Behavior of Staphylococcus aureus in Culture Broth, in Raw and Thermized Milk, and during Processing and Storage of Traditional Greek Graviera Cheese in the Presence or Absence of Lactococcus lactis subsp. cremoris M104, a Wild, Novel Nisin A–Producing Raw Milk Isolate

2014 ◽  
Vol 77 (10) ◽  
pp. 1703-1714 ◽  
Author(s):  
JOHN SAMELIS ◽  
ALEXANDRA LIANOU ◽  
ELENI C. PAPPA ◽  
BOJANA BOGOVIČ-MATIJAŠIĆ ◽  
MARIA PARAPOULI ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Lactococcus Lactis ◽  
Starter Culture ◽  
Raw Milk ◽  
Culture Broth ◽  
Microbial Consortia ◽  
Aureus Strain ◽  
Lactococcus Lactis Subsp ◽  
Log Reduction ◽  
And Storage

This study was conducted to evaluate the behavior of Staphylococcus aureus during processing, ripening, and storage of traditional Greek Graviera cheese in accordance with European Union Regulation 1441/2007 for coagulase-positive staphylococci in thermized milk cheeses. Lactococcus lactis subsp. cremoris M104, a wild, novel nisin A–producing (NisA+) strain, also was evaluated as an antistaphylococcal adjunct. A three-strain cocktail of enterotoxigenic (Ent+) S. aureus increased by approximately 2 log CFU/ml when coinoculated (at approximately 3 log CFU/ml) in thermized Graviera cheese milk (TGCM; 63°C for 30 s) with commercial starter culture (CSC) and/or strain M104 at approximately 6 log CFU/ml and then incubated at 37°C for 3 h. However, after 6 h at 37°C, significant retarding effects on S. aureus growth were noted in the order TGCM+M104 > TGCM+CSC = TGCM+CSC+M104 > TGCM. Additional incubation of TGCM cultures at 18°C for 66 h resulted in a 1.2-log reduction (P < 0.05) of S. aureus populations in TGCM+M104. The Ent+ S. aureus cocktail did not grow but survived during ripening and storage when inoculated (at approximately 3 log CFU/g) postcooking into Graviera mini cheeses prepared from TGCM+CSC or TGCM+CSC+M104, ripened at 18°C and 90% relative humidity for 20 days, and stored at 4°C in vacuum packages for 2 months. A rapid 10-fold decrease (P < 0.05) in S. aureus populations occurred within the first 24 h of cheese fermentation. Reductions of S. aureus were greater by approximately 0.4 log CFU/g in CSC+M104 than in CSC only cheeses, concomitantly with the presence of NisA+ M104 colonies and nisin-encoding genes in the CSC plus M104 cheeses and their corresponding microbial consortia only. A high level of selective survival of a naturally nisin-resistant EntC+ S. aureus strain from the cocktail was noted in CSC+M104 cheeses and in coculture with the NisA+ M104 strain in M-17 broth. In conclusion, although S. aureus growth inhibition is assured during Graviera cheese ripening, early growth of the pathogen during milk curdling and curd cooking operations may occur. Nisin-resistant S. aureus strains that may contaminate Graviera cheese milks postthermally may be difficult to control even by the application of the NisA+ L. lactis subsp. cremoris strain M104 as a bioprotective adjunct culture.

Growth, nisA Gene Expression, and In Situ Activity of Novel Lactococcus lactis subsp. cremoris Costarter Culture in Commercial Hard Cheese Production

2017 ◽  
Vol 80 (12) ◽  
pp. 2137-2146 ◽  
Author(s):  
Dimitrios Noutsopoulos ◽  
Athanasia Kakouri ◽  
Eleftheria Kartezini ◽  
Dimitrios Pappas ◽  
Efstathios Hatziloukas ◽  
...  
Keyword(s):  
Gene Expression ◽  
Lactococcus Lactis ◽  
Starter Culture ◽  
Fold Increase ◽  
Raw Milk ◽  
Good Growth ◽  
Lactococcus Lactis Subsp ◽  
Quantitative Expression ◽  
Hard Cheese

