BIOL 3150 Lab4 - ,youshould 1 (microbialload 2...

This preview shows page 1 - 2 out of 10 pages.

45 LABORATORY 4 – FOOD MICROBIOLOGY AND MICROBIAL GENETICS EXERCISE 1: Food Microbiology (Part 1) — Total Microbial Load and Coliform Counts In Meat Products Introduction Although it is not always obvious, practically all types of foods are contaminated by microorganisms such as bacteria and fungi. This contamination is often referred to as the microbial load. In some cases, the presence of microorganisms in food is beneficial while in others it is considered harmful. For example, certain microorganisms are necessary in the preparation of foods such as cheeses, pickles, sauerkraut, yogurt and sausage. On the other hand, the presence of organisms such as Escherichia coli, Clostridium botulinum and Staphylococcus aureus are often responsible for serious and sometimes fatal food poisoning and toxicity as well as spoilage. Because milk contains carbohydrates, fats, minerals, vitamins and proteins, and has a pH of approximately 6.8, it is very susceptible to degradation by various species of microorganisms. Milk, as drawn from healthy cows, contains few microorganisms. However, the milk can be contaminated by dust and manure in the milking area, the milking machinery and containers, or by the handlers. Fortunately, these days, the microbial load in most milk is reduced substantially by selective heat treatments such as pasteurization. Meats are the most perishable of important foods because they contain abundant quantities of the nutrients required for the growth of bacteria, yeasts and molds. Ground meats as well as multi ingredient meat products such as hot dogs, meat pies and sausage, have higher microbial loads than whole meat foods such as steak. In general, the number of organisms in the final meat products reflects the quality of the ingredients used and the way the products have been handled. In the lab exercise this week, you will assess the microbial load of a series of meat samples. Since microorganisms normally associated with animal fecal matter ( enteric bacteria or coliforms ) should not be found in food and since some of these organisms are potential pathogens, their presence in food and water is often monitored as an indicator of microbial contamination. Most coliforms are Gram Objectives for Week 4 After completing these exercises, you should: 1. Know how to analyze food for microbial contamination (microbial load). 2. Use differential/selective media to isolate putative enteric bacteria (coliforms) from food. 3. Understand and use DNA technology to identify microorganisms. 4. Transform E. coli cells with an R plasmid by heat shock.
Image of page 1

Subscribe to view the full document.

Image of page 2

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern