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Asked by isabelnoble to Andy, Cathie, Jules, Les, Ricarda on 25 Jun 2012.
Question: By genetically modifying food, is it possible to increase the shelf life of food without having to use artificial preservatives?
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Cathie Martin answered on 25 Jun 2012:
Yes. The original flavr savr tomato, sold but later withdrawn, in UK Supermarkets was silenced for the polygalacturonase gene in tomato that breaks down cell walls during late ripening. Not only did this have a longer shelf life, because it inhibited late ripening, it tasted better too. Many longer shelf life tomatoes carry mutations in genes that are required for early ripening. These mutants hold the tomatoes at an earlier stage of development for longer. This also explains why so many consumers complain that super-market bought tomatoes don’t taste as good as they used to – they do not ripen fully so they do not develop flavour fully.
There are several other strategies for delaying late-ripening by GM to extend shelf life. These strategies allow full flavour to develop and do not depend on treatment of fruit with artificial preservatives or ripening accellerants. The problem is that such traits are in crops that do not command the same market share as the big crops like corn, cotton, canola and soybean. So the multinationals who can afford deregulation do not place such crops high on their list of priorities. So who knows if they will ever become available to consumers.
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Ricarda Steinbrecher answered on 26 Jun 2012:
Depends what you mean by ‘increasing shelf life’. There is more to aging than meets the eye. During any stage of development – from growing to maturing, ripening and eventually degrading and decomposition – there are hundreds of processes running within an organism at the same time, whether that is a fruit, a vegetable, a tuber, fish or an egg. The time clock will keep ticking, even if one or two of the processes might have been stalled.
There is for example the ‘non-browning GM apple’ that is currently going through the regulatory system in the US and in Canada. It is genetically engineered to block the production of the enzyme polyphenol oxidase, involved amongst other activities in the browning of a cut or bruised apple. When on sale within the ready meal section, this apple is designed to keep looking freshly cut and attractive, irrespective of its real age and actual composition. This might be why some critics refer to the non-browning apple as the botox-apple.
So is it looks that increase shelf life? The fruit/veg not feeling squashy or looking bruised? The smell? All these signals commonly offer a person a way by which to judge the quality or age of the food they are about to buy or eat. These signals are – from our experience and our history with foods – linked to other qualities of the food. Qualities that we take for granted and might not even be able to name.
These signals might now become delinked from qualities such as nutrient content. And what about compounds that are good for health, such as anti-oxidants, bioflavonoids? Or the presence of metabolites (derivatives) that accumulate during partial aging decomposition and that constitute anti-nutrients?Changes will also have occurred due to the genetic engineering process.
The GM flavr savr tomato – genetically engineered/modified for delayed ripening and longer shelf life and briefly commercialised in the US between 1994 and 1996 – had a number of problems, including feeding trial data showing gastric (stomach) erosions in 4 out of 20 rats, ie 20 per cent (Fred A. Hines, Pathologist, 1993). The latter was not revealed to the public at the time. -
Julian Little answered on 28 Jun 2012:
Well as Cathie points out, one of the original GM crops, the FavrSavr Tomato had a modification to stop the tomato ripening. The result was that the tomatoes did not have to be harvested so early to avoid spoilage. And the taste of these tomatoes was fab hence its name (surprised that Ricarda thought otherwise). These days, the same effect is achieved through advanced breeding. It is being looked at again, however in China and especially India, where even a few extra days would have a massive effect on fruit provision.
Likewise there has been a lot of effort in finding a genetic solution to potato blight – a really difficult problem for farmers both here and overseas – and of course the cause of the Irish potato famine. Solve this problem and you not only dramatically reduce the amount of fungicides used on this crop, but you save a lot of potatoes that would be lost to this disease, even when you do spray. BASF, the university of Leeds and the Sainsbury Laboratory in Norfolk have trialled GM potatoes, each of which seem to work really well. I understand that BASF is applying for regulatory approval for this in Europe but who knows when it might be available.
Not sure whether this answers your question, Isabel, but there is a lot of work going on to try and do just that.
Comments
dingo commented on :
Interesting that Cathie Martin should say the Flavr Savr tasted good–this report from a US extension scientist says “The failure of Flavr Savr tomato has been attributed to the poor taste of the cultivar”: http://www.ag.ndsu.edu/pubs/plantsci/crops/a1219w.htm
And as Ricarda Steinbrecher points out, this GM tomato caused health problems in rats. This is something that should flag up warning signs to any scientist.
Cathie commented on :
The point about Flavr Savr was that the introduced gene improved the taste of the variety compared to the untransformed control. Hence the name. Nobody ever claimed that they were particularly tasty.
This is entirely consistent with the comment from the US extension scientist that you quote.
