Defining, predicting and delivering 'fresh' in the context of leafy salads

This project addresses the BBSRC priority of increasing crop yield and quality, with the emphasis on increasing the postharvest quality of horticultural crops in the retail environment. Consumers are very aware of the 'five a day' message and yet compliance is poor, with only 2-3 portions consumed per person on average. Consumers frequently cite high prices and poor shelf life of fresh fruit and vegetables as a reason not to buy them; both of these factors can be addressed by producing, handling and packaging the crops in a way that gives more consistent quality and longevity. A second point that will be addressed in this project is one of consumer confidence. We will enable retailers and consumers to define the 'freshness' of a product, allowing the company to predict shelf life and the consumer to understand the duration over which the product is safe and desirable to eat. This will change the way that longevity is presented on pack so that consumers are more confident in determining the length of time that they can keep a product before eating, thereby decreasing food waste and increasing their likelihood to purchase fruit and vegetables. Considerable progress has been made in the last 15 years in understanding the biochemical and physiological changes that occur in commodities after harvest and also in improving the way that they are packed and handled. However, there is very little available in the way of technologies or methods which are predictive of shelf life or quality, despite the number of physiological and biochemical processes which are now known to occur postharvest. Recent research from our group has shown that volatile compounds can be good indicators of product quality and can be sampled in a non-destructive manner. Many of these are produced before the crop becomes visibly compromised so these are good candidates for being evaluated as quality indicators. Packaged leafy green vegetable crops are also prone to protein catabolism and fermentation reactions during shelf life as a result of senescence; the project will also evaluate the potential of such metabolites to be used as an indicator of the physiological status and potential postharvest longevity of the crop. Whilst we anticipate that the project will focus on these novel methods of quality determination we recognise that innovation brings with it a risk of failure. We will not therefore exclude the possibility that the student will study rather more traditional measures of postharvest quality but in this case will focus on developing a robust and reliable method for using them to indicate the freshness and remaining postharvest life of the crop. This second category of potential quality indicators includes compounds such as ethylene, visible changes such as colour, biochemical changes in compounds such as sugars and ascorbic acid.