constituents with health-promoting properties and suitability for processing have all been assessed together, which has given us a much more thorough and complete knowledge of the selection of varieties than we had previously. As far as I am aware, this collaborative approach is pioneering work at international level," says Merete Lunde.

New varieties needed to maintain the jam tradition

The overall intention of the project is to find varieties of strawberries and raspberries that are suitable for use by jam manufacturers and that have growing properties which will make them attractive to berry producers.

In recent years, there has been a definite focus on producing Norwegian strawberries and raspberries for direct consumption, at the expense of berries that are more suitable for processing. This means that there is now a great need for supplies of berries that are primarily intended for processing.

"We have a long tradition in Norway of making jam from berries. In order to uphold this tradition, new and modern varieties of strawberries and raspberries are absolutely essential," says Lund.

Varieties of strawberry and raspberry that are suitable for industry is the name of the project that Lerum has been leading.

"This project has contributed to some useful network building in the raspberry and strawberry value chain, and we can see the benefit of working together in R&D projects where we face a large common challenge. The results of the work will make an important contribution to the task of securing and developing Norway's production of strawberries and raspberries for industry and to exploiting the market potential in Norwegian-produced berries and the products made from them," says Lund.

The project participants come from plant breeding (Graminor), research (Nofima and Bioforsk), Norgro, agricultural consultancy (Landbruk Nordvest, Landbruksrådgivningen Sogn & Fjordane and Forsøksringen Bær Oppland & Hedmark), berry producers (Gartnerhallen), freezer plants (Valldal Grønt) and the jam and fruit preserve industry (Lerum, Findus, Stabburet, Røra and Tine). A PhD student has been attached to the project, carrying out work at both Bioforsk and Nofima.

The project has been financed by the Research Council of Norway, the Foundation for Research Levy on Agricultural Products and research funds from the Agricultural Agreement. The project was initially for a four-year period and was extended by a further year in 2013.

The way forward - seeking funding for a new R&D project

Breeding and evaluating new berry varieties, from the point of view of both quality and growing properties, takes time. The participants in this berries-for-industry project now hope to continue the work in a new project and also extend the scope to cover berries for the consumer.

The aim of the new project, in addition to continuing the essential testing and assessment of promising new berry selections, will be to find out even more about the constituents of the berries and how these affect the quality and stability of berries and their products.

Finding new varieties and increasing our knowledge of their constituents is important for being able to offer consumers products with good sensory and health-promoting properties.

"This needs participants from the whole berry value chain, because only then can we develop the value chain innovations that are necessary to maintain a value-creating and competitive jam industry and berry production in Norway," concludes Lunde.

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