Joseph Irudayaraj
The quality of agricultural products is important to us all. That the products are free from contamination and of utmost purity are the chief concerns to regulatory agencies such as the USDA, FDA, and consumers. These are also two of the main research themes of Dr. Joseph Irudayaraj, Associate Professor of Agricultural and Biological Engineering, and his research group. Dr. Irudayaraj is developing new methods for detecting food borne pathogens using IR and Raman spectroscopy, Surface Plasmon Resonance (SPR) and fiber optic Fluorescence based biosensors. As for the purity of agricultural products, Dr. Irudayaraj uses IR and Raman spectroscopy coupled with Chemometrics to determine to what level products have been adulterated with lower quality ingredients.
Traditional culture based methods of detecting food borne pathogens such as E. coli, Salmonella, Listeria, and Shigella, can take days to complete, during which time the freshness of the agricultural product can degrade. However, by using IR, Raman, SPR, and fiber optic Fluorescence based biosensors Dr. Irudayaraj is able to reduce the amount of time necessary to detect these pathogens in products such as apple juice, milk, ground beef and drinking water. Detecting pathogens using FTIR and Raman poses significant challenges in that the pathogens do not display a single, well defined response. Rather, through extensive use of control groups, Dr. Irudayaraj has collected fingerprint spectrums for each pathogen that can then be used to detect contaminants in agricultural products. SPR and fiber optic Fluorescence based biosensors are used to detect pathogens through the use of antigen-antibody binding; monitoring the change in refractive index in an SPR sensor or fluorescence through the use of tagged molecules in the fiber optic Fluorescence based biosensors tests could be completed in about 45 min.
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While these techniques provide quicker analysis of products over traditional techniques, sensitivity can be an issue. Using traditional cell culturing techniques, microorganisms could be detected in about 72-48 hours. FTIR and Raman methods although rapid may not be as sensitive, however, SPR and fiber optic Fluorescence based biosensors were shown to be sensitive to about 10 CFU/ml. To increase the sensitivity of detection and keep the analysis time as short as possible Dr. Irudayaraj plans to focus on the use of nanowires as biosensors. He believes that using nanowires may provide the necessary sensitivity levels needed to adhere to USDA and FDA's "zero tolerance" guidelines where, if present, a single pathogenic cell can be found in a sample of an agricultural product.
From a safety standpoint, it is very important that our agricultural products are pathogen free, but as consumers we are also concerned that our products are pure; that the label matches the contents. Dr. Irudayaraj's laboratory has developed methods to assess food adulteration. When a consumer purchases olive oil, the consumer assumes that the product is 100% olive oil. However, a producer could deliver a product that has the consistency, aroma, and taste of virgin (or extra virgin) olive oil, but the product could contain less costly oils such as olive pomace oil. This adulteration of the product with a cheaper product dupes the consumer and increases the profit margin of the producer. By examining key features in FTIR and Raman spectra with Chemometrics, a collection of multivariate analysis techniques including Principal Component Analysis (PCA), Dr. Irudayaraj can determine the level to which pure products have been diluted with less costly products. To date, he has applied this detection approach to olive oil, honey, and maple syrup. By assembling vast libraries of standards, Dr. Irudayaraj is able to determine not only the purity of the product in question, but also the type and concentration of the dopant. In the case of olive oil, a dopant can be any of a number of lower quality oils, while in the case of honey and maple syrup, the typical dopants are sugar syrups such as corn syrup. This detection method can be used at points of entry to the US to test the purity of foreign agricultural products.
Dr. Irudayaraj received his Ph.D. in Food Process Engineering from Purdue University in 1990 and joined the Penn State materials community five years ago after three years of an Assistant Professorship with Utah State University. His research group currently consists of three post doctoral fellows and nine graduate students. His labs are located in the Agricultural Engineering Building located behind the Penn State Creamery.
