How to use volatiles to assess quality and shelf-life of fresh-cut produce
The aim of this research group within the QUAFETY project has been to develop an easy-to-use system to assess product quality and safety for pre-packaged fruit and vegetables [See news item "Food safety and quality all wrapped up", September 2012]. As part of an assessment of product quality, effects of processing, or shelf life, the system developed enables the collection of volatile organic compounds (VOCs) with a simple collection system, operated by minimally trained staff. Data on product quality, or markers for possible pathogen contamination, can be obtained within a few days. The time limitation is dependent on transport of collection tubes to the laboratory; results from the analysis can be available within hours.
Matthew Bates explained that Markes International is responsible for providing the technical solution to Cardiff University to give the most robust and sensitive technique possible for the detection of VOCs which make up the aroma of fruit and vegetables. Natasha Spadafora explained that they have analysed VOCs, after headspace was taken on sorbent tubes, by using: thermal desorption (TD) for sampling and injection, gas chromatography (GC) for compound separation and mass spectrometry (MS) for compound detection. Matthew Bates went on to say that the combination of TD, GC and MS is a very powerful tool for quantitative and qualitative analysis of the compounds that are responsible for odour.
The scientists, working on rocket and melon, found that wounding during processing, storage temperature and microbial spoilage were the main factors affecting the levels and the composition of VOC profiles. Hilary Rogers said that the aroma bouquet of produce consists of hundreds of compounds. She explained: "We are now moving on to identify small numbers of compounds that are sufficient to discriminate between different states of the post-harvest material. In some cases, we are able to identify about six compounds that are diagnostic of the time and temperature of storage."
Dr Rogers went on to say that the most important classes of compounds found in rocket are aldehydes and isothiocyanates, while in melon they are esters, ketones and alcohols. She said "melon is very sensitive to changes in temperature, and we have studied the effect of cut size on melon, showing that VOCs change with increased damage to the tissue. [In contrast], rocket leaves produce a much smaller number of VOCs at lower levels and so are more challenging to work with."
Further info:
www.quafety.eu
www.freshplaza.com/sector/109/quafety
www.tacler.com
Contact:
Dr Hilary Rogers
Email: RogersHJ@cardiff.ac.uk