PROJECT REPORT FILE. The difference between organic and non-organic vegetables. Research team: Dominik Hansabut and David Paun, 3A

Transcription

1 PROJECT REPORT FILE The difference between organic and non-organic vegetables Research team: Dominik Hansabut and David Paun, 3A

2 CONTENTS Plagiarism pledge... 3 Abstract... 4 A. Introduction B. Aim C. Hypothesis D. Materials and methods C1. Materials C2. Nitrate content C3. Vitamin C C4. Rabbit trial... 6 C5. Data interpretation... 7 E. Results... 7 E1. Nitrate content E2. Vitamin C content E3. Rabbit trial F. Discussions F1. Discussions of results F2. Errors and modifications G. Conclusions H. Acknowledgements I. References

3 Plagiarism pledge 3

4 English abstract. Many consumers have questions at the vegetable shelves. Which is more nutritious: organic or non-organic veggies, more expensive or cheaper ones? Our study comes to help them by estimating the difference in vitamin C and nitrate content in lettuces from several shops and our own garden. We have found that cheaper or non-organic lettuces have had more Vitamin C, but also more of the potentially harmful nitrate, than more expensive or organic vegetables. Some of the most expensive and organic lettuce was imported from abroad and was not so fresh in the shop, which may have influenced the quantity of Vitamin C in those samples. German abstract. Viele Verbraucher haben Fragen an den Gemüseregal. Welche ist nahrhafter: Bio oder nicht Bio-Gemüse, teurer oder billiger? Unsere Studie kommt zu ihnen durch Abschätzen der Unterschied in der Vitamin-C- und Nitratgehalt in Salat aus verschiedenen Geschäften und dem eigenen Garten zu helfen. Wir haben festgestellt, nicht nur dass billiger oder Nicht- Bio-Salate mehr Vitamin C haben, sondern auch dass der potenziell schädliche Nitrat in teuren Bio Salate in höheren Konzentrationen vorkommt. Aus dem Ausland importierte und teuere Bio Salate haben im Geschäft nicht mehr frisch ausgeschaut was auch die Menge des Vitamin C Inhalt beeinflusst hat. A. Introduction. In the present days consumers are overwhelmed in shops with extensive choice of products. The range of products normally goes through a wide price scale. If we consider organic vegetables their price can be several times higher than non-organic veggies, but it is not always certain that the higher price comes with an added value. For example, according to The Independent [1] at the British supermarket Sainsbury s, organic food shoppers need to pay on average 1 more per product that non-organic shoppers. However, organic products aren t necessarily any better than non-organic ones regarding vitamin and nutrient contents, some claim (for example [2, 3]). Despite these, the British supermarket Waitrose reports rising organic sales by 11% every year [1]. Other benefits of organic food may be a better taste and smaller content in potentially harmful pesticide and fertiliser residues. From our experience, we know we normally cannot taste the difference from bio and non-bio vegetables and fruits. 4

5 Pesticides and fertilizers are traditionally used to help plants thrive so they can produce a better crop. Pesticides kill insects, weeds, mold and fungi, while synthetic fertilizers nourish a plant's growth. Some of chemical ingredients in pesticides and fertilizers have been shown to be carcinogenic or toxic to humans and animals, especially in high concentrations [4]. Discount shops like Lidl, Hofer, Penny and Zielpunkt have a smaller offer in bio vegetables. Merkur, Spar and Billa have both bio and non-bio veggies. Of course, Merkur, Spar and Billa are more expensive. B. Aim. Our aim in this project is to compare the quality and properties of organic and nonorganic vegetables. C. Hypothesis. In this project we want to test the hypothesis that the price difference of products follows a quality difference. We will focus on vegetables and we will test our hypothesis with two questions: 1) Are the more expensive organic vegetables any better than non-organic veggies? 2) In general are the more expensive vegetables better quality than those that are cheaper? D. Materials and methods. C1. Materials. We focused on leafy vegetables, in particular lettuce, as a representative. When they are sprayed, we think leafy vegetables will take up more chemicals than other vegetables. We have bought salads from Penny, Spar, Lidl, Hofer, Merkur, Billa, and Zielpunkt and collected some from our own garden. We have used Billa and Merkur bio salad and non-bio salad for the rabbit trial (see below). We have measured Vitamin C and nitrate (NO 3 ) content. For these measurements, we have blended 5 g from one middle leaf of each lettuce, together with 25 ml distilled water. We have used a simple kitchen blender in this research step. Each lettuce-water mixture has been blended for 1 min in order to obtain a raw lettuce extract. Further, we have centrifuged the raw extract to separate the bigger pieces left from the lettuce from the liquid. The upper part of the liquid has been used for further analyses. 5

