Evaluation of microbial survival post-incidence on fresh Mozzarella cheese

Abstract

Commercial fresh Mozzarella cheese is made by direct acidification and is stored dry or in water without salt addition. The cheese has a shelf life of 6 wk, but usually develops an off-flavor and loses textural integrity by 4 wk, potentially due to the lack of salt and high moisture that allow the outgrowth of undesirable bacteria. To understand how microbial incidence affects cheese quality and how incident pathogen-related bacteria are limited by salt level during refrigerated storage, we made fresh Mozzarella cheese with high (2%) and low (0.5%) salt. The high-salt cheese was packaged and stored dry. The low-salt cheese was packaged and stored either dry or in 0.5% salt brine. One portion of cheeses was evaluated for surviving incident microbes by aerobic plate counts, coliform counts, and psychrophilic bacterial counts, of which coliforms and psychrophiles were not detected over 9 wk. Aerobic plate counts remained at 100 to 300 cfu/g up to 2 wk but increased by 1,000- to 10,000-fold between 4 and 6 wk at all salt levels and storage conditions. Other portions of cheeses were inoculated with either Escherichia coli or Enterococcus faecalis, both of which increased by 100-fold over 90 d of storage. Interestingly, E. coli added to the cheese brine first grew in the brine by 100-fold before attaching to the cheese, whereas Ent. faecalis attached to the cheese within 24h and grew only on the cheese. We conclude that incident bacteria, even from similar environments, may attach to cheese curd and survive differently in fresh Mozzarella cheese than in brine. Overall, 2% salt was insufficient to control bacterial growth, and slow-growing, cold- and salt-tolerant bacteria may survive and spoil fresh Mozzarella cheese.

Microbiological Quality of Asadero Cheese Manufactured with a Plant Based Coagulant from <i>Solanum elaeagnifolium</i>

“…At day 28, treatment with CE showed a decrease in the number of coliform colonies (p < 0.05), compared with CR cheese. Similar results have been reported in related cheeses during ripening [11,18,20]. This behavior is caused by the development of starter cultures, as they at pH 4 and 5 in dairy products inhibit the common and pathogenic flora, achieving lengthen the shelf life of product.…”

“…Several authors have reported the use of plant's enzymes (cardosins from Cynaras) in different handmade cheeses and showed that the sensory characteristics of those cheeses are similar or better than cheeses manufactured with commercial rennet [8][9][10]. Similar cheeses to asadero cheese have a shelf life of 6 wk, but usually develops an off-flavor and loses textural integrity by 4 wk, potentially due to the lack of salt and high moisture that allow the outgrowth of undesirable bacteria [11].…”

Changes in quality of nonaged pasta filata Mexican cheese during refrigerated vacuum storage

“…Coliform counts were slightly higher than those found in a previous study on raw-milk Oaxaca cheese, whereas counts of E. coli were similar (Caro et al, 2013). Coliforms and E. coli are related to fecal contamination and are used as an index of hygiene in cheese (Ganesan et al, 2012). Moreover, coliforms are considered one of the most important spoilage bacteria in mozzarella cheese (De Angelis et al, 2008).…”

Effect of Post Manufacture Thermal Dip Treatment on Proteolysis of Commercial String Cheese During Storage

“…It has a mild flavor (Rankin et al, 2006) that tastes like lightly salted, fresh milk (Ganesan et al, 2012). Just as Swiss cheese is known universally for its holes, string cheese is known for its stringing properties, as shown in Figure 2.…”

“…Because string cheese has a high moisture content (> 45 but ≤ 52 percent) and low salt content (1.6 percent), it has greater potential to spoil due to yeast, mold, and coliform growth (Guinee, 2004). Proper pasteurization, refrigeration and low pH of less than 5.4 are the only deterrents to the growth of unwanted microorganisms during storage (Ganesan et al, 2012).…”