Knowledge Based Bio-Economy


Replacement of sulphur dioxide (SO2) in food keeping the same quality and shelf-life of the products (Food processing)

Project acronym: SO2SAY

Title of project: Replacement of sulphur dioxide (SO2) in food keeping the same quality and shelf-life of the products

Research area: Food Processing

Contract No: 226930

EU contribution: €2 995 468

Start date: May 2009

Duration: 40 Months

Status: finalised

Sulphur dioxide (SO2) is traditionally used as an antioxidant and preservative in many foodstuffs, such as dried fruits, some fruit juices, snack products, seafood, convenience foods (especially those containing potatoes) and wine. The main advantage of SO2 is its ability to prevent enzymatic and non enzymatic browning in foods, especially fruit and vegetable products. In addition, sulphur dioxide has significant antimicrobial capacity and protects food from microbial spoilage.

However, SO2 and sulphites strongly reduce vitamin B1 uptake in humans, which can lead to several health problems, such as chronic headaches and memory disturbances. For asthma patients, less than 10 mg of sulphite might be enough to provoke an asthma attack. And exposure to large amounts of SO2 is also suspected to cause cancer – through promoting the formation of nitrosamines in the gut – and to be mutagenic, causing damage to genes. High dosages of sulphite can also block enzyme activities that are important for healthy organisms, especially of renal and hepatic enzymes.

Food is the main source for the uptake of sulphur dioxide in humans.

The main objectives of SO2SAY were to reduce the amount of SO2 in food, develop new agents and processing techniques to replace SO2 in food products, prevent the enzymatic browning of food, and improve the shelf-life and appearance of food products not containing SO2. The team also planned to identify alternative natural ingredients with benefits for human health.

An important aspect of the project for food applications is the preservation of the sensory quality and shelf-life of SO2-free products. The reduction or replacement of SO2 was likely to change the sensory quality characteristics, especially taste, texture and mouth-feel properties, and this has proven to be so for several foods. In order to combat consumers' refusal of such food alternatives because of these new sensorial properties, all developments in the SO2SAY project were accompanied by comprehensive sensory studies. The correlation between the consumer acceptance data and the descriptive data was used to optimise the sensory characteristics of the final products.

The success of the project was closely linked to the maintenance of sensory quality and shelf-life in the products manufactured without sulphur dioxide treatment, in order to reach the highest acceptance possible.

The project took three major research directions:

  1. Inactivation of the enzyme polyphenol oxidase (PPO) to prevent enzymatic browning,
  2. Development of plant extracts containing secondary plant metabolites with a high antioxidative capacity (e.g. plant polyphenols) and antimicrobial activity.
  3. Processing and packaging under an oxygen-reduced atmosphere,

A number of product-specific solutions have been developed and the work has highlighted new research results, as well as important areas for further research, which have attracted immense industrial interest, especially in SME wineries.

The project results include the identification of suitable reducing and chelating agents to inactivate PPO to prevent enzymatic browning. It found useful structure-function relationships that were published, as along with a report on neohesperidin dihydrochalcone (NHDC), which was recently recognised as a PPO inhibitor.

Further results showed the advantages and pitfalls of processing technologies such as ultrasound treatment and ultrafiltration, and the beneficial impact of MAP processing and various packaging materials and conditions. Finally, more than 60 plant extracts were screened, their functionality was measured and sensory effects were recorded and partly investigated in more depth in shelf-life and consumer testing. A substantial amount of usable data for targeted food development has been collected, which can be turned into a powerful tool for high-quality or even organic/minimal processing that can contribute greatly to developing food- and sector-specific solutions faster.

The project generated great interest with food magazines and even broadcasting companies following a successful dissemination strategy and early press releases.

Website of project:

Coordinator: Kolja Knof,

Organisation: TTZ Bremerhaven, Verein zur Förderung des Technologietransfers and der Hochschule Bremerhaven e.V., Germany,