6 C2. Nitrate content. Nitrate (NO 3 ) is a natural compound found in many plants. In artificial conditions of agriculture when pesticides and fertilizers are commonly used, nitrate content can significantly increase [4]. However, in high concentration, nitrate is poisons for people. European Union regulations stipulate maximum amounts of nitrate content allowed in different commercial vegetables [4]. We have measured nitrate content found in organic and non-organic lettuce. Starting with the lettuce extracts, we used a commercially available kit the NO 3 test from JBL GmbH (normally used for aquaristics) to colour the extractions according to their nitrate content. We have then used a spectrophotometer with the help of Mag. Johann Schinnerl (University of Vienna) to determine the relative nitrate content of each sample. The spectrophotometer measures the intensity of light that can pass through a sample, according to its colour. C3. Vitamin C. We have measured the Vitamin C content of each sample as a representative image for nutritional value. Vitamin C can help people recover from a cold and can be a protection against immune system deficiencies, cardiovascular disease, prenatal health problems, eye disease, and even skin wrinkling [5]. Despite our need of Vitamin C for a healthy life, humans are one of the few mammals who cannot synthesize themselves Vitamin C [5]. Therefore we need to take up Vitamin C from our food on a daily basis. Different vegetables and fruits differ in their content in Vitamin C. We have used a commercially available stripe kit (MQuant Vitamin C test, Merck Millipore, Germany) to measure Vitamin C in each of the samples. The end of the stripes has been immersed in the lettuce extract for 30 s and, after drying for 10 min, the colour of this ends have been evaluated against a stepwise colour scale in the range mg/l. The shade of the colour of the end of stripes is indicative of the Vitamin C content of each sample. C4. Rabbit trial We have used the help of rabbits for parts of our research, because of their increased tasting and smelling capacity. We think rabbits are better tasters and smellers than humans and that is why we think they may be able to distinguish between organic and non-organic lettuce. In our test we aimed to investigate: what is the first choice of rabbits between organic and non-organic lettuce and which of the two samples will be totally consumed first. 6

7 We have taken care to place near one rabbit a similar area of leaf from the alternative sample types. C5. Data interpretation For each of our tests, we will compare averages of the investigated measures for each group of samples (organic vs. non-organic) in order to see if they are different. In addition we will try to test for correlations between each measurement and price. For the nitrate test we will measure a relative nitrate content. This will be a dependent variable. In the Vitamin C test, the colour of the stripes will be indicative of Vitamin C content. This will be also a dependent variable. One independent variable that we will use is the nature of our samples, and the possible values will be organic and non-organic. Another independent variable is the price range. We will also work with several fixed variables. Those are: the volume of water used for the initial lettuce extraction (25 ml), the weight of lettuce used for extraction (5 g), the time used for blending the material (1 min), the time used for colouring the strips (30 s), etc. We have drawn boxplots and histograms to help us visualize the data. These steps have been done in SPSS v. 10.0, with the help of Dr Ovidiu Paun (University of Vienna). In addition we have visualized the relationship between nitrate and, respectively, Vitamin C content and the price paid for the respective lettuce with Scatter Charts constructed in Microsoft Excel. E. Results E1. Nitrate content. The relative nitrate content of organic lettuce ranged from 0.7 to 1.4, with a mean value of 1.1. For non-organic samples the nitrate content ranged from 0.9 to 2.1, with a mean value of 1.6. A boxplot graph (Fig. 1A) showing how the data is distributed for the two categories indicates that there is a difference between the two, with organic veggies having a much smaller nitrate content than non-organic lettuce. Histograms (Fig. 1B-C) of the data in the two categories indicates that the mode of relative nitrate content of non-organic lettuce is higher than 1.5, while the mode for organic samples was lower than

8 Price ( ) Relative NO3 2,5 A B C 2,0 1,5 1,0 0, Non-Organic Organic Non-Organic Organic Figure 1. Relative nitrate content in commercially-available lettuce. A. Box-plots of relative nitrate content in organic versus non-organic lettuce. B. Histogram of relative nitrate content in non-organic lettuce as measured in this project. C. Histogram of relative nitrate content in organic lettuce as measured in this project. The Scatter Chart (Fig. 2) constructed in Excel to visualize the relationship between nitrate content and price, showed an inverse relationship between the two variables. This means that a cheaper lettuce is more likely to contain more nitrate, whereas a more expensive lettuce is more likely to contain less nitrate. For this analysis we excluded the samples obtained from our own garden, as they no price was available for them NO3 content Figure 2. Relationship between relative nitrate content and price paid for the respective lettuce. 8

