Much research effort is being directed into the understanding of these processes, with the expectation that better methods of control will both lead to more efficient commercial operations and an improved product for consumers. This is particularly relevant to consumer expectations regarding the availability of exotic and 'out of season' fruit and vegetables.
These ideas are illustrated by recent developments involving tomatoes.
In order to reach the shops in a ripe state, tomatoes have traditionally been picked whilst still green, being left to develop their red colour and softer texture whilst in storage and transit. However, this results in a loss of flavour and many fruits are lost due to over ripening, with consequent mushiness, rotting and damage in transit and handling.
Researchers have managed to modify tomato plants by inserting a gene which prevents one of the plant's 'ripening' genes from working at the usual rate. The tomatoes may then be left on the plant until red to develop a full flavour. They soften more slowly, suffer less damage in transit and have a much longer shelf life, cutting out waste.
Background
Fruit ripening involves many genes, but the pathway to softening can be simplified for students as follows:
(Candidates will not be required to recall this pathway; if questions involving it are set, appropriate information will be provided in the question).
In one approach, the gene required for stage X has been inhibited and, in the USA, whole tomatoes (marketed as Flavr SavrTM are produced in this way.
In the second approach, using technology developed by Zeneca in the UK, a gene for stage Y is inhibited. Other aspects of ripening, such as development of colour and flavour, are unaffected. The UK Regulatory approval for the marketing of tomato puree (paste, which contains no living cells) made from these transgenic tomatoes has been gained and the product, the world's first genetically engineered processed food to be licensed, is widely available in supermarkets. J Sainsbury plc produce an information leaflet about their Californian tomato puree, available free of charge by telephoning the Helpline on 0800 636262. Since the tomatoes contain more pectin, a thicker paste is produced which spends less time in the evaporator, saving greatly on energy costs. Besides being thicker in texture, the puree is said to be superior, in both flavour and appearance, to that produced from non-engineered tomatoes.