ABSTRACT This study evaluated in situ expression of the nisA gene by an indigenous, nisin A–producing (NisA+) Lactococcus lactis subsp. cremoris raw milk genotype, represented by strain M78, in traditional Greek Graviera cheeses under real factory-scale manufacturing and ripening conditions. Cheeses were produced with added a mixed thermophilic and mesophilic commercial starter culture (CSC) or with the CSC plus strain M78 (CSC+M78). Cheeses were sampled after curd cooking (day 0), fermentation of the unsalted molds for 24 h (day 1), brining (day 7), and ripening of the brined molds (14 to 15 kg each) for 30 days in a fully controlled industrial room (16.5°C; 91% relative humidity; day 37). Total RNA was directly extracted from the cheese samples, and the expression of nisA gene was evaluated by real-time reverse transcription PCR (qRT-PCR). Agar overlay and well diffusion bioassays were correspondingly used for in situ detection of the M78 NisA+ colonies in the cheese agar plates and antilisterial activity in whole-cheese slurry samples, respectively. Agar overlay assays showed good growth (>8 log CFU/g of cheese) of the NisA+ strain M78 in coculture with the CSC and vice versa. The nisA expression was detected in CSC+M78 cheese samples only, with its expression levels being the highest (16-fold increase compared with those of the control gene) on day 1, followed by significant reduction on day 7 and almost negligible expression on day 37. Based on the results, certain intrinsic and mainly implicit hurdle factors appeared to reduce growth prevalence rates and decrease nisA gene expression, as well as the nisin A–mediated antilisterial activities of the NisA+ strain M78 postfermentation. To our knowledge, this is the first report on quantitative expression of the nisA gene in a Greek cooked hard cheese during commercial manufacturing and ripening conditions by using a novel, rarely isolated, indigenous NisA+ L. lactis subsp. cremoris genotype as costarter culture.

Inhibition of a Methicillin-Resistant Staphylococcus aureus Strain in Afuega'l Pitu Cheese by the Nisin Z–Producing Strain Lactococcus lactis subsp. lactis IPLA 729

2004 ◽  
Vol 67 (5) ◽  
pp. 928-933 ◽  
Author(s):  
NATALIA RILLA ◽  
BEATRIZ MARTÍNEZ ◽  
ANA RODRÍGUEZ
Keyword(s):  
Staphylococcus Aureus ◽  
Lactococcus Lactis ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Aureus Strain ◽  
Northern Spain ◽  
Potential Threat ◽  
Methicillin Resistant ◽  
Initial Inoculum ◽  
Lactococcus Lactis Subsp ◽  
Nisin Z

Methicillin-resistant Staphylococcus aureus strains are a potential threat for food safety because foodborne illness caused by methicillin-resistant Staphylococcus aureus has been reported even though these strains were only associated with nosocomial infections until recently. This article focuses on the inhibitory effect of the nisin Z–producing strain Lactococcus lactis subsp. lactis IPLA 729 on the growth of Staphylococcus aureus CECT 4013, a methicillin-resistant strain. S. aureus was inhibited by the presence of the nisin producer IPLA 729 in buffered Trypticase soy broth, milk, and Afuega'l Pitu cheese, an acid-coagulated cheese manufactured in Asturias, Northern Spain. A reduction of 3.66 log units was observed in Trypticase soy broth at the end of the incubation period. In milk, viable counts of S. aureus were undetectable or were reduced by 2.16 log units in 24 h depending on the initial inoculum (1.8 × 104 and 7.2 × 106 CFU/ml). The staphylococcal strain was also undetected in test cheeses in which the nisin Z producer was present whereas 2 log units were detected in control cheeses at the end of ripening.

scholarly journals Influence of soft cheese technology on the growth and enterotoxin production of Staphylococcus aureus

2009 ◽  
Vol 27 (No. 2) ◽  
pp. 127-133 ◽  
Author(s):  
L. Necidová ◽  
Z. Šťástková ◽  
M. Pospíšilová ◽  
B. Janštová ◽  
J. Strejček ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Technological Process ◽  
Raw Milk ◽  
Toxin Production ◽  
Milk Products ◽  
Model Experiments ◽  
Soft Cheese ◽  
Strict Compliance ◽  
Technological Processing ◽  
And Storage