9 Vitamin C (mg) E2. Vitamin C content. The estimated Vitamin C content of organic lettuce ranged from 25 to 75 mg/l, with a mean value of 40 mg/l. For non-organic samples the Vitamin C content ranged from 50 to 100, with a mean value of 71 mg/l. A boxplot graph (Fig. 3A) indicates that there is a difference between the two categories, with organic veggies having much less Vitamin C than non-organic lettuce. Histograms (Fig. 3B-C) of the data in the two categories indicates that the mode of Vitamin C content of non-organic lettuce is 75 mg/l, while the mode for organic samples was 25 mg/l. The Scatter Chart (Fig. 4) constructed in Excel to visualize the relationship between estimated Vitamin C content and price, showed an strong inverse relationship between the two variables. This means that a cheaper lettuce is more likely to contain more Vitamin C, whereas a more expensive lettuce is more likely to contain less Vitamin C. For this analysis we excluded the samples obtained from our own garden, as they no price was available for them. 125 A B C Non-Organic Organic Non-Organic Organic Figure 3. Vitamin C content in commercially-available lettuce. A. Box-plots of Vitamin C content in organic versus non-organic lettuce. B. Histogram of Vitamin C content in nonorganic lettuce as measured in this project. C. Histogram of Vitamin C content in organic lettuce as measured in this project. 9

10 Price ( ) Vitam C (mg) Figure 4. Relationship between estimated Vitamin C content and price paid for the respective lettuce. E3. Rabbit trial. Our rabbit trial failed because when we have put the samples in their enclosure according to our plan, the rabbits did not eat the samples while they were watched. Later we observed that one sample was missing, but we were not sure if it has been eaten or blown by the wind. F. Discussions F1. Discussions of results. Our analysis shows that the more expensive, organic lettuce is more likely to contain less nitrate than non-organic lettuce. This confirms our original hypothesis, as we expected that an organically grown vegetable will be sprayed less with pesticides and fertilizers than non-organic veggies, so the former should show less potentially harmful chemicals, such as nitrate. As organic lettuce costs also more, we also expected to see an inverse relationship between price and nitrate content. Regarding the nutritional value of organic versus non-organic lettuce, as shown by their Vitamin C content, our findings are surprising and contradict our hypothesis. Indeed, organic lettuce has been found to contain less Vitamin C than non-organic ones. We think that this relationship may be due to three causes. First, some of the organic lettuce was coming from abroad and were the some of the least fresh salads from our samples. All of the non-organic lettuce was produced in Austria 10

11 and was mostly fresh. We think that the time from picking lettuce to eating it could influence the Vitamin C content. Second, as the non-organic lettuce benefits from more fertilizers, it may produce more Vitamin C, at the cost of having also more harmful chemicals, such as nitrate. Third, the scale of the kit used for Vitamin C estimations was very rough, with steps of 50 mg/l. In addition, the colours of the stripes of the kit were very similar which made us feel unsure about our measurements. Therefore, our Vitamin C estimations may be wrong due to human error, and we think that a more accurate measurement would be needed for reliable conclusions. F2. Errors and modifications. Apart from the potential errors in our estimations of Vitamin C content, our rabbit trial did not work at all. We think the rabbits had to be hungry to participate with success in our trial. It is clear that it is very difficult to work with living beings while performing experiments. G. Conclusions Our results indicate that there is a visible difference between organic and non-organic lettuce, both in their nitrate and Vitamin C content. Whereas with regard to nitrate content organic lettuce seems of higher quality, with regard to Vitamin C it is of lower value. This may be due to importing it from abroad. In addition, a similar conclusion can be drawn with regard to the price more expensive lettuce contains less nitrate, but also less Vitamin C. H. Acknowledgements We thank Mag. Johann Schinnerl (Univ. Vienna) for helping with the spectrophotometer measurements of nitrate content. We thank also Dr. Ovidiu Paun (Univ. Vienna) for supervising us while doing the lab experiments and helping us with the statistical analyses. I. References. [1] Online version of The Independent from 15 March 2008 available at 11

12 [2] Genevra Pittman, Thomson Reuters article from 9 April 2012, available at [3] Organic food webpage on Wikipedia last updated on 28 January 2013, available at [4] Pesticides and fertilizers webpage on ehow last viewed on 11 January 2013, available at [5] Vitamin C webpage on medicinenet from 10 January 2013 available at 12