I conducted this project as part of Professor Pringle’s EEB321 class at Princeton University.
I was able to use my Foldscope both in Princeton, New Jersey, and at my home in Wisconsin. In Princeton, I used my Foldscope to look at raspberry juice from a container of Driscoll’s raspberries that I had purchased at Target. The Driscoll’s brand is one of the country’s largest producers of raspberries. Grown throughout large fields in California and Mexico, these raspberry fields are often treated with insecticides and other pesticides in order to maximize crop yield. Many pesticides are used specifically for pests that can carry and spread plant disease, but others are targeted at specific bacteria that can cause crop damage. Pictured below is an image of raspberry juice from the Driscoll’s brand. From looking at the image, you can see that there are no distinguishable features aside from an overall red hue.
While it was interesting to look at the raspberry under the Foldscope, the images did not initially seem especially ecologically interesting until going home. I had the pleasure of working on an organic farm last summer, where all produce was grown without treatment of any pesticide. While my farming experiences have taught me a lot about the differences between produce grown organically and non-organically, I had never had the opportunity to study these differences on a microscopic scale. I decided to look at juice from raspberries grown organically to determine if there were any obvious and distinguishable differences between the two. The images of the organically-grown raspberries are pictured below.
As you can see, the juice from the organically grown raspberries takes on a much lighter and transparent appearance, suggesting a high water content. The organic farm uses processes like mulching and cover crops consistently in order to maximize water retention, which could be a possible explanation for a higher water content. This could also potentially be explained by the simple fact that the organic raspberries were frozen, so they contributed more water in the melting process. In addition to this, the images of organically grown raspberries appear to have more small, distinct structures in them, which could be a potential indicator of the presence of bacteria. Because these raspberries were grown without pesticides, I originally thought it would make sense that one would detect a higher volume of bacteria and other pathogens that would typically be eradicated by chemicals. However, after doing further research I found that this is not necessarily true. While some studies have shown that organic produce may indeed carry a higher risk of bacterial contamination, others have actually shown that organic and conventional food are about equally likely to be contaminated with disease-causing bacteria (Konkel). Further, some studies even found that conventional farming methods produced crops with more bacteria, as the plants sometimes confer resistance to the antibacterial chemicals being used. The presence of bacteria on produce is highly dependent on the specific farming techniques used, the geographical location, and the soil makeup of the farms. It is also important to note that the presence of bacteria is not necessarily harmful to the plant or to its consumers, and could even be beneficial. Regardless of this, the shape of the structures on the organic raspberry juice seem to resemble simple bacterial structures typically found on fresh produce. I suspect that this difference is either a result of a lack of pesticide use during plant growth, which could allow for more bacteria to persist for longer, or that it is due to the cleaning process after the raspberries were harvested. Large scale farms often add additional chemicals such as sulphur dioxide, benzoic acid, propionic acid, ascorbic acid and sorbic acid. These are all chemicals that delay ripening by inhibiting the growth of yeasts and molds (Canon).
Both of these theories have the potential to explain why there were more bacteria/additional structures in the raspberry juice grown organically. It is also possible that the differences are explained by something I have not considered, or are even not significant at all. Either way, I found it intriguing to analyze the differences between produce grown organically and inorganically, and would love to learn more about what I am seeing and whether it actually has any significance.
Konkel, Lindsey. “Organic Foods No More Nutritious, Safe than Conventional, Study Says.”
Canon, Tony. “What you need to know about chemicals sprayed on produce after harvest.”