Using volatile organic compounds to monitor shelf-life in rocket salad

Rocket salad (Diplotaxis tenuifolia or Eruca sativa) is a perishable product of increasing interest due to its high content of nutritionally relevant compounds including glucosinolates and vitamin C. There is an increasing consumption of readyto- eat salads which are sold to the consumer in bags, often packed under modified atmosphere. Shelf-life and sell-by dates are commonly applied to these products and are usually dictated by the appearance of the product rather than its nutritional value. During shelf-life, postharvest deterioration leads to a loss of nutritionally relevant compounds such as vitamin C. This is accelerated by suboptimal conditions during storage and transport such as breaches of the cold-chain. Volatile organic compounds (VOCs) are easy and quick to sample use of thermal desorption gas chromatography time of flight mass spectroscopy (TD-GC-TOF-MS) enables remote sampling and a very sensitive analysis of VOC profiles. We have used TD-GC-TOF-MS to sample VOCs from rocket salad bags sourced from a local supermarket to assess changes during the shelf-life of the product. Using statistical analyses that treat the whole VOC profile as a single variable we show that it is possible to differentiate between day of purchase, use by date and time points beyond sale. We conclude that this methodology is therefore of use for assessing rocket salad quality through the supply chain.