The aim of this study was to monitor <I>S. aureus</I> growth and toxin production in soft cheese during the technological processing. In model experiments, raw milk was inoculated separately with five <I>S. aureus</I> strains isolated from milk and milk products. All the strains were producers of staphylococcal enterotoxins (SEs) of types A, B, or C. SEs were detected by the enzyme-linked fluorescence assay (ELFA) performed in the MiniVIDAS device. This study has shown that the amount of SEs varied with the tested strains and stages of the technological process. SEs were detected in soft cheese made from pasteurised milk inoculated with 2.9 × 10<sup>5</sup> CFU/g of <I>S. aureus</I>. The prevention of <I>S. aureus</I> contamination and multiplication during the cheese making process is a prerequisite for the production of safe soft cheese. The most important enterotoxin dose build-up factor can be overcome by strict compliance with the cooling requirements during the manufacture, distribution and storage of the product.

Behavior of Staphylococcus aureus in Cheddar Cheese Made with Sodium Chloride or a Mixture of Sodium Chloride and Potassium Chloride

1982 ◽  
Vol 45 (11) ◽  
pp. 996-1002 ◽  
Author(s):  
SUSAN KOENIG ◽  
ELMER H. MARTH
Keyword(s):  
Staphylococcus Aureus ◽  
Sodium Chloride ◽  
Potassium Chloride ◽  
Starter Culture ◽  
Salt Content ◽  
Cheddar Cheese ◽  
Ph Values ◽  
Radio Immunoassay ◽  
Low Levels ◽  
And Storage

Stirred-curd Cheddar cheese was manufactured from milk artificially contaminated with &lt; 1000 Staphylococcus aureus cells/ml. Lactic starter culture was added to the milk at the rate of 1.0 or 0.5% (v/v). Curds were divided and salted with either NaCl or a mixture of KCl/NaCl to achieve final salt concentrations of approximately 2.4 or 1.2%. Some portions of curd remained unsalted. Cheeses were analyzed for moisture and salt content and were stored at 4 or 10°C for 8 weeks. Bacterial counts and pH values were determined during manufacture and storage of cheeses. Unsalted cheeses had the lowest and the 2.4%-salted cheese had the highest S. aureus counts. Cheeses salted with KCI/NaCl had considerably lower S. aureus and non-S. aureus counts than did cheeses salted with NaCl. All cheeses made with 1.0% starter culture had appreciably lower counts of S. aureus than did cheeses made with 0.5% starter culture. Low levels (0.05 to 0.52 ng/g) of enterotoxin A were found in 16 of 17 samples tested with the radio immunoassay procedure. Presence of enterotoxin was not directly associated with the kind or amount of salt used to produce the cheese.

scholarly journals Effects of starter culture and storage on volatile profiles and sensory characteristics of yogurt or cream butter

2020 ◽  
Vol 70 (3) ◽  
pp. 184-200
Author(s):  
Engin Gundogdu ◽  
Songul Cakmakci ◽  
Ali Adnan Hayaloglu
Keyword(s):  
Volatile Compounds ◽  
Lactococcus Lactis ◽  
Leuconostoc Mesenteroides ◽  
Starter Culture ◽  
Hexanoic Acid ◽  
Sensory Properties ◽  
Sensory Characteristics ◽  
Volatile Profiles ◽  
And Storage ◽  
General Acceptability

In this study volatile compounds and sensory properties of butter produced from cream or yogurt using Lactococcus lactis subsp. lactis biovar. diacetylactis or Leuconostoc mesenteroides subsp. cremoris as well as a mixture of these two bacteria were investigated over 60 days. A total of 10 esters, 6 aldehydes, 11 ketones, 16 alcohols, 6 acids, 2 sulphides, 3 terpenes, and 3 miscellaneous compounds were detected. There were more volatile compounds in cream butter than in yogurt butter. While S-methyl thioacetate was only found in yogurt butter samples, hexanal, ethanol, 2-nonanone, 2-pentanone, 2-heptanone, acetic, butanoic (butyric) and hexanoic acid were the most abundant volatiles in both cream and yogurt butter. The results showed that the use of starter in the manufacturing of yogurt butter, which is traditionally produced without starters, affected the volatile compounds and sensory properties. The highest general acceptability scores were given to the butter samples containing mixed cultures at the end of storage.

