Rachael Brown, Emilio Ernesto, Douglas Olson and Kayanush Aryana
LSU AgCenter researchers are studying how to increase the tolerance of beneficial bacteria to the high temperatures required in manufacturing processed cheese. They are also testing methods for improving salt tolerance of health beneficial bacteria.
Lactococcus lactis is used in the manufacture of most natural cheeses and is a mesophilic culture, which grows best at moderate temperatures between 45 and 113 degrees Fahrenheit. Natural cheese can be converted into processed cheese, which has more versatility of use, such as individually wrapped slices for sandwiches. Processed cheese is made by mixing and heating several lots of natural cheese with suitable emulsifying agents into a hot, melted homogeneous mass. The temperatures involved in this process range from 167 to 185 degrees Fahrenheit, which kills these mesophilic cultures.
These mesophilic cultures (L. lactis) provide several health benefits, including the treatment and prevention of irritable bowel diseases and Crohn’s disease. If the heat tolerance of these mesophilic cultures can be improved, then a new generation of healthier processed cheese with natural cheese microflora is possible.
Researchers at the LSU AgCenter exposed L. lactis to various mild temperatures for various lengths of time and then grew these preheated cells in broth and repeated the process for the second-generation cells. The second-generation cells were then subjected to higher temperatures. Cultures survived the higher temperatures that had earlier killed them. Heat tolerance in this mesophilic culture was thus enhanced.
Salt has been used as a preservative in foods since ancient times. Salt kills most microorganisms through osmosis by drawing water out of the bacterial cell. Salt is a low-cost ingredient, and in third world countries, because of the poor hygienic environments in food manufacturing, salt is relied upon to kill microorganisms in foods to make them safe.
Use of excessive salt has been linked with high blood pressure and stroke. Therefore, researchers around the world have tried several approaches to reduce salt including: a) using several salt substitutes, b) altering tastes to emphasize sourness rather than saltiness, and c) nano-sizing salt particles to increase salt surface area for less use of salt on the surface of salted foods. On supermarket shelves, there are a range of food products with reduced salt.
In certain foods such as cheeses, salt is multifunctional, having a role other than just flavoring. Salt helps in the release of whey during cheese manufacture and regulates microbial growth during manufacture and cheese ripening. Salt is the single ingredient that plays a key role in boosting cheesy flavor in cheeses.
Improving salt tolerances of health beneficial bacteria, such as Lactococcus lactis and probiotic Lactobacillus acidophilus can increase its use in salt-containing products, such as cheeses and canned foods, such as beans, fish and vegetables, in salt solutions. LSU AgCenter researchers have found that the salt tolerance was enhanced with exposure to mild heat, low hydrogen peroxide and low ethanol concentrations.
Rachael Brown and Emilio Ernesto are former students of Kayanush Aryana, who holds the Doyle Chambers Professorship in Animal Sciences in the School of Nutrition and Food Sciences; Douglas Olson is a research associate in the school.
(This article appears in the fall 2019 issue of Louisiana Agriculture.)