ASLT Continues

I am in my second semester of research in food microbiology.  The Spring semester of 2012 was dedicated to accelerated shelf-life testing of numerous sauces for a local company that manufactures these sauces for big-named customers.  Our first assay showed mixed results.  Our second assay of 5 sauces that were fresh off the line and sealed performed much better.  The attached photo shows growth of yeast in small numbers.  We did not have any bacterial growth.  All 5 sauces held up at the 37 C temp with no changes to color or odor.

Since we did not repeat results from the first assay to the second, we discovered that the sauces given to us in the first one were significantly old and were not hermetically sealed.  Additionally, I cultured one of the plates with bacterial growth and did a Gram stain.  We found Gram + and a Gram - organisms with a diplococci morphology.  We did some tests to try and identify the bacteria.  Motility, TSI, citrate and some others I am not recalling at the moment.  The results did not lead to any common bacteria that we, as budding microbiologists, were familiar with.  Dr. Bates, our supervising instructor, concluded it was environmental as in dirt.  We did take a pic of the Gram stain and I need to ask for a copy so I can post.

Right now we are repeating the first assay with the same 19 sauces.  This time the sauces are fresh off the line and hermetically sealed.  They are performing just as well as the sauces did in our second assay.  No bacteria and low yeast growth with some no growth at all.  No significant odor changes and a few of the sauces showing color change.  This is the start of a long-term study requested by the company.  Although we gave them our ASLT results, they tell us their customer wants real-time data so this study is set up to take place over the course of 12 months.

The next post will be about the scientific experiments we designed that have nothing to do with the shelf-life studies.  My research partner and I created a spreadsheet of all the ingredients in all of the sauces so we could analyze the results to see which ingredient we want to isolate and experiment with.  Right now we are getting ready to test the antimicrobial properties of sweeteners.  Raw honey, xylitol, high fructose corn syrup, and stevia.  More to come.