Potential for Presence and Growth of Staphylococcus aureus in Brazilian Minas Cheese Whey

1981 ◽  
Vol 44 (3) ◽  
pp. 185-188 ◽  
Author(s):  
EDSON CLEMENTE dos SANTOS ◽  
CONSTANTIN GENIGEORGIS
Keyword(s):  
Staphylococcus Aureus ◽  
Cheese Whey ◽  
Starter Culture ◽  
Aureus Strain ◽  
Processing Temperature ◽  
Potential Growth ◽  
Strain Behavior ◽  
Streptococcus Lactis ◽  
Insufficient Amount ◽  
Short Time

Presently there is a great interest in further utilization of Minas cheese whey by the Brazilian food industries. The potential growth of Staphylococcus aureus in Minas cheese whey was evaluated. S. aureus strain 100 was inoculated at levels of (log10) 3 and 5 cells/ml in sterile whey along with (log10) 7.17 cells/ml of Streptococcus lactis and Leuconostoc cremoris starter and incubated at 37 C for 8 h. S. aureus growth occurred at both levels of inoculum. Better growth was observed at the higher inoculum (P &lt; 0.05). Thermonuclease was detected after 2 h of incubation only in the whey inoculated with (log10) 5 cells/ml and when growth reached about (log10) 7. Then we determined the presence of S. aureus in Minas cheese whey after inoculation of pasteurized milk with strains 100, 137 and 243 alone and in combination at levels (log10) of 4.23 to (log10) 6.20 with or without starter, and sampling the whey 60 and 70 min after the cheese processing started. A significant sampling time effect for S. aureus counts was observed (P &lt; 0.01). Duncan's Multiple Range test showed that there were significant differences in strain behavior. Starter culture effect and the interactions were not significant (P &gt; 0.05). The failure to observe a starter culture effect upon staphylococcal counts in whey may be due to the short time between starting the cheesemaking process and sampling of whey, insufficient amount of lactic acid produced by the starter culture and the detrimental effect of the processing temperature (34–36 C) upon the starter bacteria.

Survival and Growth of Staphylococcus aureus in Commercially Manufactured Brazilian Minas Cheese

1981 ◽  
Vol 44 (3) ◽  
pp. 177-184 ◽  
Author(s):  
EDSON CLEMENTE dos SANTOS ◽  
CONSTANTIN GENIGEORGIS
Keyword(s):  
Staphylococcus Aureus ◽  
Starter Culture ◽  
Raw Milk ◽  
Inhibitory Effect ◽  
Pasteurized Milk ◽  
Ripening Time ◽  
Survival And Growth

The potential for Staphylococcus aureus survival, growth and enterotoxigenesis in Minas cheese was studied. Twenty lots of cheese were made with raw and pasteurized milk and with and without starter culture. Cheese milk was inoculated with S. aureus strains 100, 243 or 137 and a pooled inoculum at levels of (log10) 4.23 to 6 cells/ml. Use of starter, type of inoculum, ripening time and interaction of starter by strain affected significantly the final pH of the cheese (5.22 with starter versus 5.45 without starter). Final NaCl content of cheeses differed significantly (P &lt; 0.01) with lot indicating lack of uniformity in salting. Moisture was affected significantly by S. aureus inoculum, time of ripening and use of starter (P &lt; 0.05). Final moisture ranged from 30.6 to 45.6%. Highly statistically significant effects on S. aureus counts during ripening were observed for use of starter (P &lt; 0.001), type of S. aureus inoculum (P &lt; 0.001) and time of ripening (P &lt; 0.05). Use of starter culture had an inhibitory effect on S. aureus growth. Use of raw or pasteurized milk did not affect significantly the staphylococcal counts. S. aureus growth occurred in all lots made without starter culture. Levels of S. aureus greater than (log10) 7 cells/g were observed in 27/47 and 7/46 cheeses made with pasteurized and raw milk, respectively. Enterotoxins A, B and C were detected in 10/16 and 0/4 cheeses made with pasteurized and raw milk, respectively, and more often in cheeses made without starter than with starter culture. This study demonstrated the need for more uniform manufacturing practices, use of starter culture and use of pasteurized milk only.

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