Microbiology and biochemistry of taleggio cheese during ripening

Tetracycline-resistant Streptococcus thermophilus isolates from soft cheeses harbored the genes tet(S), tet(M), and tet(L). Molecular analysis of these genes revealed their expression, localization on plasmids or Tn916-Tn1545 family transposons, and their similarity with published sequences. The study highlights the importance of an accurate safety assessment of using S. thermophilus as a starter culture.

supporting

confidence: 90%

Characterization of Tetracycline-Resistant Streptococcus thermophilus Isolates from Italian Soft Cheeses

Rizzotti¹,

Gioia²,

Dellaglio³

et al. 2009

“…This product was also characterized by a rapid decrease in pH and low levels of ethanol which could be attributed to the temperature of curd formation favoring the action of lactic acid bacteria rather than yeasts (4,5,43). The increase in pH and ethanol content toward the end of the ripening period, which appeared to be greater when increased amounts of starter culture were used, has previously been reported and associated with the action of yeasts (23). However, this action was limited in surface-salted cheese ripened in brine, as no increase in pH or ethanol content was observed, indicating no development of yeasts derived from the natural kefir microflora (64).…”

Section: Discussionmentioning

confidence: 59%

Evaluation of Freeze-Dried Kefir Coculture as Starter in Feta-Type Cheese Production

Kourkoutas

Kandylis

Panas

et al. 2006

The use of freeze-dried kefir coculture as a starter in the production of feta-type cheese was investigated. Maturation of the produced cheese at 4°C was monitored for up to 70 days, and the effects of the starter culture, the salting method, and the ripening process on quality characteristics were studied. The use of kefir coculture as a starter led to increased lactic acid concentrations and decreased pH values in the final product associated with significantly higher conversion rates compared to salted rennet cheese. Determination of bacterial diversity at the end of the ripening process in salted kefir and rennet cheeses by denaturing gradient gel electrophoresis technology, based on both DNA and RNA analyses, suggested a potential species-specific inhibition of members of the genera Staphylococcus and Psychrobacter by kefir coculture. The main active microbial associations in salted kefir cheese appeared to be members of the genera Pseudomonas and Lactococcus, while in salted rennet cheese, Oxalobacteraceae, Janthinobacterium, Psychrobacter, and Pseudomonas species were noted. The effect of the starter culture on the production of aroma-related compounds responsible for cheese flavor was also studied by the solid-phase microextraction-gas chromatography-mass spectrometry technique. Kefir coculture also appeared to extend the shelf life of unsalted cheese. Spoilage of kefir cheese was observed on the 9th and 20th days of preservation at 10 and 5°C, respectively, while spoilage in the corresponding rennet cheese was detected on the 7th and 16th days. Microbial counts during preservation of both types of unsalted cheese increased steadily and reached similar levels, with the exception of staphylococci, which were significantly lower in unsalted kefir cheese. All types of cheese produced with kefir as a starter were approved and accepted by the panel during the preliminary sensory evaluation compared to commercial feta-type cheese.

“…Pecorino Umbro, Pecorino Sardo, Pecorino Toscano, Pecorino Romano, Fossa, and Canestrato cheeses are the Italian ewe cheeses with the greatest market popularity (12,17,18) and differ with respect to several technological and chemical characteristics ( Table 1). The concentrations of NSLAB cells in the cheeses ranged from 5.5 to 8.2 log CFU/g, values which correspond to the values usually found in cheeses during ripening (11,13).…”

Section: Discussionmentioning

confidence: 99%

Characterization of Non-Starter Lactic Acid Bacteria from Italian Ewe Cheeses Based on Phenotypic, Genotypic, and Cell Wall Protein Analyses

Angelis

Corsetti

Tosti

et al. 2001

Self Cite

178

120

Non-starter lactic acid bacteria (NSLAB) were isolated from 12 Italian ewe cheeses representing six different types of cheese, which in several cases were produced by different manufacturers. A total of 400 presumptive Lactobacillus isolates were obtained, and 123 isolates and 10 type strains were subjected to phenotypic, genetic, and cell wall protein characterization analyses. Phenotypically, the cheese isolates included 32% Lactobacillus plantarum isolates, 15% L. brevis isolates, 12% L. paracasei subsp. paracasei isolates, 9% L. curvatus isolates, 6% L. fermentum isolates, 6% L. casei subsp. casei isolates, 5% L. pentosus isolates, 3% L. casei subsp. pseudoplantarum isolates, and 1% L. rhamnosus isolates. Eleven percent of the isolates were not phenotypically identified. Although a randomly amplified polymorphic DNA (RAPD) analysis based on three primers and clustering by the unweighted pair group method with arithmetic average (UPGMA) was useful for partially differentiating the 10 type strains, it did not provide a species-specific DNA band or a combination of bands which permitted complete separation of all the species considered. In contrast, sodium dodecyl sulfate-polyacrylamide gel electrophoresis cell wall protein profiles clustered by UPGMA were species specific and resolved the NSLAB. The only exceptions were isolates phenotypically identified as L. plantarum and L. pentosus or as L. casei subsp. casei and L. paracasei subsp. paracasei, which were grouped together. Based on protein profiles, Italian ewe cheeses frequently contained four different species and 3 to 16 strains. In general, the cheeses produced from raw ewe milk contained a larger number of more diverse strains than the cheeses produced from pasteurized milk. The same cheese produced in different factories contained different species, as well as strains that belonged to the same species but grouped in different RAPD clusters.Non-starter lactic acid bacteria (NSLAB) usually increase from a low number in fresh curd to dominate the microflora of mature cheese (36). In contrast to starters, NSLAB tolerate the hostile environment of cheese during ripening; this environment typically is characterized by 32 to 39% moisture, 4 to 6% salt in moisture, pH 4.9 to 5.3, 5 to 13°C, and a deficiency of nutrients (15,48). Mesophilic lactobacilli predominate in the NSLAB community, although pediococci and micrococci may also be found (6,11,15). Lactobacillus casei subsp. casei, L. casei subsp. pseudoplantarum, Lactobacillus paracasei subsp. paracasei, and Lactobacillus plantarum are the most frequently isolated taxa, but other facultatively and obligately heterofermentative species of lactobacilli are also found (18, 28). Adventitious mesophilic lactobacilli are usually present because of postpasteurization contamination but may also constitute part of the raw milk microflora and survive pasteurization (48).The role of NSLAB in ripening has not been resolved satisfactorily yet, although inclusion of adjunct cultures of some strains of NSLAB or use of ra...