Inhibition of Staphylococcus aureus Growth and Enterotoxin-A Production in Cheddar Cheese Produced with Variable Starter Activity

Abstract

Twelve cheese batches were made with variable starter activity, from milk inoculated with Staphylococcus aureus. At the end of cheddaring, only half the curd of each batch was salted and each portion was then pressed separately, cut and stored at 11 and 4 C for 6 weeks. Changes in bacterial counts, pH, enterotoxin A concentration and organoleptic properties were monitored. At the end of cheddaring, enterotoxin was detected in batches made with large initial inocula of S. aureus and/or low starter activities. At the end of pressing, the count of S. aureus, pH and enterotoxin concentration in the unsalted cheese (USC) were significantly lower than in salted cheese (SC), due to the adverse effect of salting on growth of microorganisms other than S. aureus. No change in enterotoxin concentration was detected in USC during storage at 11 and 4 C, and a sharp decline in S. aureus count occurred. The rate of such decline at 11 C exceeded that at 4 C. Increases in S. aureus count and enterotoxin concentration occurred in some SC batches stored at 11 C, whereas a slight decrease in S. aureus count and no change in enterotoxin concentration occurred in all SC stored at 4 C. At the end of storage, no cheeses had gas defects or significant flavor defects, which could have prohibited further processing.

Unveiling Staphylococcus aureus enterotoxin production in dairy products: a review of recent advances to face new challenges

“…These studies report that in cheddar technology, the population of S. aureus grows during the cheesemaking process until pressing and then decreases during ripening (Bachmann and Spahr 1995;Ibrahim et al 1981a;Tatini et al 1971). Cheddar cheese constitutes a favourable environment for the growth of S. aureus in the absence of an active starter (Ibrahim et al 1981b).…”

“…The activity of the competitive flora is a crucial parameter influencing the growth of S. aureus and SE production (Bachmann and Spahr 1995;Takahashi and Johns 1959;Tatini et al 1971). Salting of cheddar cheese and a temperature decrease induce an increase in the population of S. aureus, probably due to lower starter activity in response to the increased salt concentration (Ibrahim et al 1981a). Moreover, the duration of pressing is a critical parameter which must be taken into account when evaluating the risks of growth of S. aureus in cheddar cheese.…”

The Staphylococcal Enterotoxins

“…Dairy products may also contain toxins and/or toxin-producing Staph. aureus (Rose et al, 1989;Gilmour and Harvey, 1990;Burdova et al, 1994) and contaminated cheese, frequendy made from raw milk, may harbour enterotoxins or bacteria or both (Tatini et al, 1971b(Tatini et al, , 1973Ibrahim et al, 1980;Rosec et al, 1997). SEA or toxin-producing Staph.…”

Enterotoxin A Gene Barrier Staphylococcus aureus Within Traditionally Dairy Products of Tehran

“…Milk is suitable substrate for enterotoxin producing S. aureus (14). In addition, enterotoxins can retain their biological activity even after pasteurization (15). Staphylococcal enterotoxins are highly resistant to heat; e.g.…”