Reducing losses due to rotting on fresh tomatoes using SO2

ISHS Secretariat
Reducing losses due to rotting on fresh tomatoes using SO2

Tomatoes are a popular horticultural commodity prone to quick postharvest deterioration. In the absence of cold storage and postharvest fungicides to prevent spoilage, other means to preserve the shelf life of fresh tomatoes is sought. Reducing decay and extending the shelf life of such a popular and easily accessible food crop will decrease food waste. For this reason, Chanel Daniel-Swartland, a PhD candidate at Stellenbosch University Plant Pathology Department and Lead Research Scientist on the tomato project at Tessara (Pty) Ltd, is looking at methods to reduce postharvest rot on tomatoes using sulphur dioxide. Thus far, research conducted on ‘Round’ and ‘Roma’ tomatoes has shown promise in reducing rotting for up to 21 days in cold storage and subsequent shelf life. The use of SO2 reduced postharvest rots on ‘Roma’ tomatoes by more than 50%. Rot on ‘Round’ tomatoes was reduced less than 50% compared to the control group. This provided valuable insight that varietal differences may require a varietal-dependent solution. The application of SO2 did not negatively affect the firmness or taste profile of either variety of tomato used in the trial. Some drawbacks in the form of SO2 damage was noted, but a varietal response was apparent. In trials thus far, ‘Round’ tomatoes were observed to be more susceptible to SO2 damage than were ‘Roma’ tomatoes. The damage was primarily centered around the stem scar, which is known to be an entry wound for opportunistic pathogens. One action of the SO2 was to seal off that area from infection, but the SO2 damage caused thinning of the skin, or pitting, and in severe cases made the tomato unmarketable. Research is ongoing and will continue to examine aspects of reducing SO2 damage, varietal responses, and suitable applications within the industry.

Chanel Daniel-Swartland won the ISHS Young Minds Award for the best oral presentation at the V International Symposium on Pomegranate and Minor Mediterranean Fruits in South Africa in February 2022.

Chanel Daniel-Swartland, Fruit and Postharvest Research Programme, Department of Plant Pathology, Stellenbosch University, Private Bag X1, Matieland, Stellenbosch, South Africa; Tessara Pty Ltd, 35 Kinghall avenue, Epping Industrial 11, Cape Town, South Africa, e-mail:

The article is available in Chronica Horticulturae

Young Minds Award Winners