As for the health problems caused by Flavr Savr in rats, the same report included the followowing observations: ‘Gross and microscopic gastric erosions were seen in male and female control rats dosed with dionized water, in male and female rats fed the non-transgenic tomato, and in female rats fed the transgenic tomato.’ I don’t recall any call to ban the consumption of either deionised water or non-transgenic tomatoes as a result of these feeding trials. In the light of the non-reproducibility of the ‘health problems’ linked to consumption of the tomatoes carrying the silencing construct for the PG gene, the conclusion of the panel that: “[h]istomorphology and the pattern of incidence of the necrosis and erosion suggested that these lesions were incidental in nature and unrelated to the respective test articles” seems reasonable.
dingo commented on :
Calgene did two sets of studies. In a study from the first set, 7 out of 20 female rats that ate one of the 2 Flavr Savr tomato lines tested got stomach lesions. This effect was not found in the male rats or in the control rats that were fed non-GM tomatoes. The study concluded that the GM tomato given to the females “did suggest a possible treatment-related mild focal necrosis of the glandular stomach”. In other words, the GM tomato harmed the rats.
The “conclusion of the panel” that Cathie Martin cites actually seems to be the conclusion of Calgene, the GM company that developed the tomato, about their second, followup study, which they said was a “repeat” of the problematic first study but which used tomatoes prepared in a different way. Calgene’s commissioned lab staff claimed that the necrosis and erosions (1 rat from the non-GM group, 2 rats from the GM group) were “incidental”. But the FDA pathologist responded, “the criteria for qualifying a lesion as incidental were not provided” and the disparity between the initial and “repeat” studies “has not been adequately addressed or explained”. Political appointees of the FDA later claimed that the ill effects in the rats were not related to the GM tomatoes, but were due to unspecified mucolytic ingredients–an entirely hypothetical notion that has no basis in experimental data. In any case, the confused findings of the second study that Calgene did, do not in any way make the findings of the first study go away.
I would think that an objective scientific analysis of this history would find no basis for making reassuring noises about Flavr Savr or GM foods in general.
kevin_folta commented on :
Dingo, you are taking a potentially interesting finding and turning it into hard science. Seven rats with stomach lesions in the one group may seem compelling to the layperson, but to the scientist it is a curiosity worthy of further study. That’s all. Small numbers (like 20) make such occurrences due to chance or another factor unrelated to the treatment (like rats that came from a source that shared a common disease or genetic predisposition to stomach problems) a major problem. If the study were performed on 20,000 rats and 7000 had problems and the control group was clean, then there might be something there. Still, “might” is the key word.
In order to be conclusive science determines the mechanism of the effect. Mechanism is an important milestone to link cause and effect. How does the added gene cause the change? To me, there is no plausible mechanism to begin with, but certainly a remote possibility that something could happen. It is biology. However, such mechanistic studies require a firm description of the basic physiological phenomenology in large populations before they can be conducted effectively.
So this is why science dismisses these tiny tiny tiny studies. Not that they should not be considered, but they should only be considered as a starting point for more rigorous inquiry. You will note that all of the “significant evidence” that forms the base of anti-GMO claims comes from small, inconclusive studies published in lower-impact journals. Thanks.
Sandy commented on :
I think Ricarda has made a number of very valid points about how different properties of food can change during storage. Anything that that increases the “shelf life” — including changes that could be introduced using GM — can affect some properties and not others. I work in the Food Standards Agency and we always warn people not to judge the safety of food by smell and appearance. Although you might see changes when a food is past its “use by” date, this is not always the case and you can’t see or smell Salmonella or E.coli.!
Cathie and others have mentioned the Flavr Savr tomato but there seems to be some confusion between two types of GM tomato that were grown commercially during the 1990s. Flavr Savr tomatoes were available “fresh” in the USA but they were never marketed here in the UK. The GM tomato paste that was sold in some UK supermarkets came from a different GM tomato that was developed around the same time, also for its storage properties, by the British company Zeneca. Only the latter product was submitted for approval in Europe and its authorisation lapsed in 2004.
The comments about the safety of the Flavr Savr tomato shows how it is possible to find selective quotes from the same report to support different arguments. When the data on gastric lesions were examined by the EU’s Scientific Committee on Food (the predecessor of the European Food Safety Authority), their report said “The Committee concurs with the conclusion reached by the US FDA that there is an unexplained disparity between the three studies.” Taken alone this gives one impression. But the Committee goes on to say that “…gastric erosions can be readily produced in rats as an artefact of gavage studies” and it concludes that “the gastric erosions … are of no relevance to the safety assessment of GM tomatoes.” These are complex issues and regulators rely on rigorous evaluations by experienced scientists who understand the nature of the different types of experiments and who are skilled in interpreting the results. Personally I would be guided by the bottom line conclusions of these experts rather than by snippets extracted from their reports.
Sandy commented on :
I’d also like to add something about openness, which an important part of food safety assessments. Ricarda notes the lack of information when Flavr Savr tomatoes were first evaluated in the USA in the early 1990s. I can’t comment on the procedures in the USA, in 1994 or now, but the EU system (see http://www.food.gov.uk/safereating/gm/evaluating) is extremely open. Although some of the applicants may not like it, the safety data on GM foods are made available for scrutiny and the assessments are published for public comment before any decisions are taken on authorisation.