Question

4. Which food you predict will… a. have the highest number of bacteria? And why? b. have the lowest number of bacteria and why? c. have the highest number of fungi (yeasts or molds)? Why? (The “why” is, in effect, your hypothesis.) The foods are raw ground beef, potato salad, and fresh salsa

Answer 1

4.a. The food that have highest number of bacteria is raw ground beef. Because raw beef contains all the nutrients like carbohydrate, nitrogen source and proper pH needed for bacterial growth. Moreover raw ground beef naturally contains bacteria in them. That's why we should clean and cook properly before having it.

b. The food that have lowest number of bacteria is fresh salsa. Because it contains low pH which is not suitable for bacterial growth, it will also have salt and spices in it which will prevent bacterial growth. It also contains garlic, onion, chili etc which has antibacterial and antimicrobial property in it. Bacterial cells will die if they grow in the salsa.

c.  The food that has highest number of fungi (yeasts or molds) is potato salad. Because fungus needs high carbohydrate for nutrient supply and a little bit of acidic environment with room temperature. Potato contains high level of starch, a rich source of carbohydrate which is taken up by the fungus and easy to break down also. Salad will also contain lime juice which gives the proper pH needed gor fungus growth. That's why in lab we use Potato Dextrose Agar/Broth (PDA/PDB) for fungal growth.